Functionally graded metals and metal-ceramic composites: Part 2 Thermomechanical behaviour
Functionally graded metals and metal-ceramic composites: Part 2 Thermomechanical behaviour
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DOI：
10.1179/imr.1997.42.3.85
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发表时间：
1997-01
影响因子：
16.1
通讯作者：
S. Suresh;A. Mortensen
中科院分区：
文献类型：
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作者：
S. Suresh;A. Mortensen
在审查了功能分级金属和金属陶瓷复合材料的审查之后，这两个部分系列的第2部分集中在热力学行为上。讨论了各种陶瓷组合物，包括混合近似法则，平均野外理论，晶体可塑性模型，离散脱位模型以及持续的复合材料构成阶段的有限元公式，这些方法的显着性和局限性是突出显示了针对分级材料的热力学分析的问题，这是由于复合梯度不可避免地需要详细的微力学分析而引入问题的新长度。然后，在经典梁和板理论的背景下，呈现了渐变多层的热，弹性和塑性变形的模型，并与开发“设计图”的策略来确定控制热力学性能的方法。并且还提供了由于分级多层变形而引起的突然变化。宏观连续体分析之后，通过审查了对von Mises类型和晶体形态学方法的计算模型进行审查，以讨论真实的微结构分散。然后，检查了此类模型的有效性，以及加工引起的内部应力的典型结果以及在金属陶瓷浓度的模型系统中引起的热应力。改善异种固体之间的界面键合，以最大程度地减少和最佳分配热应力，抑制塑料屈服的发作，以减轻多层界面相交的多层自由边缘的奇异磁场的删除效应，以减少裂缝的有效驱动力，并逮捕裂缝。
Following a review of the processing of functionally graded metals and metal-ceramic composites in Part 1; this Part 2 of the two part series focuses on the thermomechanical behaviour. The paper begins with an overview of the fundamentals of thermoelastic and thermoplastic deformation in metal-ceramic composites. Various approaches, including the rule of mixture approximations, mean field theories, crystal plasticity models, discrete dislocation models, and continuum finite element formulations of the constitutive phases of the composites, are discussed, and the significance and limitations of these approaches are highlighted. Issues specific to the thermomechanical analyses of graded materials are then addressed. It is reasoned that the introduction of a new length scale to the problem due to compositional gradients inevitably calls for detailed micromechanical analyses of the size, shape, continuity, and spatial dispersions of the constituent phases of graded metal-ceramic composites. Models for the thermal, elastic, and plastic deformation of graded multilayers are then presented within the context of classic beam and plate theories, in conjunction with strategies for developing ‘design diagrams’ for thermomechanical performance. Methods to identify the conditions governing the onset of instability and abrupt shape changes due to large deformation in graded multilayers are also provided. The macroscopic continuum analyses are followed by discussions of micromechanics simulations of the real microstructural dispersions by recourse to computational models which invoke von Mises type and crystal plasticity theories. Experimental methods to assess the validity of such models are then examined, along with typical results of processing induced internal stresses and thermal stresses arising from temperature excursions in model systems with gradients in metal-ceramic concentrations. It is demonstrated that stepwise or continuously graded metalceramic composites can be designed to improve interfacial bonding between dissimilar solids, to minimise and optimally distribute thermal stresses, to suppress the onset of plastic yielding, to mitigate the deleterious effects of singular fields at free edges of multilayers where interfaces intersect free surfaces, to reduce the effective driving force for fracture, and to arrest cracks.