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The distributions of the mode I and mode II stress intensity factor solutions along the fronts of the pre-existing cracks of continuous and discontinuous gas metal arc welds in lap-shear specimens are investigated by three-dimensional finite element analyses. Two-dimensional plane strain finite element analyses were first carried out in order to obtain the computational stress intensity factor solutions for the idealized and realistic weld geometries as the references. Further, the stress intensity factor solutions for realistic welds obtained from the two-dimensional finite element analyses are presented for unequal sheet thicknesses for future engineering applications. Then the stress intensity factor solutions for continuous and discontinuous welds were obtained by three-dimensional finite element analyses.

The failure modes of gas metal arc welds in notched lap-shear specimens of high strength low alloy (HSLA) steel are investigated. Notched lap-shear specimens of gas metal arc welds were first made. Quasi-static test results of the notched lap-shear specimens showed two failure locations for the welds. The specimens cut from coupons with shorter weld lengths failed near the weld root whereas the specimens cut from coupons with longer weld lengths failed near the weld toe. Micro-hardness tests were conducted in order to provide an assessment of the mechanical properties of the base metal, the heat affected zone, and the weld metal. In order to understand the failure modes of these welds, finite element models were developed with the geometric characteristics of the weld metals and heat affected zones designed to match those of the micrographs of the cross sections for the long and short welds.