Modelling of the inertia welding of Inconel 718

Abstract

In this study, the inertia welding process was studied by both an FEM model and three analytical models. The thermal analysis shows that there is a steep temperature gradient near the mating surface, which is the cause for the existence of a band of high hydrostatic stress near the weld line. The holding effect of this high static stress is the reason for the presence of the very soft material at the welding interface. The models were used to predict the displacement of the weld line (upset) with a lambda model to describe the constitutive relation of IN718 at high temperature. The results from the different models are in broad agreement. The shear stress induced by friction at the interface is found to enlarge the upset value; its effect must be taken into account if the upset is to be predicted accurately. The extrusion of the burr during the last second of the welding is a direct result of the quick stop of the rotating part due to the balance of the momentum, which is clearly explained by the analytical mechanical model put forward in this work