Large-scale trajectory optimization based on air traffic complexity

In relation to the application of high-entropy alloy systems containing high-density and high-calorific value elements in the liner of shaped charge warheads, the Ta-Hf-Nb-Zr high-entropy alloy system is investigated. The study employed an INSTRON material testing machine and a split Hopkinson pressure bar testing platform to explore the mechanical response of this high-entropy alloy across a wide range of strain rates from 10⁻³ to 10³ s⁻¹, temperatures ranging from 25 to 900 °C, and stress triaxiality values ranging from 0.33 to 0.89. Yield strength and failure strain data were obtained from static round bar tensile tests and dynamic compression tests conducted under these varying conditions. By using least squares fitting, the parameters of the Johnson-Cook (J-C) constitutive equation as well as the damage failure model parameters, are derived. Subsequently, a simulation model for explosively formed projectile (EFP) made from high-entropy alloys under explosive loading conditions was developed. Pulse X-ray tests of the EFP formation were performed, and numerical simulations of the EFP formation process are conducted using LS-DYNA software. The results show that at 117 μs, the high-entropy alloy EFP remains largely intact, with a length of 51.1 mm and a diameter of 12.27 mm. At 187 μs, three fractures are observed at the tail of the EFP, with the head length measuring 24.3 mm, the diameter at 12.27 mm, and the EFP speed recorded at 2496.3 m/s. The numerical simulations demonstrate that the EFP length, diameter, and velocity at these time instants match the test data with errors of less than 8.2%. Moreover, the fracture patterns observed experimentally align closely with those predicted by the simulations. This consistency indicates that the J-C model effectively predicts the formation characteristics of high-entropy alloy EFPs under explosive loading conditions, confirming its utility in accurately simulating the EFP formation process.