Table of contents

After successfully held for seven consecutive year, 2022 8th International Conference on Mechanical Engineering, Materials and Automation Technology (MMEAT 2022) was successfully held during May 27-29, 2022 in Qingdao, China. MMEAT 2022 is to bring together innovative academics and industrial experts in the field of materials, mechanical engineering and automation technology to a common forum. The primary goal of the conference is to promote research and developmental activities in Mechanical Engineering, Materials and Automation Technology and another goal is to promote scientific information interchange between researchers, developers, engineers, students, and practitioners working all around the world. The conference will be held every year to make it an ideal platform for people to share views and experiences in materials, mechanical engineering and automation technology and related areas.

This year, more than 350 participants took part in the conference and we were greatly honored to have two professors to serve as our conference chairman and seven industry elites as our keynote speakers. The conference model was divided into two sessions, including oral presentations and keynote speeches. In the first part, some scholars, whose submissions were selected as the excellent papers, were given 15 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30-45 minutes to hold their speeches.

In the keynote presentation part, A.Prof.Thomas Fiedler, from the University of Newcastle as our first keynote speaker. His particular interest are cellular metals for impact attenuation, damping, functional applications and lightweight design. In addition, we had Prof.Zongyu Chang, Ocean University of China. His research content mainly includes: mechanical dynamics, dynamics and control of marine equipment and human factors in offshore engineering. A.Prof.Guanglei Wu, from Dalian University of Technology. His research interests include robotic technology and their applications. And then we had Assoc.Prof. Guangming Wang, Shandong Agricultural University, China. His main research interest is hydrostatic power split continuously variable tractor transmission. Assoc.Prof. Yufei Gao, Shandong University, China. He is mainly engaged in the research of digitization and simulation, precision machining, diamond wire saw slicing and high-performance electroplated diamond wire preparation, intelligent manufacturing and intelligent equipment. Assoc.Prof.Fei Gao, Shanghai Jiao Tong University, China. His current research interests include microgrids, wireless power transfer and more electric transportation systems. Prof.Zhengfang Wang, our finale keynote speaker, from Shandong University of Technology, China.

List of Committee member is available in this pdf.

All papers published in this volume have been reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing Publishing.

• Type of peer review: Single Anonymous

• Conference submission management system: Morressier

• Number of submissions received: 417

• Number of submissions sent for review: 391

• Number of submissions accepted: 243

• Acceptance Rate (Submissions Accepted / Submissions Received × 100): 58.3

• Average number of reviews per paper: 2

• Total number of reviewers involved: 80

• Contact person for queries:

Name: Xuexia Ye

Email: xx.ye@keoaeic.org

Affiliation: AEIC Academic Exchange Information Centre

Based on the numerical simulation theory, this paper establishes the two-phase flow calculation model of sand and air mixture in the sand control vortex tube, and combined with CFD numerical simulation, studies the influence rules of various design parameters of the vortex tube on the total pressure loss and sand dust separation efficiency of the helicopter intake system, optimizes the structural parameters of the vortex tube separator, and puts forward a set of vortex tube design method, it provides a basis for the design optimization of vortex tube.

Compressor has a complex internal structure and contains various kinds of motion mechanism. At present, research on compressor's vibration and sound radiation characteristics is insufficient. In this paper, structure and sound radiation modes of control objects are analysed by mode analysis. Explore the mode distribution law and correspond the structure mode to the sound radiation mode. On this basis, by suppressing the vibration mode, the influence is transmitted to the acoustic domain to realize the active control of sound radiation of the structure as a whole.

Vibration response and performance of a piezoelectric energy harvester under the hybrid excitation of base vibration and galloping is studied. Based on the Euler-Bernoulli beam theory, the distributed-parameter model of a piezoelectric cantilever beam with base and galloping hybrid excitation is derived. Subsequently, the electromechanical coupled reduced order model and the decoupling model of the system is obtained. Thereafter, the analytical solution of the vibration response and the coupling relationship between the two hybrid excitations are analyzed. In the end, the impacts of the load resistance, the excitation acceleration and the wind speed on the power generation performance of the system are examined. Results indicated that the hybrid excitation can not only increase the energy harvester power of the system by 2.4W, but also effectively broaden the frequency band compared with the single foundation excitation. The research result is helpful to the dynamic design of a piezoelectric vibration energy harvesters under hybrid vibration excitation.

A novel piezoelectric vibration energy harvester structure is designed. The output voltage is employed as the objective function, and the structural parameters of the vibration energy harvester device are optimized by Taguchi method. The best parameter combination of A₃(95mm), B₃(45mm), C₁(60mm), D₂(35mm) and E₁(50mm) is determined. Through the analysis of variance, it is concluded that parameter A has the most obvious effect on the response of the piezoelectric energy harvester, with the contribution rate reaching 26.02%, and the influences of B, C, D and E decrease successively. The finite element model of the piezoelectric vibration energy harvester is established, then the load impedance matching characteristics and acceleration dependence of voltage are discussed.

In practical engineering, for instance the aerospace aircraft and engine industry, fastener connection is a very common joint structures, the current engineering typical strength analysis for bolt connection structure doesn't include bolt bending analysis. In the engineering research and design phase, if the bolt connection plate is too thick or it contains shims or spacers that cause the bolt itself to be too long, then bolt bending failure analysis is also necessary. The bolt bending analysis is a complex failure mode, there is no unified analysis method for effective assessment for it. This paper introduces an improved calculation method which is proposed to specifically calculate the bending load of the bolt according to the force characteristics of the bolt for bolt bending analysis.

This paper analyses the working principle of RV reducer and the actual tooth profile equation of cycloid wheel, and deduces the distribution law of contact load on cycloid wheel in transient state by considering the initial meshing gap between pin teeth and cycloid wheel and the contact deformation generated during meshing. Taking an RV reducer as the research object, the contact load of the cycloid wheel is calculated by using MATLAB programming, and the change curve of contact load and crank shaft rotation angle is obtained, which provides theoretical support for the analysis and design of RV reducer.

In order to optimize the sealing machine, this paper takes the heat sealing block in the heat sealing structure of the sealing machine as the research object, and improves the working efficiency and stability of the sealing machine by changing the size and structure of the heat sealing block. The 3D modeling of the sealing machine was carried out by using SOLIDWORKS; then the reliability of the simulation in this paper was verified by comparing the experimental data and the simulation data; finally, the comparison of the simulation data of the heat sealing block before and after the modification found that the modification of the heat sealing block reduced the heating time by 7.5 s , the variance value is reduced by 96.8%, and the uniformity of heat distribution is significantly improved.

Precision reducers used in aerospace servo mechanisms often have the characteristics of high accuracy and strong bearing capacity due to the particularity of their working environment. Transmission error, as an important parameter affecting the accuracy of precision reducer, is different from ordinary reducers, and often requires that its maximum transmission error can be effectively controlled within 3'. In order to efficiently test the accuracy of the reducer, this paper designed a set of test devices for the accuracy measurement of the reducer of the aerospace servo mechanism, and now conducts a systematic error analysis of the overall test device, determines the error range, and finally, the uncertainty is integrated to confirm that the error meets the design requirements.

Sensors have a wide range of applications in environmental monitoring, for example, as temperature transmitters in industrial control processes. In order to reduce the chip area and improve the digital-to-analogue conversion accuracy, large loads are driven. This study proposes a current-shunted DAC for sensor interfaces with an R-2R structure, using a Class-AB amplifier to buffer or amplify the signal. Spectre simulation shows that the DAC has a current consumption of 63uA when the supply voltage and reference voltage are 1.8V and can drive a 15pF capacitive load.

Many domestic traffic accidents are caused by high-temperature friction of truck's brake drum resulting in failure of brake system. Therefore, it is the key to solve the problem of decline on brake drum performance caused by temperature. The following schemes are mainly adopted: improving brake structure and friction materials, adding auxiliary brake devices, and installing cooling devices for brake system. This paper summarizes the structure and characteristics of most intelligent cooling devices for brake system in China. In addition, based on these intelligent cooling devices, the paper also puts forward new intelligent cooling devices for truck's brake system. The system uses sensors to analyze the temperature state of the brake drum. According to the analysis results, the central controller innovatively combines air pump and water pump to transform low-pressure water into high-pressure water, and then sprays and cools the brake drum through the water pipes and arc spray devices to ensure the normal operation of the brake system.

Due to the low frequency and small amplitude of the input signal of the leakage current protection chip, an operational amplifier with low offset and low power consumption is designed by using the chopper stabilization technique and the dynamic element matching technique. Based on the TSMC 0.18um process, the spectre environment in cadence is used for design and simulation. The power supply voltage is 1.8V. The post simulation results show that under the TT corner, the average current of the operational amplifier is 139uA, the loop gain is 85.9dB, the phase margin is 68.01°, and the power supply rejection ratio(PSRR) is 101.62dB@50Hz, the common mode rejection ration(CMRR) is 104.52dB@50Hz, the equivalent input noise is 129.86nv/sqrt(Hz)@50Hz, and the value of equivalent input offset voltage is 8.2uV(mean).

With the strategic transformation of our country's navy, the defense capability of long distance needs to be improved, which has higher requirements on the reliability and life of gas turbines. Bearing system is one of the factors that restricts the life and reliability of gas turbines. The fundamental reason is that the rolling bearings used have limited life and low reliability. Since sliding bearings have higher reliability, longer service life and lower maintenance costs, in order to improve the operation stability of a certain type of gas turbine which works under complex conditions, the former supporting elements were replaced with the more reliable tilting-pad sliding bearings. Its structure is designed according to the original structural dimensions. After finishing the structure design, we analyze the static characteristics of the designed bearing from the aspects like oil film pressure, oil film thickness, bearing capacity and so on, combining with the relevant Matlab program and provide a reference for the subsequent theoretical analysis after completing the subsequent bearing on-machine test.

The astronauts need to re pressurize the sealed cabin after returning to the sealed cabin. The noise generated in the process of re pressurization is too large, so a silencer shall be set to reduce the noise in the cabin. Through theoretical analysis, this paper selects the small hole injection muffler, makes theoretical calculation, and determines the specific structural size of the muffler. The test shows that when the cabin pressure rises to 85kpa, the use of the small hole injection silencer can reduce the cabin noise from 85.7db to 66.3db, which meets the medical requirements of astronauts.

By means of finite element analysis and topology optimization methods, the structural optimization and lightweight design of the robotic arm for the installation of gas drainage pipelines are realized, so that it can realize more complex actions under the premise of ensuring stability. SolidWorks 3D modeling and Ansys Workbench analysis software are used to build models of the robotic arm and perform static analysis. The structural design is optimized through the deformation and stress distribution when grasping the maximum weight. The topology optimization mathematical model of the variable density method and the SIMP (Simplified Isotropic Material with Penalization) interpolation model was constructed, and the topology optimization of the robotic arm was performed in the Shape Optimization module in Ansys Workbench. On this basis, the structure after topology optimization is analyzed and studied. The results show that compared with before topology optimization, the mass of the manipulator is reduced by 29.65%, and the maximum deformation and maximum stress are both reduced by 10%, which confirms the feasibility of lightweight design and structural optimization of the manipulator.

In recent years, the automobile industry have shown the de-velopment trend of intelligence and networking. OSEK OS, the kind of traditional vehicle control operating system, has the characteristics of static configuration, but it cannot support new industry demands such as ADAS and OTA. Automobiles have become an important part of smart cities, and are currently developing in the direction of intelligence, networking, openness and sharing. However, OSEK OS, the traditional vehicle control operating system, statically configures tasks, alarms and other modules before running, which cannot be changed at runtime. Therefore, it is difficult to meet the needs of intelligent networked vehicles. AUTOSAR OS, the next-generation vehicle control operating system, adds sev-eral new functional modules and security mechanisms and is totally compatible with OSEK OS. In order to verify the re-liability of the new functional modules and security mecha-nisms of AUTOSAR OS, we tests the security mechanisms of VKware OS, which is an open source AUTOSAR OS, and designs a test set that conforms to the specification of AU-TOSAR OS, the test case can also be used for functional and security mechanism test of various AUTOSAR OS.

According to the development demand of automatic yarn tube loading equipment in textile field, a fingertip gripping stability evaluation method is proposed and applied to the end-effector structure design suitable for multi-size yarn tube gripping. Firstly, by studying the human hand mechanism, the tendon type underdrive principle is used to design the rope sheave layout and tendon path of the end-effector finger, and its overall structural design is introduced; secondly, a virtual spring is used to establish an equivalent model of fingertip contact, and the grasping stability is evaluated from the perspective of system potential energy by constructing a stiffness matrix; on this basis, an elliptical curve under geometric constraints is used as the fingertip profile curve, and the release sample is used to Finally, quantitative analysis of gripping stability based on a yarn tube gripping model. The research results lay the foundation for the design of an efficient and reliable yarn tube gripping device. The working principle and design ideas of the bionic end-effector have some implications for the design of robotic end-effectors serving other fields.

PEMF therapy, a non-invasive technology, is frequently reported in medical journals. It can send electric and magnetic fields to the body through induction coils [1,2], so as to provoke cells to stimulate nerves and muscles. Based on performances of large PEMF equipment on the market, on average, the low frequency emitted by most PEMF equipment is 0-300HZ An appropriate single chip is selected to make an extremely low frequency 0-30HZ that can be easily developed and easily changed. And has bipolar pulse wave so that simple equipment can also get enough effect.

The high gap self-propelled sprayer has the characteristics of wide boom width and high working efficiency. Aiming at the problem that the spray boom is prone to mechanical vibration along with the body and affects the spraying effect, the static analysis and modal analysis of the boom suspension of its two-link trapezoidal mechanism are carried out, based on the ANSYS simulation method. The results show that the optimized stress at the end boom suspension connection is reduced from 161MPa to 22MPa, and the maximum displacement is reduced from 35mm to 7mm. The maximum stress of the inner boom suspension was reduced from 128.36MPa to 88.07MPa Stress distribution and displacement conditions achieve the desired effect. The modal analysis results show that the first six natural frequencies of the boom suspension do not coincide. And this frequency reasonably avoids the external excitation frequency range, and avoids unnecessary damage caused by the resonance of the boom suspension in the actual operation of the sprayer.

Aiming at the optimization of cogging torque of 12 pole 36 slot embedded permanent magnet motor, analyzing the generation principle of cogging torque, putting forward the optimization design of auxiliary slot based on Taguchi method, using Maxwell finite element simulation tool, analyzing and selecting the optimized data, through orthogonal experiment and data processing, finding the final optimization scheme of auxiliary slot. The simulation results show that, the auxiliary slot optimization method based on Taguchi method can effectively suppress the cogging torque under reasonable slotting rules, which is also of reference significance to other types of parameter optimization.

