SHAPE-MEMORY MATERIALS: CRYSTALLOGRAPHIC TEXTURE AND ITS CONSEQUENCES

形状记忆材料：晶体结构及其后果

• 批准号: 0002930
• 负责人: Lallit Anand
• 金额: --
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-12-01 至 2005-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0002930&HistoricalAwards=false
• 关键词: SHAPE; MEMORY; MATERIALS; CRYSTALLOGRAPHIC; TEXTURE

0002930It is now well recognized that shape-memory materials derive their unusual and inherently nonlinear and anisotropic properties from the fine-scale rearrangements of phases, or ``microstructures,'' and that the strain produced in the pseudoelasticity effect, as well as that recovered during the shape-memory effect, depends on crystal orientations. Specially oriented single crystals of some shape memory materials can produce sizeable strains (~ 10%) due to phase transformations. Practical shape-memory materials are typically polycrystalline in nature, and because of their thermo-mechanical processing history, they are initially textured. It has recently been recognized that the initial crystallographic texture of sheets, wires and rods of shape-memory alloys is crucial in determining the overall properties of these materials. The pronounced anisotropies caused by the initial texture need to be properly accounted for in developing a robust computational capability for the improved design of geometrically-complex engineering components made from shape memory materials. We shall Experimentally study the effects of initial texture on the thermo-mechanical response of the shape-memory alloy Ti-Ni, in both bulk form, and thin films. This material is finding increased use as a functional/smart-material for a variety of applications. Ti-Ni alloys in thin-film form are promising materials for microactuators, because of the enhanced rate of heat transfer in thin films. Develop constitutive equations and computational procedures for modeling and simulation of the important pseudoelasticity and shape-memory effects observed in these materials. The mathematical models and procedures that we plan to develop should be usefulin the design of components for enhanced thermo-mechanical performance.

0002930现在人们已经认识到，形状记忆材料的不同寻常的、固有的非线性和各向异性特性来自于相的精细重排或“微观结构”，并且在伪弹性效应中产生的应变以及在形状记忆效应中恢复的应变取决于晶体取向。某些形状记忆材料的特殊取向单晶由于相变可以产生相当大的应变（~ 10%）。实用的形状记忆材料本质上通常是多晶的，由于它们的热机械加工历史，它们最初是有纹理的。最近人们认识到，形状记忆合金片、线和棒的初始晶体结构对决定这些材料的整体性能至关重要。为改进形状记忆材料制造的几何复杂工程部件的设计，需要适当考虑由初始织构引起的明显的各向异性。我们将实验研究初始织构对形状记忆合金Ti-Ni的热-机械响应的影响，包括体形和薄膜。这种材料作为一种功能/智能材料的用途越来越广泛。薄膜形式的Ti-Ni合金是很有前途的微致动器材料，因为薄膜形式的热传递率提高。发展本构方程和计算程序的建模和模拟重要的伪弹性和形状记忆效应观察到这些材料。我们计划开发的数学模型和程序应该对增强热机械性能的组件设计有用。