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用大直径分离式霍普金森压杆冲击砂岩的压缩单裂纹圆孔板,成功地监测到Ⅰ型动态断裂的全过程。实验中由裂纹扩展计分别纪录了动态起裂、扩展、止裂、和再起裂时刻,采用分形裂纹扩展模型分析曲折裂纹的扩展速度,最后用实验-数值-解析法确定砂岩的动态起裂韧度、动态扩展韧度、动态止裂韧度以及二次动态起裂韧度。动态断裂全过程的实验结果表明:裂纹扩展路径为不规则曲线,此时裂纹动态扩展速度表征的普适函数值会比假设裂纹路径为直线时小;利用分形模型得到更加接近真实的动态扩展韧度;砂岩的动态起裂韧度大于动态止裂韧度;由于初次动态起裂时的裂纹实为人工切槽,而二次动态起裂时为天然形成的裂纹因而非常尖锐,初次动态起裂韧度略大于二次动态起裂韧度。
The large-diameter split Hopkinson pressure bar was used to impact the compressed single-crack circular hole plate of sandstone, and the whole process of type Ⅰ dynamic fracture was successfully monitored. In the experiment, the dynamic crack initiation, propagation, crack arrest and re-initiation time were recorded by the crack extensometer. The fractal crack growth model was used to analyze the propagation speed of the flexural crack. Finally, the dynamic fracture initiation Degrees, Dynamic Expansion Toughness, Dynamic Toughness, and Secondary Dynamic Toughness. The experimental results of the whole process of dynamic fracture show that the crack propagation path is an irregular curve, and the universal function value of the crack propagation velocity is smaller than that of the assumed crack path. The fractal model is more dynamic Degree of dynamic fracture toughness of the sandstone is greater than the dynamic fracture toughness; because the first dynamic crack initiation is actually artificial slotting, and the second dynamic cracking is a natural formation of the crack and therefore very sharp, the first dynamic cracking Toughness slightly larger than the second dynamic initiation fracture toughness.