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Research Papers

Dynamic Response of Battery Tabs Under Ultrasonic Welding

[+] Author and Article Information
Bongsu Kang

Engineering Department,
Indiana University—Purdue University,
Fort Wayne, Fort Wayne, IN 46805-1499
e-mail: kang@engr.ipfw.edu

Wayne Cai

Advanced Propulsion Manufacturing
Research Group,
Manufacturing Systems Research Lab,
General Motors Global R&D Center,
Warren, MI 48090-9055
e-mail: wayne.cai@gm.com

Chin-An Tan

Mechanical Engineering Department,
Wayne State University,
Detroit, MI 48202
e-mail: tan@wayne.edu

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the Journal of Manufacturing Science and Engineering. Manuscript received August 29, 2012; final manuscript received May 7, 2013; published online September 13, 2013. Assoc. Editor: Robert Landers.

J. Manuf. Sci. Eng 135(5), 051013 (Sep 13, 2013) (11 pages) Paper No: MANU-12-1257; doi: 10.1115/1.4024535 History: Received August 29, 2012; Revised May 07, 2013

Ultrasonic metal welding (USMW) for battery tabs must be performed with 100% reliability in battery pack manufacturing as the failure of a single weld essentially results in a battery that is inoperative or cannot deliver the required power due to the electrical short caused by the failed weld. In ultrasonic metal welding processes, high-frequency ultrasonic energy is used to generate an oscillating shear force (sonotrode force) at the interface between a sonotrode and few metal sheets to produce solid-state bonds between the sheets clamped under a normal force. These forces, which influence the power needed to produce the weld and the weld quality, strongly depend on the mechanical and structural properties of the weld parts and fixtures in addition to various welding process parameters, such as weld frequencies and amplitudes. In this work, the effect of structural vibration of the battery tab on the required sonotrode force during ultrasonic welding is studied by applying a longitudinal vibration model for the battery tab. It is found that the sonotrode force is greatly influenced by the kinetic properties, quantified by the equivalent mass, equivalent stiffness, and equivalent viscous damping, of the battery tab and cell pouch interface. This study provides a fundamental understanding of battery tab dynamics during ultrasonic welding and its effect on weld quality, and thus provides a guideline for design and welding of battery tabs from tab dynamics point of view.

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References

Figures

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Fig. 1

Schematic of the weld unit and ultrasonic welding setup

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Fig. 2

Thin bar with co-ordinate x and displacement u

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Fig. 3

Schematic of the battery cell assembly (with the cell pouch partially shown)

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Fig. 5

Wavenumber loci of the first six longitudinal vibration modes, k∧eq = 5.23 × 10-3

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Fig. 6

Longitudinal natural frequency loci up to 400 kHz. L = 20 mm and keq = 150 kN/m for (a) aluminum and (b) copper tabs. The dashed line represents the current ultrasonic welding frequency Ω.

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Fig. 7

Axial stress distribution in the tab due to longitudinal vibration of the tab with keq = 150 kN/m for (a) aluminum and (b) copper tabs, where L1 = 20 mm and the numbers indicate meq in grams

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Fig. 8

Tab-end force as a function of the weld spot location with keq = 150 kN/m for (a) aluminum and (b) copper tabs, where the total length of the tab is L = 20 mm and the numbers indicate meq in grams

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Fig. 9

Tab-end force as a function of the weld spot location, where the total length of the tab is L = 20 mm. The numbers indicate ceq in (Ns/m). (a) Aluminum tab, C-bend, keq = 105 kN/m, and meq = 0.0063 g and (b) copper tab, C-bend, keq = 147 kN/m, and meq = 0.012 g.

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Fig. 10

Energy dissipation per cycle by the equivalent viscous damper at the tab-end, as a function of tab length L1. The numbers indicate ceq in (Ns/m). (a) Aluminum tab, C-bend, keq = 105 kN/m, and meq = 0.0063 g and (b) copper tab, C-bend, keq = 147 kN/m, and meq = 0.012 g.

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Fig. 11

Experimental setup for measurement of the equivalent mass of the tab-end. (a) Experimental setup and (b) equivalent 2-DOF system.

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Fig. 12

Velocity (X·45 deg) of the dummy mass for Al-tab for (a) C-bend and (b) S-bend

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Fig. 13

Velocity (X·45 deg) of the dummy mass for Cu-tab for (a) C-bend and (b) S-bend

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Fig. 14

Axial stress distribution due to longitudinal vibration of the tab, where L1 = 20 mm

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Fig. 15

Tab-end force versus weld spot location, where the total length of the tab is L = 23 mm

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