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用大直径(φ100 mm)分离式霍普金森压杆径向冲击边裂纹平台圆环试样,测试砂岩的Ⅰ型动态断裂韧度。使用裂纹扩展计(crack propagation gauge,CPG)测定试样起裂时刻和裂纹扩展速度,结果表明裂纹扩展计测定比传统电阻应变片更为灵敏,测定结果更接近裂纹破坏真实情况。用实验-数值法确定了试样的动态起裂韧度,采用实验-数值法并结合普适函数进一步求得砂岩的动态扩展韧度。研究发现在一定范围内动态起裂韧度随加载率的增加而增大,而动态扩展韧度随裂纹扩展速度的变大而略微增加。
The type Ⅰ dynamic fracture toughness of the sandstone was tested with a large diameter (φ100 mm) split ring specimen of the radial impact cracked platform of Hopkinson pressure bar. Crack propagation gauge (crack propagation gauge, CPG) was used to determine the crack initiation time and the crack growth rate. The results show that the crack expansion meter is more sensitive than the traditional strain gauge and the results are closer to the real situation of crack damage. The dynamic fracture toughness of the sample was determined by the experiment - numerical method. The dynamic expansion toughness of the sandstone was further obtained by the experiment - numerical method combined with the universal function. It is found that the dynamic fracture toughness increases with the increase of the loading rate within a certain range, while the dynamic expansion toughness slightly increases with the crack growth rate.