Determination of constitutive relation and fracture criterion parameters for ZL114A aluminum alloy
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Abstract:In order to study the containment properties of aero-engine casing made of ZL114A(ZAlSi7Mg1A) aluminum alloy under the impact of blade fragments at different temperatures, the material models describing the large deformation and failure behavior of ZL114A aluminum alloy under a large range of temperatures were established. Firstly, quasi-static tensile tests at various temperatures and dynamic compression tests were conducted in the universal testing machine and the SHPB (Split Hopkinson Pressure Bar), respectively. Based on the force-displacement data obtained in tensile tests, the finite element code and optimization algorithm were used to reversely identify the material hardening parameters at temperatures of 25°C~375°C. In this process, the accuracy of two hardening laws, Ludwik and Hockett/Sherby, describing the plastic flow behavior of ZL114A aluminum alloy under large deformation were compared. Subsequently, combined with the dynamic behavior relation of ZL114A aluminum alloy at strain rates of 1310s-1~5964s-1, a modified empirical constitutive model incorporating plastic strain, temperature, and strain rate was established, based on the Hockett/Sherby hardening law and Cowper-Symonds model. Further, the tests of notch tension, notch compression and shear were carried out, and the parallel finite element models were numerically calculated. The limitation of failure parameters related to failure criterion by the theoretical formula was analyzed, and the failure parameters are obtained by combining experiment and finite element method. Johnson-Cook failure criterion in branch form was used to describe the relationship between failure strain and stress triaxiality of ZL114A aluminum alloy. Considering the influence of temperature and strain rate, the failure criterion describing the failure behavior of ZL114A aluminum alloy was obtained. Finally, the validity of the fracture criterion and its parameters were verified by the ZL114A aluminum alloy flat plate penetration tests and the numerical simulations at various temperatures. The results show ZL114A aluminum alloy has obvious characteristics of strain hardening, temperature softening, and high strain rate strengthening. The Hockett/Sherby hardening law with stress saturation characteristics more accurately describes the stress flow behavior of ZL114A aluminum alloy than that of Ludwik under large deformation. The modified constitutive relation effectively describes the stress flow behavior of ZL114A aluminum alloy to a certain degree under large strain, wide temperature, and high strain rate. At the same time, the fracture criterion in branch form has good applicability to predict the impact failure behavior of flat plates at different temperatures.
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