Effect of Fatigue Step Loading Sequence on Residual Strength

Abstract Miner's rule is often assumed to hold in accelerated fatigue tests. This rule implies that the order in which loads are applied is not significant. Whether particular loads are applied early in the test or later is unimportant; they are expected to cause the same amount of damage if they are imposed for the same number of cycles. In order to test this hypothesis, we have investigated the effect of loading sequence on residual strength using two levels of tensile strain and several representative rubber compounds. In all cases, a series of increasing strains was found to reduce the strength to a greater degree than the same strains applied in decreasing order. Thus, Miner's rule does not hold for the fatigue failure of these compounds. However, the relative rankings of the compounds remained the same in both step-up and step-down strain sequences.