基于显微组织图片的涂层热导率有限元计算研究

综合数字图像处理技术与有限元网格模型生成原理,提出了基于涂层显微组织图片的有限元网格模型生成方法。利用有限元程序,通过热障涂层特定区域的热导率计算,研究分析了涂层的隔热性能。以等离子喷涂ZrO2涂层为例,先将得到的ZrO2涂层物理图像由图形格式转换成数字格式;然后,通过阈值分割处理和有限元网格生成方法,生成包含涂层材料组元属性的有限元网格模型;在生成的有限元网格模型基础上,再进行ZrO2涂层热作用下的温度场模拟;最后,利用傅立叶热传导方程,计算了ZrO2涂层显微组织图片所代表区域的有效热导率。进一步分析了横向热导率和纵向热导率之间的差异。分析表明:等离子喷涂ZrO2涂层的横向热导率比纵向热导率要高,涂层有效热导率受孔隙率和孔隙形状共同影响。     

The influence of defects on the effective Young’s modulus of a defective solid

It is difficult to establish structure-property relationships in a defective solid because of its inhomogeneous-geometry microstructure caused by defects. In the present research, the effects of pores and cracks on the Young’s modulus of a defective solid are studied. Based on the law of the conservation of energy, mathematical formulations are proposed to indicate how the shape, size, and distribution of defects affect the effective Young’s modulus. In this approach, detailed equations are illustrated to represent the shape and size of defects on the effective Young’s modulus. Different from the results obtained from the traditional empirical analyses, mixture law or statistical method, for the first time, our results from the finite element method (FEM) and strict analytical calculation show that the influence of pore radius and crack length on the effective Young’s modulus can be quantified. It is found that the longest crack in a typical microstructure of ceramic coating dominates the contribution of the effective Young’s modulus in the vertical direction of the crack.