PBX炸药含各向异性损伤的黏弹性统计微裂纹本构模型初步研究

Initial Study on Constitutive Model of PBXs via Viscoelastic Statistical Crack Mechanics Including Anisotropic Damage

建立含损伤本构模型是研究炸药动态力学响应规律的基础。基于PBX炸药材料的宏观黏弹性特征和细观上微裂纹面的方向性,建立了含各向异性损伤的黏弹性统计微裂纹(Aniso-Visco SCRAM)本构模型,简化后得到单轴应力加载下的本构方程。利用数值计算程序,以PBX9501为例,分析了微裂纹扩展的各向异性、PBX炸药破坏强度及临界应变的拉压异性和应变率相关性,考察了微裂纹数密度、初始微裂纹尺寸、微裂纹面摩擦系数及断裂表面能4个主要参数的敏感性及影响规律。结果表明,它们对微裂纹的扩展演化有较大影响,进而导致材料表现出不同的力学响应。

Building constitutive models that include damage is the foundation for the research of dynamic mechanical responses of explosives.Based on the viscoelastic character on macroscale and the crack directions on mesoscale,we established a viscoelastic statistical crack mechanics including anisotropic damage,and then obtained the simplified constitutive model under uniaxial loading.By using a numerical program,and taking PBX9501 as an example,we analyzed the extension rules of cracks with various directions,and the strength-difference and strain-rate dependence of failure strength and critical strain of explosives.Furthermore,we discussed the sensitivity of 4main parameters,the crack number density,the initial crack size,the friction coefficient between crack surfaces and the fracture surface energy.The result demonstrates that the 4parameters greatly affect the extension and evolvement of cracks,which causes the different mechanical responses of explosives.