Effect of Strain Load History on Fatigue Behaviour of the 7075-T651 Aluminium Alloy

Abstract

This paper aims to investigate the effect of strain-loading sequence on fatigue lifetime in the 7075-T651 aluminium alloy. In the first stage, a set of constant-amplitude fully reversed strain-controlled tests are performed to obtain the cyclic plastic properties used in most of the standard fatigue design approaches. In the second stage, two series of tests are conducted under different variable-amplitude loading conditions with non-zero mean strain. Experimental fatigue lives are then compared with those evaluated via the standard fatigue design approaches. The results show significant differences between experimental and predicted lives, which clearly demonstrates the need to account for, as accurate as possible, the mean stress relaxation rates and the cumulated fatigue damage.