论文部分内容阅读
人字形切槽巴西圆盘(CCNBD)岩石试样由于诸多优点,被国际岩石力学学会确定为岩石I型断裂韧度测试建议方法,并被众多学者应用于复合型(包括纯Ⅱ型)断裂试验研究。然而,CCNBD在复合型荷载下的渐进断裂机理尚未完全获悉,复合型断裂韧度测试基于的穿透直裂纹扩展假设并未严格评估,用于复合型断裂研究的合理性还未得到有效验证。采用细观损伤力学软件首次模拟得到CCNBD在复合型荷载下的渐进破坏过程。结果显示:裂纹不仅萌生于人字形韧带尖端,且易产生于切槽边缘,造成真实裂纹前缘为曲线形,与人字形切槽试样断裂韧度测试所基于的穿透直裂纹假设不符;裂纹并非沿着预制人字形韧带平面扩展到其根部,切槽边缘的破裂方向均朝向加载端,形成扭曲的三维翼形裂纹。数值模拟结果同物理实验对比,十分吻合。CCNBD的裂纹形态和渐进扩展规律不符合当前普遍采用的复合型测试原理,因此采用CCNBD试样进行岩石复合型(包括纯Ⅱ型)断裂韧度测试值得商榷。
The Herringbone Grooved Brazilian Disc (CCNBD) rock specimen has been identified by the International Society of Rock Mechanics as the recommended method for testing Type I fracture toughness due to its many advantages and has been used by many scholars in composite (including pure Type II) fracture tests the study. However, the mechanism of progressive fracture of CCNBD under composite loading is not fully understood. The assumption of composite fracture toughness test based on penetrating crack propagation is not critically evaluated. The rationality of composite fracture research has not been validated yet. Using the meso-damage mechanics software, the progressive failure of CCNBD under composite loading was obtained. The results show that the cracks not only originate from the tip of the herringbone ligament but also tend to occur at the edge of the groove. The leading edge of the real crack is curvilinear, which is inconsistent with the hypothesis of penetrating straight crack based on the fracture toughness test of chevron notched specimen. Cracks do not extend along the plane of the prefabricated herringbone ligament to their roots. The rupture direction of the notch edges is toward the loading end, forming a distorted three-dimensional wing crack. The numerical simulation results are in good agreement with the physical experiments. CCNBD crack morphology and gradual expansion of the law does not meet the currently commonly used composite test principle, so the use of CCNBD composite rock specimens (including pure type II) fracture toughness test is open to question.