Fundamental Investigations of Adiabatic Shear Localization in Materials with Mesoscale Heterogeneities

关键技术的进步往往是由新材料开发的进步推动的，高性能结构材料是新材料的一个重要类别。这些材料的主要功能是以最小的重量承受严重的机械载荷，通常在恶劣的环境中。该奖项支持基础研究，以开发新的和相对未被探索的材料，其中材料的中尺度结构可以被合理设计，以产生优异的性能。该项目将推进未来动态加载应用的材料设计战略，例如保护装甲的高速撞击、结构的爆炸加载和高速加工，从而促进国家健康、繁荣和福利；并确保国防安全。这项研究将产生的基本材料设计原则可以被现代添加剂制造技术用于制造具有合理设计的中尺度结构的材料。此外，该奖项还支持本科生的教育活动，他们将在多学科团队中工作，以初中生可以接触到的方式开发简短的教育动画并传播科学发现。该奖项还支持为布朗大学的一个外展项目开发教育模块，该项目为科技领域代表性不足的群体的学生提供服务。该研究计划的重点是了解中尺度非均质性在绝热剪切带(ASB)形成和传播中的作用，绝热剪切带是材料和结构在动态载荷下经常灾难性破坏的重要机制。这项研究旨在通过原位高速显微镜实验研究ASB如何与受控非均质相互作用的机制，这是一种能够同时实现高空间(高达0.7微米)和时间(250纳秒)分辨率的新技术。当传播的ASB遇到受控几何形状和性质的异质性时，有几种可能的结果：ASB可能被阻止、偏转或继续通过该非均质性传播。通过现场测量这些相互作用过程中的瞬时变形场，这项研究试图确定每种结果占优势的条件。ASB-非均质相互作用的计算模拟将被用来解释实验结果，指导关于非均质材料性质和几何形状的选择的实验设计，并发展预测能力以帮助设计更复杂的中尺度结构。从这些研究中获得的新的基础知识可以帮助开发具有显著增强的抗ASB能力的新型中尺度体系结构。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Progress in critical technologies is often enabled by advances in development of new materials, an important class of which is high-performance structural materials. The primary function of these materials is to withstand severe mechanical loads, often in harsh environments, with minimal weight. This award supports fundamental research to develop new and relatively unexplored materials in which the mesoscale structure of materials can be rationally designed to result in superior performance. The project will advance future materials design strategies for dynamic loading applications, examples of which include high speed impact of protective armor, explosive loading of structures, and high-speed machining, thereby advancing national health, prosperity, and welfare; and securing national defense. The fundamental materials design principles that will emerge from this research can be exploited by modern additive manufacturing technologies in manufacturing materials with rationally designed mesoscale architectures. In addition, the award supports educational activities for undergraduate students who will work in multidisciplinary teams to develop short educational animations and disseminate scientific discoveries in a manner accessible to middle and high school students. The award also supports development of educational modules for an outreach program at Brown University that serves students from underrepresented groups in science and technology. The research program focuses on understanding the role of mesoscale heterogeneities in the formation and propagation of adiabatic shear bands (ASB), which are an important mechanism by which materials and structures subjected to dynamic loading often fail catastrophically. The research aims to experimentally investigate the mechanics of how a propagating ASB interacts with a controlled heterogeneity through in situ high-speed microscopy, which is a new technique capable of high spatial (up to 0.7 micrometer) and temporal (250 nsec) resolutions simultaneously. When a propagating ASB encounters a heterogeneity of controlled geometry and properties, there are several possible outcomes: the ASB can get arrested, deflected or continue to propagate through and across the heterogeneity. Through in-situ measurement of the transient deformation fields during such interactions, the research seeks to determine the conditions under which each outcome prevails. Computational simulations of ASB-heterogeneity interactions will be carried out to interpret the experimental results, guide the experimental design with respect to the choice of material properties and geometry of the heterogeneities, and develop a predictive capability to help design more complex mesoscale architectures. The new fundamental knowledge gained from these studies can help develop novel mesoscale architectures with significantly enhanced resistance to ASB.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.