Investigation on the Effect of Dimension on the Compression Mechanics of Metal Rubber

Abstract

Metal Rubber (MR) is an attractive porous material used in vibration absorbers within extremely harsh environments. It is in general acknowledged that the sliding friction existing at the contact points between individual wires dominates the damping performance of MR products, but few people concern the effects of the dimension of metal rubber on the mechanical characteristics including modulus and damping. In order to discover the influencing laws of initial height and initial bearing area of metal rubber on its properties, three batches of MR specimens were fabricated and a series of experiments were carried out. This study describes the manufacturing and testing of metal rubber (MR) samples made of stainless steel, and subjected to compression-compression loading in quasi-static regime. Three batches of MRs with different dimensions and similar relative density have been fabricated, and their mechanical properties (tangent modulus and loss factor) have been investigated and compared at different strains and under cyclic loading. The experiments show the significant effect of the MRs’ initial height and bearing area over the global mechanical compression properties, with the loss factor decreasing in samples with higher height and smaller bearing area, and the tangent modulus increasing with higher height. The phenomenon was explained by the MR spiral wire model, which employed MR’s boundary effect and different contact types of interaction. When a metal rubber sample is manufactured, the final process is to be formed in a specially designed mold by applying a compressive force, the MR is then shaped in the mold, and when the compressive force gradually decreases, the MR will rebound along molding direction, but restricted by the mold along the non-molding directions. This manufacturing process causes the different properties between the boundary and the inner part of the metal rubber solid, and the different contact types between individual wires contribute to the different properties. In this work, MR samples with different height were tested and compared, the results were consistent with the analysis that the boundary part along molding direction has more slip interaction, and samples with different bearing area were tested and compared to investigate the boundary effect along non-molding directions, the results were consistent with the analysis that this boundary part has more stick interaction. The results show that the dimension effect should be considered in the design of vibration dampers made with MR material, and we can control the mechanical properties of MR component by changing the size and combination form.