For the landing process of a large-scale airdrop system, flared-maneuver is a common approach to decelerate to prevent huge impacts while touching down. A 6-DOF model of parafoil-load system is used to investigate the effects of different deflection modes on airdrop system's landing performance. By numerical simulation, three main factors, distance of deflection, rate of deflection and the pattern of rate changing, are discussed according to the results. The conclusion derived is of some significance in assisting control and design of landing procedure of such unpowered heavy airdrop systems.

In order to solve the problems of large vibration and noise caused by the unreasonable design of the rubber vibration isolator of the electromagnetic vibrating feeder. Firstly, the relationship between vibration isolation performance and vibration isolation system parameters is theoretically analyzed. Secondly, a multi-objective optimization function is established with the vibration isolation coefficient and amplitude ratio as the optimization objectives. The genetic algorithm is used to optimize the objective function, and the structure and parameters of the rubber vibration isolator are designed according to the optimization results. Finally, using computer simulation, the vibration isolation performance before and after optimization is analyzed and the strength of the vibration isolator is verified. The results show that after optimization, the amplitude of the base of the electromagnetic vibrating feeder decreases by 28.6%, and the amplitude ratio decreases by 53.2%, which achieves a good optimization effect, and the strength of the rubber vibration isolator meets the requirements;

To address the problems of unstable and noisy compressor operation caused by excessive mass of the connecting rod of reciprocating piston compressor, a multi-objective topology optimization algorithm based on the compromise planning method is used to optimize the design of the connecting rod by considering both dynamic low-order inherent frequency and stiffness, and a multi-objective function of joint stiffness and inherent frequency is proposed. The finite element model is established and the optimized model is revalidated. The analysis results show that the optimized connecting rod mass is reduced by 21.6%, the low-order inherent frequency is improved, and the material meets the requirements of strength and stiffness.

Based on RNG k-ε turbulence model and dynamic grid technology, the internal fluid dynamics model of splash lubrication three stage planetary gear reducer system is established. The distribution of lubricating oil and convective heat transfer characteristic in the system at different input rotational speeds are analyzed. The results show that at high speed condition, the oil gas mixing volume and the degree of atomization of lubricating oil are higher, and the convective heat transfer coefficient of tooth surface is larger, and it takes less time for the convective heat transfer coefficient to reach equilibrium. Meanwhile, the mean convective heat transfer coefficient on the tooth surface of sun gear, planetary gear and ring gear decreases successively.

The paper takes a type of flexible air bearing as the research object, and the bearing structure is analyzed in detail. Combined with the traditional analysis method of tilting pad bearing and the fluid-solid coupling theory, a new analysis model for performance prediction of the bearing was established. The performance of air bearing with inner diameter of 70mm was calculated by changing the input pressure or the inlet capillary diameter. The structure of the bearing was optimized by analyzing the calculation results, and the structure of the separate inlet nozzle was added. A bearing testing machine is designed for the flexible air bearing test to verify the improvement of bearing performance.

In this paper, magnetic powder brake is used to load the starting motor in the design of the test bed, so that the loading and transmission is stable and reliable. The star type elastic coupling is used to connect the starting motor and reduce the vibration and noise. At the same time, high precision speed and torque sensor is used to improve the accuracy of the speed and torque data testing of the starting motor. After the test, the test report can be generated automatically and the test data can be stored. The reliability of design and simulation calculation is verified by debugging and continuous operation of the test bed, which provides an effective experimental basis for the design and research of similar products.

The metal micro-truss porous structures demonstrate industrial application values in lightweight, high specific strength, impact resistance and energy absorption. 3D printing brings a feasible path to design and directly fabricate metal micro-truss parts. Spatially geometrically uniformly distributed and unit-symmetrically arrayed porous structures still need to further improve the structural performance. This work studies the design principles and several design cases of geometrically non-uniform micro-truss porous structures via metal 3D printing method. The high-stress localized micro-regions are filled with denser and more reinforced micro-truss cell arrays that conform to the main loading direction of localized stress.

This paper uses CFD software ANSYS Fluent, based on RSM Reynolds stress model and VOF two-phase flow model, to calculate the turbulent flow field inside the ∅75mm heavy dispersed phase particle separation cyclone. Combined with the experimental working parameters under different inlet pressures, the experimental results were compared. Check the accuracy of the formula calculation results and the numerical simulation results. The results show that the air column inside the cyclone is stable and the internal pressure gradient is continuous Well, the numerical simulation results of the axial and tangential velocity fields are consistent with the reality. Compared with the empirical formula, fluent numerical simulation software can more accurately predict the processing capacity of hydrocyclone, and the classification efficiency obtained is close to the experimental value.

The mounting bracket of the front bumper spotlight of the automobile is mainly produced by the method of wire cutting and processing. This method is difficult to achieve mass production and the performance becomes poor after processing. In order to improve this phenomenon, this paper adopts the method of sheet metal stamping to form it. The main tasks include the determination of the process plan, the simulation of Dynaform 5.9, the design of the layout, the calculation of the punching force, the bending force and the design of a set of 7-station progressive die. This design has certain practical guiding significance for the processing of the same type of products.

In this paper, a fiber-reinforced resin matrix composite missile wing with a wave-transparent function is studied, which has the function of wave-transparent and meets the requirements of the mechanical properties of the missile during flight, and the missile wing structure is made of aluminum alloy, carbon fiber composite material, and glass fiber composite material, and the weight reduction is about 30.3% compared with the overall aluminum alloy structure of the missile wing. In the design process, the finite element simulation method is used, the plastic deformation of aluminum alloy is fully considered, and the antenna is built into the airfoil of glass fiber composite material, which successfully realizes the wave-transparent function of the missile wing and provides a new design idea for the composite wing.

In this paper, a centrifugal pump of medium specific speed is taken as the research object, and the performance changes of the centrifugal pump are studied by setting five different ratio degrees of blades. The results show that due to the shortening of the blade length, the pump head and efficiency both decrease with the decrease of the ratio degree. In terms of static pressure distribution, the high pressure area in the volute expands from the outlet to the upstream with the decrease of the ratio degree, and forms an obvious boundary layer with the pressure in the impeller. Under the rated flow, the model pump with ratio degree R=2/3 has the best cavitation performance. When the number of impeller blades with a ratio of 2/3 was optimized, the flow field performance of the model pump with 8 blades was the best, and the head increased by 7.33% compared with the prototype pump at rated flow.

The detection and characterization of cracks is one of the key issues in oil and gas transmission pipeline inspection. The weak degree of spatial magnetic field distortion caused by the small size of the crack creates great difficulties for signal extraction. In this paper, we propose an ACM crack detection probe with poly-magnetic structure, and investigate the influence of the core, shield on the detection signal through numerical simulations. The results show that the crack detection probe with the core and shield can effectively improve the distorted magnetic field component in space acquired by the magnetic element, increasing the distorted magnetic field signals in the vertical and horizontal directions by a factor of 2.10 and 1.76 respectively. Verification that ACM probe with poly-magnetic structure can effectively increases the crack-induced magnetic field distortion signal and reduce the probability of misses.

In the control system of a quantum gravimeter, the optical signal containing phase information is weak and usually at the nV level. This situation puts forward high requirements for the measurement performance of the system. As the coupling input component of the measurement system, the noise level of the preamplifier has a dramatic influence on the noise performance. In this paper, the input current signal is provided by the photodiode. According to the photodiode output characteristics, we design three preamplifiers with different gain and bandwidth, which is verified by the optical system. Under the condition of meeting the design requirements, the noise performance is compared with the common commercial detector Model 2307. The results show that the noise performance of the photoelectric converter designed in this paper is about 1.5 times that of model 2307.

In order to meet the high vacuum requirement of neutral beam source, cryosorption pump is used as the main pump, and the pumping performance of cryosorption pump depends on its cryogenic performance. To test and verify the feasibility of cryosorption pump steady running, modular design based on cryosorption pump, composed of 16 extraction unit in series, in a single suction unit as the research object, respectively for radiation and cryosorption pump baffle panel of the theory of heat load, and will result in finite element analysis software, the analysis of the temperature field of two structures, respectively and extraction unit structure optimization direction is put forward. The simulation results show that the normal operating temperature of the cryosorption pump can be reached under steady-state operating conditions, and the cryogenic performance of the extraction unit can be improved after the optimization of the structure, thus providing reference for the optimization of the cryogenic pump group.

in order to study the phenomenon and mechanism of paint low-pressure atomization spraying and improve the spraying technology, the effect of liquid concentration on the atomization performance of low-pressure atomizer was studied. In this paper, an experimental platform for measuring the spraying of low-pressure atomizing nozzle was built. Mixing the same paint with clean water to obtain liquids of three different concentrations and using them as the mediums respectively, the flow, the atomization angle and the atomization characteristics of low-pressure fine atomizing nozzle with aperture of 0.33mm under the pressure of 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa and 0.8MPa were studied. The measured experimental data show that there is a positive correlation between the flow of atomizer and atomization pressure, and the larger the liquid concentration is, the smaller the flow is; The variation trend of atomization angle with the increase of pressure is related to the liquid concentration and is stable between 45 ° and 60 °; The average droplet size of atomized droplets has a negative correlation with atomization pressure, and the higher the liquid concentration, the larger the average droplet size. The experimental results show that the liquid concentration has a significant impact on the atomization performance of low-pressure atomizer, and the measured data are helpful for the application of paint spraying under low-pressure conditions.

For low-fluidity alloys such as TiNb-rich high-entropy alloys, casting parts with complex geometry normally encounter the forming problems like incomplete filling, shrinkage cavities and porosity. Additive manufacturing (AM) is suitable for fabricating those complex parts. However, for the regular portion of a complex part such as the disc of an impeller, AM is not a cost-optimal choice. This work proposes a facile route to fabricate high-performance parts with complex geometry, in which the portion with regular geometry is cast whereas the complex portion that requires high performance is additively manufactured. The results show that the failure always occurs in the cast portion of the hybrid manufactured sample rather than at the interface between the AM portion and the cast one. The strong interfacial bonding is quite different from the welding joint which is commonly the weak link. Moreover, compared with the cast portion with coarse equiaxed grains, the equiaxed fine-grained AM portion exhibits higher strength without sacrificing ductility. Hybrid manufacturing does not introduce weakness, but rather can strengthen the targeted portion by a reasonable structural design.

To meet the requirements of ultra-low space flight in pesticide spraying applications, a quadcopter with independent attitude control was proposed. It is a new product of a miniature quadcopter aircraft powered by solar cells. The innovation of this study was the adoption of circular frame structure, which increases the laying area of solar panels. The solar energy is used to convert lithium battery power supply to increase the altitude during navigation. Describes in detail the selection of components and the assembly process of this quadcopter, and conducts a test flight of the quadcopter. on this basis, the flight test was carried out. From the fight results the performance indicators of the quadcopter meet the design requirements. This research has a positive effect on the development of farm operation devices

High-performance ultraviolet (UV) photodetectors play a very important role in many fields, especially in the military, biomedical and other fields. ^[1]In recent years, many studies have realized ultraviolet photodetectors of 2D layered materials, overcome the problems of traditional ultraviolet detectors that are large and use high voltages. ^[1]Up to now, most of these works use atomically thin layers and simple p-n van der Waals (vdW) heterostructures, which have difficulty meeting the conditions of high sensitivity and ultrafast response at the same time. we report the double p-n van der Waals (vdW) heterostructure built on a large electrode. The two p-n junctions connected in parallel were proven to be able to effectively separate photo-generated carriers and suitable for ultraviolet light. This new type of photodetector exhibits competitive performance, including high R up to 254.8 A/W under UV light, and fast photoresponse τ_r = 7.9 μs and τ_d = 3.9 μs. These results provide an ideal platform for realizing highly sensitive UV photodetectors.

The tubing load measurement system is used to monitor the force and vibration of the tubing string in the process of perforation, fracturing and extraction and judge the safety of the tubing string during use based on the monitoring values, which is a key equipment for obtaining downhole information of the gas oil and gas development process. In this study, a load measurement system is designed for high-temperature and high-pressure tubular strings in wells, and the full-scale mesh modeling and finite element force calculation are performed to obtain stress distributions and safety factors. The results show that under the condition of axial force of 1000kN, internal pressure of 100MPa and composite loading state, the safety factors of the instrument are 2.0, 2.01 and 1.97 respectively, all of which meet the requirements of safe use.

In this study, the effect of microtab (MT) with different deployed positions and heights on the performance of a vertical-axis wind turbine (VAWT) is investigated through two-dimensional CFD simulation. The simulation results show that optimum deployed position for better turbine performance is 96% of chord from leading edge and optimum height is 0.5% of chord, which makes the power coefficient of turbine increase by 13% at TSR = 3.2. The observation of flow fields around turbine blade with MT indicates that MT decreases area of stall region at azimuthal angles ranging from 90° to 270°, leading to the increase of pressure and torque of turbine blade. The simulated results demonstrate that MT is an effective solution to enhance flow characteristics around turbine blade and improve turbine performance at high tip-speed-ratios.

Ball screws are widely used as feed systems for machine tools due to their high transmission efficiency and long service life. However, the large inertia force generated by the ball screw in high-speed motion will excite its flexible mode and cause system vibration. In the actual working condition, the dynamics of the system will also change with the nut position and workpiece mass. In order to further study the modeling method and dynamic properties of the ball screw feed system, this paper firstly improves the traditional hybrid model by introducing an energy loss factor to modify the hysteresis damping of the model. Further, the rationality of the improved model is verified by hammer test. Finally, the model was used to analyze the dynamic properties of the system and to obtain the influence law of workpiece mass and nut position on the system natural frequency.

A method of using the demand response mechanism of the power grid to promote the consumption of surplus wind power is proposed for the consumption of new energy generation. In the proposed method, the replacement of the output of the gas turbine is used as an important way to consume the surplus power, and the consumption of the surplus wind power is realized by using the surplus wind power to replace part of the output of the gas turbine. With the objective function of the maximum consumable surplus wind power and the constraints of the maximum replaceable output of the gas turbine, the cost of the replacement output and the balance of supply and demand of the grid, a model of the maximum consumable surplus wind power considering the cost of the replacement output is constructed. In addition, a cost optimal allocation model considering the different quotations of surplus wind power resource owners is constructed to obtain the optimal surplus power resource consumption scheme.

