2.4.2. Mechanical Boundary Condition

All degrees of freedom of the workpiece are constrained to prevent rigid displacement and rotation of the workpiece during welding. Therefore, the velocity in the z direction of the bottom surface of the workpiece is defined to be 0. The velocity in x and y directions on the side of the workpiece is 0. The tool is defined to rotate around the z-axis in the positive direction—that is, counter-clockwise. When the welding is at the plunging stage, the speed of the tool is along the z-axis. The speed of the tool is in the x-direction during welding.
