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.
Highlights
Ultrasonic metal welding (UMW) is an effective welding process for both similar and dissimilar materials [1, 2], especially for thin material [3, 4] in various industrial applications including electronics, electrical, automotive [5,6,7], and aerospace [8] industries
To establish UMW quality and robust process parameter ranges for multi-layer dissimilar material joints, this paper focuses on an experimental investigation based on three layers of Al welded with a single Cu sheet
A process robustness and shear strength analysis were conducted for ultrasonic metal welding considering multi-layered dissimilar materials
Summary
Ultrasonic metal welding (UMW) is an effective welding process for both similar and dissimilar materials [1, 2], especially for thin material [3, 4] in various industrial applications including electronics, electrical, automotive [5,6,7], and aerospace [8] industries. Large joint areas and excellent joint strength are required to support high power application as automotive vehicles are often exposed to adverse thermal and impulse conditions [7] Making these tab joints involves several challenges, including joining of thin multiple stack-ups of dissimilar materials, highly conductive and reflective surfaces, mechanical/vibrational or thermal damage during joining, and joint durability [13]. Dynamic stress analysis, vibrational energy loss or simulations for understanding the ultrasonic welding considering multiple layers were reported in literature [37,38,39,40] Despite these studies which have been conducted on UMW, to understand its fundamental behaviours, there exists a lack of quality guidelines for implementing the UMW into volume production for joining multi-layers of dissimilar materials.
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