Comprehensive data for calculating the higher order terms of crack tip stress field in disk-type specimens under mixed mode loading

• The dimensionless form of coefficients of singular, second and third stress terms at the vicinity of crack tip were calculated for two disk-type specimens in wide range of mixed mode I/II loading.
• The state of pure mode II conditions was found for both specimens.
• As important parameters for predicting the size and geometry effects in mode I fracture resistance of quasi-brittle materials, the coefficient of third stress term was comprehensively determined for both disk-type samples.

The aim of this paper is to determine the coefficients of singular, T-stress and third terms of crack tip stress field for two disk-type specimens under wide range combinations of mixed-mode I/II loading. The first specimen is a centrally cracked circular disk subjected to diametral load (CCCD sample) and the second one is a semi-circular disk under three-point bending (SCB sample). Using finite element method, the stress intensity factors KI and KII are calculated for two samples and then the state of pure mode II loading is expressed for each specimen. As an important parameter to predict the fracture toughness of quasi-brittle materials taking into account the geometry effect, the sign and magnitude of term A3 are determined for both samples under pure mode I condition. It is found that the sign of A3 is negative for any configurations of SCB sample under pure mode I while its sign for CCCD can be negative or positive corresponding to the ratio of a/R.