Optimizing and selecting tool design of micro friction stir spot weld for corrugated sandwich panel applications

Abstract

Abstract Tool geometries and plunge depth play significant roles in the stirring process of micro friction stir spot weld (µFSSW). Those two variables affecting the hook and joint formation, which leads to the joint strength of a single spot weld. The present work investigates the influence of tool geometry and plunge depth on the weld's quality. Furthermore, the result from the investigation will be used for reference to optimize the tool's design in the future based on the joint strength characteristics. It is performed on a 0.42-mm-thick AA1100 lap-shear joint and investigates each tool's macrostructure and mechanical properties. There were seven tool designs and three plunge depth variations. The plunge depth was varied to determine the hook and joint formation evolution in each tool design using macrostructural studies and determine the best plunge depth for the highest tensile shear load. While the tool design variation investigates the influence of size and geometry on joint characteristics, finding the best geometry corresponds with the highest tensile shear load. Regression and prediction interval analysis is used for the tensile shear load (max. load). The result shows that the formation of a hook, such as a straight or bending shape, depends on the feature of the stir zone, which is affected by the tool's geometry. The hook shape and location would determine the possibility of crack propagation path and ultimately affect the max load.