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THEORETICAL RESEARCH ON IMPACT RESPONSE OF POROUS MATERIALS WITH INITIAL ULTRA-LOW DENSITIES

Author: GengHuaYun
Tutor: WuQiang；TanHua
School: Chinese Academy of Engineering Physics
Course: Condensed Matter Physics
Keywords: Porous materials Impact response Equation of state Shock dilation Plasma oscillation
CLC: O414.2
Type: Master's thesis
Year: 2001
Downloads: 81
Quote: 1
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Abstract


High velocity impact response of porous materials with initial ultra-low densities are discussed allsidedly in this article, including shock Hugoniot, shock temperature and bulk velocity at high pressure and so on. Potential plasma oscillation for porous metals at high shock temperature is also involved simply. An extended Hugoniot equation of state (EOS) including thermoelectronic contribution is obtained in an EQS frame in which pressure is as an independent variable. This EOS has the capability of predicting the shock Hugoniots of porous materials with initial theoretical densities larger than 5% perfectly. The rebuilding of the J. M. Walsh method for shock temperature is also accomplished to calculate the shock temperatures for special matters, for example, porous materials which have their Hugoniots dilated. Besides, a new calculation method for bulk sound velocities of porous materials with ultra-low densities is derived and the influence of plasma oscillations in porous metals to its EQS is discussed. Progress in these fields is important theoretically for experiments on porous materials to investigate the thermodynamic properties of matters in the so- called Blind Region, with pressure P 20 - 3OGPa, density p <normal density p0, and temperature T 30000K. The arrangement of this article is as follows: at Chapter 1, following a retrospect to the evolution history of EQS and constitutive relations of porous materials at low pressures, some reviews of the EOSs existing so far for porous materials are given briefly. Then, for the convenience of discussing, a new statistical mechanics based EQS frame in which pressure is independent is discussed in detail at chapter 2, where some properties of T-P distribution and its applications to some typical models, as well as a contracted calculation method for partial volumes are given. The statistical interpretation of Wu-Jing EQS is obtained at chapter 3 on the harmonic oscillation model of lattices, followed by a discussion about the statistical mechanics expression of its characteristic parameter and theinfluence of anharmonic oscillations of lattices to the specific heat at constant pressure. At chapter 4, a series ?II ? of new methods for shock Hugoniots, shock temperatures and bulk velocities at highpressures fOr porous materials are deduced. The calculated results are compared withthe corresponding experimental and theoreticaI data published previously to validatethis new model. Finally, a simple discussion about plasma oscillations in porousmetals due to its particular smictUre and impact behaviors is made at chapter 5. Thensome potential difficulties may encounter in measurements of maller pararneters ofporous materials by dynamic highpressure technologies are discussed.

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CLC: > Mathematical sciences and chemical > Physics > Theoretical Physics > Thermodynamics and Statistical Physics > Statistical physics
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