Bonding analysis of ultrasonic welded multi-wire joints with additional root gaps

This work presents four sets of welded multi-wires on Cu sheet (e.g., A-(95/95mm2), B-(35, 35, 25/35, 35, 25 mm2), C-(50, 35, 10/50, 35, 10 mm2), D-(35, 35, 25/50, 35, 10 mm2)) using ultrasonic wire harness welding (USWW). Forming quality of multi-wire joint, examination of microstructures, root gaps influence, fractographic analysis and surface micro-topography were investigated and clarified. Tensile strength and microhardness of samples in B-(35, 35, 25/35, 35, 25 mm2) increases up to peak load (6527.7 N and 484.5 HV) under welding energy of 1000 J. Tensile strength of B-(35, 35, 25/35, 35, 25 mm2/(6527.7 N)) is 29.2 % higher than A-(95/ 95mm2/(3681 N)) under effect of root gap. Maximum hardness of Cu plate in group B was obtained 484.5HV and maximum hardness of sample reached 363.2HV and 251HV in group C and A respectively. Stability of sample in group B is generally increased by 20.5 % compared to A3, C5 and D2. Failure displacement of joint A3 is 35 % higher than joint B1. Failure displacement of joint C5 is 15 % higher than joint D2. EDS analysis experienced Cu content at welded interface is higher compared to rest of locations which generates more fine grains structures to increase strength and weldability of joints. Kathmatic microscope investigated microtopographical features in group B sample wherein regular surface size was measured to be approximately 10 mu m. A standard root gap allows welded sheet to penetrate amid multi-wires being joined tightly and ensures a strong bond in group B.