3d coupled thermal-electrical-structural finite element investigation on the effect of welding parameters on the geometry of nugget zone and haz in rswed trip steel joints

In this research, the effect of resistance spot welding (rsw) parameters including current intensity, welding time and welding force (coded by a, b and c) on the radius, thickness and area of the nugget and the radius of the heat affected zone(haz) of transformed induced plasticity (trip) steel joints was investigated by design of experiment(doe) and response surface methology (rsm). a 3d coupled thermal-electrical-structural fem was used to model rsw. to validate the fe model, two trip steel sheets were welded experimentally. during welding, the temperature was measured and the results were compared with the fe results and a good agreement was obtained. the boundaries of the welding zones were determined according to the critical temperatures and the responses in all samples were calculated. using analysis of variance, direct, quadratic and interaction effects of parameters on the responses were studied and a mathematical model was obtained for each response. the direct linear effect of all parameters on all responses were significant. but among the interaction effects, the effect of b×c on the nugget radius, the effect of a×b on the nugget thickness, the effect of a×b on the nugget area and the effects of a×b and b×c on the haz radius were significant. also, current intensity had the greatest effect on all responses.