Residual stress modeling of narrow gap welded joint of aluminum alloy by cold metal transferring procedure

Abstract

Research on FE method simulation of CMT+P MIX welding process has been suspended because of the absence of qualified model for characterizing cooperation between wire feeding and heat input. A novel 3D FE thermo-mechanical model was established, in which impulse input of weld wire and weld heat was simplified by decreasing the impulse frequency. Materials were modeled as elastic-perfectly-plastic with composite heat sources utilized. Numerically simulated results were validated by thermal cycle curves and residual stress distribution obtained with infrared photography instrument and X-ray diffraction tester, respectively. The numerical residual stress distribution also got well supported by the tested results obtained by the blind-hole method. Residual stress evolution was analyzed, whereas special attention was paid to the influences on residual stress distribution by the subsequent weld passes. Based upon this was the vulnerable area of the joint identified under the conduction of different strength theories. The global stress distribution was found to be dominated by the first weld pass while more residual stress in the re-melted zone than that in the HAZ could be released by the last two welding passes. The mechanism was studied through the yielding process of residual strain which was divided into two steps.