Numerical prediction and experiments for 3D crack propagation in brittle materials based on 3D-generalized maximum tangential strain criterion

Abstract

Accurately predicting and tracing the three-dimensional (3D) propagation and fracture trajectory of a crack inside brittle materials is challenging. One difficulty is that the 3D crack propagation exhibits complex I/II/III mixed-mode expansion, and there is a lack of accurate crack initiation criteria and effective simulation methods. In our previous studies, the 3D-generalized maximum tangential strain (3D-GMTSN) criterion was proposed to determine the direction and onset of 3D fracture initiation. In this study, a Python program based on the 3D-GMTSN criterion is developed and integrated into FRANC3D to predict the 3D propagation trajectory of an arbitrary crack inside brittle solids. To verify the reliability of the new method, three different types of 3D crack modes, namely Internal Inclined Cracks Cuboid (IICC), Edge Notched Disc Bend (ENDB), and Three-Point Bending (TPB), are used for fracture experiments. The 3D crack propagation morphology is identified using high-resolution CT imaging techniques. The IICC, ENDB, and TPB models are simulated using the new method and the conventional numerical method based on the maximum shear stress (MSS), maximumtensile stress (MTS), and maximum energy release rate (MERR) criteria. Comparisons indicate that the proposed method based on the 3D-GMTSN criterion can predict the 3D crack propagation trajectory more accurately than the conventional methods.