Influence of Residual Stress on Fatigue Weak Areas and Simulation Analysis on Fatigue Properties Based on Continuous Performance of FSW Joints

Abstract

The fatigue weak area of aluminum alloy for a friction stir-welded joint is investigated based on the hardness profile, the residual stress measurement and the simulation analysis of fatigue property. The maximum residual stresses appeared at the heat-affected zone of the joint in the fatigue damage process, which was consistent with the fracture location of the fatigue specimen. The fatigue joint model of continuous performance is established ignoring the original negative residual stress; considering that it will be relaxed soon when the joint is under tension-tension cyclic loading. The fatigue parameters of joint model is based on the static mechanical properties of the joint that obtained from the micro-tensile tests and four-point correlation method. The predicted results for the fatigue weak locations and fatigue lives based on the continuous performance joint model are closer to the fatigue experimental results by comparison with the simulation results of the partitioned performance joint model.

A Comparative Study on Fatigue Response of Aluminum Alloy Friction Stir Welded Joints at Various Post-Processing and Treatments

“…These stresses, however, altered during loading cycles and affected fatigue strength noticeably [19]. Sun et al [34] showed that the residual stresses induced by the FSW operation, especially those appeared in the upper surface over cyclic process, impacted fatigue and cracking. The STA heat treatment as a post-processing step on the aluminum welded joint noticeably reduced tensile residual stresses due to the welding process and formed a more uniform microstructure within the HAZ.…”

Methodology for Evaluation of Residual Stress Effect on Small Corner-Crack Initiation and Growth

“…It can significantly impact the fatigue lifetime of a structure. Compressive residual stress increases fatigue lifetime by delaying crack growth, and tensile residual stress reduces fatigue lifetime by expediting crack initiation and propagation [1,2]. To accurately estimate the fatigue lifetime, therefore, the residual stress needs to be evaluated correctly.…”