陶瓷材料热冲击开裂机理与裂纹间距预报

该文研究陶瓷材料热冲击开裂机理和热冲击裂纹的分布规律。1mm厚的99Al2O3陶瓷薄片的水淬实验显示:裂纹间距随热冲击温差增大而减小，在同一热冲击温差下，5个试件中的各个裂纹间距与平均间距的偏差不超过7%。理论上，结合传热学和力学方法，计算了热冲击过程中试件的瞬态温度场和应力场，阐述了陶瓷材料热冲击条件下的开裂机理。以裂纹间距和深度作为变量，利用最小能量原理，发展了热冲击裂纹间距预报的有限元方法。由于从文献获得的毕渥数数据分散度很大，并且难以直接测量，因此发展了“间接测量法”，逆向估计了实验过程中的毕渥数，并在其他温度点获得了与实验吻合很好的裂纹间距数值预报结果。该文的研究对深入理解陶瓷材料的热冲击失效机制，对陶瓷材料的改性和研制有重要的意义。

CRACKING MECHANISM AND PREDICTION OF CRACK SPACING OF CERAMICS UNDER THERMAL SHOCK

The cracking mechanism and crack distribution law of thermally shocked ceramics were studied. The water quenching experiment of 99Al2O3 ceramic specimens with thickness of 1mm showed that the spacing of cracks decreased with the increase of thermal shock temperature differences. The difference between individual crack spacing and the average spacing didn’t exceed 7% in 5 specimens at the same thermally shocked temperature difference. The transient temperature field and stress field were calculated by combining heat transfer and mechanical theory, and the cracking mechanism of ceramics under thermal shock was studied. A finite element method for predicting thermal shock crack spacing was developed by using the minimum energy principle with the crack spacing and depth as variables. In view of large dispersity of the Biot number in references and its difficulty in direct measure, an “indirect measure method” was put forward, the Biot number in experiment was inversely estimated, and the numerical predictions at other temperature differences which agreed well with experimental results were obtained. The present research provides help for deeply understanding the failure mechanism of ceramics under thermal shock, improving the performance and designing new ceramics.