Kinetics of lattice phase transitions

晶格相变动力学

• 批准号: 1007908
• 负责人: Anna Vainchtein
• 金额: $ 22.78万
• 依托单位: University of Pittsburgh
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1007908&HistoricalAwards=false
• 关键词: Kinetics; lattice; phase; transitions

VainchteinDMS-1007908 This project focuses on development and analysis ofphysically-motivated models of materials undergoing martensiticphase transition, a diffusionless deformation of a crystallattice from the high-symmetry parent austenite phase to thelow-symmetry martensite phase, which can exist in severalsymmetry-related twin variants. Under mechanical or thermalloading, these materials form finely layered twinningmicrostructures. The unique properties of martensites, such astheir ability to accommodate large deformations and the markedhysteresis they exhibit under cyclic loading, are determined bythe kinetics of phase and twin boundaries. Understanding howdynamics of the interfaces depends on their orientation,microstructural configuration, and properties of the crystallattice involves challenging open problems in modeling ofmartensites. The project seeks to advance the understanding ofthese phenomena from the perspective of mesoscopic latticemodels. Building on her prior work, the investigator focuses onseveral prototypical discrete models with the goal of capturingthe essential features of interface kinetics and microstructureevolution and an emphasis on higher-dimensional phenomena andrate effects. The main ingredients of the models are nonconvexinteractions between nearest neighbors allowing for the existenceof two stable homogeneous states and the long-range interactions. Among the outcomes of this project are prediction of nucleatedmicrostructural patterns and derivation of interfacial kineticlaws that can be used to solve problems involving temporal andspatial inhomogeneities. The results are compared toexperimental observations and molecular dynamics simulations. By focusing on the interface kinetics, this project helpsdetermine how the dissipative properties of martensites andrelated active materials depend on the material structure and theloading conditions. This is important in emerging civil,aerospace and industrial applications that require significantpassive damping, such as damage and vibration control incomposite structures and attenuation of earthquake- andwind-induced vibrations in buildings and bridges. Results ofthis project may also help design new materials with desiredproperties. Mathematical methods developed during the projectcan be used to solve similar problems encountered in dislocationtheory, fracture mechanics, DNA modeling, image recognition, andnumerical analysis. The broader impacts of this program are alsoachieved through training of graduate and undergraduate studentsin an interdisciplinary research program, as well as educationaland high-school outreach activities.

在DMS-1007908中，该项目专注于开发和分析物理激励的材料经历马氏体相变的模型，马氏体相变是晶体从高对称性母体奥氏体相到低对称性马氏体相的无扩散变形，低对称性马氏体相可以存在于几种对称相关的孪生变种中。在机械载荷或热载荷作用下，这些材料形成细小的层状孪晶组织。马氏体的独特性质，如适应大变形的能力和在循环载荷下表现出的显著滞后，是由相界和孪晶界的动力学决定的。要了解界面的动力学如何依赖于它们的取向、微观结构和晶格的性质，这涉及到马氏体建模中的一些悬而未决的问题。该项目试图从介观晶格模型的角度推进对这些现象的理解。在之前工作的基础上，这位研究人员专注于几个典型的离散模型，目的是捕捉界面动力学和微观结构演化的基本特征，并强调更高维的现象和速率效应。模型的主要成分是近邻之间的非凸相互作用，允许存在两个稳定的均质态和长程相互作用。该项目的成果包括有核微结构模式的预测和可用于解决涉及时间和空间不均匀的问题的界面运动爪子的推导。将结果与实验观测和分子动力学模拟结果进行了比较。通过对界面动力学的研究，本项目有助于确定马氏体耗散特性和相关活性物质如何依赖于材料结构和加载条件。这在需要显著被动减振的新兴民用、航空航天和工业应用中非常重要，例如复合材料结构中的损伤和振动控制以及建筑物和桥梁中地震和风致振动的衰减。该项目的结果也可能有助于设计出具有所需性能的新材料。在该项目中开发的数学方法可用于解决位错理论、断裂力学、DNA建模、图像识别和数值分析中遇到的类似问题。这一计划的更广泛影响也是通过对跨学科研究计划中的研究生和本科生的培训以及教育和高中推广活动来实现的。