GEOMETRICALLY NONLINEAR BEHAVIOR OF SPOT WELDED-JOINTS IN TENSILE AND COMPRESSIVE SHEAR LOADING

The geometrically nonlinear behaviour of spot welded joints including buckling and gap closure and its influence on local stress parameters at the weld spot edge (structural stresses, notch stress or fatigue notch factor, stress intensity factors) are determined by a large displacement analysis of the tensile shear specimen subjected to tensile and compressive loading. The local parameters mentioned are considered decisive for fatigue crack initiation. A continuous beam model and a plate strip model are used within a simplified procedure. A more sophisticated finite element model is applied on the specimens thereafter. The nonlinear effect is small for steel plates more than I mm thick in the medium and high cycle fatigue range of tensile loading. It may be stronger for compressive loading but is at least partially compensated for in this case by the gap closure effect.