Shock effects on the upper limit of the collision weld process window

Abstract

The maximum flyer impact velocity based on a dynamic solidification cracking mechanism is proposed to describe the upper limit of collision welding process windows. Thus, the upper limit of the weld window is governed by the evolution of dynamic stresses and temperatures at the weld interface. Current formulations for the upper limit of the collision weld window assume that both the flyer and target are made of the same material and approximate stress propagation velocities using the acoustic velocity or the shear wave velocity of the weld material. However, collision welding fundamentally depends on the impacts that generate shockwaves in weld members, which can dominate the stress propagation velocities in thin weld sections. Therefore, this study proposes an alternative weld window upper limit that approximates stress propagation using shock velocities calculated from modified 1-D Rankine-Hugoniot relations. The shock upper limit is validated against the experimental and simulation data in the collision welding literature, and offers a design tool to rapidly predict more accurate optimal collision weld process limits for similar and dissimilar weld couples compared to existing models without the cost or complexity of high-fidelity simulations.