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首页> 外文期刊>International Journal of Rock Mechanics and Mining Sciences >Experimental calibration of stress intensity factors of the ISRM suggested cracked chevron-notched Brazilian disc specimen used for determination of mode-l fracture toughness
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Experimental calibration of stress intensity factors of the ISRM suggested cracked chevron-notched Brazilian disc specimen used for determination of mode-l fracture toughness

机译：ISRM应力强度因子的实验校准表明，有裂纹的人字形缺口巴西圆盘试样可用于确定I型断裂韧性

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摘要

The choice of the revised values of mu and upsilon constants (Tables 6 and 7 [10]) for calculating the critical dimension-less stress intensity factor (Y*_(min) = mu e~(upsilon alpha 1)) for the cracked chevron notch Brazilian disc (CCNBD) test specimens did not significantly improve the results. The fracture toughness values obtained by incorporating the suggested improvements (but using the standard equation given in [6]) failed to make the reported values comparable to the values obtained by CB method for the case of Barre and Laurentian granites. This also applied to both the corrected and the original formula used in the CCNBD method. In the case of Stanstead granite, no such firm conclusion can be made because of the greater scatter in the CCNBD values obtained from the three specimen types (i.e., samples prepared along line 5, at centre and along line 2 of the valid geometrical range). The revised mu and upsilon values only resulted in an increase in the fracture toughness values obtained by the CCNBD method but did not eliminate the large discrepancy between the two methods. The main cause of the discrepancy could be traced to the erroneous substitution of 'radius' for 'diameter' in the equation for calculating fracture toughness, and therefore, the suggested changes were unwarranted. Use of the correct formula for calculation of K_(IC) as outlined in the investigation should eliminate the reported difference between CCNBD and CB values. It should also be noted that any future comparison between these two methods should take into consideration any possible anisotropy of measured K_(IC), which may be the case when the notch axis is varied randomly. In the present investigation, the notch axis was kept fixed with reference to a specific seismic velocity direction to eliminate the effects of possible anisotropy on measured fracture toughness values. The observed discrepancy between the CCNBD and CB methods, until now, is thus explained and eliminated in future studies employing the CCNBD method.
机译：选择mu和upsilon常数的修正值（表6和表7 [10]）以计算裂缝的临界无因次应力强度因子（Y * _（min）= mu e〜（upsilon alpha 1））。人字形缺口巴西圆盘（CCNBD）测试标本并未显着改善结果。通过结合建议的改进方法获得的断裂韧性值（但使用[6]中给出的标准方程式）无法使报告的值与使用Barre和Laurentian花岗岩的CB方法获得的值可比。这也适用于CCNBD方法中使用的校正公式和原始公式。对于Stanstead花岗岩，由于从三种样品类型（即，沿有效几何范围的中心5和中心2沿线5制备的样品）的CCNBD值具有较大的分散性，因此无法得出如此肯定的结论。 。修改后的mu和upsilon值仅导致通过CCNBD方法获得的断裂韧性值增加，但并没有消除这两种方法之间的巨大差异。导致差异的主要原因可归因于在计算断裂韧度的公式中用“半径”错误地替换了“直径”，因此，建议的更改是不必要的。如调查中所述，使用正确的公式计算K_（IC）应消除所报告的CCNBD和CB值之间的差异。还应注意，这两种方法之间的任何将来比较都应考虑到所测得的K_（IC）的任何可能的各向异性，这可能是切口轴随机变化的情况。在本研究中，缺口轴相对于特定地震速度方向保持固定，以消除可能的各向异性对测得的断裂韧性值的影响。因此，到目前为止，在CCNBD和CB方法之间观察到的差异已得到解释，并在以后使用CCNBD方法的研究中予以消除。

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