Your search for "Rujian Sun" returned 10 results

With the development of luxury cruise ships and large offshore platforms, the use of high-frequency electromagnetic heating power sources to replace fireworks for thin steel plate leveling is a new development trend in the shipping and offshore industries. The technical difficulty of high-frequency induction power supplies is frequency track. The frequency tracking circuit in this article uses CD4046 as the core, which not only realizes frequency tracking but also realizes the dead time setting, ensures that the power supply can realize frequency scanning and maximum frequency tracking, and ensures that the circuit always works in resonance or quasi-resonance state, The output is more efficient at this time.

The influences of laser pulse energy and impact time on high strain rate response of 7055 aluminum alloy subject to square-spot laser shock peening (SLSP) were investigate. Microstructural evolution was characterized by OM, SEM and TEM. Microhardness distribution and in-depth residual stress in 15 J with one and two impacts and 25 J with one and two impacts were analyzed. Results show that the original rolling structures were significantly refined due to laser shock induced recrystallization. High density of microdefects was generated, such as dislocation tangles, dislocation wall and stacking faults. Subgrains and nanograins were induced in the surface layer, resulting in grain refinement in the near surface layer after SLSP. Compressive residual stresses with maximum value of more than -200 MPa and affected depths of more than 1 mm can be generated after SLSP. Impact time has more effectiveness than laser pulse energy in increasing the magnitude of residual stress and achieving thicker hardening layer.

Laser shock peening is an advanced surface treatment technique in improving the fatigue properties of metallic components. In this study, the effects of different laser shock peening regions on the high cycle fatigue of 42CrMo high-strength steel were investigated. Surface deformation, residual stress, and microhardness were analyzed, and microstructural evolution including grain size, boundary distribution, and misorientation was examined. Results show that peening the specimen with both surfaces and sides resulted in a better fatigue life than only peening the surface. The compressive residual stress introduced in both the surfaces and sides provided a higher resistance for fatigue initiation. In addition, the increase of low angle grain boundary accounted for the micro strengthening mechanism for the fatigue life extension.

Laser shock peening (LSP), an innovative surface treatment technique, generates compressive residual stress on the surface of metallic components to improve their fatigue performance, wear resistance and corrosion resistance. To illustrate the dynamic response during LSP and residual stress fields after LSP, this study conducted FEM simulations of LSP in a Ti6Al4V alloy. Results showed that when power density was 7 GW cm⁻², a plastic deformation occurred at 10 ns during LSP and increased until the shock pressure decayed below the dynamic yield strength of Ti6Al4V after 60 ns. A maximum tensile region appeared beneath the surface at around 240 ns, forming a compressive-tensile-compressive stress sandwich structure with a thickness of 98, 1020 and 606 μm for each layer. After the model became stabilized, the value of the surface residual compressive stress was 564 MPa at the laser spot center. Higher value of residual stress across the surface and thicker compressive residual stress layers were achieved by increasing laser power density, impact times and spot sizes during LSP. A 'Residual stress hole' occurred with a high laser power density of 9 GW cm⁻² when laser pulse duration was 10 ns, or with a long laser pulse duration of 20 ns when laser power density was 7 GW cm⁻² for Ti6Al4V. This phenomenon occurred because of the permanent reverse plastic deformation generated at laser spot center.

With the advantages of security for life, Unmanned Surface Vehicle (USV) has a wide range of applications in military and commercial fields. However, the rules of Maritime navigation for USV and the recognition of the legal status of USV are both still in a blank stage. The existing maritime navigation rules cannot be fully adapted to the operation of USV. The legal status of USV should be implemented as soon as possible to ensure the security of USV maritime navigation and to have the legal basis for effectively resolving the dispute over the vessel in order to adapt to the rapid development of USV. Starting from the reality of the USV and drawing lessons from the research experience of the United States, this thesis analyzes the legal status of USV in three aspects: the navigation rules of USV, the navigational status of USV as a military (official) and civilian vessel in the water area and the applicable law of USV.

