Lifetime prediction of multiaxially loaded rubber springs and bushings

This work presents a proposal on how to predict the lifetime of a multiaxially loaded rubber part made of natural rubber. Two different methods for a lifetime prediction are described. One method is based on fracture mechanics while the other one on a local approach. Two criteria for fatigue calculation are presented, which show a good correlation to the fatigue. A procedure based on a local approach using the maximum principal Cauchy-stress as criterion for fatigue is presented. It is shown that a new method can reduce the number of tests necessary to measure the fatigue strength of a material. It was found, that fatigue in tension and compression can be calculated separately. To compare the internal loads with the fatigue strength of the material a linear cumulative damage rule, based on Miner’s-rule, is used. A procedure is shown which considers each region of a rubber part to conduct a reliable lifetime prediction.