Development and modification of the thermal model of the friction stir welding process with an eccentric pin

Friction stir welding (FSW) is one of the solid state bonding methods. One of the influential factors in the mechanical and metallurgical properties of the final joint is the tool shape, which, with its proper design, can ultimately achieve optimal joint quality. Among the improvements and modifications to improve the mechanical properties of the final joint is the out-centering of the tool pin against the tool shoulder. Off centering the pin will cause the heat generated in the larger area to be distributed and the volume of the deformed material will increase with the eccentric tool pin. In the present study, the development of a thermal model for tool with an out of center pin has been addressed. The modified model is a function of the temperature dependent friction coefficient and the temperature dependent yield stress, in which the effect of key parameters on the amount of heat generated in the FSW process is considered. In order to validate the developed model, three-dimensional simulation using ABAQUS package and two subroutines of USDFLD and DFLUX have been used. The results of the temperature distribution of the developed model have been compared with the experimental and analytical results of previous studies. Based on the results, the present thermal model with high precision is able to predict the maximum temperature and temperature distribution in the FSW process with an out of center tool pin.