Effect of ratcheting fatigue damage on the evolution of tensile properties of Al–Mg alloy

Abstract

This work aims to investigate the effect of damage accumulation on the evolution of tensile properties due to prior ratcheting fatigue in as-received and artificially aged conditions of Al–Mg alloy (AA 5754). Uniaxial asymmetric stress controlled tests for various combinations of mean stress and stress amplitude are performed at room temperature. Progressive degradation in the mechanical properties of structures and machines subjected to cyclic loading during service period can affect the structural integrity. In view of this, ratcheting fatigue tests are interrupted at various life fractions for particular mean stress and stress amplitude followed by tensile tests to understand the damage evolution during ratcheting for both conditions of alloy. Also, the effect of mean stress and stress amplitude on the post ratcheting tensile behaviour is analysed by conducting the ratcheting tests up to 150 cycles. Cyclic hardening is exhibited in the initial cycles followed by saturation for both as-received and artificially aged alloy. Ratcheting strain increases with the increase in both mean stress and stress amplitude. Drastic changes in tensile properties are noticed with ratcheting fatigue damage evolution for both conditions of alloy. The evolution of tensile properties due to prior loading history such as ratcheting fatigue can provide fundamental understanding in the design of structural components.