Efficient Procedure for Measuring Cyclic Softening in an Elastomer

Rubber component durability is sometimes limited not by crack growth, but rather by the loss of stiffness that can occur under cyclic loading. We present here an experiment useful for characterizing how stiffness loss rate depends on strain. The procedure is run in strain control on a simple tension strip, using a series of progressively increasing strain levels, each specified so as to produce roughly equal amounts of damage. The level and duration of each step in the series are selected such that a single test specimen can be used to extract a family of softening curves. The measurement obtains the basic information needed to represent softening effects in a finite element analysis.