Finite Element Analysis Of Welding Residual Stress Of Typical Steel Bridge Structures

Welding is a complex phenomenon which involves multiple disciplines of heat transfer,solid and fluid mechanics,electromagnetism and metallurgy material blending.Welding phenomena includes the heat transfer process,the melting and solidification of the metal,the phase transformation during cooling,and the welding residual stress and deformation and so on.There is a large amount of welding in all welded steel bridges,and at present,the residual stress can not be controlled and eliminated completely,and there is still a lot of residual stress in the weld.The existence of residual stress will decrease the stability of the structure,which is necessary to know the distribution of residual stress after welding and the existence of residual stress after welding will have an affect on the structure of the strength and bearing capacity seriously.In this paper,we use the finite element analysis software ANSYS to establish the finite element model of the T welded joints and steel truss welded joints,then we can see the distribution of temperature field and stress field.The main work is as follows:(1)This thesis introduces the basic theory of welding residual stress and the common methods of numerical simulation briefly,and the existence of influence of residual stress on the structure.(2)Ensure the thermophysical parameters and mechanical parameters of the materials at different temperatures,and the welding heat source model were determined and so on.Use the APDL command to write the cyclic command to realize the welding heat source loading and moving,and use the birth and death-element technology to achieve the generate of welding element.(3)Establish the finite element model and then calculate result of the temperature field.With the movement of heat source,the quasi steady state temperature field is formed on the welding element.In the front of the heat source,the isotherm is dense,and the temperature gradient is large;and in the back of the heat source,the isotherm is sparse,and the temperature gradient is small,which proves the correctness of the simulation of welding temperature field.Through the indirect coupling of temperature field and stress field,read the temperature load in temperature field,and calculate the result of the stress field.With the development of the welding process,the stress influence surface increases gradually,and the equivalent stress is close to the yield stress,and the equivalent stress finally runs up to the yield stress after welding.The maximum longitudinal stress of the welded joint model is 388MPa,which exceeds the yield stress.(4)On the basis of the integral joint model with the residual stress,apply the external load and analyze the result.Under the joint action of external load and welding stress,the variation of the stress in the near weld zone is obvious,and there is a stress mutation,but far from the weld zone,the stress change is not very obvious.The external force makes the stress redistribution,increases the yield surface,and relseses the partial stress.