Research On Performance Of Welding Residual Stress Under The Effect Of Alternate Loadings

The residual stress distribution is the main reason to the appearance of welding cracks and the reduction of welding joint's strength. It has a great effect on the structural performance such as static strength, fatigue strength, stability, stress corrosion cracking etc. Therefore, it is necessary to take residual stress in consideration when analysis of structural strength and evaluation of structural life are carried out. The alternate response of offshore structure is the main reason to fatigue damage under the effect of wind, wave and flow in the ocean environment. At the same time, the residual stress distribution will change as the alternate loading changes. The paper researches the effect of alternate loadings to the welding residual stress, and predicts the temperature field and residual stress field in multi-pass welding by using the numerical simulation.Based on the blind-hole method, series of experiments are carried out to analyze the effect of alternate loadings to the redistribution of residual stress. Two butt joint plates of Q235 steel were prepared for the experiments. All the plates were welded under the same condition to make sure that they have the same residual stress distribution. For each plate, the stress field can be approximately considered to be axial symmetry about the welding line. The blind-hole method was used to identify the initial residual stress distribution and the remaining residual stress after the effect of alternate loading. The experiment concludes that alternate loading does affect the redistribution of residual stress in a certain degree. The change of residual stress depends on distribution of initial residual stress, S-N curve of material, stress amplitude and cycle number under alternate loading.At the same time, this paper systemically discusses the finite element analytical system of the welding process, and uses the research result to simulate the welding process of multi-pass welding of plate by FEM soft ANSYS. Ultimately the calculation result accords with traditional analysis result. Through real-time simulation of the stress in multi-pass welding process, the thermal stress and residual stress in welding can be predicted, and may provide theory foundation and optimizing the welding technology and parameters by using the simulative analysis method in this paper.