Models for FSW forces using a square pin profile tool

Abstract

In this paper, mechanical models for FSW are developed for a square pin profile tool. The models express the oscillation of the forces over time and their mean values. The welding, transverse, radial, and tangential forces are modeled as a function of the rotational and welding speeds and the instantaneous angle of rotation. The models include the concept of a specific force, based on the mechanics of orthogonal cutting, to describe the relation between the forces and the area of the deformed material. Additionally, experimental measurements for the forces and torque are performed for different parameters to calibrate and validate the models. Due to the square profile of the tool pin, the welding, transverse, radial, and tangential experimental forces exhibit periodic variations along the tool advancing path. The maximum radial force occurs at 45° of the welding direction, and the mean welding and transverse forces present similar magnitudes in all experiments. The results show good agreement between the models and the experimental data with a correlation coefficient greater than 0.97. With increasing rotational speed, the torque decreases linearly, and the axial force is almost constant.