Separation of spot welded joints under impact is investigated with regard to geometry, loading configuration, steel grades and the rate effect. Test data were analyzed to reveal the governing parameters that could be useful in predicting dynamic structural behavior of spot welded vehicles. The following conclusions are obtained: For the first time, the loading rate is identified as a critical parameter in quantifying the dynamic pullout separation of spot welded joints. Impact speeds, both before and after the impact, alone are not sufficient. In addition, the stiffness of the combined specimen/ loading fixture also plays an important role in the interpretation of the test results. Strain rate effect on the dynamic ultimate strength (peak load) of spot welds is investigated and the Chao- Wang (CW) Model was developed and validated. The model can be used to predict the dynamic separation load of a spot weld in a structure provided the static fracture load and the loading rate at the spot weld are known. When static fracture load is not known a priori, a simple formula is recommended for estimating the dynamic fracture load for LS, CT, or combined/mixed mode spot welded specimens. Note that all discussions in this work are for spot welds failed by pullout failure mode. The sizes of all welds in the experimental study were intentionally made such that they are larger than the minimum button size required by auto industry. Conditions for guaranteeing a pullout failure are discussed. Dynamic fracture of spot welds with interfacial failure mode obviously warrants further investigation.
Dynamic separation of resistance spot welded joints: Part II - Analysis of test results and a model
Experimental Mechanics ; 50 , 7 ; 901-913
2010
13 Seiten, 14 Bilder, 3 Tabellen, 27 Quellen
Article (Journal)
English
Dynamic separation of resistance spot welded joints: Part I - Experiments
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