Experimental and numerical investigations of low cycle fatigue behavior of cryorolled AA 5754

Abstract

The objective of the present work is to study the influence of cryogenic forming on low cycle fatigue (LCF) properties of Al-Mg (AA 5754) alloy. AA 5754 is rolled at liquid nitrogen temperature (cryorolling) for maximum of 40% thickness reduction. Post-annealing heat treatment (PAHT) at 250oC for 2 hours is adopted to enhance the mechanical and fatigue properties of the cryorolled alloy. A series of uniaxial strain controlled LCF tests are executed at three different strain amplitudes from 0.4% to 0.6% for cryorolled (CR) and annealed cryorolled (ACR) AA 5754 alloy. PAHT significantly improves the tensile strength as well as ductility of CR alloys. LCF tests reveal that cryorolled alloys show mild hardening in the initial cycles followed by noticeable cyclic softening at all strain amplitudes. In contrast, only cyclic hardening behavior is depicted by ACR specimens at all strain amplitudes. The extended finite element method (XFEM) has been utilized to simulate the tensile behavior of the specimen. Finite Element Method (FEM) coupled with Chaboche kinematic hardening cyclic plasticity model is used for simulating hysteresis loop obtained during LCF test. The present study exhibits good match between simulations and experimental results.