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Research Papers

Analysis of Weld Formation in Multilayer Ultrasonic Metal Welding Using High-Speed Images

[+] Author and Article Information
S. Shawn Lee, Tae Hyung Kim, S. Jack Hu

Department of Mechanical Engineering,
University of Michigan,
Ann Arbor, MI 48109

Wayne W. Cai, Jeffrey A. Abell

Manufacturing Systems Research Lab,
General Motors R&D Center,
Warren, MI 48090

1Present address: Hyundai Motor Company, Hwaseong-si, Gyeonggi-do 445-706, Korea.

2Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received September 20, 2014; final manuscript received February 1, 2015; published online March 5, 2015. Assoc. Editor: Hongqiang Chen.

J. Manuf. Sci. Eng 137(3), 031016 (Jun 01, 2015) (8 pages) Paper No: MANU-14-1485; doi: 10.1115/1.4029787 History: Received September 20, 2014; Revised February 01, 2015; Online March 05, 2015

One of the major challenges in manufacturing automotive lithium-ion batteries and battery packs is to achieve consistent weld quality in joining multiple layers of dissimilar materials. While most fusion welding processes face difficulties in such joining, ultrasonic welding stands out as the ideal method. However, inconsistency of weld quality still exists because of limited knowledge on the weld formation through the multiple interfaces. This study aims to establish real-time phenomenological observation on the multilayer ultrasonic welding process by analyzing the vibration behavior of metal layers. Such behavior is characterized by a direct measurement of the lateral displacement of each metal layer using high-speed images. Two different weld tools are used in order to investigate the effect of tool geometry on the weld formation mechanism and the overall joint quality. A series of microscopies and bond density measurements is carried out to validate the observations and hypotheses of those phenomena in multilayer ultrasonic welding. The results of this study enhance the understanding of the ultrasonic welding process of multiple metal sheets and provide insights for optimum tool design to improve the quality of multilayer joints.

Copyright © 2015 by ASME
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Figures

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Fig. 1

Ultrasonic metal welding system

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Fig. 2

High-speed camera setup: (a) entire view of setup; (b) focused view on welding part; and (c) workpiece in PC screen view

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Fig. 3

Schematic of high-speed camera setup: (a) workpiece stack-up aligned with horn (side view); and (b) displacement measurement of metal layer (front view)

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Fig. 4

Two anvil knurl and the dimensions

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Fig. 5

T-peel test for multijoint welds

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Fig. 6

Example of displacement variation in one weld cycle (50 μs): (a) consecutive high-speed images showing single vibration cycle of a metal layer; (b) an illustration of displacement curve measured from (a)

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Fig. 7

Development of vibration cycles of multiple layers with the fine anvil: (a) 0.005 s; (b) 0.020 s; (c) 0.040 s; (d) 0.060 s; (e) 0.080 s; and (f) 0.100 s weld time

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Fig. 8

Progress of vibration amplitude of horn and four metal layers during initial stages (0–0.1 s) of welding process when using (a) fine anvil; and (b) coarse anvil

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Fig. 9

Progress of vibration amplitude of horn and four metal layers during the entire welding process when using (a) fine anvil; and (b) coarse anvil

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Fig. 10

Progress of relative displacement between metal layers during initial stages (0–0.1 s) of welding process when using (a) fine anvil; and (b) coarse anvil

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Fig. 11

Progress of vibration amplitude of the fourth layer (anvil side) during the entire welding process with different anvil knurl

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Fig. 12

Micrographs of cross-sectioned weld samples produced with a fine anvil type for: (a) 0.2 s, (b) 0.3 s, (c) 0.4 s, and (d) 0.5 s

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Fig. 13

Micrographs of cross-sectioned weld samples produced with a coarse anvil for: (a) 0.2 s, (b) 0.3 s, (c) 0.4 s, and (d) 0.5 s

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Fig. 14

Bond density development at multiple weld interfaces for different anvil knurl

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Fig. 15

Mechanical performance of multiple joints (three weld interfaces) obtained by T-peel test for: (a) fine anvil type; and (b) coarse anvil type

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