Proofs and Contradictions for Wave Formation Theories in Collision Welding

Abstract

Joining processes initiated by collisions provide several advantages in comparison to conventional welding techniques. Although collision welding is already used industrially, some effects during the bond formation, like the occurrence of waves in the interface, have not been fully understood, yet. In order to describe these effects, a number of theories have been developed that can be divided into three categories by the governing mechanism: 1) indentation theory 2) stress wave theory and 3) fluid theories. However, none of these theories has so far been conclusively proved or disproved. A unique test rig allows specifically targeted examinations of the wave formation and the transition region from straight to wavy interface as well as the evolution of the waves. Within the presented investigation, the kinetic energy and the hardness as process and material parameters have been examined regarding their influence to wave formation. For a specific investigation of the overall deformation of the bond zone a parameter, bond length elongation Φ, was introduced to connect wave length and wave amplitude. The results of the experiments provide arguments for wave formation being caused by both stress waves and fluidic effects.