Process robustness and strength analysis of multi-layered dissimilar joints using ultrasonic metal welding

Abstract

This paper investigates the effects of process parameters on the joint strength and process robustness when multi-layered joints of dissimilar metals are produced by ultrasonic metal welding (UMW). Three layers of 0.3-mm aluminium sheet are welded with a single 1.0-mm copper sheet which is representative of electric vehicle battery interconnects. A process robustness study in which welding pressure, amplitude of vibration and welding time are varied to produce satisfactory welds is reported. The weld quality is evaluated by performing lap shear and T-peel tests where maximum loads are considered as the quality indicator. Response surfaces are developed to identify the relationship and sensitivity between the input process parameters and output quality indicators. A feasible weldability zone is defined for the first time by identifying the under-weld, good-weld and over-weld conditions based on load-displacement curves and corresponding failure modes. Relying on the weldability zone and response surfaces, multi-objective optimisation is performed to obtain maximum lap shear and T-peel strength which resulted in Pareto frontier or trade-off curve between both objectives. An optimal joint is selected from the Pareto front which is verified and validated by performing confirmation experiments, and further, used for T-peel strength analysis of different interfaces of the multi-layered joint. To conclude, this paper determines both the optimal weld parameters and the robust operating range.

Weldability and shear strength feasibility study for automotive electric vehicle battery tab interconnects

“…3. Ultrasonic energy is used to produce oscillating shear to create solid-state bonds between two sheets clamped under pressure [13,14]. UMW is considered to be the best process when welding multiple thin sheets and dissimilar materials that typically produce brittle alloys at the weld area [15,16].…”

Microstructure and Mechanical Properties of Resistance Heat-Assisted High-Power Ultrasonic Dissimilar Welded Cu/Al Joint

“…During HPUSW of dissimilar joints, the thickness of the IMC layer determines the welding quality [20,21]. Figure 6a,b show backscattered images of the RUSW joint at tw = 0.2 s, FN = 1975 N, and HPUSW joint at tw = 0.5 s, FN = 1575 N, respectively.…”

Comparison of Tab-To-Busbar Ultrasonic Joints for Electric Vehicle Li-Ion Battery Applications

“…One of the widely accepted joining methods to connect the pouch cell tab to the busbar is ultrasonic metal welding (UMW) due to several advantages, including joining of dissimilar materials of varying thickness, joining of highly reflective and conductive material, multiple stack-ups and low thermal input during the welding [6,13]. Li-ion battery packs for General Motors' (GM) Chevy Volt and the Nissan LEAF are currently being manufactured using UMW where the pouch cell tabs are connected with busbars [6,14].…”

“…Li-ion battery packs for General Motors' (GM) Chevy Volt and the Nissan LEAF are currently being manufactured using UMW where the pouch cell tabs are connected with busbars [6,14]. Research has been conducted on understanding the ultrasonic metal welding joining mechanism [15][16][17][18], microstructure and material properties [19][20][21], thin to thick material joining (i.e., varying stack-ups) [22], process robustness and optimisation [13,23,24], and mechanical and vibrational behaviours of the welded joints [25,26], which are reported in the literature. In spite of UMW's extensive use and wide research, there are a few critical areas which are yet to be addressed, including electrical resistance and thermal behaviour of the joint.…”