Digital shearography approach for stress intensity factors calculation in friction stir welded nugget of AA2024 aluminum alloy

Abstract

The purpose of this paper is to calculate the stress intensity factor and fatigue life estimation in AA2024-T351 aluminum alloy welded specimens under uniaxial load with low-cycle fatigue, using digital shearography method. For this purpose, using optomechanical relations and failure mechanics concepts, the relationship between surface displacement derivatives and stress intensity factors in uniaxial loading mode is extracted analytically. To prove the validity of the model results, numerical and experimental studies have been performed on compact tension (CT) specimens that have been welded using friction stir welding (FSW) method. First, friction stir welding with different welding speeds was performed on AA2024-T351 aluminum alloy specimens. Then CT specimens were prepared and after setting the overlay arrangement, CT specimens were subjected to uniaxial loading with low-cycle fatigue. Then, by preparing images of the specimen surface while loading and processing these images, the field of surface displacement derivatives and stress intensity factors near the crack tip are extracted simultaneously. The difference between the test results and the digital shearography method indicates the appropriate ability of this optical method to calculate the stress intensity factors.