Study On Spot Welding Crack Propagation Of Dual-phase Steel Based On Thermal Elastic-plastic Analysis

Spot welding is the most-widely-used kind of bonding technology with themaximum efficiency in the car body manufacturing process. And the spot welding quality,mechanical properties and welding distortion of sheet metal, have always been a verystriking problem in the engineering practice, as it affects the safety and quality of cars.Therefore, research the mechanical properties of spot welded structures is of greatsignificance to improve product quality, enhance the market competitiveness of products.DP600dual-phase high-strength steel is a material which has recently been widely usedin machinery production, in this study, the welding process of equal-thickness DP600steel plate was firstly thermal simulated, using the thermal coupling unit established atwo-dimensional axisymmetric finite element model, simplifying the contact resistancebetween the combination surface and electrode-workpiece interface to a function oftemperature, analyzing the welding process of the equal-thickness sheet considering thetemperature-dependent thermophysical properties parameters of the material and got theresults of temperature field analysis. Then, take thermal elastic-plastic analysis onresistance spot welding process of the sheet with temperature, in the analysis we can getthe contact pressure distribution and variation of combine surface and electrode-workpiece interface, as well as the stress, strain and deformation of spot welding joints.Secondly, with the maximum circumferential strain failure criteria, respectivelynumerical simulated the crack extension process of DP600dual-phase equal-thicknesssteel plate welded structure, when it’s under a one-way stripping load and undersymmetrical cycle stripping loading, to get the trends and patterns of stress and strainduring the internal crack growth of welded structures. Finally, calculated stress intensityfactor of the crack tip point, and analyzed the trends.