Simulation of refractories fracture using non-local damage models

Refractory materials are crucial components in high-temperature industrial processes, particularly within the steel industry, where they form essential linings in furnaces, ladles, and other critical equipment. The operational reliability of refractories is paramount, as their failure can lead to significant economic repercussions due to unplanned downtime, maintenance costs, and production disruptions. This thesis aims to address the critical challenge of accurately simulating fracture mechanisms in refractories, which are inherently complex due to their microstructural heterogeneity and the extreme conditions under which they operate. The research presented in this thesis primarily focuses on detailed numerical modelling of the fracture process zone (FPZ), emphasizing the quasi-brittle behaviour that characterizes refractory materials. Advanced numerical modelling methodologies, including gradient enhanced damage (GED), phase field model (PFM), and concrete damage plasticity (CDP), are utilized to accurately capture the fracture mechanisms, with a particular focus on tensile failure. The GED and PFM are chosen for their capability to represent the complex interactions between structural elements and fracture phenomena, which are not adequately captured by conventional linear elastic fracture mechanics approaches. An aspect of this study is the comparison of various gradient enhanced damage (GED) models, specifically the standard conventional GED model, the anisotropic stress-based GED model, and the localizing GED model. Each model¿s predictive accuracy, computational efficiency, and ability to realistically represent damage initiation, evolution, and localization within refractories are thoroughly evaluated using the wedge splitting test. Moreover, to better reflect the inherent structural complexity of refractories, a heterogeneous modelling approach is incorporated. This approach implicitly models the distribution of coarse grains, fine aggregates, and matrix materials, significantly improving the simulation accuracy by realistically capturing stress concentrations and damage initiation sites. Recognizing the critical role of creep under high-temperature conditions, the Norton-Bailey creep law is integrated into the numerical framework. This allows for the study of time dependent deformation behaviours and their interactions with fracture processes. Practical application of the developed models is demonstrated through simulations of a ladle shroud, a component vital in the steelmaking process. The simulations successfully predict complex fracture patterns and operational lifespan under realistic thermo-mechanical loading scenarios. Overall, this research advances the numerical simulation capabilities for refractories, providing valuable insights into fracture behaviours and contributing to improved design methodologies and operational reliability in industrial high-temperature applications.