Thermal shock resistance of magnesia spinel refractories—Investigation with the concept of configurational forces

In magnesia-spinel refractories, spinel inclusions are embedded in a magnesia matrix in order to increase the thermal shock resistance by micro-crack toughening. The paper investigates damage evolution in the material during the cooling at the end of the production process by a sophisticated numerical analysis. After a stress-strain analysis on a large representative volume element, the development of the damage zone between spinel grains is simulated with the concrete damaged plasticity model of ABAQUS. Application of the concept of configurational forces allows the physically correct determination of the driving force for cracks in the elastic quasi-plastic matrix material. The results demonstrate that inherent matrix cracks are unable to grow during the cooling, but they strongly influence the initiation and development of the damage zone. The pronounced damage initiation, in combination with the low crack driving force, is the main reason for the good thermal shock resistance of magnesia spinel refractories.