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Collaborative Research: Connecting Atomistic and Continuum Amorphous Solid Mechanics via Non-equilibrium Thermodynamics

合作研究：通过非平衡热力学连接原子和连续非晶固体力学

基本信息

批准号：
1409560
负责人：
Christopher Rycroft
金额：
$ 20万
依托单位：
Harvard University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2014
资助国家：
美国
起止时间：
2014-09-15 至 2018-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1409560&HistoricalAwards=false
关键词：
Collaborative Research Connecting Atomistic Continuum

项目摘要

NONTECHNICAL SUMMARY This award supports computational and theoretical research, and education on materials deformation. The objective of this collaborative research project is to develop computational models to predict the deformation and failure of a class of materials known as amorphous solids, particularly focusing on structural metallic glasses. The atoms in amorphous solids are arranged in a highly disordered structure unlike crystals in which atoms are arranged into a regular repeating structure. The current research seeks to go beyond directly simulating the atomic scale behavior using techniques like molecular dynamics simulations. While molecular dynamics simulation has been groundbreaking, this technique is computationally intensive and cannot be scaled up to model structures on scales of typical practical engineering interest. This research will focus on translating information from molecular dynamics simulations to computationally efficient models at larger scales. In doing so, comparisons will be made between atomic scale representations and larger scale theories to ensure that the larger scale theories are statistically consistent and adequately verified. Particular attention will be paid to testing whether they capture the mechanisms governing material behavior and the inherent variability that results from the disordered atomic configurations. This verification will permit the use of these models for testing theories of large-scale material behavior, particularly failure and fracture; successful theories will help to enable the design of amorphous materials wherein the structure of a material is chosen to meet certain performance objectives, and permitting the assessment of the reliability of engineering materials. The insights gained and methods employed in this research have the potential to transform the way in which length-scales are spanned in the study of the mechanics of materials beyond those with amorphous structure. This award also supports educational initiatives at both Johns Hopkins University and Harvard University. These will address the critical need to integrate computational methods into the core Materials Science and Engineering curriculum while also engaging elementary school students in high-need urban schools through the NSF funded STEM Achievement in Baltimore Elementary Schools project. TECHNICAL SUMMARY This award supports computational and theoretical research, and education on nonequilibrium properties of materials with a focus on deformation. Atomistic mechanisms govern both a material's kinetics and the manner in which its structure evolves during the inherently nonequilibrium process of deformation and failure. The need to establish numerically tractable continuum descriptions of viscoplasticity that incorporate atomistic mechanisms in ways that retain their essential aspects presents a grand challenge at the intersection of physics and mechanics. The strategy employed in this research for reducing the operative degrees of freedom is to extend thermodynamic concepts beyond their common equilibrium application. The configurational entropy will be deployed in the context of the shear transformation zone theory to make quantitative predictions of deformation and failure processes in amorphous solids. This study will utilize molecular dynamics simulation to parameterize a highly optimized fully Eulerian implementation of the shear transformation zone theory that permits investigation of very large strains such as those that arise in failure processes like strain localization and fracture. This will require development and analysis of new numerical projection methods for viscoplasticity. The shear transformation zone constitutive law differs from existing relations insofar as it makes reference to a configurational effective temperature that quantifies the structure. These structural parameters can be independently measured in molecular dynamics to cross-validate the predictions of the numerical implementations of the constitutive theory. Rigorous statistical comparisons will be made through a novel stochastic framework that establishes a random field representation of the atomic potential energy that is translated to a continuum effective temperature. This work will validate predictions of the mechanical response of metallic glasses, emerging structural materials, both during homogeneous flow near the glass temperature and during the development of plastic localization and fracture at lower temperatures in a manner that accounts for inherent fluctuations and correlations associated with the material's amorphous structure. This will lead to a greatly increased understanding of deformation and failure in materials with varying degrees of disorder and predictive numerical schemes suitable for large strains that can be rigorously analyzed and deployed in engineering contexts. This award also supports educational initiatives at both Johns Hopkins University and Harvard University. These will address the critical need to integrate computational methods into the core Materials Science and Engineering curriculum while also engaging elementary school students in high-need urban schools through the NSF funded STEM Achievement in Baltimore Elementary Schools project.

该奖项支持计算和理论研究，以及材料变形方面的教育。该合作研究项目的目标是开发计算模型，以预测一类称为非晶固体的材料的变形和失效，特别关注结构金属玻璃。无定形固体中的原子以高度无序的结构排列，不像晶体中的原子排列成规则的重复结构。目前的研究试图超越使用分子动力学模拟等技术直接模拟原子尺度行为。虽然分子动力学模拟是开创性的，但这种技术是计算密集型的，并且不能按比例放大到典型的实际工程感兴趣的尺度上的模型结构。这项研究将侧重于将分子动力学模拟的信息转化为更大规模的计算效率模型。在此过程中，将在原子尺度表示和更大尺度理论之间进行比较，以确保更大尺度理论在统计上是一致的，并得到充分的验证。将特别注意测试它们是否捕获的机制，从无序的原子配置的结果，管理材料的行为和固有的可变性。这种验证将允许使用这些模型来测试大规模材料行为的理论，特别是失效和断裂;成功的理论将有助于实现非晶材料的设计，其中材料的结构被选择为满足某些性能目标，并允许评估工程材料的可靠性。在这项研究中所获得的见解和方法有可能改变的方式，其中长度尺度跨越的材料力学的研究超越了那些无定形结构。该奖项还支持约翰霍普金斯大学和哈佛大学的教育计划。这些将解决将计算方法整合到核心材料科学与工程课程中的迫切需要，同时还通过NSF资助的巴尔的摩小学STEM成就项目吸引高需求城市学校的小学生。该奖项支持计算和理论研究，以及以变形为重点的材料非平衡特性教育。原子机制支配着材料的动力学和其结构在变形和失效的固有非平衡过程中演变的方式。需要建立数值上易于处理的连续描述粘塑性，将原子机制的方式，保留其基本方面提出了一个巨大的挑战，在物理学和力学的交叉点。在这项研究中采用的战略，减少操作的自由度是扩展热力学概念超出其共同的平衡应用。组态熵将部署在剪切转变区理论的背景下，在无定形固体的变形和破坏过程的定量预测。这项研究将利用分子动力学模拟参数化的剪切转换区理论，允许非常大的应变，如应变局部化和断裂等故障过程中出现的调查高度优化的完全欧拉实现。这就需要发展和分析新的粘塑性数值投影方法。剪切转变区本构关系不同于现有的关系，因为它参考了量化结构的构型有效温度。这些结构参数可以在分子动力学中独立测量，以交叉验证本构理论的数值实现的预测。严格的统计比较将通过一个新的随机框架，建立一个随机场表示的原子势能，被翻译成连续有效温度。这项工作将验证金属玻璃，新兴的结构材料的机械响应的预测，无论是在玻璃温度附近的均匀流动和在较低温度下的塑性局部化和断裂的方式，占固有的波动和相关性与材料的非晶结构的发展过程中。这将导致对具有不同程度的无序和预测数值方案的材料中的变形和失效的理解大大增加，这些方案适用于可以在工程环境中进行严格分析和部署的大应变。该奖项还支持约翰霍普金斯大学和哈佛大学的教育计划。这些将解决将计算方法整合到核心材料科学与工程课程中的迫切需要，同时还通过NSF资助的巴尔的摩小学STEM成就项目吸引高需求城市学校的小学生。