Analysis of Residual Stress on FSW AA 6061 Using Hole-Drilling with ESPI for HFMI Treated Condition
Tensile residual stress in friction stir welded (FSW) Aluminum alloy joints is well known to be detrimental to fatigue resistance properties of joints imperiled to dynamic loading. Hence, it is important to translate the prevailing tensile residual stress to a more favorable compressive residual stress to enhance the fatigue life cycle of the welded joints. In this study, the longitudinal and transverse residual stress for FSW AA 6061 joints is measured using the hole-drilling method with electronic speckle pattern interferometry (ESPI) for various conditions. This method combines the tried-and-true hole-drilling method with digital imaging and ESPI, eliminating the application of a strain gage through stress depth profile measurements by incremental drilling. The residual stress is measured for the FSW as-welded and high frequency mechanical impact/pneumatic impact treatment (HFMI/PIT)-treated conditions.