Aiming at the problem of rolling bearing fault diagnosis caused by interference information in the process of vibration transmission, this paper puts forward the theory and method of vibration signal fault diagnosis based on Choi Williams distribution spectral kurtosis (SK) combined with hidden Markov model (HMM). The fault location method of local mean decomposition (LMD) is used to screen the PF component with obvious fault characteristic information, CWD-SK is calculated and set as the characteristic parameter to realize the feature extraction of the initial fault of the vibration signal. CWD-SK is input into HMM as the feature vector to classify and identify the fault features of the vibration signal. Finally, the effectiveness of the algorithm is verified by the simulation of the actual data. It provides a robust theoretical and methodological basis for the establishment of fault diagnosis and classification recognition technology suitable for initial rolling mechanical vibration signals.

Most traditional agricultural machines use traditional mechanical transmission with fuel drive and front wheel steering, and most of them are manned, with low transmission efficiency, poor flexibility and low level of intelligence. This paper proposes a new high ground clearance sprayer with four-wheel independent drive (4WID) with dual front and rear steering axles. This sprayer is an oil-electric hybrid that not only saves energy, but also reduces the pollution to crops. In this study, a path tracking controller and a self-correcting controller are constructed based on the kinematic model of the sprayer, respectively. The model prediction controller is used as the main controller, and it outputs the desired steering angle and speed of the sprayer based on the current state of the sprayer and the desired path to achieve path tracking control. The self-correcting controller, as an auxiliary controller, adopts fuzzy control method and designs fuzzy control rules based on the driver's experience to correct the wheel turning angle at the current moment, which not only retains the advantages of model prediction control in linear path tracking, but also improves the control effect in curved path tracking and enhances the path tracking accuracy in large curvature roads. The simulation shows that the maximum lateral deviation of 0.03 m can be achieved by the model predictive control alone, and the maximum lateral deviation is reduced to 0.0141 m after adding the self-correcting controller.

This paper proposes a liner low-dropout regulator (LDO) circuit using on-chip steady-state compensation technology. Firstly, a bandgap reference is designed with low temperature drift and low power consumption. Secondly, the on-chip compensation is adopted in the LDO, which can avoid the use of large off-chip capacitors and reduce the layout area of the LDO circuit. The circuit performances are verified in the TSMC 180 nm CMOS process. Test results show that temperature coefficient of the bandgap reference circuit is as low as 4.3 × 10^-6 °C in the temperature range of -40°C to 125°C. The static current under the 3V power supply voltage is 4 μA. The LDO output voltage V_out is 1.8V . And the core area of the chip is 0.0848 mm².

The purpose is to study the application of two-way time comparison method for time synchronization on motion platforms such as ships. Firstly, the one-way time comparison method and the two-way time comparison method are analyzed, and the characteristics of the two methods are compared. Combined with the influence of the motion platform on the time synchronization during movement, an improved two-way comparison time synchronization method suitable for the motion platform is proposed. The time synchronization technique of bidirectional comparison based on carrier ranging principle is discussed, and the conclusion of two-station time synchronization based on carrier bidirectional time comparison under weak relative motion is obtained.

As a nonlinear memory device, the memristor is often used as a circuit load. In this paper, a nonlinear memory system based on a traditional current-mode Cuk converter with a voltage-controlled memristor is constructed. By deducing the state equation of circuit topology and the continuous current mode state equation, the simulation model is constructed. The dynamic characteristics of the system are explored by using a sequence diagram, phase diagram and bifurcation diagram. In addition, parametric resonance micro perturbation is introduced to suppress the chaos of the system. Finally, by using PYTHON and PSIM for simulation, the results verify the dynamic characteristics of the system and the effectiveness of the control method.

At this stage, when judging the fault type of jointless track circuit, it mainly relies on the staff to analyze the computer monitoring data. This fault identification method has problems such as high dependence on staff and long fault identification cycle. In order to solve the above problems, the combination of the reliefF algorithm and the C4.5 decision tree is introduced into the fault diagnosis of the jointless track circuit. First, the reliefF algorithm is used to give weights to the selected 9 feature parameters according to the fault classification ability of the features. Second, sort the feature parameters according to the weight, and select the first seven feature parameters as the optimal feature subset. Finally, complete the training and testing of the classifier with the optimal feature subset. The experimental results show that the fault diagnosis accuracy of ReliefF-C4.5 Decision Tree is 93.33%, So the fault diagnosis model proposed in this paper is suitable for fault diagnosis of track circuit.

This paper introduces several commonly used constitutive models of SMA materials, expounds the relationship between material temperature, stress and strain from the perspective of one-dimensional model, and establishes the simulation model of reciprocating motion of SMA actuator based on the material parameters obtained from quasi-static mechanical property experiments in the previous paper. A double wire pull SMA actuator is designed and a prototype is made. The output displacement data obtained from the experiment is compared with the established simulation model to prove the accuracy of the simulation process.

Aiming at the layout of a certain feed array for multi-beam antenna on satellite, a feed tower design method based on 3D printing technology is proposed. This design method uses aluminum alloy 3D printing to form the main support structure under the premise of avoiding the installation holes and layout positions, and adopts the combination of the main structure of the honeycomb lattice and the local solid structure to reduce the structural quality. The mechanical analysis and optimization of the design model are carried out by combining the actual test data of the mechanical test plate and ANSYS, in which the actual product is tested and verified. The light feed tower can fully meet the requirements of high-frequency multi-beam antenna feed array for high precision and lightweight, which has a certain reference value for the miniaturized design of the antenna.

The reliable operation of turnout is the key to ensure the safe operation of railways. In order to improve the accuracy of turnout fault diagnosis, a method combining genetic algorithm and least squares support vector machine (GA-LSSVM) is introduced into turnout fault diagnosis. Firstly, we need to analyze the turnout action power curve and extract the frequency domain features. Secondly, principal component analysis (PCA) is used to achieve feature dimensionality reduction. Thirdly, the features obtained by screening are input into GA-LSSVM to realize the fault diagnosis of speed-up turnout. Finally, an experimental study is performed by the failure sample set. The accuracy of the fault diagnosis method proposed in this paper reaches 96.875%. The research results show that the method in this paper can effectively improve the efficiency and accuracy of turnout fault diagnosis.

In this paper, a single-phase open-circuit fault-tolerant control method for three-phase permanent magnet synchronous motor (PMSM) is proposed. Based on the 4-leg inverter and the redesigned vector transformation method, the switching of the motor control strategy after a single-phase open circuit can be realized, and the control characteristics of the motor are unchanged. This fault-tolerant control method can be easily combined with other control strategies and has a wide range of applications.

A Battery Charge Regulator system based on the Superbuck converter is presented, the working principle of the Superbuck converter is analyzed and the small signal model is established. In order to meet the requirements of wide input range and high dynamic response of the Superbuck converter, a double closed-loop control system is designed with output voltage and output current dual loop control as outer loop and input current control as inner loop. The stability of the control loop is verified by the Bode plot, and the simulation result of the system in two working conditions are given to support the theoretical analysis.

Electromagnetic contactors are the key components of high-speed trains. A reasonable evaluation of the remaining life of the contactors can optimize the replacement cycle of the contactors and ensure the safe operation of the train. Aiming at the problem of remaining life prediction of contactors, a contactor life prediction method based on the fusion of improved particle filter algorithm and performance degradation model is proposed. Firstly, on the basis of analyzing the failure mechanism of the contactor and establishing its electromagnetic and dynamic simulation model, a performance degradation model based on overtravel time is established. Then design the contactor life test to obtain its full life cycle degradation data. Next, the adaptive genetic algorithm is used to optimize the resampling process of the particle filter algorithm. Finally, the optimal parameter values of the performance degradation model are obtained by the improved particle filter algorithm, and then the prediction of the remaining life of the contactor is realized. The prediction results show that the method can effectively predict the remaining life of the contactor, and the prediction accuracy meets the actual engineering needs, which provides an important reference for the operation and maintenance of the electromagnetic contactor for high-speed trains.

A multi-channel sEMG signal acquisition system based on the analog front-end chip ADS1299 is designed. The whole acquisition system consists of a 2×9 high-density electrode array, ADS1299 multi-channel high-precision A/D conversion chip; A MCU named STM32F103C8, an upper computer, and PC. We carried out electrode array design, The introduction of the function of the ADS1299 chip, and the circuit design of the analog signal acquisition part. The test results show that the acquisition system designed in this paper can ideally collect the sEMG signal of 8 channels on the back of the hand, which proves the effectiveness of this design in extracting weak EMG signals. Therefore, it has reference significance for designing larger-scale sEMG signal acquisition circuits.

In small-size Complementary Metal Oxide Semiconductor (CMOS) technology, the size of Very Large-Scale Integration (VLSI) below 90nm becomes higher and higher due to the enhancement of the short channel effect of transistors. CMOS Buffer is a very common circuit unit in VLSI. In this paper, a Pileup effect transistor (PET) is proposed to reduce the subthreshold leakage current of the CMOS buffer. The main principle of PET technology is to reduce the voltage difference between gate and source and the voltage difference between drain and source by lowering the voltage of source so as to reduce the subthreshold leakage current. Through simulation-based on Cadence and Taiwan Semiconductor Manufacturing Company (TSMC) N65 library, PET technology can reduce leakage current power consumption by about one-twelfth of the original while maintaining the function of the original CMOS buffer. PET technology has also been found to reduce current consumption in the transition state by about 40%.

This paper investigates the problem of wireless power transmission in underground pipeline detection systems. In response to the fact that during the study of the underground pipeline detection system, the coil inductance value changes due to environmental and anthropogenic factors, making the system detuned and unable to effectively acquire the underground microtag ID signal. Therefore, we raised a novel capacity compensation method to solve the problem mentioned above. Firstly, the hardware structure of the system is modelled, derived and analysed with the system in a resonant state. The topology applied to the system is then subjected to capacitive compensation operations to obtain the power transfer efficiency of the system in the resonant state with the best topology model. Finally, it is demonstrated through functional tests that the capacitive compensation of the optimal topology model achieves a good power transfer performance and acquires an effective ID signal.

Memristor is a new type of electronic component with small size and non-volatile, and it is the most promising new electronic component to replace MOS tube. The computing and storage parts of the computing electronic machines we use today are separate. With the development of technology and new materials, the indicators of CPU and memory have undergone qualitative changes, but the data transmission of CPU and memory still needs to rely on the bus, which greatly reduces the performance of computing and storage. This paper studies the integration of storage and computing. The ultimate purpose of this experiment is to integrate computing and storage into one chip. This paper proposes a 1T2M memory-computing integrated circuit design based on threshold-type memristors. This circuit is a new circuit structure. This circuit consists of an NMOS transistor and two threshold-type memristors. This structure can realize "OR logic operation" and "storage". The circuit structure is simple, the performance is better, the number of transistors is less, the integration level is higher, and the reading and writing speed is faster. The simulation verification is carried out by LTSpice.

Aiming at the problems of using optocouplers to achieve logic level matching in the current communication circuit, there are many components, high cost, and high requirements for component parameters. Based on the basic requirements of circuit logic level matching, this paper combines The research on the basic principle of triode switch, using the Schottky diode's unidirectional conduction and low conduction voltage drop characteristics, introduces a logic level matching circuit for inter-module communication with switch isolation function in communication circuits. Through the verification of relevant experiments such as functionality, stability and reliability, the circuit has a simple structure and stable performance, and is very suitable for use in communication circuits between modules of different voltage levels.

Aiming at the problem that the capacitive load of the source measure unit (SMU) system affects the stability of the loop control, this paper makes an in-depth theoretical analysis of the loop control system based on the SMU. A theoretical and circuit model is established after the analysis. In the control loop structure, an integrator with proportional amplification serves as an error amplifier for the control loop system to obtain sufficient phase margin at the optimal bandwidth. A phase-lead compensation capacitor scheme is studied and proposed to achieve the maximum tolerance range to achieve the loop stability. The results show that the simulation and experimental results are basically consistent. The results verify the theoretical correctness and practical value of this SMU control loop system, and provide a theoretical basis for the research of the SMU control loop structure of the subsequent SIP process.

Periodic inspection and maintenance of cracks have great influence on the reliability and safety of metal structures of bridge cranes. However, the influence of maintenance factors on the fatigue reliability of in-service bridge cranes is rarely considered at present. Taking a metal structure of a certain type bridge crane as an example, this paper establishes the limit state equation according to the residual strength of the structure. Considering the reduction of section modulus by fatigue cracks, the influence of periodic inspection and maintenance is quantitatively analyzed. The fatigue reliability of metal structure of bridge crane is analyzed and calculated by using MATLAB program. The results show that the fatigue damage will lead to the continuous decrease of reliability, and the fatigue reliability of metal structure can be restored to a certain extent by considering maintenance, which delays the decrease of reliability.

Unbalance is a major factor influencing rotating machinery vibration. In general, vibration problems caused by mass imbalance can be solved by dynamic balancing method. When dynamically balancing a flexible rotor, if the counterweight plane does not coincide with the unbalanced plane, it will cause the rotor to bend and deform, and the bending deformation will produce a new unbalance force. So, it is important to identify the unbalanced force on each plane. A method to solve this problem using strain gauges was presented. The equation to identify unbalance force at three or more planes of a shaft is set up. A series of tests were done on a rotor bearing rig. The tests show that unbalance weights and angles at different rotating speeds were identified with high accuracy. It is a new and effective method for multi-disk shaft balance.

In order to improve the efficiency of fault diagnosis of hot die forging multi-station feeding manipulator, according to the fault characteristics of the feeding manipulator, an expert system structure based on fault tree analysis and binary decision graph was designed, and a diagnosis method based on expert system was proposed. Firstly, according to the fault causes of multi-station feeding manipulator, the fault tree is established. Secondly, the binary decision graph is used to analyse the fault tree, acquire the diagnosis expert knowledge, and establish the knowledge base of fault diagnosis. Then, the binary decision graph is used to quantitatively analyse the fault tree, the importance of the minimum cut set is solved, and the rule priority is determined, so as to solve the rule conflict problem and improve the efficiency of fault diagnosis. Finally, a case study is conducted. The results prove the validity and feasibility of the fault diagnosis method proposed in this paper.

