Mechanical joining behavior of Cu-Fe dissimilar metallic foils in laser shock clinching

Laser shock clinching is a novel joining method derived from laser shock forming in which the metal foil is plastically deformed under the pulsed laser induced shock wave, and then two or more metal foils can be joined together based on plastic deformation. However, the present researches are less concerned with the mechanical joining behavior of metal foils during incremental impacts of multiple laser pulses. In the present study, the mechanical joining behavior of pure copper foil and pre-pierced stainless steel sheet in laser shock clinching was investigated. A finite element model was established to analyze the material flowing and clinching behavior of metal foils under multiple laser pulses. Based on the validated model, the deformation stages, thickness change, and shock wave propagation features were studied. The temperature rise during clinching was assessed considering both the compression by shock wave and plastic deformation at high strain rates. It is revealed that the laser shock clinching process can be divided into three deformation stages, that is, free bulging forming, radial expansion, and formation of interlock. Both experimental and numerical results prove that the formation of clinched joints relies on the plastic deformation of the joining partner I. The thinnest region of the joint locates at the material of the joining partner I in contact with the upper corner of the joining partner II. In addition, there is no obvious influence of temperature increase on the mechanical properties of joining partners. Moreover, the shock wave propagation characteristics along axial direction and the influence of laser power density on interlock value and thickness distribution were also discussed.