| Based on the conventional mechanical properties of 2024T351 aluminium alloy,quasi-static and dynamic failure tests were carried out on notched specimens using electronic universal testing machine and spilt Hopkinson tension bar respectively.Combined with the results of numerical simulation,the quasi-static and dynamic tensile fracture processes under different stress states were studied and compared.Elastic-plastic strain variation of 2024T351 medium aluminium alloy.At the same time,the fracture surface of the specimen was tested by SEM,and the effect of stress triaxiality and strain rate on the fracture mechanism was analyzed.The main contents are as follows:1.Five kinds of tensile specimens with different notch radius were designed according to the stress triaxiality theory.The quasi-static and dynamic mechanical properties of 2024T35 1 aluminium alloy specimens at room temperature were tested.2.Based on the experimental results,the J-C constitutive equation and the J-C failure equation are selected to fit the parameters.The fitted J-C constitutive equation and the failure equation are embedded in the finite element method.The quasi-static and dynamic tensile tests are simulated.The stress-strain curves calculated are compared with the experimental results,which proves the applicability and accuracy of the finite element calculation.3.The elastic and plastic deformation stages of the specimen in the simulation calculation are distinguished,and the strain energy before the same volume breaking at the minimum section of the specimen is calculated.The elastic and plastic strain energy in the same volume of the specimen in the quasi-static and dynamic tests are obtained.It is found that the material in the dynamic fracture process is better than that in the quasi-static tension.The elastic strain energy decreases and the plastic strain energy increases.4.Microscopic observation and transverse comparative analysis of quasi-static and dynamic specimen fracture surface by using SEM show that the fracture mechanism of quasi-static specimen changes from normal fracture to non-void shear with the decrease of stress triaxiality,while the dynamic failure fracture surface changes from more biased to plastic deformation and larger shear.When the stress triaxiality is the smallest,the fracture mechanism of materials becomes dominated by plastic shear without voids. |