The dual active full-bridge (DAB) DC-DC converter is an important module for realizing bidirectional energy transmission. At present, it has been widely used in solid-state transformers, DC microgrids, electric vehicle charging piles and other fields. It can carry out high-capacity transmission, and can electrically insulate the primary and secondary sides, and has a wide range of uses.

the control system of petroleum drilling engineering has been in a bad and high temperature environment for a long time. In the unknown downhole working environment, the signal detection accuracy of turbine motor determines the drilling quality and cost of rotary steering drilling engineering. In order to design a high-temperature voltage sensor that meets the needs of oil drilling engineering, this paper takes 206B voltage sensor as the experimental object, simulates the downhole environment, carries out high-temperature experiments on this type of sensor, and analyzes the influencing factors of its error. The experimental data show that the downhole turbine motor voltage sensor is most affected by temperature, and the 206B sensor can withstand a maximum temperature of 125 °C. In view of its temperature influence, the least square method is used to compensate the error. The compensated voltage sensor error is reduced to 1~3.048%, which effectively improves the accuracy of the turbine motor voltage detection device and can accurately receive the downward signal of rotary steering drilling, so as to greatly reduce the drilling cost.

In the valve opening control of spacecraft, electro-hydraulic servo position-controlled loading is generally adopted. The nonlinear factors and uncertain interference in the loading system will affect the system accuracy. In order to improve the loading tracking accuracy and response speed, the nonlinear model of dual-channel valve-controlled symmetrical cylinder electro-hydraulic position servo loading system was established. A disturbance observer is used to estimate the unmodeled disturbances of the system, which is set up in combination with the sliding mode controller. Cross-coupling control is used to improve the synchronization accuracy of the two cylinders. The simulation study shows that the sliding mode control method based on exponentially converging disturbance observer can effectively improve the position tracking accuracy and synchronization control accuracy of the system compared with the traditional PID control. It has shorter response time and better anti-disturbance capability, which makes it have good control performance.

In this paper, considering the actual situation of the track circuit, aiming at the fault diagnosis of the 25Hz Phase-Sensitive track circuit, because the BP neural network (BPNN) model possess the characteristics of succinct construction and powerful nonlinear fitting ability as well as good fault tolerance performance, A fault diagnosis system of 25Hz Phase-Sensitive track circuit based on BPNN is designed. In addition, considering that the BPNN is greatly affected by the initial weight. Different results can be obtained when BPNN fault classifier is initialized with different weights, and it is easy to converge to the local minimum, so the genetic algorithm is selected to optimize the initial weight and threshold of the BPNN. The research results show that the BPNN optimized by genetic algorithm has fewer iteration steps, lower average error, higher classification accuracy, and is simple and easy to handle, which can better deal with nonlinear system problems such as track circuit fault diagnosis.

The optimal power flow is very important in the study of power system, and it is of great significance for the economic operation of the power system to solve the active power output of the generator through the optimal power flow. In order to solve the problem that the traditional method is sensitive to the initial state and the large iteration times, this paper applies the holomorphic embedding method to solve the optimal power flow. By embedding holomorphic variables, the holomorphic embedding forms of constraints and KKT conditions are obtained. The power series coefficients of node voltage and generator active power output are calculated by non-iterative solution. Finally, the active power output of the generator is obtained by the method proposed in this paper, and then the lowest power generation cost of the system is calculated. Simulation results on IEEE study Case 3, Case 4, Case 30 and Case 39 verify the feasibility and accuracy of the proposed method.

In this paper, one of the state-of-the-art deep reinforcement learning (DRL) algorithms, the proximal policy optimization (PPO) algorithm is used to achieve the learning of the attitude controller of hypersonic vehicles (HSVs). The HSV attitude-tracking control problem belongs to continuous control problems, which means the state space and the action space of the HSV are both continuous. The goal of DRL is to maximize accumulated rewards rather than the instant reward, so a fixed time length training episode and a normalized instantaneous reward function are presented to facilitate a comparison of each episodic return. Numerical simulation results show the proposed training manner can effectively make the learning controller track the attitudes for the longitudinal motion of HSVs with uncertainties. This training manner also can generalize to other continuous control problems.

Hammer mill cuttings cleaner is an efficient low-temperature drying cuttings equipment. In order to investigate the main components of energy dissipation and the flow characteristics of granular flow in grinding systems. The energy dissipation model of dense particle flow is established by numerical simulation and validated by macroscopic experiment. The results show that the particle flow mainly moves in a circle along the wall of cylindrical vessel. The main parts of energy dissipation are sliding friction consumption of particle, the inelastic collision between particles and sliding friction between particles and container; the input energy is a linear function of particle filling rate. The flat blade can provide higher efficiency at the same operational conditions. The study lays a theoretical foundation for the industrial application of Thermal-mechanical cuttings cleaner of drill cuttings and provides a reference for the optimization of blade configuration.

In the production of wide titanium strips cold rolled by 20 high mill, when the diameter of the 1^st intermediate roll is reduced, the work roll with a large roll diameter will be used to match it, which is called non-standard roll diameter configuration in this study. In order to master the control characteristics of the 1^st intermediate roll shifting under non-standard roll diameter configuration, the coupled static model of roll system and strip is established by FEM, and the model is verified by using the corresponding relationship between the change of load roll gap and the change of titanium strip residual stress after cold rolling. The simulation results show that under the same rolling force, the contact stress peaks of non-standard roll diameter configuration in flat area and cone area of the 1^st intermediate roll are about 1.44 times and 1.51 times of standard roll diameter configuration respectively. Compared with the standard roll diameter configuration, when the roll shifting amount increases, the longitudinal plastic strain of non-standard roll diameter increases most significantly in the range of 0-300mm from the titanium strip edge. Under the non-standard roll diameter configuration, increasing the roll shifting amount is more prone to occur the high-order buckle problem.

Since the traditional cellular cell communication system is no longer suitable for the development needs of the continuously accelerating high-speed railway, the distributed antenna system and the two-hop architecture are used to construct a system network architecture suitable for high-speed railway. Under the architecture of this system, for the problem of frequent handover between remote antenna units (RAUs) under the control of the same centralized unit (CU), this paper proposes an MFC/FSW algorithm by combining the concept of moving frequency concept (MFC) and frequency switching algorithm (FSW). Using FSW to trigger MFC, the frequency of RAU is changed by applying fiber optic radio technology in MFC. Due to the speed change has a greater effect on the success rate of the scheme, a correction factor is defined to mitigate the effect of speed on the success rate. The results show that the scheme can eliminate the traditional switching between RAUs, and the defined correction factor effectively mitigates the effect of the speed on the success rate. Compared with the traditional handover scheme, the switching success rate is not affected by the threshold in the switching judgment condition.

Ultrasonic cleaning technology has been used to a certain extent in home, but the resonant frequency of the ultrasonic transducer shift with the change of temperature and external environment, eventually leading to ultrasonic transducer work in a non-resonant state, resulting in lower power output. The amplitude of the transducer decreases, which affects the cleaning effect. In view of the above problems, a frequency tracking design scheme based on the fuzzy adaptive PID is proposed, which aims automatically track the ultrasonic cleaning power supply. In this scheme, the current - phase difference composite tracking method is selected, which improves the tracking speed and accuracy under the condition of ensuring that the optimal resonance point can be tracked. The static model and dynamic characteristics of the transducer are also analyzed to derive the design of matching circuit, which enables the transducer to get the maximum power input. The feasibility and high efficiency of the design scheme are demonstrated by LT-spice and MATLAB simulation experiments, which provide a reference for the practical application of ultrasonic cleaning devices.

A welding robot is a standard industrial robot, and its base is the essential component of the robot, which needs to ensure its safety, stability, and reliability. Using Solid Works software, taking a robot base in an automobile workshop as an example, a three-dimensional model of the robot base structure was established. The model was then directly imported into ANSYS Workbench without error. The finite element analysis method was used to carry out static analysis, modal analysis, and harmonious response analysis of the base model. According to the finite element calculation, the equivalent stress and deformation distribution cloud diagram of the robot base structure model is obtained. The structure size is optimized, and the original model is compared with the improved and optimized design scheme for finite element analysis. The solution's size is reduced, but the dynamic and static performance is also more advantageous, which achieves the expected structural optimization goal. The finite element simulation experiment verified that the welding robot base could be optimized in size to make its strength and working space better meet the design requirements. The simulation experiment analysis results are accurate and the design scheme is feasible.

Target orientation estimation is the premise to achieve target positioning and tracking. The classical DOA estimation algorithm needs to know the array structure and other informations. When those information cannot be obtained accurately, the performance of the algorithm will be degraded or even invalid. In this paper, a DOA estimation method for array signals based on blind source separation is proposed. The received mixed signals are separated by blind source separation, and the array steering matrix is estimated. Then the signal receiving channel is dimensionally reduced and transformed, and the covariance matrix is reconstructed. Finally use the MUSIC algorithm to achieve DOA estimation. Through simulation experiments, the results show that the method can realize DOA estimation under the condition of unknown array steering matrix, and it is robust.

Many areas of industrial production are inseparable from cleaning technology, and traditional cleaning technology is increasingly unable to meet the requirements of modern industry. Laser cleaning technology is a new cleaning technology with high efficiency and no chemical pollution. It has the characteristics of non-contact, environmental protection, high efficiency, flexibility, energy saving and wide application range. Compared with mechanical friction cleaning, chemical corrosion cleaning, ultrasonic cleaning, dry ice cleaning and other technologies, it has obvious advantages. At present, laser cleaning technology has been widely used in the fields of aerospace body paint removal, cultural relics sample cleaning, mold and mechanical parts product cleaning, mainly used for paint treatment, rust removal, oil removal and particles. This paper discusses the development trend of laser cleaning technology compared with the traditional laser cleaning technology.

The fuel metering system is an essential component of gas turbine and an in-depth research on its characteristics is the basis for the design and optimization of the gas turbine fuel system. This paper presents a mathematical modeling analysis of the main components of the fuel metering system and uses AMESim to build a numerical model for computer simulation. The model is used to verify and analyze important performance indicators such as differential pressure and fuel metering response, and to propose key points for optimization in the fuel metering system.

Under the background of intelligent manufacturing, the quality inspection of printed circuit board (PCB), as the carrier of electronic products, plays an important role. In view of the shortcomings of existing traditional detections, this paper has put forward a PCB detection method based on machine vision, focusing on image preprocessing algorithm and detection analysis. The median filter algorithm was used to remove the noise in the image. Logarithmic transformation was used to enhance image contrast. Sobel operator was used for edge detection to obtain the geometric center of the defect area. On this basis, the PCB image was registered by template matching method, and the difference between the preprocessed PCB image to be tested and the standard PCB image was calculated to get the difference map. Subsequently, morphological algorithm was used to remove the slight differences and obtain the defect map. In the end, the simulation results have shown that the proposed algorithm has good detection effect and high precision in PCB defect detection.

Parachutes have been closely linked to many space missions. Many vehicles launched into space have had parachutes on board for recovery or landing deceleration, and relative research mainly adopts computer simulation methods due to high test costs. In order to investigate the aerodynamic force and the surrounding flow field structure of the parachutes in the process of vehicle return, a physical model is established for the main parachute used in spacecraft return, using trimmed mesh for spatial division, and numerical simulations of the steady-state flow field of the large ring-sail parachute at different angles of attack are conducted. The results show that, the drag coefficient increases and then decreases, and the lift coefficient decreases and then increases with increasing angle of attack; the high-low-high-low-incoming flow velocity of the axial flow field generated by the ring-sail canopy is demonstrated and analyzed. The simulation results provide theoretical guidance for the structural design of the return parachute.

Based on the gearing theory, the calculation formulas of comprehensive curvature radius, relative sliding speed and tooth surface contact stress of internal and external meshing gear pair of the planetary gear system are deduced in this paper. Combined with load sharing theory and thermal elastohydrodynamic lubrication analysis method, the oil film thickness, film bearing ratio and friction coefficient are solved and the effects of roughness and input power on the friction coefficient are studied. The results show that with the increase of tooth surface roughness, the film bearing ratio decreases and friction coefficient increases; As the input power increases, the film temperature increases, the oil viscosity and film thickness decreases, which causes the tooth surface friction coefficient increases.

In view of the fact that the point cloud 3D model will be interfered by environmental factors, measurement methods and other random factors in the process of data scanning and acquisition, there will be some invalid points, outliers and internal noise points. In this paper, a point cloud denoising method based on adaptive density clustering and statistical filtering is proposed to process vehicle point cloud data. which can effectively preserve vehicle features while obtaining optimal denoising effect. Compared with the existing point cloud noise processing algorithms, this algorithm can remove noise better, and has shorter time-consuming and good applicability.

To address the shortcomings of the traditional firefly algorithm in global optimization seeking, such as low solution accuracy, unstable convergence and slow optimization speed, a new evolutionary model of firefly algorithm based on the improved Chebyshev chaos mapping is proposed. Firstly, the population distribution is initialised with the improved Chebyshev chaos mapping to improve the population diversity. Secondly, the non-linear dynamic adaptive inertia weights are introduced to regulate the balance between convergence speed and local optimality seeking ability. Then, the boundary variation strategy is introduced to solve the boundary crossing problem to avoid falling into local optimum and continue to improve the population diversity. Finally, simulation experiments are conducted under six benchmark test functions to compare with the traditional firefly algorithm. The experimental results show that the improved algorithm has higher solution accuracy and faster convergence speed.

The quadruped robot can overcome the unevenness of the wheeled chassis on steps and gravel roads, and has good passability. The Trot gait is the basic gait of the quadruped robot, and the walking is realized by the gait of alternating footsteps. In this paper, the dynamic simulation of the static equilibrium state of the quadruped robot in different poses on the ground and stair is carried out, and the movement of the robot body under the trot gait is simulated to obtain the joint torques of the upper and lower leg of the quadruped robot, which is the driving torque of the joint motor. The model selection provides a theoretical basis, and at the same time, the motion analysis of the quadruped robot is carried out, and the moving distance of the chassis under the extreme posture is planned.

In order to study the flow field characteristics in the transfer rack area during the operation of high-speed train and the influence law on the wind resistance torque of brake disc, the train aerodynamic model is established, and the flow field of high-speed train under six working conditions of 200km-450km per hour is simulated. The calculation results show that the resistance and torque of the brake disc are directly proportional to the square of the speed, and the power consumption is directly proportional to the cubic of the speed. When the train runs at 450km / h, the maximum wind resistance torque of a single brake disc can reach 71.26Nm. The energy loss caused by the brake disc resistance torque accounts for 31.32% of the total power consumption of the bogie, which is 2.47 times of the contribution value of brake disc resistance power consumption.

A hydraulic energy recovery and control system is proposed to solve the energy loss problem of the current vehicle transmission shaft torque test bench. On the basis of the original system, power recovery is realized by parallel hydraulic compensation. PID module is used to control the displacement of piston variable pump and motor respectively to adjust the speed and torque to achieve the established working conditions. The feasibility of the hydraulic system and control scheme is verified by AMEsim-MATLAB software and experiments. The results show that the proposed system can not only adjust the set speed and torque dynamically, but also achieve high power recovery.

