Method of analyzing spot welded sheet
metal structures subjected to forces that promote one or more basic failure
modes of either shear tension, in-plane rotation, coach peel, normal tension, or any combination of such basic
modes, the method comprising: (i) providing spot welded sheet
metal test coupons for analysis of the selected failure mode for the structure to be analyzed and subjecting such test coupons to progressively increasing forces that eventually achieve failure in the selected failure mode to thereby generate measured load and displacement
test data; (ii) analyzing the data from the basic
modes to derive and extract spot
weld strength and stiffness information and then
surface fitting such extracted data to create a
database; (iii) establishing a computer math model for simulating the spot weld failure modes of the structure and populating the
database thereinto to enable simulated physical tests of the structure; (iv) creating a cumulative-damage failure criterion for the spot welded structure that ratios (a) the
resultant strength information from the populated math model for selected combinations of load and selected combinations of time and structure thickness, and (b) the measured strength information derived for such combinations of load derived from the
test data; and (v) solving the criterion to determine whether it indicates failure for the combination of
resultant strength and other values selected.