Damage evolution and fracture behavior of different materials specimens containing a central hole subjected to local loading.

The strength of the different materials specimens containing a central hole subjected to varying loading areas constitutes lots of underground engineering such as entry arrangement and mining process. In this study, the failure resulted from micro-fracturing in the specimen, which can be characterized by the crack propagation path if the damage events are monitored by using Digital Image Correlation (DIC), infrared thermal imager and high-speed camera. The experimental results demonstrate that there are three different types of typical failure modes for specimens with central holes according to the loading areas. The evolution of the temperature field is shown for various loading areas, the smaller loading area, the greater the stress concentration, and the more pronounced the thermodynamic features. The temperature field can also be associated with material properties in addition to loading area. Additionally, failure around the hole with redistributed stress has been observed, and strain energy density (SED) can help explain the failure mechanisms. The progressive damage process, which takes into account the heterogeneity in elastic modulus and rock strength characteristic, is demonstrated by developing a constitutive model that uses the uniaxial compression and Brazilian disc tests to parameterize it. By comparison with plastic zone, the proposed constitutive model is used to quantitatively evaluate the accumulation of damage. Failure mechanisms are established based on this work and are anticipated to be extensively utilized in engineering applications.