Analysis And Relaxation Study Of Residual Stress In T Joint Welding

Rotary drilling rig is widely used in basic construction engineering,the pipe-bar in drilling rig is subjected to alternative loading.Welding residual stress influences the stability and utility of pipe-bar,and failure often occurs in zone of joint.It is extremely important for engineering design to predict and control welding residual stress accurately.The loading conditions are comparatively complex in real working process,the overall objective of this thesis is to propose a procedure providing useful calculation of effects of welding groove and cyclic loading,the welding joint between pipe and bar will be simplified as T-joint welding.A finite element model is presented to predict the welding residual stress distribution,and the effectiveness of numerical simulation is verified by compared with experiment results.Thermal-structural analysis is utilized to simulate the whole welding process,birthdeath element used to simulate the filling of welding material.The calculation results show that,welding groove influences the final residual stress,but the influence to distortion is not much.Based on the predicted residual stress field,the effect of the magnitude,stress ratio and direction of cyclic loading on residual stress is investigated.The results show that,the relaxation of residual stress depends on the magnitude of cyclic loading,the relaxation magnitude is increasing with the increasement of cyclic loading.In addition,longitudinal cyclic loading only changes the magnitude of residual stress rather than distribution pattern.The relaxation mostly occurs in the first cyclic period,the cyclic loading influences transverse residual stress and have little influence on longitudinal residual stress.