The FEM Simulation Of Residual Stress In Welding Steel Truss Bridge Node

Due to welding structure's many advantages, it is widely used in industry,boats,buildings and bridges. In recent years, with the development of welding material and technology, the welding structures become larger and larger. Especially in tall buildings and large span bridges, big even super structures stand out in our visions more and more.. But because of the existing of residual stress, it will leads to the decrease of structure's function. For example, the reduction of fatigue resistance, brittle fracture resistance, erosion resistance and stability .Welding process is that parts of an area is quickly heated to high temperature and then rapidly cooled. With the heat source moving, the whole welding temperature sharply changes, and the material's physical property parameters also sharply change. At the same time, there is latent heat of melt and phase-change. Therefore, the analysis of welding temperature field is a typical nonlinear transient heat conduction problem. Because of non-uniform temperature distribution, at the course of welding and post weld, welding takes on serious welding stress and deformation. Calculation of welding stress and deformation includes geometrical nonlinear problem and material nonlinear problem. Welding temperature field and stress, strain field are bi-directional couple, but the influence of stress and strain field on temperature is not so much,So this paper only considers the single couple which temperature field effects on stress and strain field.The paper firstly describes the basic theories and numerical analysis methods of the temperature field and residual stress field. In the process of numerical simulated calculating, with the thermal-structure coupling function of ANSYS software and indirect coupling this paper deals with the single coupling whose temperature field effects on stress and strain field and calculates the temperature field for the K-section welding line of bridge node. In order to improve the solution accuracy, it selects suitable material properties, refines the girding, chooses the Gauss function moving heat source model and uses ANSYS APDL language to compile program to apply moving heat source load in the process of numerical simulated calculating .Finally dynamic pictures of welding temperature field and temperature distribution curve of each point in welding line are shown, as well as heat circulation in heat response areas and welding centre line is described by post-solution.Based on accurate temperature field results, welding residual stress are also calculated by changing thermal elements into structural elements. A curve of regularity on transverse and longitudinal welding residual stresses and tendency of their distribution is presented by post-solution.