Abstract: Analytic solutions and numerical solutions were employed to analyze the effect of the crack face contacting on the Mode-II 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 30°~50° for compression-shear fracture tests.

Key words: centrally cracked Brazilian disk, weight functions, stress intensity factor, crack face contact, confining pressure