关键词: 多相状态方程/
相变/
斜波压缩/
声阻抗
English Abstract
Phase transformation kinetics of zirconium under ramp wave loading with different windows
Chong Tao1,2,Wang Gui-Ji1,
Tan Fu-Li1,
Zhao Jian-Heng1,
Tang Zhi-Ping2
1.Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China;
2.Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant No. 11327803), the project of Youth Innovation of Science and Technology of Sichuan Province, China (Grant No. 2016TD0022), and the National Challenging Plan, China (Grant No. JCKY2016212A501).Received Date:10 October 2017
Accepted Date:03 January 2018
Published Online:05 April 2018
Abstract:The effect of window acoustic impedance on the wave profile of phase transition of zirconium under ramp wave compression is investigated in experiment and simulation. In the experiments, a ramp wave driven by magnetic pressure is applied to the zirconium samples backed windows with different acoustic impedances such as LiF, sapphire and free surface based on the compact pulsed power generator CQ-4. The experimental wave profiles measured by an advanced laser interference velocimeter show that the characteristic particle velocity of the onset phase transition from to is about 331.0 m/s in the conditions of LiF widow and free surface with low acoustic impedance, and it is approximately 301.9 m/s for the sapphire window with higher acoustic impedance. The corresponding onset pressure of phase transition varies from about 9.14 GPa to 8.27 GPa. The result shows that this onset pressure of phase transition, which is affected by diverse factors, is not the inherent value of phase transition belonging to the material properties. In order to describe these dynamic responses in experiment well, the numerical simulation of phase transition dynamics of zirconium is conducted in one-dimensional hydrodynamic code, in which included are the muti-phase equation of state based on Helmholtz free energy, the equation of non-equilibrium phase transition dynamics, and Steinberg constitutive relationship. The simulated results show that they can reflect the physical processes of elasto-plastic transition and - phase transition as well, which are excellently consistent with the experimental data. The relaxation times of - phase transition in three different acoustic impedance experiments are nearly the same (30 ns), and their finishing times of phase transition are all about 100 ns. The calculated quasi-isentrope of zirconium below 20 GPa in the pressure-volume and temperature-pressure thermodynamic planes shows that the isentrope and shock adiabat exhibit tiny difference before phase transition, and then separate gradually with the increase of pressure. The isentrope lies below the shock adiabat after the onset of phase transition. At about 20 GPa, the temperature of zirconium under ramp wave loading is bout 100 K lower than that under shock loading. Meanwhile, the abrupt change of volume at phase transition causes the Lagrange sound speed to reduce about 7% and then comes back to the bulk sound speed again after the phase transition has been finished.
Keywords: multiphase equation of state/
phase transition/
ramp wave compression/
acoustic impedance
