岩石Ⅱ型断裂韧度测试的三个基本问题与分析

Three basic problems and analysis in testing mode Ⅱ fracture toughness of rocks

针对测试岩石Ⅱ型断裂韧度的单边切槽试样,提出三个必须解决的基本问题:试样与压头的摩擦、裂缝面间摩擦分别对测试结果影响如何;若裂缝面无接触,该试样能否测得有效的Ⅱ型断裂韧度。通过有限元软件ABAQUS,计算其不同情况下的岩石Ⅱ型断裂应力强度因子K_(Ⅱ),研究发现:试样与压头间摩擦对Ⅱ型断裂韧度的计算影响很大,应予以考虑;若裂缝面接触,应采用数值方法计算;若裂缝面无接触,该试样仍能测得有效的Ⅱ型断裂韧度。最后,提出试验测试与数值模拟相结合的更为准确的方法。

Aiming at single-notched specimen which is used to test mode Ⅱ fracture toughness of rocks, three basic problems that must be solved were proposed: what the effects of the friction between the specimen and the indenter, friction between the crack surfaces on the test results. When the crack surfaces are not in contact, whether effective mode Ⅱ fracture toughness could be tested by single-notched specimen. The finite element software ABAQUS was used to calculate the mode Ⅱ fracture stress intensity factor of single-notched specimen under different conditions. It is found that: the friction between the specimen and the indenter has a great influence on the calculation and should be considered when calculating mode Ⅱ fracture toughness by numerical method. When the crack surfaces is in contact, the friction between the crack surfaces also should be considered. When the crack surfaces are not in contact, effective mode Ⅱ fracture toughness could be tested by single-notched specimen. In the end, a combined method of experimental test and numerical simulation is proposed to obtain a more accurate mode Ⅱ fracture toughness of rock.