| Welding process is a high concentrated of instantaneous heat input process, whichinevitably produces welding residual stress and deformation. The magnitude anddistribution of welding residual stress will seriously affect on the static load strength,fatigue strength, brittle fracture and stress corrosion cracking and so on for the weldstructures. Welding deformation will seriously affect size accuracy and appearance ofthe structure, or even break off normal fabricate process. So it is necessary to clarify themagnitude and distribution of welding residual stress and deformation induced bywelding. With the rapid development of the computer technology and the gradualperfection of welding numerical calculation theory, the welding numerical simulationtechnology in theoretical predicting the welding residual stress and deformation playsan important role.616armor high strength steel is a special steel, and the final heat treatment status isquenching and tempering or quenching and low temperature tempering, themicrostructure is low carbon lath martensite and bainite, the yield strength at roomtemperature is greater than1400MPa, welding cracks are easily induced in the weldingprocess, so the austenitic stainless steel is usually used to welding the616armor steel.The fusion area and rich austenite area with high residual stress in corrosiveenvironment may cause stress corrosion crack or corrosion fatigue crack. At the sametime, the deformation induced by welding is difficult to use mechanical correction andflame correction, which serious affects the assembly of the structure. This paper basedon ABAQUS finite element software, a thermal elastic-plastic finite element methodwas developed to study the welding temperature, welding residual stress anddeformation of butt-joint and T-joint in the616armor car door. Also study the effect ofwelding heat input and welding materials on welding residual stress and deformation,and aims to provide basic data for the following inherent method predicting the weldingdeformation of vehicles.In the simulation, the thermal physical properties and material mechanicalproperties dependent with temperature characteristics, and the strain hardening of fillingmaterial were considered. The geometrical nonlinearity was also considered in themechanical analysis, which used the large deformation theory. The sequential coupledmethod, namely considering the influence of the temperature field on stress and ignoring the effect of stress field on temperature field，was used in the finite elementmethod.The simulation results of butt joint show that weld area have a high tensile stress,the peak stress is greater than the yield strength at room temperature of fill material，it ismainly because the austenitic has a significant work-hardening and bear most of theplastic deformation in the welding process. The peak tensile stress is found near heataffected zone, witch is greater than the base metal yield strength at room temperature,this may be a reason for welding crack produced in the welding.The simulation of T-joint, with homonymous discontinuous double-sided welding,shows that, the residual stress near first welding area is less than near the near thesecond welding, it is mainly because that the heat source with the second welding has aequivalent heat treatment role for the first welding, and makes the magnitude of residualstress near the first welding less than the second welding.The results of the study show that, with the heat input conditions in this paper,transverse contraction deformation increases with increasing welding heat input, whileangle deformation is decreased. With the increase of welding heat input, and thedifference with temperature of welding surface is reduced, in high temperature areaabove the mechanical melting point difference decrease, and angle deformationdecrease. The results of the numerical simulation can provide references for the actualwelding process to reduce the deformation by reverse deformation law.The effect of filler materials on the welding residual stress and deformation resultsshow that the steels have smaller linear expansion coefficient, large elastic modulus,large yield strength, reducing the welding deformation. The results of numericalsimulation have a certain theoretical guidance to choose proper welding material ordesign new welding material to reduce the welding deformation. |
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