岩石断裂韧度CCNSCB方法渐进破坏机制与无量纲应力强度因子宽范围标定

国际岩石力学学会建议了4种岩石I型断裂韧度（KIC）测试方法。将建议方法的人字形切槽巴西圆盘试样与直切槽半圆盘试样结合，可以得到具有诸多优点的人字形切槽半圆盘（CCNSCB）三点弯曲试样。近年来，CCNSCB方法受到许多关注，然而，其渐进破坏过程却尚未进行有效的评估。为此，对其进行了数值研究，其内容包括：进行细观损伤力学模拟，直观展现CCNSCB试样渐进断裂过程；考虑不同支撑跨距与直径之比（ ）的影响，发现 愈大，愈加符合测试原理，建议 取0.8；采用有限元子模型技术对CCNSCB方法（ 0.8）中计算KIC的关键参数-临界无量纲应力强度因子（ ）进行了宽范围标定，可供相关研究直接查取；细观损伤力学模拟峰值力对应的临界裂纹与有限元标定 对应的临界裂纹较为一致，证明CCNSCB方法测试原理的合理性，以及数值模拟与 标定结果的有效性。

Progressive fracture mechanism of CCNSCB rock fracture toughness specimens and calibration of wide-range dimensionless stress intensity factors

International Society for Rock Mechanics has suggested four methods for measuring Mode-I fracture toughness (KIC) of rocks. By combining the suggested semi-circular bend specimen and cracked chevron notched Brazilian disc, the cracked chevron notched semi-circular bend (CCNSCB) specimen is produced, which inherits many merits from previous methods. The CCNSCB method has recently received much attention by researchers for testing KIC of rocks, but has not been numerically assessed. Thus，the method is numerically studied and the progressive fracture process is presented via meso-damage mechanical analysis. Considering different span to diameter ratios , the results show that the real fracture is more aligned with the measuring principle while β is greater. Therefore, β=0.8 is suggested. The minimum dimensionless stress intensity factor , which is critical to determine the KIC value, is calibrated by finite element method (FEM) with a sub-modelling technique for diversified CCNSCB geometries in terms of β=0.8. The calibrated values are conveniently obtained for other relevant researches. The critical crack corresponding to the peak load simulated by microscopic damage mechanics is quite consistent with that corresponding to the calibrated via FEM. It is indicated that the CCNSCB method is appropriate to measure KIC of rocks and the numerical simulations as well as the calibration of values are effective.