Thermomechanical Numerical Simulation Of Friction Stir Welding

There have been significant experimental investigations into friction stir welding (FSW) of different materials ever since its invention in the beginning of 1990's, but computational modeling efforts to simulate the welding process are more recent. Because FSW is a complicated process which involves in such four interactive factors as temperature variation, microstructure transformation, strain and metal flow, only numerical simulation can be adaptively used to understand its mechanism.In this thesis, temperature and residual stress field in FS welded plate was calculated by ANSYS code. The transient temperature distribution, three-dimensional residual stress distribution and welds' distortion were analyzed. It was shown that the calculated results were in good accordance with the experiments.To eliminate the flaw associated with conventional friction based heat generation model, an input-torque based heat generation model was proposed by considering the characteristic of FSW process and other researchers' work. This novel approach was formulated in a three-dimensional finite model and implemented for 8mm thick 7075-T7351 alloy to successfully predict the temperature distributions during FSW process. Excellent agreement between the calculated temperature profiles and experimental data demonstrated the functionality of the model. An attempt had been made to simulate residual stress distribution in FS welded plate by sequentially coupling the thermal histories developed by the thesis into a mechanical model. The characteristic and distribution of residual stress was analyzed. Compare of calculated value and experimental data demonstrated the functionality of the thermomechanical model.