Conventional impact dampers often utilize the steel balls because of its low cost and handling easiness. But the steel-ball impact dampers sometimes collapse or generate very large noise because of large shock at the impact. And as for the design of the impact damper, in the conventional approaches, the analytical modeling for the impact force is based on the contact theory proposed by H. Hertz, in which the restitution coefficient is assumed to be constant, i.e., the dependency on the relative velocity is not taken into consideration. However, some experimental results show that the restitution coefficient depends on the relative velocity at the impact. In this study, the elasto-plastic materials are employed as an impact damper material in order to suppress the large shock for the damper vessel and large impact noise. Therefore, the impact force modeling is modified so as that the elasto-plasticity of the material can be considered. This modeling can also consider the dependency of the restitution coefficient on the relative velocity. An impact damper which composed of a vessel and several particles made of elasto-plastic material such as lead is treated. The frequency response of the damper vessel and the damping effect of the damper are evaluated for the 2 kinds of impact force modeling by numerical simulations. Also, the effects of the particle number and the vessel configuration are evaluated. As a result, the effects of the above mentioned parameters are clarified.

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