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

基于微力学的陶瓷/金属功能梯度材料设计方法。

基本信息

批准号：
06452318
负责人：
WAKASHIMA Kenji
金额：
$ 4.54万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

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

这项研究涉及基于计算力学的陶瓷-金属梯度多层结构，称为“功能梯度材料（FGM）”，其主要应用目标是改进热结构部件中的传统热障涂层。这些多层结构最重要的特点是通过最外层全陶瓷层和全金属层之间各个复合层的成分和微观结构控制来实现隔热和热应力减轻功能的可定制性。这涉及到热机械载荷的各种规定条件下的热传导和嵌套应力，并且由于 FGM 结构固有的双尺度异质性，这些堆叠需要“宏观机械”和“微观机械”方法。本工作中开发的计算程序具有非弹性分析，允许产生金属相的塑性流动。这是通过经典层压板理论的直接扩展来制定的，因此结合了约束塑性的微观机械模型来推导。对弹塑性区域中的层层本构方程进行了系统的计算研究，以证明热应力的分布如何通过改变成分和微观结构的级配而变化。还对圆盘状的氧化锆-镍体系进行了一些相关实验。通过热压粉末混合物的成分分级多层生坯制备的样品，其中包括（i）通过热成像技术测量稳态厚度温度分布，以“原位”测定。各层的热导率，(ii) 与各层相对应的成分均匀样品的“盘弯曲”测试，以确定其在等双轴加载条件下的失效强度，以及 (iii) 分级多层样品的重复热加载测试从这项研究得出的一般结论是，FGM 概念确实非常有吸引力，并且当前基于计算力学的方法可以为 FGM 架构提供许多有用的指导。