Methodology for Testing of Spot-Welded Steel Connections Under Static and Impact Loadings

Spot-welds are the primary joining methods for steel sheet metals used in the manufacturing of automobile body structure. Often the impact responses are significantly affected by the characteristic properties, such as stiffness, failure strength, etc of spot-welds. In view of this, understanding the behavior and the properties of spot-welds under static and impact loadings are critical for accurate CAE analysis of vehicle impact events. To this end, a comprehensive DOE based spot-weld testing has been undertaken by considering a wide variety of variables. The test data thus obtained were analyzed to determine the requisite mechanical properties of spot-welds as a function of the key variables such as gage, yield strengths, speed, etc. Spot-weld connections have been tested for gages ranging from 0.7 to 3.0 mm using a unique specimen configuration developed at Ford. In addition, a new test fixture was also developed during this study to test spot-welds along different load paths ranging from pure tension to pure shear. Different combinations of gages and materials were used in the fabrication of the spot-weld connection specimens. Three different impact speeds were (0 mph, 10 mph, and 20 mph) also used to evaluate the rate dependency of the spot-weld properties. The test data has been analyzed to obtain peak forces, rupture displacements, and energy absorption characteristics of spot-welds.