横观各向同性岩石亚临界裂纹扩展实验研究

Experimental study for subcritical crack growth of transverse isotropy rock

在MTS Insight电子拉力试验机上采用常位移松弛法,对具横观各向同性的板岩开展亚临界裂纹扩展试验研究,获得应力强度因子KI与裂纹扩展速率v的关系及I型断裂韧度KIC,揭示不同节理倾角α下裂纹亚临界扩展规律。研究结果表明:各个节理倾角下的lgK_I-lgv具有很好的线性规律;当节理倾角为0°~45°时,回归参数a随倾角的增大而增大,回归参数b随倾角的增大而减小;当节理倾角为45°~90°时,回归参数a随倾角的增大而减小,回归参数b随倾角的增大而增大,亚临界裂纹扩展参数A和n分别与回归参数a和b变化规律相同;断裂韧度KIC以及松弛最大荷载P_(max)均符合"U"型抛物线分布,当节理倾角为0°~45°时,两者随倾角的增加而减小,当节理倾角为45°~90°时,两者随倾角的增加而增大,同时,两者均在节理倾角为0°时取得最大值,在节理倾角为45°时取得最小值。

Subcritical crack growth in transverse isotropy slate was investigated experimentally using constant displacement load relaxation method on MTS insight electronic tensile testing machine. The relationship between the stress intensity factor KI and the crack velocity v and the fracture toughness KIC were obtained by the test. The growth behavior of subcritical crack was connected with different joint inclination angles. The results show that lg KI-lgv relationships are in accordance with linear rule, i.e. when the joint inclination angle α is in the range of 0° to 45°,the regression parameter a increases with the increase of α and the regression parameter b decreases with the increase of α, and when the joint inclination angle α is in the range of 45° to 90°, a decreases with the increase of α and the regression parameter b is just the opposite. The change laws of subcritical crack growth parameters A and n are the same with those of the factors a and b, respectively. Both the fracture toughness KIC and the relaxation maximum load Pmax obey the ＂U＂shaped parabolic distribution. When α is in the range of 0° to 45°, these two factors decrease with the increase of α,and when α is in the range of 45° to 90°,these two factors increase with the increase of α. In addition, the two factors reach the maximum value when the angle is 0° and reach the minimum when the angle is 45.