The electronic map of railway track can realize the monitoring and evaluation of line status, so as to reduce the workload of manual operation. In order to improve the fitting accuracy of the existing railway track electronic map, the measured data of the railway line are obtained by Global Positioning System (GPS), and the Gaussian coordinates of the measured data points are obtained through coordinate transformation. Based on the analysis of GPS data, the Hough transform is improved to eliminate the outliers in the straight track and curved track scenarios respectively. With the help of the idea of taking the average value of multiple measurements to eliminate errors, the processed data are corrected and the track line is fitted. The results show that the track route electronic map generated by the outlier elimination method based on Hough transform has high accuracy and has important practical significance and practical application value.

Based on yolov4-tiny deep learning neural network, an improved yolov4-tiny network model is proposed in order to achieve the reduction of the network model for overlapping fruits and branch-obscured fruits in natural environment and to realize the accurate and fast recognition of apple-pear fruits, the main improvement measures include: firstly, the CSPBlock residual network module of the backbone network is introduced in the module of the backbone network to replace the 3×3 convolution kernel in it, which improves the perceptual field of the feature layer in the network and enhances the extraction capability of the target feature information through the spatial consistency and channel specificity of the Involution operator. second, the output of the first layer of the CSPBlock module in the backbone network containing the rich surface information of the image is extracted in the feature pyramid with the first and second scale feature maps for multi-scale feature fusion to enhance the extraction capability of dense small target feature information, by conducting training experiments on the apple pear dataset collected by ourselves, the experimental results show that the accuracy of the improved network structure is 95.45%, an improvement of 2.84%, and the recall rate is 94.92%, an improvement of 2.83%, compared with yolov4-tiny, the improved method improves the accuracy of fruit recognition and provides the theoretical basis for the subsequent apple pear picking robot to quickly identify picked apple-pears.

The magnetically driven micro soft robot is a hot research topic in the field of micro robotics. The magnetic torque of each part of the robot rotates with its deformation, so the magnetic torque and magnetic force to which the robot is subjected are difficult to be calculated directly. The lack of physical interfaces for torque distribution in many finite element software reduces the speed and accuracy of calculating the deformation of a robot using finite element simulation methods. In this paper, a fast simulation method to convert the local magnetic torque into equivalent load density for the deformation mode of the sheet micro soft robot is proposed. A finite element model of the fabricated micro soft robot is established, and the deformation and total magnetic moment of the robot under different magnetic field strength and magnetic field gradient are simulated and calculated. Experiments are executed to verify the validity of the simulation results.

It is difficult to establish an accurate mathematical model for the lower limb exoskeleton system of a rehabilitation robot, and there are unknown external disturbances. In this paper, an accurate model-independent closed-loop PD-type iterative learning control algorithm is adopted, which enables the system to track a given desired trajectory with uncertain dynamic models and parameters. The simulation results show that the algorithm can effectively improve the control accuracy of the trajectory tracking of the lower limb exoskeleton.

In order to improve the operation ability of unmanned aerial vehicles (UAV), this paper designs a lightweight manipulator for quadrotor UAV. First, according to the requirements of the task and the load of the UAV, an aerial manipulator with lightweight and small moment of inertia is designed, and the 3D model of the manipulator is established in the Creo software. The maximum deformation and stress under different load conditions were analyzed by Ansys Workbench software, and the dynamic analysis was carried out in ADAMS software to obtain the driving moment required by each joint of the manipulator under load conditions. Finally, the dynamic model of the aerial manipulator system is established according to the Newton-Euler method, and the maximum workspace of the manipulator in the hovering state is generated by the Monte Carlo method. The research results show that the deformation and stress level are small, and the workspace meets the operation requirements, which proves that the designed manipulator has certain engineering application value.

In order to solve the forced shaking problem of the Autonomous Underwater Vehicle (AUV) facing dynamic obstacles in the path planning when the Artificial Potential Field Method is used, a method of removing the shaking state based on a favorable path is proposed, and on this basis, Visibility Graph Method is used to optimize the path of the AUV to avoid dynamic obstacles. By judging the relative motion direction of AUV and dynamic obstacle, the moving direction of AUV is adjusted based on Visibility Graph Method when it is far away from the obstacle. When it is close to the obstacle, the direction conducive to approaching the target point is selected as the favorable forward direction to bypass the obstacle. The simulation results show that the dynamic obstacle avoidance path optimization method based on the Visibility Graph Method reduces the number of moving steps by about 19% compared with the traditional method when dealing with a single dynamic obstacle, and can be applied in complex environments with multiple dynamic obstacles.

An indoor top mobile service robot based on the improved RRT algorithm is proposed. The robot is mainly composed of a lifting truss platform and a manipulator, which avoids the mapping and positioning of complex ground and obstacle avoidance planning. At the same time, the kinematics analysis of the manipulator is carried out. In view of the function of obstacle avoidance planning when the manipulator completes the task, the traditional RRT algorithm is improved to overcome the shortcomings of the low efficiency of path planning in the traditional RRT algorithm, and the planned path quality is uncertain and not smooth enough. The simulation environment is built based on ROS platform to verify the feasibility of the algorithm. To a certain extent, it improves the autonomy of robots to complete tasks.

At present, the prediction of shipboard cabin noise is mainly obtained by simulation calculation using FEM, BEM or SEA. These methods are not convenient for rapid engineering prediction. By making a test platform of shipboard cabin noise prediction, we make an experimental study of a simplified engineering prediction approach for shipboard cabin noise based on Source-Path-Receiver system approach. The experimental study shows that this approach is feasible and valid when applied to predict air borne noise level in a sound source shipboard cabin.

A novel packaging designing for high density and high voltage power module, namely TPak was proposed. It uses flip-chip welding technology and through-hole technology to avoid the parasitic parameters introduced by wire bonding in traditional electrical interconnection, so that the proposed efficiency of the entire high-voltage module is close to 100%, parasitics are reduced by an order of magnitude, and module manufacturing is simplified and the module mechanical stress capability is improved. The finite element simulation anakysis of heat and force are carried out by means of simulation software, and the problems existing in the current Tpak packaging are analyzed from the perspective of materials, and improvement methods are proposed to optimize performance and improve its reliability.

A method for the recognition of macrostructure crack defects based on feature position information is proposed. Establish a deep learning module based on the UNet network, which includes spatial location information. According to the location information of different crack defects, add the spatial information extraction module behind the convolution layer. The defect location feature information and up sampling feature information are fusion, recognition of crack defects with different macrostructures by network training. This method realizes the automatic recognition of crack defects, reduces the labor intensity and improves the recognition efficiency.

In this paper, the sliding mode control algorithm is designed for the deceleration curve tracking problem that affects the quasi-stop of mobile robot, and the tracking performance of the sliding mode control algorithm and PID control algorithm is simulated and analyzed in MATLAB. Through comparison, it is verified that the designed sliding mode control algorithm has better tracking performance. Finally, the parking error of the mobile robot is tested by experiments, which proves that the sliding mode control can effectively improve the quasi-stop accuracy of the mobile robot.

The ankle is the most weight-bearing joint in the body, which plays a vital role in ensuring people's walking. Aiming at the problems of complex mechanism, rigid drive and difficult control of the current ankle joint rehabilitation equipment, a 3-SPS/S type ankle parallel rehabilitation mechanism based on pneumatic artificial muscles is developed, and a self-tuning PID controller based on BP neural network is proposed to improve the accuracy of the control system. According to the static characteristics of the pneumatic artificial muscle, the physicians mathematical model of the artificial muscle is optimized, the kinematic position inverse solution of the ankle joint parallel rehabilitation mechanism is analysed and the control system is established. Combined with traditional PID control and BP neural network control algorithm, the BP_PID controller is completed, the control system is simulated and analysed. The simulation results show that BP_PID controller can meet design requirements for the ankle joint parallel rehabilitation mechanism, and is obviously superior to the PID controller in response speed and control accuracy.

In the wake of the successive construction of new railway lines, new lines and existing lines are adjacent, approached and surpassed. In the early stage of line construction, if the influence of adjacent lines is not considered in subsequent planning, the original lines need to be adjusted, and the reconstruction of the base station (BS) coverage along the railway increases the hardness of buliding and the invested funds. Therefore, a Global System for Mobile Communications – Railway (GSM-R) wireless field strength coverage prediction model based on particle swarm optimization (PSO) algorithm optimized radial basis function neural network (RBFNN) was proposed. Aiming at the problem of slow network convergence caused by improper selection of network parameters and structure of RBFNN, PSO algorithm is used to optimize the parameters of RBFNN, and combined with the actual measurement data on site, a PSO-RBFNN model is established to simulate and predict the field strength coverage. The results show that the prediction effect of PSO-RBFNN is the best, followed by RBFNN, and the worst of HATA model, which is very beneficial to the future railway GSM-R wireless network coverage and provides a feasible idea.

A new dynamic window algorithm is proposed to solve the problem that the optimal trajectory is difficult to plan and the trajectory is not smooth due to the dense obstacles in the complex workshop path planning task. The algorithm sets the initial direction angle, and then improves the evaluation function through the direction angle change factor to improve the efficiency and flexibility of the algorithm; The fuzzy controller is used to adjust the coefficient of the evaluation function, which improves the adaptability of the mobile robot to the complex workshop environment. The MATLAB simulation results show that the improved DWA can plan a more reasonable and smooth running path in the area with dense obstacles, and has better obstacle avoidance effect while ensuring the safety of the robot.

Least squares reverse time migration imaging is an imaging theory based on the accurate description of geological structures by seismic waves, which can greatly improve the detection accuracy. In the complex environment of deep region, the influence of noise on the imaging resolution of reverse time migration is particularly significant. In this paper, an optimized least squares reverse time migration imaging method with better amplitude fidelity and higher imaging accuracy is proposed. This method suppresses the noise interference by reducing the residual value between the inversion data and the actual data. The experimental results in the paper show that the optimized least squares reverse time migration can achieve high accuracy and high resolution imaging, especially in the deep region. This method is effective and feasible.

Frequently, cracks are found in welded joints of the insert plate assembly of a nuclear reactor containment vessel. To study the residual stress state of the dissimilar steel welded joint of the insert plate assembly and ensure that there are no defects after welding, the ABAQUS finite element analysis software was used to simulate the temperature field and the post-weld residual stress field of the dissimilar steel inserted into the plate assembly in the containment of the nuclear reactor. The insert plate and sleeve material are SA738GR.B and A350, respectively; the heat treatment process after welding is simulated to predict the residual stress state of the welded joint after heat treatment. The simulation results show that the weld zone is the most sensitive to the circumferential cracks, and the maximum residual stress appears near the weld toe near the tube side.

In this paper, the strength analysis and fatigue life calculation of multi-component coupling of crankshaft, connecting rod and engine body of highly strengthened single cylinder diesel engine are carried out. The stress of crankshaft, connecting rod and engine body in two working cycles is calculated by multi-component coupling transient dynamics, and the strength is analyzed based on the third strength theory firstly; Then, the accuracy of the transient calculation results is verified by the strength experiment of the crankshaft and connecting rod reduced scale model and the calculation of the static stress of the body; Finally, according to the stress fatigue life calculation method, the fatigue life of crankshaft, connecting rod and engine body is calculated. The maximum stress of crankshaft, connecting rod and body is less than the yield limit of corresponding materials; The fatigue life calculation results show that the damage accumulation of the engine body is very little, which meets the design requirements of infinite life. The damage accumulation of the crankshaft at the fillet of the main journal and the connecting rod at the side of the rod is 32005.6 hours and 102841.7 hours respectively, which meeting the design requirements of 20000 hours.

The rubber isolator with metal embedded inside has been developed and has been used in ships. In this paper, based on Abaqus software, static characteristics of the metal-rubber isolator under rated load are calculated by finite element method. The simple deformation experimental data processing of the rubber material, the fitting method of the hyperelastic constitutive model and the model simplification of the metal-rubber isolator are described in detail. The feasibility and effectiveness of the finite element method to analyze the static characteristics of the metal-rubber isolator is verified by experiments. The conclusions obtained in this paper can provide guidance for the rapid development of serial products of the metal-rubber isolator.

In order to solve the problems of low joint strength and poor welding efficiency in fusion welding of 7075-T6 aluminum alloy, the double wire pulsed cold metal transition (DW-CMTP) welding method was used to weld 7075-T6 aluminum alloy. The microstructural and mechanical characteristics of the joints were analyzed by energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), tensile test and Vickers hardness measurement. The results showed that the DW-CMTP welded joints had good mechanical properties. The highest tensile strength of the joint is 320 MPa without post-weld heat treatment, reaching up to 63% of the basic material. The presence and distribution of micropores in weld joint were manipulate by welding parameters and weakened the joint strength. The fracture location transferred from the heat-affected zone to the fusion zone with the increase of heat input, owing to the change of pore distribution.

In this study, the wave-front aberrations of medium and high myopia with different CCT after SMILE were studied by the finite element method. Then, the various trend of wave-front aberrations with clinical significance was obtained. When CCT was the same, the wave-front aberrations of myopia with different diopters were different. When CCT increased, the variations of wave-front aberrations of myopia with different diopters were different. However, regardless of the degree of myopia, the variations of defocus and primary spherical aberration were the most obvious. The larger the CCT, the smaller the absolute values of defocus and primary spherical aberration.

The enhanced Loran signal transmits the signal through the atmospheric channel. Considering the obstacles and other factors, the radio wave will be affected by path loss, shadow fading and multipath fading. Therefore, the signal power at different distances from the transmitting point is different. The scaled model antenna is used to transmit and receive the enhanced Loran signal, and the Loran receiver is used to receive. According to the different power of the received signal of the receiver, the signal propagation distance can be deduced by using the correlation model, so as to correct the path delay, that is, the timing accuracy can be improved.

Based on the finite element analysis software of ANSYS Workbench, the sealing performance of a V-shaped seal ring is analyzed. It is found that the position of the maximum shear stress of the V-shaped seal ring is on both sides of the bottom of the opening. Then, the effects of root height h and opening arc diameter D on the maximum shear stress and maximum contact pressure of the seal ring are studied, and the parameters are optimized accordingly. Further, the ultimate working pressure of the optimized structure is analyzed. The results show that the maximum shear stress and maximum contact pressure of the seal ring increase with the root height, but there is a downward inflection point at h-0.2. The maximum shear stress of the seal ring increases with the opening arc diameter, but there is a rising inflection point at D-0.2. Further, the maximum contact pressure of the seal ring first increases rapidly and then increases slowly with the opening diameter. The working oil pressure that the V-shaped seal ring can bear is 1.3 MPa. The simulation results can guide the design of the V-shaped seal ring.

