Atomistic Simulation Based Crack Evolution Models for Crystal Plasticity FEM of Crystalline Metals

这笔赠款的研究目标是开发用于晶体塑性有限元模型的多晶金属材料中基于物理的裂纹演化模型。统一的形变-断裂模型将由原子尺度的分子动力学模拟变量发展而来，显式地描述原子结构和形变机制。提升尺度将为沿特定滑移系统的变形变量的内聚力定律和相关的演化规律提供一个框架。将采取一种系统的方法，包括以下任务：(I)对3D晶格系统进行分子动力学(MD)模拟，以模拟在各种力场下延性和脆性裂纹的演化；(Ii)开发加速MD方法，以模拟与实验一致的较长时间尺度；(Iii)描述和识别裂纹尖端变形机制，随后量化局部原子结构和演化，以及(Iv)通过分配对应于不同物理机制的总能量，发展基于能量的规则来控制过程区域中的裂纹扩展。通过建立在材料分析和设计中至关重要的新的裂纹演化模型，以获得更好的断裂韧性和延展性，将为科学界带来好处。在加速分子动力学建模方面的进展将允许在现实实验的应变率下建模。与Sandia和Brown Deer Technology的合作将使可交付成果的技术转让得到更广泛的利用。学生们将与桑迪亚国家实验室和一家小规模开发公司的知名研究人员进行强有力的互动，以了解他们的工作的直接影响。

The research objective of this grant is the development of physics-based crack evolution models in polycrystalline metallic materials for use in crystal plasticity finite element models. The unified deformation-fracture models will be developed by upscaling variables from atomic-scale, molecular dynamics simulations with explicit depiction of the atomic structure and deformation mechanisms. Upscaling will provide a framework for cohesive laws and associated evolution laws for deformation variables along specific slip systems. A systematic approach will be undertaken, encompassing the following tasks: (i) molecular dynamics (MD) simulations of 3D crystalline lattice systems to simulate the evolution of ductile and brittle crack evolution under a variety of force fields, (ii) development of accelerated MD methods to simulate longer time scales consistent with experiments, (iii) characterization and identification of crack tip deformation mechanisms, followed by quantification of the local atomic structure and evolution, and (iv) development of energy-based laws governing crack growth in the process zone by partitioning the total energy corresponding to different physical mechanisms.Benefits to the scientific community will be accomplished through the establishment of novel crack evolution models of critical importance in analysis and design of materials for better fracture toughness and ductility. Advancement in accelerated molecular dynamics modeling will allow modeling at strain rates of realistic experiments. Collaboration with Sandia and Brown Deer Technology will enable technology transfer of deliverables for broader utilization. Students will have strong interactions with eminent researchers at Sandia National Laboratories and a small-scale development company to see the direct impact of their work.