2A97铝锂合金的Johnson-Cook本构模型及失效参数

The finite element simulations of explosion and high-speed collision often involve the process of large deformation and fracture of materials. The 2A97 Aluminum-Lithium (Al-Li) alloy was selected to investigate the Johnson-Cook (J-C) failure model, and the new experimental and numerical framework for determining of revised J-C failure parameters was conducted. The specimens with different notch sizes were designed, and the strain distribution and stress triaxialities of the notch samples were studied by using the finite element simulation. Results show that the maximum strain of the notch samples was concentrated at the notch surface, and the variations of stress triaxialities at the notch surface during the loading process were obtained. Based on the results, the fine speckle was made, and the failure strains of the quasi-static and dynamic loading samples under 293K-573K were obtained by 2D digital image correlation (DIC)measurement method. Thus, the revised stress triaxialities, strain rate and temperature were accurately corresponded to the failure strains, which helps to obtain the accurate J-C failure parameters. In addition, the fracture of Al-Li alloy specimen was observed by SEM, and the microcosmic mechanism of effect of stress triaxiality on the failure strain of Al-Li alloy was investigated. Results show that the micropores produced in the deformation process no longer accumulate into dimples with the increase of stress triaxiality.