Determination of self-adaptive slip rate at tool/workpiece interface in numerical model of friction stir welding

Abstract

As a key parameter affecting the heat generation and the interface material velocity, the interface slip rate is a prerequisite for numerical simulation of friction stir welding of lightweight materials. The contact state on the tool/workpiece interface is related to friction stress and material yield strength, and a new calculation method of the self-adaptive interface slip rate was established. The interface velocity of material flow, heat generation due to friction and plastic deformation near the tool and temperature distribution were analyzed quantitatively. The calculated self-adaptive interface slip rate has a wider range than the previous used one, from a sticking dominant for the material near the inner part of the shoulder to a sliding dominant for the material near the edge of the shoulder. With application of this improved method determining the slip rate, the material flow velocity at the tool/workpiece interface is roughly in a "M" shape, which first increases and then decreases as the radial distance rises, and the maximum interfacial material velocity no longer appears at the shoulder edge. The experiments were made to validate the method. The slip rate distribution at tool/workpiece interface in (a) Previous mode; (b) Improved mode.