Influence of Workpiece Mating Gap on Friction Stir Welding of 316L for Fixture Design on a Machine

Abstract

The low shrinkage and less residual stress during friction stir welding (FWS) process makes it more advantageous compared to other welding processes, especially for the aerospace application materials. The weldments strength and mechanical properties are function of various input parameters such as tool pin diameter, spindle speed, traverse velocity, advancing and retracing angle of tool. The workpiece mismatch and workpiece mating gap are inherent process variation because of welding process setup. The workpiece mating gap also has a significant influence on the weldment strength. The understanding of workpiece mating gap on the temperature distribution in weldment can help in achieving the desired strength. This understanding of gap is very critical for designing a fixture for a friction welding machine. The design for fixture must have high rigidity to avoid the large variation in workpiece mating gap during the friction welding process. Consequently, the present work studies the effect of workpiece mating gap on temperature generation and distribution in welding zone by carrying out the modelling of friction welding process. The workpiece mating gap has been introduced in the finite element modelling of the friction welding process. The mating gap between the plates is considered as a percentage of tool pin diameter, varying from 0 to 25%. The heat generation in friction welding process is due to friction between the tool and the workpiece and hence, a varying contact frictional coefficient has been used in the present work for contact modelling. Stress generation and distribution is also studied and correlated with the input parameters. The simulation has been carried out with Tungsten Carbide as the tool with a rotational speed of 1250 rpm and 60 mm/min as linear velocity and this was kept constant for all the gap widths.