A non-linear damage accumulation fatigue model for predicting strain life at variable amplitude loadings based on constant amplitude fatigue data

摘要

A new phenomenological technique for using constant amplitude loading data topredict fatigue life from a variable amplitude strain history is presented. Acritical feature of this reversal-by-reversal model is that the damageaccumulation is inherently non-linear. The damage for a reversal in thevariable amplitude loading history is predicted by approximating that theaccumulated damage comes from a constant amplitude loading that has the strainrange of the particular variable amplitude reversal. A key feature of thisapproach is that overloads at the beginning of the strain history have a moresubstantial impact on the total lifetime than overloads applied toward the endof the cycle life. This technique effectively incorporates the strain historyin the damage prediction and has the advantage over other methods in that thereare no fitting parameters that require substantial experimental data. The modelpresented here is validated using experimental variable amplitude fatigue datafor three different metals.