| Resistance spot welding is a important welding technology,it is applied inrailway vehicle widely and car bodies manufacturing,it is a multiple technologicalprocess,it involve in heat,electricity．force.Its research process is difficult,because ofinternal nucleation process is instantaneous and invisible,numerical simulationtechnology can resolve this problem easily. Using coupling field can simulate multiplephysical environment, numerical simulation analy under the condition of differentwelding parametersand and set up models that close to actual situation,by this way wecan obtain information that experiment cannot obtain.Have a more indepth andsystematic understand about the mechanism of resistance spot welding.In this dissertation,using the finite element software ANSYS to simulate theresistance spot welding process of SUS304stainless steel,using coupling field of heat,electricity, force combined with birth-death unit technical analy electric potential field,temperature field and distribution of current density in process of resistance spotwelding,and simulate the influence of different welding parameters on nucleationprocess and the influence of shunting current on welding temperature field.This paper analysis distribution of stress strain distribution and contactconditions of electrode/workpiece and workpiece/workpiece. The analysis shows thatthe stresses in electrodes and workpieces are compressive stress, the maximum axialcompressive stress on the workpiece/workpiece contact surfaces, axial compressivestress distribution of compressive stress are uniform inside the workpieces,themaximum radial compressive stress on electrode/workpiece contact surfaces, radialcompressive stress decreases along the radial direction.Peak contact pressure betweenelectrode/workpiece and workpiece/workpiece occurred near the center of symmetry,the contact compressive stress increasing over time, gradually decreases along theradial direction. Contact radius between two workpieces is obviously bigger than theinterfaces between electrode and workpiece.With the increase of electrode pressure,contact stress and contact radius are increasing. The contact information that obtain by preloading analysis are used as initialcontact conditions,establishing two sequential models contain thermal-electriccoupling and thermal-force coupling,complete transformation between therm fieldand force field.Solve the problem of dynamic variation of the contact area bybirth-death unit technical,considering material parameters in the process of simulationcomprehensive,especially the set of contact resistance.understand nucleationmechanism and welding deformation through the analysis of results. The results showthat in the process of electricity, melt nuclear temperature is rising, finally formmolten nuclear, and along with the increase of welding current, weld nuclear size isincreasing, the effect of increasing welding time is similar to increase weldingcurrent,along with the increase of welding pressure, weld nuclear size isreducing.Maintain stage, temperature falling rapidly, melting temperature areagradually shrink, at the end of maintain,the isotherm into sparse parallel lines,andperpendicular to radial.The shunt phenomenon may cause diameter of melting nuclear and penetrationrate drop, affected the bearing capacity of welded joint seriously.The situation ofshunting current has been analyzed as the spot distance changing and thicknesschanging by set up different models in this dissertation,and compare the effect ofdifferent spot spacing on molten nuclear size.We can learn that with the spots distanceincreasing, the phenomenon of shunting current is reducing, the impact of shuntingcurrent in the thick plate is bigger than the sheet, shunting can decrease meltingnuclear size,the spots distance of SUS304stainless steel couldn’t be less than30mm.By contrast of experiment,the error between test and simulation is not big,resultverify correctness of the simulation,simulation result has important significance toguide practical production. |
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