George Robert Cowan

Mechanism of bond zone wave formation in explosion-clad metals

Results of experiments in which the collision variables were carefully controlled showed that bond zone wave formation during explosion cladding is analogous to the formation of vortex streets in fluid flow around an obstacle or in the collision of liquid streams. The fluid flow analogy explains the observed transition from a smooth metal-to-metal bond zone to a wavy bond zone above a critical collision velocity. This model is capable of predicting the minimum collision velocity necessary for bond zone wave formation in different metal systems and it also predicts correctly the strong dependence of wave size on collision angle. The magnitude of the wave size agrees with that predicted from fluid flow past a flat plate. Two other mechanisms of bond zone wave formation were explored experimentally and found to be invalid.

Flow Configurations in Colliding Plates: Explosive Bonding

The collision of plates at high velocity sometimes causes them to be metallurgically bonded. A study has been made of the nature of the bonds and of the conditions required to produce bonding. A necessary requirement is the formation of a jet in the space ahead of the region of impact. When the collision region moves along the plates at a velocity which exceeds the bulk sound velocity of both materials, the relative velocity of the plates must exceed a critical value for jetting. Clarification of these critical conditions in symmetric collisions, and a correct extension to asymmetric collisions have been obtained by consideration of the effect of downstream boundary conditions on the configuration of the shock waves attached to the collision line in the jetless case. When the velocity of the collision is subsonic, bonding is obtained when the elastic strength of the material is exceeded. Metallographic examination shows that three types of bond may be formed: (1) a direct bond, (2) a uniform layer of soli...