Numerical modeling of friction stir welded aluminum joints under high rate loading

• We apply a nonlinear consistent finite element based method for predicting shear band formation.
• Fundamental impact analysis cases are investigated for friction stir welded aluminum joints.
• Results provide insight into the failure process and the effect of microstructure on response.
• Failure generally initiates at material zone interfaces rather than process-weakened areas.
• Results suggest the importance of manufacturing methods which minimize abrupt property changes.

Prediction of shear band formation and other strain localization processes presents many computational challenges that must be overcome to enable dynamic failure prediction and material design of ductile material systems. The current work presents a finite element based computational framework accounting for this critical deformation process, as applied to a detailed investigation of friction stir welded (FSW) aluminum joints. A stir welded joint has several zones, each with distinct microstructural characteristics and material properties. For applications in Army land vehicles, which may be subject to under-body blast, an understanding of the energy absorption capability of these joints is needed. Thus material inhomogeneity, dynamic loading, and detailed understanding of small scale failure processes must all be accounted for to accurately model FSW material behavior. In this study, an implicit nonlinear consistent (INC) or monolithic solution technique is used to predict shear band formation and estimate the energy absorption and failure strain of a stir welded aluminum joint. It has been shown that failure initiating at material interface regions can be predicted, and furthermore that abrupt material property gradients predominantly contribute to FSW joint failure.