Influence Of Geometry Of Aluminum Alloy Weldments On Welding Deformation And Residual Stress

With the rapid development of rail vehicles,the requirements for the quality of vehicle body materials are getting higher and higher.Aluminum alloy has the characteristics of good corrosion resistance,high strength-to-weight ratio and good tensile properties,the application of which in rail vehicle bodies has been recognized by various countries in the world.Because of the large thermal conductivity and large expansion coefficient of aluminum alloy,it is very easy to produce welding hot cracks during welding,which brings difficulties to rail vehicle production.With the rapid development of rail vehicles,the requirements for the quality of vehicle body materials are getting higher and higher.Aluminum alloy has the characteristics of good corrosion resistance,high strength-to-weight ratio and good tensile properties,which has been recognized by various countries in the world.Because of the large thermal conductivity and large expansion coefficient of aluminum alloy,it is very easy to produce welding hot cracks during welding,which brings difficulties to rail vehicle production.Therefore,the analysis of the correlation among the geometric shape of the aluminum alloy weldments,the welding deformation,and the residual stress,can guide the selection of high quality railway vehicles’ welding structure design for reducing welding distortion and residual stress.Therefore,in this thesis,a three-dimensional finite element model was established on the ABAQUS platform,with the 5052 aluminum alloy tubular and plate welded parts as the mock object,basing on the thermal elastic plasticity finite element numerical analysis theory,and considering the thermal physical properties and geometric nonlinearity of the materials.This thesis has taken full consideration of the two-way coupling effect of the temperature field and the stress,investigated the distribution change of temperature field and the plastic strain field of welded parts at welding speeds of 10mm/s,11mm/s and with heat source power of 1540 w,1820w,and then reached related conclusions of the influence of the welding parameters based on the direct coupling method on the welding of the aluminum alloy weldments.On this basis,the heat source power was selected at 1820 w and the welding speed was selected at 10mm/s,and the temperature field,stress field and welding deformation of the plate weldment and tubular weldment were investigated by direct coupling method,and then the author analyzed the equilibrium state of welding heat input and heat loss.Also,the welding deformation and residual stress of aluminum alloy welds with different geometrical shapes were compared with respect to temperature field and restraint intensity.Through the above related simulation,the effect of different geometry of aluminum alloy weldment on welding deformation and residual stress was studied.According to the simulation study,it is concluded that the change of welding speed in a certain range has little influence on the distribution of the longitudinal residual stress of the aluminum alloy plate,but has a great influence on the distribution of the transverse residual stress.The biggest stress variation is 3MPa,and the largest change proportion is 31%.The change of heat source power in a certain range makes obvious difference of welding residual stress in transverse distribution,but not in longitudinal distribution.The biggest transverse residual stress is 21 MPa,and the largest change proportion is 181%.At the same time,different geometry shapes of weldments cause different temperature fields and the restraint intensity of the welding parts during welding,which will affect welding deformation and residual stress.For one thing,different geometry shapes lead to different restraint intensity of the welding parts,which affects plastic deformation during welding and further affects residual stress.For another,the geometric shape has a great influence on the heat exchange of welding parts with the outside.The biggest temperature variation of 191℃occurs at the formation of stable weld pool,while the largest change proportion appears at the cooling stage,of 122%.It affects the length of the welding parts at high temperature and the difference of temperature field,which affects the material properties of the weldments.Therefore,the time of yield strength at low value is not equal,so the maximum plastic deformation is not consistent,and the amount of stress in the whole weld is not equal,so it will affect the residual stress after welding.The biggest deformation variation of the two mock weldments is 1.35 mm,and the largest change proportion is 540%.The bilateral influence of the two factors is dependent on specific shape change.