Impact force attenuation capabilities of elastomer, springs and their combination

In various engineering applications like automotive safety, structural engineering, and industrial machinery, mitigating impact forces is of at most importance to protect structures, equipment and most importantly, human lives. Understanding the impact force attenuation capabilities of dampers, springs, and their combination is crucial. Dampers like elastomers are known for their exceptional ability to absorb and dissipate energy due to their visco-elastic properties. Spring on the other hand, store and release mechanical energy when compressed, offering a different approach to impact forces attenuation. Study is experimental and parametric in nature, where different damping materials like elastomers, polystyrene & foam are individually and in combination with springs of different stiffness are tested for their impact energy absorption capabilities. Tests are conducted in a dedicated test rig, wherein specimen is kept on a rigid plate which intern mounted on a peizo-electric load sensor and weights are dropped from same heights and force transmitted with time of travel is measured for each specimen and compared. Results revealed that the energy absorbed by springs is around 30% individually, which is less compared to dampers and, the combination of damper & springs. In conclusion the specimen with combination of damper & springs has high potential in absorbing impact force.


Introduction
Impact force is a term used to describe the powerful and sudden force that occurs when two objects collide or when an object experiences a rapid change in its speed.This force is usually quite strong and applied in a short amount of time.Impact forces can cause deformation (changing the shape of an object), damage (causing harm to a thing), or displacement (moving an object from its original position) when they occur.As a result, there is a quick shift in momentum, and a considerable amount of energy is generated quickly.Impact attenuation refers to the methods and techniques employed to reduce the harmful effects of sudden forces or impacts on objects, structures, or individuals.Intense forces are produced when things meet or undergo abrupt motion changes; if these forces are not effectively controlled, they can cause damage, injury, or structural failure.Impact attenuation aims to mitigate the impact of these factors to protect against unfavourable outcomes.Utilizing different substances, systems, and constructions that absorb, distribute, or dissipate the energy generated by effects is required for this.The severity of the impact is lowered as a result, reducing the possibility of distortion, harm, or injury.Common examples of impact attenuation techniques include using elastomers, springs, shock absorbers, Safety Padding, and cushioning materials.Impact attenuation is crucial to the success of sectors including automotive, Military and defence, sports, construction, Industrial Machinery, etc.

Materials and Method
Two different elastomers and compression springs were selected for experimental test and the mechanical properties of both rubber materials are shown in table 1 and table 2, were the compression springs mechanical properties are shown table 3, Besides the hardness and density, the compounds ingredients are given, were the carbon black is a form of elemental carbon is used to increase the resistance of rubber and also to improve tensile strength and the compression springs also have good withstand strength.

Vibration isolation elastomers:
Vibration isolation elastomers are materials that efficiently minimise vibration transmission by absorbing and dispersing mechanical energy, enhancing overall stability, and reducing influence on neighbouring structures concerning this item.Natural rubber, hardness of vibration isolation elastomer 65, colour black, shape square, product dimensions 100(L) x 100(W) x 12(t) mm.Uses include vibration reduction, noise reduction, surface protection, and increased comfort.3 Compression springs: are helical mechanical parts that store compressed energy and withstand axial compressive forces.They expand back to their original length when the power is removed.About this item, the Material is steel wire, the Colour is Grey, and the Shape is helical.Fig. 3 (c) Springs with plate sample We have chosen a 0.3mm metal piece on springs, upper plate and lower plate in between we have placed 5 piece of springs at a distance of 25mm each side and using silver brazing process attached the springs with a plate, like these three different properties of springs are attached with a three set of spring system.

2.4:
The experimental setup for a drop impact test typically involves the following component 1) Drop Apparatus: For providing predictable and controlled impact forces, a drop apparatus is used.It might be a pendulum system or a drop tower.The impact energy applied to the test specimen can be changed by adjusting the drop height.2) Test Specimen: The material or object tested for drop resistance to impact is the test specimen.It might be a finished product, a component, or a solid sample.The sample must accurately reflect its intended use or application.

3) Mounting or Fixture:
To ensure that the test specimen remains stationary during the impact, it is firmly mounted or fixed.The type of fixtures used will depend on the specimen's features, size, and shape.To avoid incorrect movement or distortion during the test, it is essential to provide sufficient support and position.4) Instrumentation: During the drop impact test, various sensors and instruments are used to measure and record data.These could be high-speed cameras, data acquisition systems, force sensors, accelerometers, strain gauges, or accelerometers.The parameters being measured, as well as the desired level of accuracy and resolution, all influence the instrumentation choice.5) Drop Surface: The target or impact surface onto which the test specimen is 15 dropped is known as the drop surface.It might take the form of a rigid surface, a flexible surface, or a particular fixture created to imitate actual environmental factors.The drop surface should be carefully selected to represent the intended effect situation accurately.6) Safety Measures: During the drop impact test, safety measures must be in place to safeguard people and property.To ensure a safe distance between operators and the test setup, safety barriers, personal protective equipment (PPE), and other measures may be used.To avoid accidents or injuries, proper safety procedures must be followed.7) Experimental Parameters: The experimental parameters include drop height, drop orientation, drop weight, and the number of repetitions.These parameters can be altered to simulate various impact situations or to investigate the material's conduct under different conditions.

