Fatigue life prediction using critical distance on aluminum alloy wire containing indentation produced marks

Abstract

The present study aims to predict fatigue life in aluminum alloy 6201-T81 wires containing defects produced by hardness indentation procedures. The wires tested were obtained from a 900 MCM All Aluminum Alloy Conductor (AAAC 900 MCM) used in power transmission lines. The stress field in the vicinity of the defect and the determination of the crack initiation site (hotspot) were obtained by applying elastic–plastic simulations via the Finite Element Method (FEM). Such a simulation considered both the indentation process, and the fatigue loading on the wire. The Smith-Watson-Topper multiaxial fatigue criterion applied to an equivalent stress computed by the Volume Method (MV) was used to estimate life. Challenges presented by the incorporation of the residual stress field and the choice of the best calibration procedures were addressed. Comparison between stress gradients in simulations and failures observed in fractographic analyses of specimens subjected to fatigue testing suggested similar potential crack propagation regions. A new and wide experimental campaign showed that presence of indentation defects reduced the fatigue life of the wires. 84% of the lives computed by the proposed methodology were within a factor of 3 compared with tests, being the worst estimate within a factor of 5 .