Simulation of welding residual stresses in resistance spot welding, FE modeling and X-ray verification

Abstract This research investigates the effect of SiC wt% on mechanical and microstructure behavior of transformation induced plasticity (TRIP) 780 steels by resistance spot welding. The resistance spot welded samples were characterized for their properties such as hardness, tensile shear, scanning electron microscope, X-ray diffraction, ductility ratio and elongation. Results showed that the width of the nugget was closely associated with shear failure of the spot welds. X-ray diffraction analysis illustrated that the weld steels chemical composition improved in the heat-affected zones and retained austenite detected due to the influence of Si and C. Sample 4 microstructure exposed the equiaxed dimple and finer dendrites in the fusion zone. It also exhibited maximum force and fracture energy. Nano hardness was significantly decreased in the fusion zone of sample 4 due to the interface among micro alloying elements and the formation of nonmetallic presences that affected the TRIP steel hardness. Low ductility ratios were observed in steel 4 than the other weld steels due to higher tensile shear strength (TSS) and cross-tension strength (CTS) results. Fracture analysis exhibited ductile fracture with dimples and dendrites in the TRIP steels surface. The spot-welded samples mechanical properties are correlated to chemical elements, mainly Si existing in casted TRIP steels through the cooling phase of the resistance spot welding process.

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Investigation of the effect of sheet thickness on residual stresses in resistance spot welding of aluminum sheets

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406216685124 ◽

2016 ◽

Vol 232 (4) ◽

pp. 621-638 ◽

Cited By ~ 5

Author(s):

M Sedighi ◽

D Afshari ◽

F Nazari

Keyword(s):

Residual Stresses ◽

Resistance Spot Welding ◽

Spot Welding ◽

Sheet Thickness ◽

Diffraction Method ◽

Welding Current ◽

Electrical Current ◽

Element Model ◽

Resistance Spot ◽

Aluminum Sheets

The main purpose of this study is to investigate the effect of sheet thickness on nugget size and residual stresses in resistance spot welding. A two-dimensional coupled electro-thermo-mechanical finite element model is employed to predict the residual stresses in aluminum alloy 6061-T6. The simulation results are compared with the results obtained from the experimental nugget size and the residual stresses are measured by the X-ray diffraction method. The results indicate that the highest tensile residual stress occurs at the center of the nugget and diminish along the nugget radius. The residual stresses increase on increasing the electrical current and reducing the welding time. By increasing the sheet thickness, the affordable range of welding current and welding cycle increase. It also leads to the enlargement of the nugget, which consequently results in the increase of the residual stresses.

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