Micromechanics-Based Approach to the Design of Ceramic/Metal Functionally Graded Materials.

这项调查是有关的计算力学为基础的架构的陶瓷-金属梯度多层结构，称为“功能梯度材料（FGM）”，其主要应用目标是针对传统的热障涂层在热结构部件的改进。这些多层结构的最重要的特征是通过在最外面的全陶瓷层和全金属层之间的各个复合层的成分和微观结构控制来调整热屏蔽和热应力缓解功能。这种剪裁涉及在各种规定的热机械载荷条件下的热传导和应力分析，并且由于FGM结构固有的双尺度异质性，这些分析需要“宏观力学”和“微观力学”方法。 关于我们 和金属相的塑性流动。这是制定通过一个简单的经典层压板理论的延伸，其中的约束塑性的细观力学模型被纳入推导出的层本构方程在弹塑性制度。本文对氧化锆-镍系合金的热应力分布随成分梯度和显微结构梯度的变化进行了系统的计算研究，并对成分梯度多层绿色压坯热压成形的盘形试样进行了相关的实验研究。这些方法包括（i）通过热成像法测量稳态厚度方向的温度分布，以“原位”确定各层的热导率，（ii）对与各层相对应的成分均匀的样品进行“圆盘弯曲”试验，以确定它们在等双轴载荷条件下的破坏强度，在准单向热流条件下对梯度多层试样进行了反复热载荷试验，得出的一般结论是：梯度功能材料的概念确实很有吸引力，目前的计算力学-的方法可以产生许多有用的指南FGM架构。少

This investigation is concerned with a computational mechanics-based architecture of ceramic-to-metal graded multilayr constructions, called "functionally graded materials (FGM) ", their prime application target being directed toward the improvement of conventional thermal barrier coatings in hot structural components. The most important feature of these multilayr constructions is a tailorability of heat-shielding and thermal stress-mitigating functions through compositional and microstructural control of individual composite layrs in between the outermost fully ceramic and fully metallic ones. The tailoring as such involves heat conduction and stress analyzes under various prescribed conditions of thermomechanical loading and, because of the dual-scale heterogeneity inherent to the FGM structure, these analyzes require both "macromechanical" and "micromechanical" approaches.The computational procedure developed in the present work features an inelastic analysis that permits yielding a … More nd plastic flow of the metal phase. This is formulated via a straightforward extension of the classical laminated plate theory, wherein a micromechanical model of constrained plasticity is incorporated to derive the lamina constitutive equation in the elastoplastic regime. A systematic computational study has been carried out to demonstrate how the distributions of thermal stresses change by changing the gradations in composition and microstructure.Some related experiments have also been done on the zirconia-nickel system using discshaped samples fabricated by hot pressing composition-graded multilayr green compacts of powder mixtures. These include (i) the measurement of steady state through-the thickness temperature distributions by means of thermography for "in situ" determination of the thermal conductivities of individual layrs, (ii) "disc-bending" tests of compositionally uniform samples corresponding to individual layrs in order to determine their failure strengths under equi-biaxial loading conditions, and(iii) repeated thermal loading tests of graded multilayr samples under quasi-unidirectional conditions of heat flow.A general conclusion drawn from this investigation is that the FGM concept is quite attractive indeed and the present computational mechanics-based approach can produce many useful guidelines to the FGM architecture. Less