Abstract
It is well known that two metallic plates are bonded momentarily at a high velocity impact. It is guessed that the plastic work occurring on the contacting surface is converted into heat so that the bonding proceeds due to the heat. Although this phenomenon is observed on an explosive welding, it is considered that the bonding mechanism of the dynamic compaction is also the same. The exposive welding and the dynamic compaction have been already used industrially. However, the bonding mechanism is not clarified sufficiently.
The aim of this paper is to investigate the formation of bonding area at the impact welding using a longitudinal impact test. In the longitudinal impact test, a projectile accelerated by a gas gun collides with a target so that the welding occurs at the interface between two metals. The material used for the projectile is a commercial pure aluminum and the target materials are mild steel, copper and stainless steel. The bonding area is observed using a scanning acoustic tomograph and the bonding strength is examined by a quasi-static tension test. Additionally, the profile of the crater on the target after impact is also measured.
It appears that the formation of the bonding area is dependent on the deformation processes of the projectile and the target, as indicated by the following results. The radial deformation of the impact face of the projectile is very restricted by the friction force at the interface or the deformation of the target so that the bulging accompanied with the folding of the projectile side occurs and the mushrooming profile appears after impact. Although a few areas considered to be bonding ones are found from an ultrasonic image after the bonding, the bonding force of the central part is much stronger than that of the other parts. Subsequently, it is presumed that the bonding mechanism of the copper target differs from those of the other targets.
