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首页> 外文期刊>Engineering Fracture Mechanics >Crack initiation, propagation and coalescence from frictional flaws in uniaxial compression
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Crack initiation, propagation and coalescence from frictional flaws in uniaxial compression

机译：单轴压缩中的摩擦缺陷引起的裂纹萌生，扩展和合并

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摘要

An extensive experimental program has been conducted on pre-cracked specimens of a rock-model material to investigate crack propagation and coalescence from frictional discontinuities. Prismatic gypsum specimens have been prepared with three pre-existing closed cracks (flaws). The flaws all have a constant length of 12.7 mm and are parallel to each other. Different geometries are obtained by changing the angle of the flaws with respect to the direction of loading, the spacing, and the continuity of the flaws. In the experiments, three different types of cracks have been observed: wing cracks, coplanar shear, and oblique shear cracks. These are the same types of cracks observed with open flaws. Crack initiation occurs simultaneously at all the tips of the flaws for wing and shear cracks. Mean crack initiation stress is higher for secondary cracks than for wing cracks. The differences however decrease as the flaws are oriented at smaller angles with the direction of loading. The types of coalescence (i.e. the type of cracks and crack pattern that link two flaws) from closed flaws are similar to those from open flaws. However, the type of coalescence observed in a specimen with open flaws is not necessarily produced when using the same geometry but with closed flaws. The most important conclusion reached in this research is that the fracturing processes in open and closed flaws are similar. Friction along the flaws increases the initiation and coalescence stress and favors linkage through shear cracks.
机译：在岩石模型材料的预开裂标本上进行了广泛的实验程序，以研究由于摩擦不连续而导致的裂纹扩展和合并。已准备了具有三个预先存在的闭合裂纹（缺陷）的棱柱形石膏标本。裂纹均具有12.7毫米的恒定长度，并且彼此平行。通过改变缺陷相对于加载方向，缺陷的间隔和连续性的角度，可以获得不同的几何形状。在实验中，已观察到三种不同类型的裂纹：机翼裂纹，共面剪切和倾斜剪切裂纹。这些是观察到具有开放缺陷的相同类型的裂纹。裂纹的产生同时发生在机翼和剪切裂纹的所有裂纹尖端。次生裂纹的平均裂纹萌生应力高于翼形裂纹。但是，随着裂纹与载荷方向成较小角度取向时，差异减小。闭合缺陷的合并类型（即连接两个缺陷的裂纹和裂纹模式的类型）与开放缺陷的相似。但是，当使用相同的几何形状但具有闭合缺陷时，不一定会在具有开放缺陷的样品中观察到的聚结类型。这项研究得出的最重要的结论是，开放和闭合缺陷中的压裂过程是相似的。沿裂纹的摩擦会增加初始应力和聚结应力，并有利于通过剪切裂纹进行连接。

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