| Fatigue damage of welded joint is one of the main failure modes of steel structures.As the instantaneous high concentration of uniform heat input during the welding process,it is inevitable to generate the residual stress on welded joint after welding.Obviously,the residual stress will affect the stress and strain during the period of service,and will adversely affect the low cycle fatigue performance of structure.Therefore,it’s of great significance to research the residual atress relaxation in the process of loading and the effect to low cycle fatigue performance of steel structure based on the analysis of welded residual stress.Firstly the basic theory of welding temperature field and stress field are expounded.Analysing the welding temperature field and stress field of plate component and H component by using ANSYS,and analyzing the impact on H component’s residual stress because of the changes of metal materials,web thickness,weld form and current.Measuring the residual stress of welded components by hole-drilling method and X-ray diffraction(XRD)method.The measurement and the finite element calculation results are close,which verifies the reliability of the model and calculation results.Measuring the residual stress of component that is tempered and polished after welding,the result shows that thoses methods can reduce the residual stress.By measuring the residual stress of H component that is butt welded,analysing the interaction of residual stress that were produced by fillet weld and butt weld.Applying low cyclic load to plate component and H component,then measuring the residual stress to analyse the rules of residual stress relaxation.If the residual stress is added to stress by loads exceeds the material yield strength,not only the residual stress on loading direction but also the other direction will reduce.Otherwise,the residual stress relaxation won’t occur.In order to research the low cycle fatigue property of H components,applying low reversed cyclic load to the components.The fatigue crack occurres near the weld.The welded residual stress has a negative effect to low cycle fatigue performance of H components.Through material preheating before welding,after welding tempering,grinding and vibration aging can effectively reduce the welding residual stress,and improve the low cycle fatigue performance of components. |