In recent years, high-strength micro-alloyed cold heading steel has developed rapidly, mainly by adding Nb, V, Ti and other micro-alloying elements to the steel for grain refinement and precipitation strengthening, it is widely used in automobiles, bridges, construction machinery and other fields due to its excellent strength and toughness, fatigue resistance and corrosion resistance. However, the common quality defects in the process of continuous casting and hot rolling of such steels - transverse cracks on the surface and corners, are still one of the technical difficulties in the production of the world's iron and steel enterprises. Therefore, it is of great scientific and engineering significance to deeply explore the evolution law of high temperature mechanical properties of niobium microalloyed cold heading steel, to analyze the common generation mechanism of surface transverse cracks and to propose general improvement measures. In this work, the high temperature thermoplastic properties of niobium microalloyed cold heading steel was studied by using Gleeble-3500 thermal simulator, combined with optical microscope (OM) and scanning electron microscope (SEM), the tensile fracture morphology and nearby microstructure were observed, and its high temperature plasticity mechanism was analyzed. The results show that the niobium microalloyed cold heading steel has two brittle temperature ranges: the first brittle zone is from the melting point to 1200°C, the temperature range of the third brittle zone is below 700°C, and the optimum plasticity zone is 700-1200°C. At 650°C, the fracture mode is ductile fracture and cleavage fracture; at 800°C, it is a typical cleavage-brittle fracture type; at 950°C, the fracture mode is dimple fracture, with good plasticity; at 1100°C, the particles become finer and the plastic deformation is more uniform. In order to avoid the occurrence of cracks in the continuous casting billet, the straightening temperature of the continuous casting billet should be higher than 700°C, it should be heated slowly in the early stage of heating, and the hot rolling temperature should be controlled at 700-1100°C.

The development of plastic product prototype by incremental sheet forming (ISF) has attracted extensive attention. Forming polyvinyl chloride (PVC) sheet into parts by ISF has a wide application prospect in many industrial fields. However, torsion is a problem that needs to be solved. In this paper, some truncated pyramids were formed by different feed speeds and tool paths with a certain spindle speed of the tool. Torsion angle of central line and accuracy of each formed part were measured. In addition, numerical simulation was also used to get the influence of tool path on the torsion of PVC parts. The results show that PVC part appears torsion around the central axis when it was formed by the unidirectional direction tool path, and torsion increases and accuracy reduces with increment of feed speed of the tool. Otherwise, the alternating bidirectional direction tool path can effectively eliminate the torsion of PVC part.

Liquid lead-bismuth eutectic (LBE) was an important candidate material for the fourth generation reactor coolant. Its high temperature and heavy metal corrosion conditions put forward higher requirements for the corrosion resistance of reactor structural materials. As a new kind of special material, glass-ceramic material, which possesses the excellent properties of glass and ceramics, has good mechanical property, wear-resisting property and corrosion resistance. The LBE corrosion behavior of glass-ceramics at typical operating temperatures of nuclear reactors was investigated. The lead bismuth corrosion test was carried out under the condition of oxygen saturation at 500°C for 500h. The lead bismuth corrosion resistance of the two glass ceramic samples in static LBE was analyzed by means of scanning electron microscope (SEM) and X-ray diffraction (XRD). After 500 h corrosion in oxygen saturated liquid LBE at 500°C, there was no obvious corrosion on the surface of CMAS glass ceramics. Its dense microstructure and stable phase composition effectively prevented the penetration of Pb and Bi elements, and had good resistance to corrosion; The surface of LZS glass ceramics was covered with a layer of loose and porous compounds, and the thickness of the corrosion zone was 10 μm, which occurred a certain degree of lead-bismuth corrosion, and its corrosion resistance was poor. The results showed that under the same corrosion conditions, no lead bismuth corrosion behavior was found on the surface of CaO-MgO-Al₂O₃-SiO₂ (CMAS) glass-ceramic, while there was a corrosion layer with a thickness of about 10 μm on the surface of Li₂O-ZnO-SiO₂ (LZS) glass-ceramic, indicating that the lead bismuth corrosion resistance of CMAS glass ceramics was significantly better than that of LZS glass ceramics.

In the future, advanced aircraft proposes to reduce the gaps on the surface of the body to improve the flight performance and stealth performance of the aircraft. This requires a sealing device between the movable surface of the leading and trailing edges of the wing and the fixed wing surface. Based on the sealing of the wing gap, this paper uses CATIA software combined with HyperWorks and ABAQUS software to design and optimize a large-deformation composite structure that can follow the large-scale movement of the movable surface without affecting the movement of the movable surface of the wing.

The metal/fluoropolymer reactive materials (RMs) have been widely studied in the past years. Almost no reported Al/THV RMs, which was prepared in this work, shows better mechanical properties than well researched Al/PTFE. In addition, the mechanical properties and reaction characteristics of Al/THV composites with two particle sizes and different contents of aluminium particles were tested. The effects of particle size and content of aluminium on Al/THV RMs were analysed. The result shows that Al/THV composite with high contents of 4 μm Al particles shows better mechanical properties and reaction characteristics than the other Al/THV composites. Besides, the low impact-induced reaction percentage of Al/THV (35/65) composite under ~7000 s^-1 compression was explained by the low combustion velocity and plasticity.

As a member of low-carbon alloy steels, 20CrMnTi has been widely used to manufacture key-parts, such as gears and shafts, owing to its attractive fatigue resistance and easy of processing. To improve its the mechanical and frictional properties, the preparation of composite is required. In the present study, graphene was added in 20CrMnTi to form Gr/20CrMnTi composites by vacuum high-energy ball milling process and hot-pressing technique. The addition of graphene has a profound influence on the microstructure and properties of 20CrMnTi. A high hardness of 5.83 GPa and a good tensile strength of 1183 MPa were obtained in the 0.5 wt.%-Gr/20CrMnTi, increased by 18.5% and 27.8%, respectively. Meanwhile, the wear resistance reaches a maximum value of 2276.5 cm^-3 in the 0.7 wt.%-Gr/20CrMnTi, showing a 491.1% increase than that of pure 20CrMnTi. The layered graphene played an important role in absorbing energy and preventing the propagation of micro-crack.

In this study, the denitrification performance of steel slag modified by manganese slag was studied. Different proportions of steel slag and electrolytic manganese anode mud mixtures were configured. The different proportions of the mixture would have varied physical and chemical properties. SS1+EMAM2 catalyst showed the nearly 100% NOx removal efficiency at 175°C. The specific surface area of steel slag is enhanced dramatically after modification by EMAM. Adding EMAM enhanced the weak acid sites and Brønsted-acid sites on the catalyst surface, resulting in a higher low-temperature SCR activity.

Compared to mechanical bearings, active magnetic bearings eliminate mechanical friction, resulting in lower energy losses. However, due to the magnetization characteristics and high-frequency working characteristics of the core material of the active magnetic bearing, there will be high wind friction loss, eddy current loss, hysteresis loss and copper loss in the active magnetic bearing. These losses will generate heat and increase the internal temperature of the bearing, which will not only affect the control accuracy of the active magnetic bearing and the stability of the rotor suspension, but may also cause irreversible damage to the components inside the active magnetic bearing. In this paper, different heat dissipation schemes are established to discuss the influence of the active magnetic suspension bearing on the loss and heat generation of the active magnetic bearing.

The membrane-based gas separation is well-suited for the recovery of hydrocarbons from nitrogen-rich exhaust gases. However, the separation performance of the existing polymeric membranes was insufficient. In this study, zeolitic imidazolate framework-67 (ZIF-67) was synthesized and then incorporated into polydimethylsiloxane (PDMS) to prepare ZIF-67/PDMS mixed matrix membranes via the spin-coating method. The resultant ZIF-67 and membranes were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscope. The C₃H₆/N₂ (20:80 vol) mixed gas separation tests indicated that the ZIF-67/PDMS membranes achieved the higher C₃H₆/N₂ separation factor but the lower C₃H₆ permeance in contrast with pure PDMS membrane. At the ZIF-67 loading of 5 wt%, the membrane displayed the optimal separation factor of 16.5 with comparable C₃H₆ permeance of 86.9 GPU. Besides, the relatively low operating temperature and pressure were advantageous to gaining good gas separation performance.

Atmospheric pressure low temperature plasma jet (APPJ) is a technical direction that has attracted much attention in recent years. In this paper, argon is used as the working gas to produce highly active ions through funnel shaped glass tubes to modify the surface of carbon nanotubes. After the carbon nanotubes treated for 4 mins, SEM, water contact angle and FTIR detection results were compared before and after the experiment. The results showed that the hydrophobicity of carbon nanotubes was enhanced and the surface dispersion was improved after DBD plasma jet treatment.

In order to explore the influence of different element contents on selecting the prediction model of gray cast iron's modulus, we apply Meta-analysis to retrieve Chinese journals related to gray cast iron and elastic modulus and adopt fixed effect models to evaluate and analyze the introducedδ value, hoping to provide theoretical basis for prediction model of elastic modulus. According to the analytical results: (1) When the silicon content is relatively low, the model E₀=101.32+2.51Si/C is suggested for prediction. (2) When the carbon content is relatively low, the model E₀=313.175-49.014C-14.082Si is suggested for prediction. (3) When the two elements are both relatively low, Si/C value-based judgment needs to be made that the model E₀=101.32+2.51Si/C is suggested when the value is relatively low. (4) When either the silicon content or the CE (carbon equivalent) is relatively low, the model E₀=194.55-27.85CE+58.2Si/C or the model with three variables-E₀=20.527-0.021Si/C+59.2841Si+0.004CE is suggested for prediction. (5) When some of the above cases exist simultaneously, the preferable model selection should be considered in the following order of priority: C=Si>Si/C>CE>S.

According to the influence of welding process between 304 austenitic stainless steel and 20 steel dissimilar steel on the weld seam, the effects of welding current of 150A, 180A and 200A, normalizing and solution treatment on the microstructure and properties of the weld seam were studied by using MAG. The results show that the 150A current welding seam has incomplete fusion, which leads to its low strength and fracture toughness. With the increase of current, the necking fracture occurred on one side of 20 steel, and the brittleness and hardness of weld increased, all of which indicated that carbon element diffused from 20 steel to weld and 304 stainless steel. Although the corresponding post-welding heat treatment can reduce the hardness to a certain extent, improve the machining performance of welded joints and homogenize the microstructure of welded joints, it can't significantly improve the performance of welded joints of dissimilar steels.

Using software, the analysis of temperature field of H-beams after ultra-fast cooling and air cooling was made. On the basis of numerical computation result of temperature distribution. The surface temperature of web and flange dropped to 420°C after UFC, while the other, that of R corner was 400°C. The center temperature of web was 650°C, while that of flange and R corner was still about 800°C, so the temperature drop of web was the biggest. The duration of temperature rise in R corner was longer. The entrance of the UFC system in hot rolling H-beam production line, and the temperature of upper web and flange was both 850±15°C, while the other, the exit after UFC 4.5s, and the temperature of upper web and flange was both 440±20°C, which was consistent with the simulation results.

NdFeB rare earth permanent magnets are widely applied in numerous fields including consumer electronics, industrial motors and new energy vehicles. Sintered NdFeB magnets are prepared by pressing and high-temperature sintering, followed by machining into desired shapes with anisotropism and high magnetic properties. During industrial production process, the appearance of non-magnetic impurities adhering on NdFeB magnet surface is a critical problem, which takes bad influences to not only magnetic properties of NdFeB, but also the qualification rate of subsequent assembled parts. There are two forms of impurities, one is gelatinous and the other is filamentary. In this paper, non-magnetic impurities on the surface of NdFeB magnets were characterized and analyzed by FTIR, EDS and SEM, and the methods to remove impurities were studied. The results showed that gelatinous impurities are stearamide derivative, which can be dissolved by xylenes under heating conditions. Filamentous impurities are cellulose derivative that can be removed by economical sodium hydroxide-urea system instead of expensive AmimCl, without damaging magnet plating and magnetic properties.

In this paper, zinc particles were grafted on the surface of graphene by KH550. It was proved that zinc powder was successfully connected to the surface of graphene by KH550 through IR, SEM, energy spectrum and thermogravimetric analysis. The modified graphene is added to the anti-corrosion coating, which effectively improves the anti-corrosion performance of the coating.

In this study, 1 mol%La₂O₃-2 mol%Gd₂O₃-2 mol%Yb₂O₃-6 mol%Y₂O₃ co-doped ZrO₂ (LGYYSZ) with 0 mol%, 5 mol% and 10 mol% TiO₂ additions were synthesised by solid-state reactions. The effect of TiO₂ addition on the phase stability of LGYYSZ and its sintering behaviour at 1500 °C were investigated using XRD, SEM and EDS. The results show that the eutectic temperature of LGYYSZ decreases with increasing TiO₂ content. SEM, EDS and XRD results show that the TiO₂ addition is reacted with the La₂O₃ in LGYYSZ to form a orthorhombic La₂Ti₂O₇ phase. When held at 1500 °C, La₂Ti₂O₇ is precipitated on the surface of the samples by evaporation-condensation mechanism. This resulted in the anti-sintering properties of LGYYSZ at 1500 °C decreasing with increasing TiO₂ content.

In order to measure the friction torque of planetary thread roller bearings, a friction torque testing machine was developed based on the principle of transfer method. The test of dynamic friction torque and starting friction torque under axial and radial continuously adjustable large load conditions is realized. The test machine has good stability, and the test data are accurate and reliable, providing data support for in-depth understanding of the friction performance of planetary thread roller bearings.

For the reliability evaluation of rolling bearing life, this paper proposes a parameter estimation method based on the correlation coefficient optimization method and the maximum likelihood estimation method (Cor-MLE), which can obtain more accurate Weibull distribution parameter estimation. Subsequently, the feasibility of Cor-MLE method for Weibull parameter estimation was verified by Monte Carlo simulation data and rolling bearing life test data. Compared with the parameter estimation results of least square method, grey model method and correlation coefficient optimization method, it is proved that the estimation results of this method have high accuracy and can meet the life analysis of rolling bearings.