With the wide application of unmanned ships in the fields of water surface bleaching, sea exploration, water quality monitoring and emergency rescue, unmanned ship technology has attracted more and more people's attention. Due to the navigation environment of unmanned ship is very complex, diverse and changeable, it has become the primary task of unmanned ship technology research to study how to use path planning algorithm to integrate a large number of multi-sensor data, quickly and accurately make navigation strategies and achieve accurate motion control. This paper mainly summarizes the current research status of unmanned ship path planning algorithms, analyzes the differences and advantages of various path planning algorithms in practical applications, and finally points out the research trend of unmanned ship path planning algorithms.

At present, the track control of unmanned surface vessel (USV) is mainly divided into direct track control and indirect track control, both of which have their advantages in the aspect of USV track control. Though having high control precision, the former still fails to meet the related requirements. To tackle this problem, the nonlinear model predictive control (NMPC) algorithm was optimized based on the convolutional neural network (CNN) in order to design a direct USV track controller. In consideration of the nonlinearity and time lag problems that are likely to occur in USV track control, the convolutional neural network was used to solve the optimal control sequence of the predictive control algorithm. The simulation test indicates that this algorithm has effectively improved the accuracy and real-time performance of track control.

Due to the incomplete data collected, it will increase the difficulty of inversion location in the field source inversion of the static magnetic field data of underwater vehicles. Therefore, it is very necessary to study the influence of data loss on the static magnetic source location of underwater vehicles and the field source location for timely remedy of missing data. In this paper, the static magnetic equivalent source model of underwater vehicle was established. Then the inversion positioning algorithm was used to locate the magnetic field source of the underwater vehicle obtained from the test, and the influence of the location result under the incomplete data information was analyzed. We used deleting method, linear interpolation method and sliding filling method to populate the data to fill the remedy of missing data. Using the localization algorithm to carried out the inversion location of source, then we took the location of source inversion and the size of the magnetic dipole moment to the ellipsoid model to get fitting curve of magnetic field. The simulation curve of contrast verification test data with experimental data and the lack of remedial method was feasible. The results show that the missing data can not be ignored for the location of the underwater vehicle's magnetic field source, and the data pairs filled with missing data can be effectively located for the equivalent static magnetic field source of the underwater vehicle through using deletion method, linear interpolation method and sliding filling method.

On basis of grade-standard deviation method, two sensitive grain size components (component 1:5.8∼10.0μm, component 2:60.3∼104.7μm) and a less sensitive grain size component (component 3:15.1μm∼22.9μm) were extracted from the samples of the sedimentary age of LX02 profile, which were collected from Longcheng Yardang region on the northeast edge of Tarim Basin. The study discusses the material sources and action forms of different grain size sensitive components, which can be used as an indicator to reveal the regularity of the lake and the intensity of wind-sand activity respectively. The lacustrine transgressive and regressive history of the region has been reconstructed for 72−51ka B.P. by the characteristics of the content of sensitive grain size component 2, and the palaeoclimate information of the sediments was restored, which provided the basis for exploring the distribution law of other environmental factors in lake sediments. This paper is helpful to explore the law of environmental evolution and the history of climate change in arid regions.

Hot-wire laser welding is additive manufacturing (AM) technique that allows for the direct creation of complicated objects by melting layers of wire. This process is characterized by the use of hot-wire process, unification with the laser welding (LW) process in AM process. The empirical investigation of AM employing a hot-wire laser welding on a titanium alloy (grade 2) workpiece is presented in this research. There are three parameters in the hot-wire laser process namely wire current, welding speed, and wire feeding speed; this research examined porosities, microhardness, tensile stress, and residual stress. The filler metal used titanium AMS (American welding society) 4951F welding wire of grade 2 and measures 1.6 mm in diameter. Finally, the suitable hot wire laser welding parameters should be 0.183 cm s⁻¹ for the welding speed, the wire current of 40 A, and the wire feeding speed of 1.00 m min⁻¹ are 0.183 cm s⁻¹ for welding speed, 40 A for wire current, and 1.00 m min⁻¹ for wire feeding speed, which will give the average Vicker microhardness of 321.00–345.80 HV, the average tensile strength of 432.02 MPa (substrate); 670.30 MPa (horizontal direction), 497.39 MPa (vertical direction).