Fatigue analysis of friction stir welded butt joints under bending and tension load. (1st February 2019) - Ranjan, Rakesh
Graphical abstract: Highlights: Presented fatigue test results for friction stir welded aluminum joints in bending. Investigated the effect of misalignment on the fatigue life of FSW joints under tension loading. Showed that slight angular misalignment may results in non-conservative fatigue life estimates under tension loading. Predicted fatigue test results with nonlinear fracture mechanics (SBFM) model. Abstract: Friction stir welding is rapidly gaining attention for a wide range of structural applications as well as for innovations in improvement of the welding technique itself. Most of the study on friction stir welded joints has been done under uniaxial tensile loading without considering the presence of geometric or welding defects. Very few studies have been done to assess the fatigue strength of friction stir welded aluminum joints under bending load. Herein, the fatigue behavior of friction stir welded single-sided aluminum butt joints has been studied under bending and tension load through small-scale specimen testing and fracture mechanics analysis. The test results are compared with data available in the existing literature, as well as with standard design curves. The effect of angular misalignment on the fatigue life of welded joints is also studied. An analysis of the test results is performed using a strain-based fracture mechanics model. This study shows that the fatigue performance of the investigated friction stir welded joints is better than typical arc welded joints and top side of the weld has better fatigue performance as compared to the root or bottom side of the weld under bending load. It is shown that even a slight misalignment of the order of 0.5° can generate significant secondary stress, which – if ignored – can result in non-conservative fatigue life estimates under pure tension loading.