Numerical study on the phase-transition characteristics of debris cloud under hypervelocity impacts

Hypervelocity impacts can cause material phase transitions. Solid-phase fragments retain the material strength and exhibit high penetration performance. Liquid- and gas-phase fragments have a much lower penetration performance but can still generate momentum and thermal impact on the rear plate. This study adopted the finite element-smoothed particle hydrodynamics (FE-SPH) adaptive method to simulate the phase transitions of debris clouds under hypervelocity impacts. The Johnson–Cook and maximum tensile stress failure criteria were used to simulate material compression and tensile failures, respectively. The material liquefaction temperature was considered the threshold of the temperature failure criterion. Three phase-transition criteria are proposed using temperature and pressure methods and a material phase diagram, in which the intermediate phase states are also defined, i.e., the melting-phase of the solid–liquid intermediate state and the hot-liquid phase of the liquid–gas intermediate state. A symmetric plate impact was used to verify the reliability of the physical quantities. The reliability of the numerical results was verified using experimental and numerical phase diagrams of the debris clouds at different velocities. The phase evolution characteristics of the debris clouds under hypervelocity impacts were studied using the FE-SPH adaptive method and temperature phase-transition criteria. The initial projectile phase model was obtained by the inversion of the debris cloud phase distribution at the steady-state moment, laying the foundation for the debris cloud phase model.