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采用分离式霍布金森压杆(split Hopkinson pressure bar,SHPB)试验系统对灰岩,白云岩和砂岩3类岩石进行动态冲击试验,得到岩石的动强度因子,耗散能密度及破碎尺寸与应变率的变化关系。在此基础上结合晶体离散元方法,采用高分辨率扫描和图像处理技术建立了晶体尺度试样模型,研究岩石材料高应变率力学特性和损伤特征。通过与室内SHPB试验对比,验证数值模拟的准确性。结果表明:岩石材料的动态屈服强度具有明显的率相关性,但弹性模量没有随应变率的增加而显著增加;在高应变率下,材料的动强度因子与应变率更符合Ханукаев公式;随着应变率的增加,岩石的破坏形态出现完整型→劈裂破坏→粉碎性破坏转化,这是由细观裂纹的激活数目以及裂纹间的相互作用关系所决定的。裂纹密度的变化和扩展路径的选择是材料动断裂机制,其宏观表现为材料的率效应和破碎成形。
Dynamic rock burst tests on three types of rocks, limestone, dolomite and sandstone, were performed using a split Hopkinson pressure bar (SHPB) test system. The dynamic strength factor, dissipation energy density, crushing size and strain The rate of change relationship. On this basis, a crystal scale specimen model was established by using high-resolution scanning and image processing combined with the discrete element method of crystal. The mechanical properties and damage characteristics of rock materials at high strain rate were studied. By comparing with indoor SHPB test, the accuracy of numerical simulation is verified. The results show that the dynamic yield strength of rock material has a significant rate dependence, but the elastic modulus does not increase significantly with the increase of strain rate. Under high strain rate, the dynamic strength factor and strain rate of the rock material conform to Ханукаев formula. With the increase of strain rate, the failure mode of the rock is characterized by complete type → splitting failure → comminuting failure transformation, which is determined by the number of the mesoscopic cracks and the interaction between the cracks. The change of crack density and the choice of extended path are the mechanism of material dynamic fracture. The macroscopic manifestation is the material rate effect and the crushing forming.