GEOMETRICALLY NONLINEAR BEHAVIOR OF SPOT WELDED-JOINTS IN TENSILE ANDCOMPRESSIVE 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 no tch factor, stress intensity factors) are determined by a large displa cement analysis of the tensile shear specimen subjected to tensile and compressive loading. The local parameters mentioned are considered de cisive for fatigue crack initiation. A continuous beam model and a pla te strip model are used within a simplified procedure. A more sophisti cated finite element model is applied on the specimens thereafter. The nonlinear effect is small for steel plates more than I mm thick in th e medium and high cycle fatigue range of tensile loading. It may be st ronger for compressive loading but is at least partially compensated f or in this case by the gap closure effect.