Interference-fit joining of Cu-SS composite tubes by electromagnetic crimping for different surface profiles

Abstract

This paper explores the possibility of producing an improved interference-fit tubular joint between pure copper and stainless steel tube by electromagnetic crimping (EMC). Successful joints are obtained with optimal parameters consisting of the outer surface profile of the inner tube and discharge energy. Joints exceeding the strength of the parent tube are formed without any metallic bond formation. Three destructive testings, namely, pull-out, compression and torsion tests, have confirmed the successful joint formation as the failure occurs in the copper base tube. Analysis of failure mechanisms has revealed joint behaviour at various discharge energies and surface profiles. Among smooth, knurled and threaded surface profiles with different discharge energy levels, knurled surface provides best joint strength at 6.2 kJ, which has shown a failure in the parent Cu tube during all three destructive testings. Radial deformation of the tubes is measured and compared for different discharge energy and surface profile. No metallic bond formation and the wavy interface are observed between the joining partners during microstructural analysis. Furthermore, no elemental overlapping is observed during energy dispersive spectroscopy mapping analysis indicating an absence of diffusion. Higher micro-hardness is observed near the Cu-SS tubular joint interface due to strain hardening caused by high-velocity impact.