Finite Element Simulation Of Effect Of Post Weld Heat Treatment On FSW And TIG Welding

High asymmetrical plastic strain can be found in numerical models duo to the high welding temperatures. The induced thermal stress can lead to the residual stress after welding. The final residual stress can be an important factor for the determination of the service life of the welded structure. A post-weld heat treatment (PWHT) is usually used to decrease the residual stress and enhance the mechanical property in the industrial engineering.A sequentially coupled thermo-mechanical model is used to simulate the FSW and TIG welding processes. The comparison of temperature field and welding residual stress in FSW and TIG is studied. The effect of the input power and PWHT on residual stress is further discussed. Results shows that the maximum temperature in FSW is 1062 ?, which is smaller than TIG. The region with higher residual stress is smaller than that in TIG. The distribution of residual stress in FSW is much better than that in TIG. With the increase of the input power in FSW and TIG, the peak welding residual stress are slightly decreased. The PWHT is efficient to release the welding residual stress. The residual stress can be decreased with the increase of the PWHT temperature.A welding of impeller simulated is simulated based. The welding temperature field and residual stress are studied and then a series of models with different structural parameters are applied to discuss the variation of residual stress. Then the PWHT was used to decrease welding residual stress for better fatigue behavior of impeller. The high temperature concentrates near the welding line is very small in other regions. The maximum residual stress along the welding line is about 1138 MPa and the one perpendicular to welding line is 783.9 MPa. The changes of impeller thickness and blade thinness can affect the thermal strain and residual stress. The thermal strain becomes smaller with the increase of the impeller thickness but the residual stress becomes higher. With the increase of the blade thickness, the thermal strain becomes smaller. The residual stress can be obviously decreased by the PWHT in the impeller. With the increase of PWHT temperature, the residual stress becomes lower. But the excessive high PWHT temperature can lead to stress concentrations in the border of the blade. The residual stress can be also decreased with longer holding time in PWHT.