Resistance Spot Welds (RSW):

RSW is the primary joining method for thin metal sheets and has been used in all passenger vehicles since mid-20 century.  It is however the weakest link under fatigue and crash conditions.  Working with steel and auto industries, we study the fabrication issue, fatigue life, and crash strength (i.e. strain rate effect) of the  RSW made of many grades of steels, e.g. mild steel, AHSS (Advanced High Strength Steels).   Investigations have focused on (1) failure mode, e.g. pullout vs interfacial failure, (2) prediction of static failure strength, (3) prediction of dynamic failure strength, (4) how to implement the test data into finite element numerical simulation, and (5) prediction of fatigue life of RSW.

Representative Publications

1. Chao, Y.J., “Ultimate Strength and Failure Mechanisms of Resistance Spot Weld Subjected to Tensile, Shear and Combined Tensile/Shear Loads,” ASME Journal of Engineering Materials and Technology, pp.125-132, vol. 125, 2003.

2. Chao, Y.J., “Failure of Spot Welds:  Interfacial versus Pullout,” Science and Technology of Welding and Joining, 133-137, 8(2), 2003.

3. Miller, K. W., Chao, Y.J., Martinez, A., Zhu, X., Liu, S. and Wang, P.C., “Quasi-static and Impact Strength of Fatigue Damaged Spot Welds,” in Welding and Joining, SP-1766, Editor: J. Pan,  SAE paper 2003-01-0610, paper presented at the SAE 2003 World Congress & Exhibition, March 3-6, 2003, Detroit, MI, USA.

4. .K. W. Miller, Y .J. Chao, and P. C. Wang, “A Comparison of Testing Techniques for Spot Weld Strength,” Proceedings of the Sheet Metal Welding Conference IX, paper 1-6, American Welding Society, Detroit, Michigan, October 18-20, 2000.

5.   Miller, K, W., Chao, Y.J., and Wang, P.C., “Strength of spot welded joints pairs as determined by layout,” Society of Automotive Engineering Paper #2000-01-2676, 2000 International Body Engineering Conference and Exposition, Cobo Center, Detroit, Michigan, October 2-5, 2000.