PBX有效力学性能及本构关系研究

【作者】 敬仕明；

【导师】 龙新平； 李明；

【作者基本信息】 中国工程物理研究院 ， 武器系统与运用工程， 2009， 硕士

【摘要】 本文的主要研究内容如下:1.对PBX有效弹性性能的最新研究进展以及PBX本构关系(即应力应变关系)的研究现状进行了综述。在总结分析文献的基础上,提出了以PBX作为研究对象,着重对其有效弹性性能进行细观力学模拟,以及对不同应变率下(准静态、动态)的力学行为及本构关系进行研究。2.选取了以TATB为基的PBX作为研究对象,在获得单组份力学性能的前提下,采用三种经典的细观力学模型对其有效弹性模量(体积模量、剪切模量)进行了理论计算。模拟计算结果与实验值的对比表明,采用Hashin—Shtrikman法和三阶界限法模拟的有效弹性模量要优于采用Voigt—Reuss界限法所获得的结果。3.设计了系列组分相同但压制密度不同的以TATB为基的PBX样品,测试了它们的弹性模量值。基于细观力学模型的模拟结果,通过引入一个含有密度因素的修正系数,对Hashin-Shtrikman模型进行了改进,获得了该PBX的有效模量跟压制密度的函数关系。改进后的模型能较好地预测以TATB为基的双组份PBX的有效弹性模量。4.测试了以TATB为基的两种PBX(即PBX-1和PBX-2)在准静态加载下的应力-应变曲线,研究了弹性模量、压缩强度等的率相关规律。获得了用于表征两种PBX应变率敏感程度的两个材料参数A和B的值。结果表明,PBX-2力学性能对应变率的依赖性显著弱于PBX-1。5.基于Lemaitre的损伤演化方程,建立了适用于PBX在不同应变率下的损伤演化方程,考虑应变率效应,建立了一个准静态加载下考虑损伤演化的非线性本构方程,该本构方程较好地描述了PBX在低应变率下的力学行为。6.利用Hopkinson压杆,分别测试了以HMX为基的PBX在老化前后的动态应力-应变曲线。研究了老化前后动态强度的变化规律以及率相关规律,并对老化前后的应力应变曲线进行了比较分析。采用忽略低应变率项、含五参数模型的“朱王唐”本构模型,对老化前后的PBX进行了本构曲线的拟合,结果表明该模型能较好地描述以HMX为基的PBX在高应变率下的力学行为,同时拟合出的五个参数并不是常数,而是与应变率相关。更多还原

【Abstract】 The main work of the dissertation is as follows:1. In the first chapter of this dissertation, the effective mechanical properties and the constitutive relations of PBX were reviewed. On the basis of many references, we take PBX into consideration as main work of this dissertation. This dissertation composed of two parts: one is the elastic properties of PBX by micromechanics-based methods, the other is the mechanical behavior and the constitutive relations in quasi-static and dynamic (means in various strain rate)state are explored.2. It is focused on the study of TATB-based PBX, the effective elastic properties of PBX can be obtained by three classical micromechanical models if the elastic properties of the components are known. The bulk modulus and shear modulus of PBX-2 are computed by these theoretical models. The results show that "Hashin-Shtrikman" model and "Third-order bounds"model are better than "Reuss-Voigt bounds" model.3. The samples with different densities were prepared to conduct compressive tests to measure elastic modulus. On the basis of the micromechanics, A new term named "interface bonding parameter" which contains the density of the bulk PBXs was promoted and a modified model of Hashin-Shtrikman model was obtained. The elastic modulus were calculated by classical Hashin-Shtrikman model and by modified model respectively. The results show that the modified model with "interface bonding parameter" can give much more accurate estimates compared to classical hashin-shtrikman model. It proves that the modified Hashin-Shtrikman can be used to predict well the effective modulus of double-composition PBXs.4. The stress-strain relations of two TATB-based PBX are measured by experiment in quasi-static state. And the elastic modulus and compress strength with the strain rate are investigated respectively. As a result, the two parameters, that can characterize the rate denpendency of matrerials, have been obtained. The results show that PBX-2 has less dependency of strain rate than that of PBX-1。5. On the basis of Lemaitre damage evolution laws , the modified damage evolution laws which is applicable for various strain rate of PBX are derived. Consideration that strain rate effect, the nonlinear damage evolution constitutive equations at low strain rate are obtained. The results show that the constitutive equations can describe the mechanical behavior of PBX at low strain rate. 6. By the help of Hopkinson bar, the dynamic stress-strain relations of HMX-based PBX with fresh and aged samples are measured respectively. The relationship between fresh and aged samples of dynamic compress strength and rate-dependency laws are explored respectively. At last, the stress-strain relations with fresh and aged samples are compared also.By using the simplified ZWT model, which be ignored the item of low strain rate -that is include five parameters, the constitutive relations are fitted with fresh and aged samples. The results show that "simplified ZWT model" can describe the mechanical behavior of HMX-based PBX at high strain rate. The results also show that the five fit parameters are not constants, but related to the strain rate.更多还原