Simulation of Wave and Jet Formations in Explosive/Impact Welding

Explosively driven impact welding is a process to produce bi-metallic plates and tubes. Whilst well established it has been essentially an empirical process. Recent work to numerically analyse part of the process is described. Using a finite difference engineering package, the oblique impact of a thin flyer plate on a relatively thick base was modelled. The results were validated by data from carefully controlled experiments using a pneumatic gun. Straight and wavy interfaces and jetting phenomena were modelled, and the magnitude of the waves and the velocity of jet predicted. The numerical analysis predicted a hump ahead of the collision point. Wave formation appears to be the result of variations in the velocity distribution at the collision point and periodic disturbances of the materials. Higher values of plastic strain were predicted in wavy interfaces. Bonding was found to be a solid state welding process. Phase changes which occur may be due to high temperatures (but less than the melting temperature) at the collision point.