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

TL;DR

This paper introduces a non-linear damage accumulation model for fatigue life prediction under variable amplitude loading, utilizing constant amplitude data without fitting parameters, validated across three metals.

Contribution

The paper presents a novel reversal-by-reversal damage model that inherently accounts for non-linear damage accumulation in fatigue life prediction.

Findings

Model accurately predicts fatigue life for variable amplitude loads.

Overloads early in the cycle have greater impact on fatigue life.

No extensive experimental fitting required for the model.

Abstract

A new phenomenological technique for using constant amplitude loading data to predict fatigue life from a variable amplitude strain history is presented. A critical feature of this reversal-by-reversal model is that the damage accumulation is inherently non-linear. The damage for a reversal in the variable amplitude loading history is predicted by approximating that the accumulated damage comes from a constant amplitude loading that has the strain range of the particular variable amplitude reversal. A key feature of this approach is that overloads at the beginning of the strain history have a more substantial impact on the total lifetime than overloads applied toward the end of the cycle life. This technique effectively incorporates the strain history in the damage prediction and has the advantage over other methods in that there are no fitting parameters that require substantial experimental data. The model presented here is validated using experimental variable amplitude fatigue data for three different metals.