Determination of crack initiation and propagation in two disc shaped specimens using the improved maximum tangential stress criterion

The crack initiation angle and propagation path for two different disc shaped test specimens
(i.e., SCB and CBD specimen) are investigated experimentally and theoretically. The Maximum
Tangential Stress (MTS) criterion does not calculate the crack initiation angle in SCB
and CBD specimens correctly. Moreover, at the angles after occurrence of pure mode II,
where the stress intensity factor of mode I becomes negative, this criterion is not applicable.
Therefore, in this research work, Improved MTS (IMTS) criterion which has been implemented
in the extended finite element method and is applicable under tensile and compressive
loading conditions to examine the crack propagation path in the aforementioned disc shaped
specimens. Furthermore, an experimental study on a cracked Brazilian disc specimen has
been conducted at different angles. Results of IMTS criterion in these specimens show that
the crack propagation path and the crack initiation angle can be predicted theoretically by
using IMTS criterion.