Theory and Simulation of the Transition from Amorphous to Nanocrystalline Mechanical Response

非晶态到纳米晶态机械响应转变的理论与模拟

• 批准号: 0808704
• 负责人: Michael Falk
• 金额: $ 24.42万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-05-01 至 2013-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0808704&HistoricalAwards=false
• 关键词: Theory; Simulation; Transition; Amorphous; Nanocrystalline

TECHNICAL SUMMARYThis award supports theoretical and computational research on plastic deformation, an inherently non-equilibrium process. The PI intends to advance understanding of plastic deformation in non-crystalline solids to materials with increasing degrees of structural order. Non-crystalline solids find industrial application as metals, ceramics, semiconductors and polymers, but the fact of their disorder has discouraged the development of adequate theories for their deformation. Recently large-scale atomistic simulation has allowed dramatic progress in analyzing the structural disorder in these solids and in relating their mechanical properties to their structural evolution. In the process constitutive laws have been developed that use concepts from non-equilibrium statistical physics to connect macroscale behavior to atomic scale structure. These constitutive laws differ from existing relations insofar as they make reference to certain temperature-like intensive variables that quantify the structure. These structural parameters can be independently measured in simulation to validate the relations. Evidence of the success of these methods has been established by predictions of the mechanical response of metallic glass, an emerging structural material, both during homogeneous flow near the glass temperature and during the development of plastic localization at low temperatures. This research project will extend these investigations to include partially crystalline and nanocrystalline solids. Examining a continuum of structures over this range will test the generality of these theories of deformation for predicting plastic behavior in partially ordered solids. This will lead to a greatly increased understanding of deformation and failure in materials with varying degrees of disorder.This computational and theoretical research program will be integrated with an educational program at Johns Hopkins University (JHU) that addresses a critical need to integrate computational methods into the Materials Science and Engineering core curriculum. This will be done in the context of courses on kinetics, phase transformations, mechanics of materials and physical properties of materials. The PI is continuing to develop a course on the graduate level covering computational materials science methods for molecular simulation. In addition the PI has a history of involving undergraduates in research. This project will involve both JHU undergrads and undergraduates recruited through the NSF MRSEC and PREM programs at JHU that bring in students from around the U.S. and majority-minority institutions.NON-TECHNICAL SUMMARYThis award supports research that combines simulation and theoretical statistical physics to investigate how materials deform when stressed and to develop a framework to predict plastic behavior. When a small force is applied to a material, a material will bend or deform in such a way that the material will spring back to its original size and shape when the force is removed. As the force is increased, a point is reached where the material deforms and no longer springs back to original size and shape when the force is removed. The PI aims to understand how this plastic deformation occurs in a range of materials from metals that are a mosaic of tiny crystals the size of a few nanometers to amorphous metals where the atoms are not arranged in any apparent pattern. The PI aims to directly address issues critical to the development of emerging new materials with potential applications due to their high strength and hardness. By making a strong connection between the structure of the material and the resulting mechanical properties, these investigations will provide predictive theories that can be used to analyze the connection between processing, structure and properties and the onset of precursors to materials failure. These investigations will increase understanding beyond subject metals to other materials including glassy polymers, granular media, colloids and the processes that accompany friction.This computational and theoretical research program will be integrated with an educational program at Johns Hopkins University (JHU) that addresses a critical need to integrate computational methods into the Materials Science and Engineering core curriculum. This will be done in the context of more traditional courses on materials. The PI is continuing to develop a course on the graduate level covering computational materials science methods for molecular simulation. In addition the PI has a history of involving undergraduates in research. This project will involve both JHU undergrads and undergraduates recruited through the NSF MRSEC and PREM programs at JHU that bring in students from around the U.S. and majority-minority institutions.

该奖项支持塑性变形的理论和计算研究，这是一个固有的非平衡过程。PI旨在推进对非结晶固体中塑性变形的理解，以提高材料的结构有序度。非晶态固体在工业上有着广泛的应用，如金属、陶瓷、半导体和聚合物等，但它们的无序性阻碍了它们变形理论的发展。最近，大规模的原子模拟已经允许在分析这些固体的结构紊乱，并在其机械性能，其结构演变的戏剧性的进展。在这个过程中，本构定律已经发展，使用非平衡统计物理学的概念，连接宏观尺度的行为，原子尺度的结构。这些本构关系不同于现有的关系，因为它们参考了某些类似温度的强度变量，量化了结构。这些结构参数可以在仿真中独立测量以验证关系。这些方法的成功的证据已经建立了金属玻璃，一种新兴的结构材料，在玻璃温度附近的均匀流动和在低温下的塑性局部化的发展过程中的机械响应的预测。这个研究项目将扩展这些调查，包括部分结晶和纳米晶体固体。考察在这个范围内的连续体结构，将检验这些变形理论在预测部分有序固体塑性行为方面的普遍性。这将导致对不同程度的无序材料的变形和破坏的理解大大增加。这一计算和理论研究计划将与约翰霍普金斯大学（JHU）的教育计划相结合，该计划解决了将计算方法融入材料科学与工程核心课程的迫切需要。这将在动力学、相变、材料力学和材料物理性能课程中进行。PI正在继续开发研究生水平的课程，涵盖分子模拟的计算材料科学方法。此外，PI有让本科生参与研究的历史。该项目将涉及JHU的本科生和通过JHU的NSF MRSEC和PREM项目招募的本科生，这些项目将来自美国各地和少数民族院校的学生。非技术总结该奖项支持将模拟和理论统计物理相结合的研究，以调查材料在受力时如何变形，并开发一个框架来预测塑性行为。当对材料施加小的力时，材料将以这样的方式弯曲或变形，即当力被移除时，材料将弹回到其原始尺寸和形状。随着力的增加，达到一个点，在该点处材料变形，并且当力被移除时不再弹回到原始尺寸和形状。PI旨在了解这种塑性变形如何发生在一系列材料中，从几纳米大小的微小晶体镶嵌的金属到原子没有以任何明显图案排列的非晶金属。PI旨在直接解决由于其高强度和硬度而具有潜在应用的新兴新材料开发的关键问题。通过在材料的结构和由此产生的机械性能之间建立强有力的联系，这些研究将提供预测理论，可用于分析加工，结构和性能之间的联系以及材料失效的前兆。这些研究将增加对金属以外的其他材料的理解，包括玻璃状聚合物，颗粒介质，胶体和伴随摩擦的过程。这个计算和理论研究项目将与约翰霍普金斯大学（JHU）的教育项目相结合，解决将计算方法融入材料科学与工程核心课程的迫切需要。这将在更传统的教材课程中进行。PI正在继续开发研究生水平的课程，涵盖分子模拟的计算材料科学方法。此外，PI有让本科生参与研究的历史。该项目将涉及JHU本科生和通过NSF MRSEC和PREM项目招募的本科生，这些项目将来自美国各地的学生带到JHU。