Shape memory polymers (SMPs) possess multiple advantages as a sealing element for a packer. The contact stress between the SMP rubber and a casing (or the formation) is an essential indicator in evaluating the sealability of packers. This work conducts a finite element simulation based on the generalized Maxwell viscoelastic model and the time-temperature equivalence (TTE) principle to analyze the contact stress during the setting. The proposed model simulates the mechanical response of the polymer, including the stretch at a high temperature, cooling with a fixed shape, unloading at a low temperature, the shape recovery with reheating, and the stress relaxation. The results show that the contact stress distribution in the middle section of the packer is relatively uniform. The average contact stress is over 7.5 MPa and meets sealing needs. More significant stresses occur at the shoulders of the packer due to stress concentration. Both the shape recovery and the stress relaxation finish fast that it needs about 228.7 s to obtain stable contact stress after shape recovery. This study provides a method to evaluate the performance of the packer based on SMPs.

Black silicon with micro-nano structures were fabricated by irradiating silicon with 1064nm laser pulses of 8.7-ps duration, 4.5 μJ per single pulse, 100mm/s scanning speed in vacuum, and doping the black silicon by irradiating the silicon coated with Si-Se bilayer film. SEM images show that the surface micron-scale grooves covered with nano-scale particles pattern was produced on Si for both the sample with no film and with Se film, but the surface structure are smoother and more uniform in the presence of Se film. EDS graph demonstrated the presence of Selenium in the black silicon micro-nano structures. Furthermore, Raman spectra results indicate that the micro-nano structured black silicon is still crystal phase.

In this paper, the aerodynamic and aerothermal performance of the simplified two-dimensional wedge-shaped waverider bluntness leading edge and high pressure capture wing(HCW) combined configuration in a hypersonic continuous flow basin is numerically simulated by the Computational Fluid Dynamics (CFD) method, the flow field structure of the model is analyzed, and the law of anti-thermal rise is revealed. The main contents of the study include the surface heat flux and lift-drag ratio characteristics of the bluntness leading edge under different bluntness radii, the lift-to-drag ratio, and surface heat flux characteristics of the composite configuration of the bluntness leading edge and the high pressure capture wing under different bluntness radius. Within the scope of the study: 1. The larger the bluntness radius is, the more effective it is to reduce the heat flux of the head. When the bluntness radius is 2mm, the decrease is about 82.5%;2. The larger the bluntness radius is, the more serious the lift-drag ratio decreases. When the bluntness radius is 2mm, the lift-drag ratio decreases by about 72.4%;3. The combined configuration of the bluntness leading edge and the high pressure capture wing can effectively reduce the head heat flux under the premise of ensuring a certain lift-drag ratio. The optimal bluntness radius is 1mm, the head heat flux decreases by about 76% and the lift-drag ratio only decreases by 24%.

In the context of green and clean energy, latent heat energy storage by phase change materials is considered as one of the important energy technologies. In this paper, a new metal foam embedded graphene aerogel composite phase change material is developed, and pore-scale numerical simulations are performed in order to investigate the thermal properties of this composite phase change material. Among them, this paper designs copper foam with cubic periodic unit structure, which not only has high thermal conductivity, high porous structure and low relative density, but also can be rapidly fabricated by new fabrication techniques, while paraffin and erythritol are selected as PCM embedded in the metal foam. By analyzing the temperature-time and liquid phase-time relationship graphs, it is known that the new composite phase change material has more uniform internal temperature distribution and shorter melt condensation time compared to graphene-aerogel composite PCM, which provides a method for thermal management of PCMs.

Compared to autoclave-cured prepreg, liquid composite moulding (LCM) is a cost-effective alternative to produce advanced composites, thanks to the less-expensive intermediate materials, lower capital investment and shorter cycle time. A separate preforming step is typically required within the process chain to convert 2D fabric blanks into complex 3D geometries before moulding. Numerical models are therefore important to ensure near net-shape preforms during the design phase, in order to minimise the material wastage related to preforming. In this study, a microscale finite element (FE) model was employed to assist in determining the ply shape of multi-ply biaxial non-crimp fabrics (NCF) to achieve net-shape preforms made by double diaphragm forming (DDF) using a spar-like geometry. The forming deformation of the NCF was predicted by simulations considering the in-plane stiffness of the NCF. The location of wrinkles was indicated by the simulation using membrane elements. By continuously removing the redundant fabric material making contact with the machine bed and tool surface, net-shape preforms were achieved for the target geometry using single and multiple NCF plies respectively. Compared with the original ply shape, the number of wrinkles was reduced for the net-shape case due to the reduction in the bridging force induced by the contact pairing between fabric-diaphragm assembly and the machine bed.

A novel superhydrophobic Ni-graphene coating is synthesized on mild steel by one-step electrodeposition. The microtopography and contact angle of coatings deposited at varied deposition conditions were investigated to obtain the optimized preparation parameters. The anti-corrosion performance of the coatings was investigated by electrochemical polarization in synthetic seawater. The results illustrate that the Ni-graphene coatings deposited at GO concentration of 0.2 g·L^–1 and current density of 4 A·dm^–2 possessed dual roughness structures. After stored for 14 days in a vacuum drying chamber, the coating exhibited a contact angle of 156.1° and a sliding angle of 6.2°. Furthermore, the corrosion current density of the superhydrophobic coating was only 2.3×10^–8 A·cm^–2. This facilely prepared fluorine-free Ni-graphene superhydrophobic coating can potentially provide a pathway for corrosion control in the oil and gas industry.

Electrochemical machining process parameters will affect the surface integrity, surface roughness, service life and other properties of the workpiece. In order to realize high-efficiency and high-quality ECM of aluminum alloy rifled barrel, a method of process parameter optimization based on GA-BP neural network is proposed. The model of BP neural network is established by using MATLAB software. Machining clearance and surface roughness are objective functions. The MSE and linear regression value are analyzed. Genetic algorithm is used to optimize the connection weight and output threshold of BP neural network model. The change of fitness function and the error between predicted value and actual machining value are analyzed. The results show that the GA-BP neural network model can better predict the objective function. The optimal parameters of aluminum alloy rifled barrel ECM are: electrolyte temperature of 29.5±0.2 °C, electrolyte inlet pressure of 1.23±0.02 MPa, power supply voltage of 8.4±0.1 V, and working current of 3600±50 A.

The quality of the n-type cuprous oxide film is the key to improving the conversion efficiency of the cuprous oxide homojunction solar thin film battery, and its preparation is very difficult. In this paper, pulsed laser deposition (PLD) was used to stably prepare n-type Cu₂O films on (0001) sapphire (c-Al₂O₃) substrates, and the influence of the oxygen pressure in the chamber on the structure and electrical properties of the films was studied in detail. The measurments of X-ray diffractometer, scanning electron microscope, atomic force microscope, and Hall effect show that the Cu₂O films exhibited n-type conductivity uder the oxygen pressure of 0.5, 1, 2, and 5 Pa, respectively. At the same time, the film under the oxygen pressure of 0.5 Pa produce the best crystal quality and electrical properties of an electron concentration of 2.753×10¹¹cm^-3and mobility of 19.76cm²/vs.

In the present work, PtNi-loaded defective carbon (Pt/ZnPPC) was prepared by solid-phase method. Carbon support with specific defect types, such as Zn metal nitrogen carbon (ZnPPC850), N-doped carbon (ZnPPC950) and defective carbon (ZnPPC1050), were selectively obtained by optimizing the pyrolysis temperature to explore the effect of defect types on oxygen reduction reactions (ORR). Electrochemical measurements showed that the half-wave potential of the PtNi metal nanoparticle-loaded ZnPPC1050 catalyst (PtNi-ZnPPC1050) outperformed the commercial JM-Pt/C by 35 mV, and by 45 mV compared to the PtNi-loaded ZnPPC950 catalyst (PtNi-ZnPPC950), suggesting that the defects in the ZnPPC1050 support resulting from the evaporation of N by pyrolysis can interact well with Pt metal electrically, allowing the PtNi nanoparticles to be uniformly distributed. Meanwhile, the defects lead to the carrier containing a large number of active sites making its catalytic performance even much better than the pyridine nitrogen sites in ZnPPC950. The carbon defect structure is loosened and porous with high specific surface area, which can effectively load PtNi nanoparticles and enhance the mass transfer. We obtained a new bimetallic oxygen reduction catalyst loaded with PtNi on defective carbon and elucidated the effect of five-membered ring carbon defect structure and N-doped structure on metal-carrier interaction.

The continuous fiber-reinforced thermoplastic composites (called CFRTPCs) have been used in transportation, aerospace, sports and leisure products because of their great green recyclability and mechanical performances. This study evaluated the 3D printing process for the rapid manufacturing of CFRTPCs. The effect of laser and drilling processes, the size and shape of holes on mechanical performances of CFRTPCs were evaluated individually and mutually. The results proved that the small holes and low fiber content helped improve the strain at break while the big holes and the high fiber content helped improve the ultimate tensile strength and elastic modulus. The ultimate tensile strength and elastic modulus of specimens with square or big holes were higher than those of samples with circle or small holes. The ultimate tensile strength and elastic modulus of specimens with circle holes by laser were higher than those of samples with circle holes by drilling while the trend of strain at break was opposite. The micro morphology of the tensile breakage was observed and analysed to study the failure mechanism. This work makes an important contribution to the design of 3D printed CFRTPCs parts with holes.

Preparing fine tungsten particles tungsten heavy alloys (WHAs) is a method to improve the susceptibility to adiabatic shear of WHAs. In this paper, W-AlCrFeNiV alloy (W-HEA) with different size W particles were prepared by laser ultrashort-time liquid phase sintering (LULPS) and liquid phase sintering (LPS). The effects of W particle size of W-HEA on mechanical property and susceptibility to adiabatic shear are studied. The results show that W-HEA with 3 μm W particles has excellent mechanical properties-tensile strength nearly 1500 MPa. The tensile strength is 58% higher than that W-HEA with 20 μm W particle. W-HEA with 3 μm W particle dynamic compression strength is 2200 MPa under 4000 s^-1. The dynamic strength is 22% higher than that tungsten heavy alloy with 20 μm W particle. And the smaller W particles are, the stronger susceptibility to adiabatic shear is. The adiabatic shear band width of W-HEA with 3 μm W particles is 10 μm after dynamic compression.

Homogenization of refractory high entropy alloys (RHEAs) usually requires very high annealing temperatures and long periods due to the high melting temperature of alloying elements and the sluggish diffusion effects. TiVTaNb is a typical RHEA with excellent mechanical properties. The present work takes TiVTaNb as a model alloy and shows the influence of cold-deformation, annealing temperature, and annealing time on its homogenization microstructure. The optimal process parameters are determined as cold deformation of 80% thickness reduction, followed by annealing at 1250 °C for 48 h. The tensile deformation behavior of the homogenized alloy is then studied based on quasi-in situ tensile testing, showing a tensile strength of 766 MPa. The tensile deformation is accompanied by grain rotation, meanwhile, a large number of geometrically necessary dislocations piles-up at the grain boundaries.

In order to meet the demand for high strength of Al alloy in aerospace, automobile, shipbuilding and other fields, the effects of aging treatment on the microstructure and properties of Al-4.5Cu-0.8Mg alloy were systematically studied. The results show that the main strengthening phase in the microstructure of the alloy after aging was θ' And S' phase, the comprehensive mechanical properties of single-stage aging after aging at 165 °C for 12h was better. In the alloy aged at 185 °C for 12 hours, the strengthening phase was coarsen obviously, the tensile strength and yield strength was decrease greatly and showed obvious over aging characteristics. The comprehensive mechanical properties of two-stage aging at 105 °C / 12h + 165 °C / 5h was the best. The tensile strength, yield strength, elongation and hardness are 543 MPa and 374 MPa, 17.5% and 170.6 HV respectively.

Due to the excellent physiochemical properties of graphene oxide (GO), the fabrication of superamphiphobic coatings based on GO can explore the application fields of GO. Herein, superamphiphobic GO coatings are fabricated by simple dip coating GO and organosilane polymer (GO-FAS) dispersion on the cotton fabric, with GO acting as solid lubricant originating from its low friction coefficient. Through compound with PS/PTFE and PVDF-HFP/FAS, the PVDF-HFP/FAS/GO-FAS coating exhibit enhanced anti-abrasion property and can withstand 200 cycles of sandpaper abrasion. This study provides an opportunity for the applications of graphene oxide as superamphiphobic materials.

Body-centered cubic (BCC) high entropy alloys (HEAs) usually have poor ductility, limiting their engineering application. Here we present a TiZrNbAl non-equal atomic-ratio HEA (Z25) which shows martensitic transformation during tensile deformation. This transformation effectively improved the uniform ductility to around 17%. The gradually induced martensite lamella shows the "dynamic Hall-Petch" effect during transformation, which reduces the mean free path of dislocation slip, resulting in Z25 alloy with excellent ductility and remarkable work hardening effect.

Through electrochemical hydrogen permeation experiment at different hydrogen charging current densities, the hydrogen diffusion kinetic parameters such as penetration time t_B, steady-state hydrogen permeation current density I_∞, hydrogen diffusion coefficient D, adsorbed hydrogen concentration C₀, hydrogen flux J, and hydrogen trap density N_T in the heat-affected zone of X80 steel welding with different heat input were analyzed. The results show that the penetration time gradually decreases, and the I_∞ gradually increases with the increase of hydrogen charging current density. The penetration time of BM at the same hydrogen charging current density is the smallest, and the penetration times of CGHAZ specimens with different heat input conditions are relatively close. BM has the most significant hydrogen diffusion coefficient and negligible hydrogen trap density at the same hydrogen charging current densities. For CGHAZ, D significantly decreases and N_T substantially increases, and there exists a threshold value that makes the lowest D in the CGHAZ with different heat inputs.

Ti-Zr-Hf-Nb-Ta system refractory high-entropy alloys (RHEAs) exhibits outstanding tensile ductility in room temperature. However, the moderate yield strength of them is insufficient. In this work, the Fe element with small atomic radius was added into a non-equiatomic Ti-Zr-Hf-Nb-Ta RHEA for furtherly improving the yield strength. As a result, the yield strength of modified RHEA is as high as ~970 MPa, while retains a considerable fracture train of ~17.5%. However, the Hf₂Fe brittle precipitates were formed at grain boundary after aging treatment, leading to a further increment of yield strength but severe deterioration of ductility.

The effect of low-pressure carburizing (LPC) on the mechanical properties of open cellular structures was studied by taking the 316L stainless steel body-centred cubic (BCC) lattice fabricated by selective laser melting (SLM) as an example. The mechanical properties of the corresponding solid material and the microstructure of the carburized layer were also analyzed. The results showed that the depth of the carburized layer was about 450μm, composed of three sub-layers. After carburized, the yield strength of the 316L solid was obviously decreased accompanied by the reduced elongation at break. The embrittlement was also reflected in the carburized lattice so that the fracture occurred and the energy absorption capacity weakened. Simultaneously, the compressive proof strength of the lattice was improved after low-pressure carburizing due to the toughness inherent in the structure.

