Investigation into inter-pass cooling time effects on distortion and residual stress

چکیده مقاله

Inter-pass cooling time as an important factor during welding processes not only affects the microstructure and mechanical properties of welding zone, it is also effective on welding time and cost. In the current research, the effect of inter-pass cooling time on residual stress and especially distortion is investigated numerically as well as experimentally. A three-dimensional thermo-mechanical analysis using uncoupled thermal-mechanical analysis, by application of the element birth and death technique, is applied to model the welding process. According to this technique, weld region is neglected initially, and it is born as heat source approaches to the correspondent region. According to the death and birth technique, the deactivation of elements is done by reducing their contributions to stiffness matrices and removing their contributions to load vectors. Abaqus software was used for simulation. The effect of inter-pass cooling time on induced residual stress and developed distortion for a T-joint consisted of St37-2 steels was investigated. Two welding conditions were studied. Welding condition (a) which inter-pass cooling time was 120 sec and welding condition (b) which second welding pass took place after cooling of specimens to room temperature. This means that for the second welding condition the inter-pass time was extensively higher than the first welding condition. During the simulation process, the heat from the moving welding arc was applied as a volumetric heat source with a double ellipsoidal distribution. Good agreement between experimental and numerical results was observed. Additionally, it was found that the inter-pass cooling time did not affect the induced residual stress largely; however, it affected the distortion.