Analysis of friction stir welds using an inverse problem approach

A preliminary analysis of friction stir welds is presented using an inverse problem approach which entails representing the rotating tool as a three-dimensional surface distribution of heat sources. In this approach, the heat generated from these heat sources is proportional to the local velocity of the tool surface, but the resulting temperature field can be adjusted within this constraint so that the shapes of the calculated three-dimensional temperature isotherms are consistent with experimental weld cross-sections. In the present work, experimental information about the local mechanical properties and transformation microstructures observed in the heat affected zone is used to scale the calculated temperature field in a consistent manner. In addition, procedures are discussed which can extend this approach to include more complex aspects of friction stir welding and determine an absolute scale for the calculated temperature field.