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

该基金的研究目标是开发多晶金属材料的基于物理的裂纹演化模型，用于晶体塑性有限元模型。统一的变形-破裂模型将通过原子尺度上的变量来开发，分子动力学模拟具有明确的原子结构和变形机制描述。升级将为沿特定滑移系统的变形变量的内聚规律和相关演化规律提供框架。将采取系统的办法，包括下列任务：(i)三维晶格系统的分子动力学（MD）模拟，以模拟各种力场下韧性和脆性裂纹的演化；（ii）开发加速的分子动力学方法，以模拟与实验一致的更长时间尺度；（iii）表征和识别裂纹尖端变形机制，随后量化局部原子结构和演化；（iv）通过划分不同物理机制对应的总能量，建立过程区裂纹扩展的能量规律。通过建立新的裂纹演化模型，对材料的分析和设计具有重要意义，从而获得更好的断裂韧性和延展性，从而为科学界带来益处。在加速分子动力学建模的进步将允许建模应变速率的现实实验。与Sandia和Brown Deer Technology的合作将使可交付成果的技术转移得到更广泛的利用。学生将与桑迪亚国家实验室和一家小型开发公司的知名研究人员进行密切的互动，以了解他们工作的直接影响。

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.