Numerical Study of Thermal Shock Damage Mechanism of Polycrystalline Ceramics

Zhenyuan Gong,Kang Guan,Zhiqiang Feng,Pinggen Rao,Jiantao Liu,Qingfeng Zeng

doi:10.3389/fmats.2021.724377

Abstract

A dual-scale model is proposed to study the effect of microstructure parameters (grain size and grain boundary fracture energy) on the thermal shock damage mechanism on an example of alumina. At microscale, representative volume element (RVE) models generated by Voronoi tessellation are simulated to obtain the mechanical parameters for macro models. At macroscale, a coupled thermomechanical model based on the finite–discrete element method (FDEM) is applied to simulate the crack nucleation and propagation. Energy dissipation (ALLDMD) is introduced to investigate the thermal shock cracking mechanism by combining crack patterns and crack density, which indicates that decreasing grain size and increasing grain boundary fracture energy have a positive effect on thermal shock resistance. The proposed models not only predict the critical stress temperature which is well consistent to the theoretical thermal shock resistance factor, but also quantify the two previously unconsidered stages (crack nucleation and crack instability stage). Our models suggest the crack nucleation and instability will not occur immediately when the model reaches critical stress, but the models can sustain for higher temperature difference. The thermal shock damage mechanism and the influence of microstructural parameters on thermal shock resistance have also been discussed in detail.

Highlights

Ceramic materials, with high melting point, hardness and low thermal conductivity, are widely applied in the field of machinery, aerospace and civil engineering due to their excellent performance at elevated temperature, such as Al2O3, ZrO2, ZrB2, and HfB2 (Singh et al, 1981; Opeka et al, 1999; Panda et al, 2002; Schmitt et al, 2002; Jiang et al, 2012; Shao and Song, 2017; Qian et al, 2018; Zhang et al, 2018; Li et al, 2014)
A dual-scale model was constructed to investigate the effect of grain size and grain boundary fracture energy on the thermal shock resistance property by simulating the cooling test on an example of alumina
To further comprehend the mechanism of crack nucleation and propagation caused by thermal shock, damage dissipation energy curves (ALLDMD) are introduced to study how the microstructure parameters influence the thermal cracking behavior and evaluate the thermal shock property of materials

Summary

INTRODUCTION

With high melting point, hardness and low thermal conductivity, are widely applied in the field of machinery, aerospace and civil engineering due to their excellent performance at elevated temperature, such as Al2O3, ZrO2, ZrB2, and HfB2 (Singh et al, 1981; Opeka et al, 1999; Panda et al, 2002; Schmitt et al, 2002; Jiang et al, 2012; Shao and Song, 2017; Qian et al, 2018; Zhang et al, 2018; Li et al, 2014). Yan et al (2020) used the finite–discrete element method (FDEM) coupled with a thermomechanical model to study the thermal shock cracking They investigated the influence of initial temperature, thermal conductivity, and heat transfer coefficient on thermal shock resistance by observing the crack pattern. In terms of material properties, Gc represents GIc and GIIc, respectively, which correspond to the strain energy release rates for mode I and mode II, respectively They can be expressed as follows (Munjiza and Andrews, 1998; Munjiza et al, 1999; Munjiza and Andrews, 2000; Munjiza et al, 2004; Lisjak et al, 2013; Yan et al, 2019): Or. Sequentially coupled thermomechanical model was used to analyze the thermal shock behavior of ceramic in our study. CpM where Qtotal is the total heat flowing, M is the mass of model, and Cp is the specific heat of the solid

AND DISCUSSION

CONCLUSION