Dynamic characteristics of rubber pad for vibration mitigation

Lau, Jia Rong (2022) Dynamic characteristics of rubber pad for vibration mitigation. Final Year Project, UTAR.

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Abstract

Rubber pad is a material that is vastly used in mitigating mechanical vibration. The material composition of a rubber pad is made to determine the dynamic characteristics of the rubber pad. For the best mitigation of vibration to occur, the rubber pad used in certain systems must achieve critical damping. However, critical damping is hard to achieve every time as the dynamic characteristics of the rubber pad is affected by the dynamic load of the system supported by the rubber pad. Although rubber pads are usually produced with a specified range of dynamic properties, end-users often find that the rubber pad does not work within the specified range. The problem arises here is the equipment needed to justify the dynamic properties of the product is unavailable in the market if not relatively expensive. A reliable test rig that is capable of applying preloads on rubber pads has been developed. The test rig utilised the instrumented hammer impact method and the concept of single-degree-of-freedom system in determining the dynamic properties of rubber pads that adapt the dimension of a standard railpad. The dynamic stiffness of rubber pads are found to increase as the applied preload increases. Throughout the range of preload, the store bought EPDM achieved the highest dynamic stiffnesses amongst the three rubber pads, which is from 906 to 951 MN/m, the natural rubber pad followed in second with a range from 625 to 950 MN/m, while the EPDM railpad has the lowest dynamic stiffness with a range from 377 to 840 MN/m. In terms of the damping coefficient, the store bought EPDM has a range from 1305 to 4354 Ns/m, the EPDM railpad has a range from 2340 to 4668 Ns/m, and the natural rubber pad has a range from 1719 to 6868 Ns/m. The grooves profile that the natural rubber pad possesses appeared to aid the rubber pad in stress dissipation when the load applied is slow and steady.

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