Finite element study of mixed mode loading of the cracked semicircular disc under bending

Numerical and experimental works are performed on the mixed-mode I/II brittle fracture by two types of edge cracked semicircular bend specimens. The first type is edge cracked semi-circular bend (SBC) specimens with vertical and inclined notches. The second type of specimens is semi-circular samples in which the contribution of Mode I and Mode II components varies by changing the bottom loading support. In the test numerical program fracture tests were conducted at crack inclination angles of 0º, 10-45º, 49º, 50-80º. The stress intensity factors for Mode I and Mode II loading and T-stresses are obtained numerically in FEM package SIMULIA Abaqus/CAE. The results of FEM modeling are compared with the experimental results obtained by the photoelasticity method. The experimental approach based on the photoelasticity method allows us to observe the von Mises equivalent stress distribution in the whole specimen and confirm the FEM studies performed. The comparison shows that in the specimens the pure Mode II loading cannot be realized. Analysis of numerical studies and isochromatic fringe patterns allows us to conclude that in the semicircular disc the mixed mode loadings are realized for all angles from 0 to 85º. The pure Mode II or sliding fracture can not be created by so- called Mode II loading in disc-type specimens SCB, because there are opening displacements observed for all the specimens investigated numerically and experimentally.