Testing apparatus, including the drop tower system used:
1) Drop Tower: A drop tower is a vertical structure that has a platform or release system that holds the test specimen.To control the drop height and, subsequently, the impact energy, the tower's size can be changed.After being securely mounted or fixed to the platform, the test specimen is released, allowing it to fall freely under the force of gravity.The model then contacts the target surface, and the ensuing response is recorded and examined.Drop towers can hold a variety of specimen sizes and shapes and are highly versatile.
Fig. Quantum Data Acquisition Systems An impact load was applied to a sample dropping a mass of 0.25 kg in a height of 0.37m, first we have tested without placing any rubber and again we have placed spring system and tested each three trails sample test on each three-spring system with elastomers and without elastomers, combination of two and combination of all three were tested.Three spring systems were found to have distinct properties of performance based on drop impact tests.The spring system with the highest stiffness, s1, displayed a force of 2.2 KN, the spring system with the lowest stiffness, 3 KN and the spring system with the least stiffness, 3.9 KN.Interesting results were obtained when springs were combined: s1 + s2 reduced force to 1.7 KN, s2 + s3 produced 2.2 KN, and s1 + s3 averaged 1.9 KN.Combining all three springs (s1 + s2 + s3) resulted in the largest force decrease, which was 1.6 KN in the end, indicating a synergistic effect on impact absorption, As shown in table 4.  In our efforts to mitigate impact forces, we incorporated vibration isolation elastomers alongside spring systems.The force was lowered to 5.8 KN by a single vibration pad and to 3.8 KN by two more pads.A setup with two pads produced a force of 1.8 KN, whereas the introduction of spring system s1 on a single pad produced a force of 2 KN.The experiment was expanded to include combinations such elastomer + s2, elastomer + s2 + elastomer, elastomer + S3, elastomer + s3 + elastomer, elastomer + s1 + s2 + elastomer, and elastomer + s1 + s2 + s3 + elastomer.These pairings demonstrated different levels of force reduction, highlighting the possibility of spring systems and elastomers working together to provide efficient impact isolation, the results shown in table 5.  Vibration pads used in combination with the spring system produced a more significant reduction in impact force than the spring system, which showed a relatively small reduction in the comparison of the various mitigation measures.However, adding sorbothane isolation elastomers produced the best outcomes.With the addition of another pad, the force dropped even further to 2.6 KN.A single sorbothane pad demonstrated a significant force reduction of 3.5 KN.The force of 1.9 kN was obtained by applying spring system S1 on a sorbothane pad; adding more pads reduced the force to 1.6 KN.This all-inclusive method, which included sorbothane elastomers in conjunction with other spring systems, highlighted the complex interactions and showed that sorbothane offered the best impact reduction in all of the conditions which were reviewed, as shown in table 6.

Conclusion
As a result of the drop impact tests conducted on the three spring systems, Figures 18 to 31 display the obtained results.the average impact force of every spring system is displayed.and it was determined that the synergistic effect of the three springs (s1 + s2 + s3) produced the greatest force decrease, which was recorded at 1.6 KN.This demonstrates how crucial it is to take into account spring systems' collective behavior.Furthermore, the integration of vibration isolation elastomers with spring systems demonstrated efficacy, as evidenced by the example of (Es+s1 + s2 + s3+Es) yielding 1.1 KN, underscoring the possibility for enhanced impact mitigation.Sorbothane isolation elastomers, on the other hand, showed the most promising findings, with (sorb+s1+s2+s3+sorb) producing an amazing force decrease to 0.7 KN.This all-encompassing strategy highlights sorbothane as the most effective selection, showing its significant impact reduction abilities under all tested conditions.

Future scope and work
Looking at higher positive margin of safety available, there is scope for force reduction by various means of approaches force reduction can be explored.

Table 1 .
Materials mechanical properties Sorbothan vibration isolation: Sorbothane is a proprietary viscoelastic polymer.Sorbothane® is a thermoset polyurethane based on polyether.Concerning this item Material: viscoelastic polymer, hardness, colour: black, shape: square Product Dimensions: 127(L) x 127(W) x 12.7(t) millimeters.Applications: Sorbothane lowers impact force by up to 80% and slowly restates the mass.A steady deceleration protects delicate equipment better.When compared to other materials, Sorbothane has a shallow rebound.

Table 2 .
Materials mechanical properties

Table . 3
Material mechanical properties of compression springs

Table . 4
Impact test results of spring system 3.2: Vibration isolation elastomers with Spring system Behaviour

Table . 5
Impact test results of spring system with vibration isolation Sorbothan vibration isolation elastomers with Spring system Behaviour

Table . 6
Impact test results of spring system with vibration isolation