Simulation Study On The Influence Of Thermal Residual Stress On Mild Steel Damper

Flame cutting and welding belong to metal hot working technology,and are often used in energy dissipation and damping structures of metal dampers.The superposition of thermal residual stress field and working stress field formed by hot working will often reduce the mechanical properties of metal dampers.Therefore,in order to improve the quality of the structure and eliminate the hidden danger of safety,it is necessary to study the thermal residual stress quantitatively.In this paper,based on ABAQUS finite element software,combined with FORTRAN subroutines such as hetval,usdfld,film,dflux and umatht,the thermal residual stress field is simulated.In order to consider the hot working technology of the shear type soft steel damper as many as ten assembly passes,firstly,the flame cutting and welding of the simple flat plate model of the soft steel Q345 B steel are simulated.Through the subroutines of hetval and usdfld,the thermal cutting stress field is simulated accurately.The existence of forced convection makes the thermal cutting stress field only exist near the cutting surface,while the stress field distribution perpendicular to the cutting section is shown as high stress distribution in the position with small thickness of vertical cutting surface due to the existence of heat resistance value R.Through dflux and film subroutines,the stress field simulation of triangle swing welding is more accurate.Compared with the welding scheme based on the thermal cutting stress field,the effect of thermal cutting on the welding residual stress field is negligible.After that,the scheme of weld simulation material is selected,and the test results of blind hole method are compared with the simulation scheme.The result of ER50-6 weld simulation scheme is 2.5% higher than that of direct base metal instead of weld.Taking 25 t shear type mild steel damper as an example,the hot working process of assembling and welding of mild steel damper is simulated,and the single loading mode is used for comparison.The large value of welding residual stress reduces the yield force of 4.9% mild steel damper,which makes the structure enter into plasticity ahead of time.Based on the problem of welding temperature field and component failure,combined with the state subroutine sdvini and material thermal subroutine umatht,the program is used to simulate the change process of solid structure in the heat affected zone.The transformation distribution of metallographic structure in the overheated zone after welding is obtained,and the grain coarsening is caused by heat welding.Finally,the distribution of high thermal residual stress field formed by heat processing is verified.