Experimental and Numerical Analyses of Mixed Mode Crack Initiation Angle

This paper presents a study for predicting crack initiation angle in the case of mixed mode fracture i.e., opening and sliding mode. Experimental and numerical analyses were carried out using photoelasticity and ANSYS finite element program, respectively. Polycarbonate specimens with a thickness of 3mm and different angles of inclinations namely 0° and 22.5° were considered in this analysis. Predicting the crack initiation angles is dependent on the value of stress in the vicinity of the crack tip. As a result, stress intensity factor is considered as the most significant parameter in this regard because it represents the stress level at the crack tip. In experimental analysis Schroedl and Smith method is used to calculate the pure opening mode stress intensity factor (K_I) and Smith and Smith method for the mixed mode case (K_I & K_II). Then, SIF’s for straight and inclined crack are determined numerically using ANSYS. After that, the values of stress intensities are incorporated in minimum strain energy density criterion (S-Criterion) to find the crack’s angle of initiation.