Mathematical Analysis and Numerical Methods for Peridynamics and Nonlocal Models

计算机技术的进步推动了复杂应用中更真实的数学模型的发展，包括比传统局部模型更真实的非局部模型，用于研究从物理和生物到材料和社会科学的各种现象。一个例子是周向力学模型，空间非局部力学理论，它已成功地用于模拟材料缺陷和预测动态裂纹形成在各种工程应用。虽然新的非局部模型在各种应用中越来越受欢迎，但其背后的数学研究仍处于起步阶段，阻碍了计算工具的进一步发展。该项目的目标是开发有效和可靠的数值方法来模拟非局部模型，并建立相关的数学分析，作为严格的验证和验证过程的一部分。它旨在提高非局部建模的有效性和鲁棒性，同时保持建模精度。在教育方面，该项目将为学生提供数学和计算力学方面的培训。该项目旨在开发最先进的多尺度建模技术，以提高计算效率，同时保留预测动态裂缝的非局部模型的准确性，建立新的理论方法来研究模型的分析特性。 多尺度模拟的三种具体方法将被解决，其中边界痕迹和界面条件的处理起着关键作用。第一个是无缝耦合的非本地和本地模型通过异构本地化的非本地交互界面。一个新的非局部迹定理被用来确保适定性的耦合。目标是根据解决方案的开发将界面视为自由边界。第二种是准非局域耦合方法的灵感来自原子到连续耦合方法。它的目的是在离散原子模型和连续非局部模型之间架起一座桥梁。三是设计合适的非局部边界条件，以减少无界区域上问题的计算量。一个新的概念nonlocal Neumann边界条件将被引入，这将阐明区域分解方法和耦合nonlocal models.This award reflects NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的智力价值和更广泛的影响审查标准。

Improvements in computer technology are fueling the development of more realistic mathematical models for complex applications, including nonlocal models that are more realistic than conventional local models for studying various phenomena from physics and biology to materials and social sciences. An example is the peridynamics model, a spatially nonlocal mechanics theory, which has been successfully used to model material defects and predict dynamics of crack formation in various engineering applications. Although new nonlocal models have been gaining popularity in various applications, the study of mathematics behind them is still at the nascent stage, impeding the further development of computational tools. The goal of this project is to develop efficient and reliable numerical methods for simulating nonlocal models and establish related mathematical analysis as part of the rigorous validation and verification process. It aims to improve the effectiveness and robustness of nonlocal modeling while retaining modeling accuracy. On the educational side, this project will provide training to students in both mathematics and computational mechanics. This project aims to develop state-of-the-art multiscale modeling techniques to improve computational efficiency while retaining the accuracy of nonlocal models for predicting dynamic fractures, with new theoretical methodologies built to study the analytic properties of the models. Three specific methods of multiscale modeling will be addressed, in which the treatment of boundary traces and interfacial conditions plays pivotal roles. The first is the seamless coupling of nonlocal and local models via heterogeneous localization of nonlocal interactions at the interface. A novel nonlocal trace theorem is used to ensure the well-posedness of the coupling. The goal is to treat the interface as a free boundary based on the development of the solution. The second is a quasi-nonlocal coupling method inspired by the atomistic-to-continuum coupling method. It is aimed at building a bridge between the discrete atomistic model and continuous nonlocal model. The third is to design appropriate nonlocal boundary conditions to reduce the computational cost for problems on unbounded domains. A new notion of nonlocal Neumann boundary condition will be introduced, which will shed light on domain decomposition methods and the coupling of nonlocal models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.