Global damage behavior and formability prediction of AA2219 FSW blanks at cryogenic temperature

Abstract

The cryogenic deformation damage and formability of AA2219 FSW blanks were systematically studied with a novel hybrid damage model. The model combined the meso-GTN model and modified Mohr‒Coulomb ductile fracture model considering the complex stress states. The damage parameters of the weld and BM zone were obtained by the finite element reverse calibration method. The tensile properties, forming limits and deep drawability of the FSW blanks were analyzed with calibrated damage model. The damage differences and accumulation rate of the weld and BM zone both decreased, and the deformation uniformity of the FSW joints was improved at −196 °C. In addition, the proposed model can accurately predict the damage and cracking of FSW blanks under uniaxial tension, plane strain and biaxial tension. The maximum standard deviation of the major strain is only 11.7%. The global damage behavior of the weld zone was analyzed during cryogenic deep drawing of the hemispherical bottom cylindrical part. The predicted fracture position and direction of the simulations were in good agreement with those of the experiments, and the LDR increased to 1.9 at −196 °C. The improved formability of the deep drawn parts was mainly due to the increased damage resistance of the weld zone. The decreased voids coalescence rate and dense slip bands were all conducive to the improvement of damage resistance.