【作者】 冉宪文；

【导师】 汤文辉； 谭华；

【作者基本信息】 国防科学技术大学 ， 力学， 2006， 博士

【摘要】 本文对当前金属高压熔化规律研究中所涉及的物态方程、熔化判据、熔化区内材料的强度、熔化机制和实验数据分析处理等问题进行了相对系统的研究:1、Anderson所提出的等效Grüneisen系数在地球物理学和铁的高压熔化线的相关计算上得到了应用,并取得了良好的效果。根据Anderson所提出的等效Grüneisen系数的概念,本文在三项式物态方程基础上,对等效Grüneisen方程进行了推导。以等效Grüneisen方程为基础,对多种金属的冲击温度进行了计算,研究表明,该方法使用简便,计算结果与实验数据符合得很好。2、对现有熔化判据进行了分析和比较,在此基础上采用由材料零温物态方程约束的熔化判据对金属熔化线进行了计算和对比分析。研究表明,在一定条件下,该熔化判据与Lindemann熔化判据和平均场理论所给出的熔化判据具有相同的物理内涵。计算表明,该熔化判据能够较好的描述金属的高压熔化曲线。在理论分析及比照分子动力学模拟的基础上,给出了该熔化判据的物理机制。3、在SCG模型和修正的SCG模型基础上,通过引入能量权重,对材料剪切模量在固液混合相区内的变化行为进行了描述,在此基础上,对金属铝沿Hugoniot线的剪切模量进行了分析,得到的结果与实验数据基本相符。4、利用逾渗理论和重整化群方法分析计算了各向同性材料剪切模量在固液混合相区内的临界变化行为。采用Huygens原理对材料在固液混合相区内声波的传播过程进行了分析,在此基础上,通过逾渗理论给出了剪切模量在固液混合相区内随熔化质量分数变化的临界点。当熔化质量分数达到0.313左右时,材料内部出现液相贯通区,假设材料此时开始表现出熔化性质,从而可将该点与光分析法中的纵波声速向体波声速的拐点相对应;当熔化质量分数大于0.687左右时,材料内部将不再存在一个可以贯通相对表面的固相区,因而此时材料的整体剪切模量消失。通过分析材料内部沿剪切作用面上液相区和固相区的组成,给出了九种承剪能力变化较小的简立方格子,在此基础了进行了重整化群变换,计算得到了临界的熔化质量分数,与逾渗理论的计算结果相吻合。5、以铁冲击熔化结束点为参考点,黄海军等解决了长期以来令人困扰的铁动静态测量熔化温度存在差异的问题,但在冲击熔化初始压力点处,如何将Fe的冲击温度修正到平衡熔化温度的问题并没有得到解决。本文对此问题进行了研究,利用计算得到的临界熔化质量分数,在Luo等提出的过热模型的基础上,对Fe在冲击熔化初始压力点处的冲击温度进行了修正,修正得到的平衡熔化温度与黄海军等的计算结果以及Ma和Shen的实验结果能够落在同一条Lindemann熔化线上。6、采用动高压手段和光分析方法对Ly12Al高压熔化温度进行了实验研究和理论分析。Ly12Al的阻抗较低,对其高压熔化规律进行实验测量存在较大的难度,通过实验测量了Ly12Al在100Gpa附近的辐射光谱,拟合所得温度结果经理论分析初步认定为熔化温度。更多还原

【Abstract】 This thesis gives a more systematical study to the correlative problems in the melting law of metal at high pressure, such as equation of state, melting criterion, the material strength in melting region, melting mechanism and the analyse and process of experimental data:(1) The effective Grüneisen coefficient proposed by Anderson has been applied in geophysics and in the calculation of the iron’s meling curve and the results shows that it is a good method. According to the effective Grüneisen coefficient conception and basing on the three term equation of state, we derived the effective Grüneisen equation of state. As an evolution, a new method to calculate shock temperature was proposed, the calculated results with some metals agree with experimental data well.(2) Proposing a melting criterion constraint with 0K equation of state. This melting criterion can picture the high pressure melting curve of metal. Its physical mechanism was givn in the thesis by theoretical analysis and comparing molecular dynamics simulation. It has the same physical meaning as Lindemann melting criterion and the melting criterion given by mean field approach in some conditions.(3) All the proposed high pressure and high temperature constitutive equations have a same limitation, i.e. they can not give the correct behavior of shear modulus in the solid-liquid mixing phase. By introducing the internal energy as power weight, we built a constitutive equation up to liquidus and which has no such a limition. With it, the shear modulus of aluminum along Hugoniot path was calculated, the results agreed experimental data and showed that the chang of shear modulus can be divided into three stages, that is, work hardening, temperature softening and melting.(4) Discussing and analyzing the behavior of shear modulus in solid liquid mixing phase region with Percolation and Renormalized Group. The propagating process of sound in the melting material was analysed with Huygens principle. Then the critical melting mass function was calculated by using percolation and the results were that, at the critical melting mass function 0.313, a percolating liquid region appeared in the melting material, which was just corresponding to the turning point of longitudinal to bulk sound velocity; when melting mass fuction was larger than 0.687, there would be no percolation solid region in the material and this meaned that the shear modulus equaled zero. The analyzing results with percolation also indicated that the method, which was used to determine the shock induced melting region with sound velocities in shock compression experiment, had errors. By analyzing the constitution of liquid and solid of material in melting region along shearing plane, the behavior of shear modulus in melting region is predicted by renormalization group theory and is coincidence with that given by percolation theory.(5) Taking the completing point of shock induced melting region as referring point, the problem, which has been puzzling for a long time, was solved by Huang Haijun. But at the initial point of shock induced melting region, how to modify the shock temperature to the equilibrium melting temperature still is not solved. Using the calculated critical melting mass function and basing the superheating model proposed by Luo et al, we amend the shock temperatue of iron at the initial point of shock induced melting region. The amended equilibrium melting temperature, together with the calculated result by Huang Haijun, the Ma’s and Shen’s static experimental data, is on the same Lindemann melting curve.(6) With the SC experimental means and optical analyzing method, we measured the interfacial temperatures of Ly12Al/LiF around the pressure 100GPa. These interfacial temperature can thought as melting temperature by considering the gap effection.更多还原