Thermo-mechanical response FEM simulation of ceramic refractories undergoing severe temperature variations

Abstract

The development of thermal stresses inside refractory ceramics experiencing severe thermal shock is studied. The present analysis departs from the linear theory of thermal stresses as it accounts for temperature dependent thermal and mechanical material properties. Radiation surface heat exchange between the refractory component and its surroundings is included. A Finite Element Procedure is presented and a MATLAB code is developed. The nonlinear heat equation is solved for the temperature field and this solution is subsequently used in order to determine the stress field evolution. The finite element code is validated and used for the thermal shock estimation of a refractory brick. Material properties corresponding to Al 2 O 3 are selected. A thermal cycle consisting of a heating stage followed by cooling down is simulated. The results are compared with those predicted by the linear thermal stresses theory and significant deviations are observed for the examined values of the Biot number.

Simulation of thermal shock cracking in ceramics using bond-based peridynamics and FEM

“…This need is reflected by the vast scientific effort to accurately capture the variation of these parameters in a wide range of temperatures [21]- [24]. Based on experimental data for polycrystalline alumina, the temperature dependency of the specific heat capacity and thermal conductivity can be approximated with adequate accuracy by inverse power laws [19]:…”

“…It is obvious that as temperature increases, the specific heat capacity increases while the thermal conductivity decreases. This is expected, as materials at higher temperatures tend to store heat instead of conducting it [19], [23].…”

“…where, = 5.67 10 −8 W -2 K -4 , is the Stefan-Boltzmann constant and is the temperature at the surface of the solid. Following [19], heat loss due to radiation is taken as = 0.80.…”

“…More recent studies on thermal shock employ elaborate lattice [13], nonlocal ( [14] and [15]) and gradient ([5] and [16]) models to simulate the initiation and propagation of cracks as well as approaches for the incorporation of microstructural characteristics [17], [18]. Additionally, studies on the induced thermal stresses have illustrated that it is crucial to account for temperature dependent material parameters in the simulations [6], [19]. Usually, materials tend to exhibit a softening behaviour as the temperature increases due to decrease of Young's modulus.…”

“…As reported in [6], not considering the temperature dependency of the material properties tends to lead to underestimation of the actual thermal shock resistance. In their work, Papathanasiou et al [19] carried out a detailed investigation on the thermomechanical response of ceramic refractories under extreme temperature changes. The nonlinear heat equation was solved using FEM for a 2D problem, taking into consideration radiation heat exchange and temperature dependant thermal and elastic material properties.…”