Investigation of the impact of micro-cracks on fracture behavior of magnesia products using wedge splitting test and digital image correlation

For refractory materials, a large strain behavior before failure is desired to improve their thermal shock resistance during their service life in industry. Their microstructure (micro-cracked) induces a non-linear mechanical behavior.The present paper aims at applying digital image correlation (DIC) during wedge splitting test on magnesia spinel sample and comparing it to pure magnesia sample so as to study the influence of spinel addition on fracture behavior. From strain measurements based on DIC, the initiation and the propagation of the macro-crack are investigated and the development of micro-cracks network in the case of magnesia spinel which is behind crack branching phenomenon is analyzed. The evolution of the fracture energy required in crack propagation is studied for each material. The experimental results highlight also their mechanical properties dependent on their microstructure.