裂纹面接触对中心裂纹圆盘应力强度因子影响分析

Analysis of the effect of crack face contact on stress intensity factors for a centrally cracked Brazilian disk

从理论和数值两个方面进行分析,发现受径向集中力和围压作用的中心裂纹圆盘(CCBD)试件裂纹面接触会对II型应力强度因子产生较大的影响。通过理论研究,分析CCBD受集中力和围压作用裂纹面接触时圆盘内部的应力场,采用断裂力学权函数理论,推导得出在集中力和围压共同作用下,考虑裂纹面闭合时应力强度因子的解析解。然后,使用ANSYS软件建立了相应的数值模型计算应力强度因子,并与理论解和相关文献进行对比验证,证明了理论公式的正确性。无论裂纹张合与否,所提出的解析公式都能计算出不同裂纹长度、加载角、围压和摩擦系数的应力强度因子。最后,利用公式分析摩擦系数对应力强度因子的影响,结果表明:随着摩擦系数的增大,I型裂纹的应力强度因子不变,II型裂纹的应力强度因子随之显著减小;当加载角较大时,裂纹面产生更为复杂的二次裂纹,故压剪断裂测试的推荐加载角范围为30°~50°。

Analytic solutions and numerical solutions were employed to analyze the effect of the crack face contacting on the Mode-lI stress intensity factors （SIFs）. The crack face of the centrally cracked Brazilian disk （CCBD） specimen was subjected to both the confining pressure and diametrical force. Through the theoretical study, the stress field inside the CCBD specimen was analyzed under different loading conditions when the crack surface contacted. Then, an analytical formula was obtained for calculating the Mode-II SIFs in CCBD specimen under different loading conditions by using the weight function method. Meanwhile, a numerical modeling by ANSYS software is used to calculate the corresponding SIFs. By comparing numerical results and theoretical solutions, it is found that they are in good agreement, which indicates that the reliability of the theoretical analysis is valid. Even if the crack is closing, the SIFs can be obtained explicitly and easily for any arbitrary relative crack length, loading angle, confining pressure and friction coefficient. Finally, the effect of the coefficient of friction on SIFs in a CCBD specimen was investigated. The results show that the Mode-II SIF decreased significantly with the increase of friction coefficient, while the Mode-I SIF was constant. In addition, more complex secondary cracks were produced on the crack surface when the load angle was larger. Hence, the recommended loading angle range is 300-50° for compression-shear fracture tests.