Sample geometry and size effects on tensile properties of friction stir welded AA2024 joints

Dog-bone specimens with different geometries and sizes are commonly used to characterize the tensile behavior of friction stir welded (FSWed) joints. Here a significant effect of sample geometry/size on the tensile behavior of FSWed AA2024 joints was observed, caused by various ratios of weld width to gauge length of samples. The elongation drops sharply while the yield stress gradually increases with increasing the gage length from 12.5 to 25 mm. The ultimate tensile strength is independent on the sample geometry/size. A critical gauge length of about 2.5 times of tool shoulder diameter is proposed, e.g. 25 mm in this study for AA2024, which roughly equals to the transverse width across all the softened zones in the joint. Over this critical value there will be no sample geometry/size effect on the tensile properties of FSW joints.