Abstract
A joint structural fatigue due to fluctuation of stresses generated in the surviving life of mechanical systems is the primary concern in welding design for safety. Spot welded joints are widely used for jointing structural parts. This paper introduced a new procedure for the measurement of lethargy coefficient as the total defect estimation coefficient and prediction of fatigue life of spot weldment. The lethargy coefficient is based upon applications of molecular dynamics in materials research field. It is obtained from a QSTS(Quasi-Static Tensile-Shear) test and is measured by complete fracture time and ultimate stress. The applicability of the existing formulations for evaluating the loading speed effects is discussed. In this paper, the fatigue life with lethargy coefficient from QSTS test coincides with the experimental data very well. This way can make save the time and cost in processing of predicting the fatigue life of spot welding structure.