含缺陷分布的β-HMX单晶动态拉伸变形及破坏机理

Dynamic Tensile Deformation and Failure Mechanism of β-HMX Single Crystal With Defect Distribution

为研究β-HMX炸药晶体内部缺陷对其力学行为的影响,采用分子动力学方法,基于Smith力场模拟含不同缺陷特征(孔隙率、孔洞数量和孔洞分布形态)的β-HMX单晶在动态拉伸下的变形、损伤及破坏过程。研究结果表明:孔隙率由1%增大至2%,β-HMX单晶的抗拉强度与完美单晶相比下降5.3%~11.2%,杨氏模量降低3.6%~13.4%;孔隙率不变的条件下,材料的抗拉强度会随着孔洞数量的增多而下降;当孔洞间距较小时,在拉伸过程中孔洞之间发生相互作用,导致材料的抗拉强度降低;孔洞的分布形态对β-HMX炸药单晶抗拉强度影响较为明显,不同应变率下β-HMX单晶的破坏机理具有明显差异,在5×10~9 s^(-1)拉伸应变率下孔洞周围先形成细小裂纹,裂纹逐渐扩展导致β-HMX单晶发生断裂,材料具有明显断口,在1×10^(11) s^(-1)拉伸应变率下,β-HMX单晶内部形成多条裂纹,导致材料破坏失效;获得了含缺陷分布的β-HMX单晶动态拉伸变形及破坏机理,为优化β-HMX及其混合炸药的制备工艺和提高其力学性能提供了理论依据。

The deformation,damage and failure process of β-HMX single crystal with different defect characteristics(porosity,void number and void distribution morphology) under dynamic tension are simulated by molecular dynamics method based on Smith force field.The influence of internal defects in β-HMX single crystal on its mechanical behavior is studied through simulation.The results show that,when the porosity increases from 1% to 2%,the tensile strength of β-HMX single crystal is decreased by 5.3%-11.2% compared with the perfect single crystal,and the Young's modulus is decreased by 3.6%-13.4%.When the porosity is constant,the tensile strength of the crystal decreases with the increase in the nuer of void.When the distance between the voids is small,the interaction between the voids is presented during the tensile process,resulting in the decrease of the tensile strength.The distribution of voids has a significant effect on the tensile strength of β-HMX single crystal.The failure mechanism of β-HMX single crystal under different strain rates is obviously different.Small cracks are formed around the voids at the tensile strain rate of 5×10^(9) s^(-1),and the cracks gradually expand,which leads to the fracture of β-HMX single crystal.The material has obvious fracture.Multiple cracks were formed inside the β-HMX single crystal under the tensile strain rate of 1×10^(11) s^(-1),resulting in the failure of the material.The dynamic tensile deformation and failure mechanism of β-HMX single crystal with defect distribution are obtained,which provides a theoretical basis for optimizing the preparation process of β-HMX and its mixed explosives and improving their mechanical properties.