Increasing the ligand size could enlarge the pore volume of MOFs, which could further increase the gas adsorption capacity. Inspired by this, we synthesized a porous 3D metalorganic framework [Cu₂(L₁)·(H₂O)₂] ·2H₂O·3DMF·(CH₃)2NH₂] (NEM-5) with a high density of carboxylate groups and Cu^II sites, which exhibited large uptakes for C₂H₂ (65 cm³ g^-1), C₂H₄ (48 cm³ g^-1), C₂H₆ (64.7 cm³ g^-1), C₃H₆ (68 cm³ g^-1), and C₃H₈ (63.4 cm³ g^-1) at room temperature. Compared with MOF 1, NEM-5 has a similar topology and larger pore volume, but the gas adsorption capacities are significantly reduced, which might be attributed to the large pore size and low framework density of NEM-5.

During the fatigue performance verification test of the blade simulator, a fixed connecting pin on which the splint was installed broke. In this paper, the fracture properties of the connecting pin were determined by observing the macro/micro morphology of the connecting pin and the fracture surface of the coating. By analyzing the elements, structure, hardness and relative ratio of the body and coating, the differences between the connecting pins of different blades were studied, and the fracture causes of the connecting pins were comprehensively analyzed. Based on the above experiments, the influence of coating quality on fatigue cracking is analyzed, and the improvement scheme of connecting pin is put forward.

(1-x)CaCu₃Ti₄O₁₂-xCeO₂ (x=0.1, 0.2, 0.3, 0.4) and CaCu₃Ti₄O₁₂ ceramics were synthesized through a solid-state reaction technique. X-ray diffraction indicates that the CaCu₃Ti₄O₁₂ phase is formed in all ceramics. SEM micrographs show that the grain size of ceramics declines with the addition of CeO₂, which is attributed to the solute drag effect. When the addition amount of CeO₂ is 0.4, the ceramic obtains the maximum dielectric constant at low frequency. Increasing the composite content of CeO₂ can effectively reduce the dielectric loss of CCTO ceramics at high frequency. And the lowest value is 0.1 when the addition amount of CeO₂ is 0.3. Impedance analysis shows that the lowest dielectric loss obtained for the ceramic is due to the lowest grain resistance.

The inevitable vibration caused by normal operation of the spacecraft in orbit will interfere sensitive instruments, such as space telescope, reconnaissance camera, space interferometer. Serious vibrations affect the accuracy and reliability of the sensitive instruments, even cause flight mission failed. This paper presents a hybrid 6-DOF vibration isolation platform (HVIP) with six degree-of-freedom for active vibration isolation of the space sensitive instruments. The HVIP is composed of three orthogonal vibration isolation module, which composed of the active piezoelectric actuator and passive rubber isolator. The dynamic model of the HVIP is established based Lagrange equation approach. Finally, the numerical simulations are performed to verify the vibration isolation effect of the HVIP.

In order to solve the problems such as the limited field of view of traditional self-collimation detection, the inability to achieve continuous detection of 0~360° full circumference and the existence of zero drift in self-collimation measurement. The positive and negative rotation of the inner and outer axes of the dual-axis turntable is used to realize high-precision continuous angle measurement with the autocollimator as the angle reference, and the combination of the compensation target and the fixed target is used to realize the closed-loop compensation of the drift of the autocollimator. The results show that: the repeatability error of the system is 0.05", and the detection accuracy of the system reaches 1.64". On the premise of ensuring the stability of the self-collimation angle reference, the self-collimation full-scale small angle measurement is realized.

The reconfigurable wheel-track transformation mechanism is characterized by short conversion time and excellent terrain adapability, appropriately resolving the contradiction between trafficability and mobility. Based on a new transmission scheme, this paper focuses on the mechanical properties of its transformation mechanism, so as to provide theoretical support for structure optimization. The mechanical model is established by analyzing the forces of key components during the process of transformation, after which stress and strain of them is analyzed through finite element analysis software, according to previous calculations from the model. The results show that parts with direct contact with ground bear more forces than others. Maximum stress of parts is within the limit strength of materials, but structure of weaker parts should be further improved to reduce stress concentration.

A proactive search time adjustment model based on the optimally weighted LightGBM algorithm was studied in this paper for the problem of large delay fluctuations in 5G distribution terminals leading to protection blocking. The model used historical data on delay fluctuations of wireless communication terminals and feature variables such as temperature and date and time as inputs to predict delays and dynamically adjust equipment parameters. First, the original feature variables were pre-processed via feature engineering, then the data were fitted together with the historical delay data by the LightGBM algorithm. And the final weighted combination was used to adjust the predicted values in combination with the real-time monitoring delay of the terminal, finally realizing the high-precision prediction of 5G terminal delay. The results show that the proposed method can effectively achieve delay prediction and has higher prediction accuracy than random forest regression and XGBoost algorithms.

To face the problem of freight safety and reduce the traffic accidents, the influence of the response time of the pneumatic braking system on the braking performance should be investigated, which can improve the safety level of vehicle. The mathematical model of the pneumatic braking response time was established in this paper. The parameters of the pneumatic braking time and the time delay characteristics of the pneumatic braking system was discussed. The results show that the pressure and effective cross-sectional area of the brake chamber are the main factors affecting the time delay of the pneumatic braking system. When the effective cross-sectional area of the brake chamber is certain, the push rod stroke of the brake chamber increases significantly with the increase of air pressure; when the brake chamber pressure is constant, the larger the effective cross-sectional area of the brake chamber, the greater the output thrust of the brake chamber push rod.

The stress concentration of oil and gas pipelines will produce corrosion cracks and axial fatigue cracks under the action of long-term and repeated internal pressure, and will rapidly expand under fluctuating internal pressure, resulting in serious pipeline accidents. In order to effectively detect the stress concentration of oil and gas pipelines, a stress concentration detection technology of unsaturated local magnetization pipeline is proposed. This paper introduces the theoretical basis of local pipeline stress concentration detection, establishes a two-dimensional finite element model of pipeline stress concentration transient force-magnetic coupling, and analyzes the influence of excitation source position, sensor lift-off value, and stress concentration value on the response signal. The simulation results show that the corresponding signal B_x of the stress concentration changes more obviously than B_y and the signal is regular, B_x has a good two-stage linear positive correlation with the stress concentration value. The above research provides technical support for the development of pipeline on-line stress concentration detection probe.

In this paper, a production line of film extraction and transmission with traction rollers is discussed. Wrinkles sometimes appear on the whole film in a few days after the production line starts up. The film and traction rollers system's models are established. Impact factors and change laws of rollers characteristics are studied. Influence parameters such as friction coefficient, rotating speed, roller deflection and clearance are analysed to ensure the stability of the film transmission system.

The power of the medical centrifuge is provided by the permanent magnet synchronous motor, so the AC control system of the permanent magnet synchronous motor directly determines the overall performance of the centrifuge. In this paper, the permanent magnet synchronous motor is the controlled object, the DSP28335 is used as the main control chip, and combined with the vector control strategy, the permanent magnet synchronous motor AC servo control system is designed. Finally, according to the design scheme, the soft and hard design of the motor control system is completed, and the system test is carried out. The test results show that the designed servo control system has fast response, good tracking performance, and stable operation, and has a certain market application prospect.

Leading-edge erosion of wind turbines is caused by particles in wind. Impacts at a high velocity damage the blades severely and lower the aerodynamic efficiency. The aim of this paper is to estimate the flow rate hitting on the leading edge of the airfoil NACA4412, which forms the tip of a wind turbine blade, with the geometry referred to NREL offshore 5-MW baseline wind turbine. The methodology is to first compute the coordinates of the points on the boundary of the airfoil that is defined to be the leading edge, then with trigonometry relationships of the airfoil, the length that is passed through by wind can be found. Finally, relating them together, a differential equation is established. It reveals how the angle of attack and flow rate through the leading edge are correlated. With graphs plotted, the equation states that changing the angle of attack from 6 to 7 has 6.2% less erosion while Cl/Cd is dropped by 4.6% only. Hence, for situations where leading edge erosion and aerodynamic efficiency are considered equally important, it is better to vary the angle of attack to 7 degrees rather than the optimal 6 degrees.

Abnormal vibration may occur in the pipeline of cooling and lubrication system of synchronous condenser during operation. In order to solve this problem, a priori analysis method for abnormal vibration of synchronous condenser piping system is proposed in this paper. This method mainly includes three parts :(1) the modal analysis of the whole pipeline system is carried out to find the pipeline with the most dangerous abnormal vibration; (2) Analyze the cause of abnormal vibration of the hazardous pipeline; (3) According to the analysis results of vibration causes, the field measurement is carried out, the modal analysis is verified, and then the cause and location of abnormal vibration of the whole pipeline system are determined. The results of case analysis show that this scheme can quickly and accurately find out the cause and location of abnormal vibration of the synchronous condenser pipeline system, improve detection efficiency and save cost. At the same time, the natural frequency of vibration obtained by modal analysis can provide a theoretical basis for the design and transformation of the synchronous condenser pipe system.

Nine-axis motion parameters need to be calculated according to the relative pose to be simulated when the precision calibration test of rendezvous and docking optical imaging sensor is carried out with nine-degree of freedom motion simulator. Based on the structural characteristics of the system and the principle of homogeneous coordinate transformation, the inverse kinematics equations are established in this paper, in order to improve the test efficiency and ensure the accuracy of pose simulation, the iterative algorithm with fixed degrees of freedom was adopted to approximate the solution results, at last, the nine-axis weighting algorithm was used to judge the end of iteration and obtain the solution results of relative pose optimization.

Based on the basic structure and working principle of vertical scraper discharge centrifuge and combined with the actual use, this paper puts forward the main influencing factors of bell-shaped cover wear, studies the wear characteristics of materials on bell-shaped cover, analyzes its wear mechanism, and determines the easily worn parts. Taking the bell-shaped bell-shaped cover of the LLL1200 vertical scraper discharge centrifuge as the research object, the speed and angle of materials eroding the bell-shaped cover at each position are calculated through the analysis of the movement track and force of solid materials in the centrifuge. The erosion and wear speed of materials on the outer end of the rib plate side is the maximum, 23.06 m/s, the speed on the inner wall of the coal retaining ring is slightly lower, 13.87 m/s, and the speed on the upper surface of the rib plate is the minimum, 0.53~ 0.69 m/s. In addition, two methods to prolong the service life of the bell-shaped cover are proposed. The industrial application shows that inlaying alumina wear-resistant ceramics on the bell-shaped cover is the most effective and simple method.

Based on LS-PrePost software, the three-dimensional display of healthy cylindrical roller bearings was established finite element model for dynamic simulation. Based on the explicit algorithm, the model analyzes the law of bearing stress level with radial outward load under the conditions of friction contact, speed and load, and based on the healthy roller bearing model, simulates the local spalling fault of the outer raceway by setting the unit defect, and analyzes the equivalent force change process when the roller through the fault area. The simulation results are compared with the theoretical calculation results to verify the correctness of the finite element model of the faulty bearings, and provide a certain reference for the fault diagnosis of rolling bearings.

The tandem cold rolling process is continuous production, and it is desired to achieve a stable operation process, the incoming materials need to be welded in the length direction before cold rolling. Usually the head and tail of the incoming material have a thickness dimension positive deviation, and there are two alignments in the thickness direction of the front and rear strip, so that different weld zone profiles can be formed. In this research, we built an FEA (finite element analysis) model of strip rolling with weld zone and relevant simulation conditions are designed to reveal the effect of alignment on the rolling process of the strip with weld zone. The risk of strip breaking between two alignment forms of the weld zone during the rolling process is further discussed and compared. It provides a reference for the setting of the alignment method of the laser welding machine in welding the strip in order to reduce the probability of weld zone breaking during the cold rolling process.

We analyzed the power flow of the vibration transmission of the F2 mill drive system coupled with complex beams using the substructure method. The system was divided into three cylindrical substructures, which were coupled to each other by three spring-dampers. The modal analysis of the substructures was conducted to describe their dynamic characteristics; subsequently, the substructure receiving function under free interface conditions was established. The dynamic characteristics of the transmission coupling system were calculated by synthesizing the force balance conditions and geometric coordination at the coupling interface. The input energy and transmission energy in the system were effectively evaluated. The effects of spring-damper stiffness change, excitation position, and loss factor on the transmission of vibration power flow were studied and verified by field experiments. This study provides an effective theoretical basis for vibration suppression measures for hot tandem rolling mills.

Self-excited chatter vibrations are the most detrimental for the quality and safety of the machining operations. To reduce the undesired vibrations, the dynamic behaviors of the machine tool-workpiece system and the chatter stability models need to be studied. In this paper, gear hobbing is studied using analytical and experimental approaches. Firstly, based on the chatter stability theory in relation to milling, analytical model of chatter stability in gear hobbing process is derived. Secondly, a new approach is presented to identify dynamic modal parameters using operational modal analysis (OMA). Using natural excitation technique (NExT) and auto regressive moving average (ARMA) model time series analysis method. At last, the prediction capability is verified using machining experiments, and the results show that the stability diagrams is of great potential to supply guidance for the processing parameters development.

In this paper, the failure mechanism of the piston in the pneumatic down the hole (DTH) impactor has been studied. Failed piston microstructure has been analyzed using the light optical microscopy (OM) and scanning electron microscope (SEM). Impact toughness test and the Rockwell hardness test were conducted. Results showed the following: a) The carburizing layer of IQCT failed piston is mainly composed of acicular martensite and lower bainite after the carburizing-tempering-isothermal quenching-cryogenic treatment-tempering (IQCT), and there are collapses on the impact side and outer surface of the piston, mainly fatigue failure. b) IQT failed piston samples are subject to carburizing-tempering-isothermal quenching-tempering treatment (IQT). The carburized layer is mainly composed of high-carbon martensite, carbide and retained austenite. The transition layer is still composed of lower bainite and acicular martensite, but the volume fraction of lower bainite increases significantly and the core is mainly composed of lower bainite. It has the best impact toughness, up to 61.5 J/cm², which is mainly fatigue failure. c) OQT failed piston sample is subject to carburizing-tempering-oil quenching-tempering (OQT). The carburized layer is mainly composed of acicular martensite, the transition layer is composed of acicular martensite (AM) and lath martensite (LM), and the core is mainly composed of LM. The impact toughness of the sample is the worst. Therefore, fatigue fracture failure is caused.