Collaborative Research: A Unified Theory of Crack Nucleation and Growth for Materials Subjected to Repetitive Surface Acoustic Waves and Dynamic Impacts

合作研究：重复表面声波和动态冲击下材料裂纹成核和扩展的统一理论

• 批准号: 2132551
• 负责人: John Dolbow
• 金额: $ 41.79万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2132551&HistoricalAwards=false
• 关键词: Collaborative; Research; Unified; Theory; Crack

Surface acoustic waves (SAWs) are prevalent in many naturally occurring destructive phenomena, such as earthquakes and tsunamis. Further, SAWs have long been speculated to contribute to surface damage produced by cavitation on ship propellers, high-speed impact on wind turbine blades, and fragmentation of rocks by jetting streams. In emerging medical applications, such as Nano-Pulse Lithotripsy, SAWs have also been postulated to play a vital role in ensuring the success of noninvasive disintegration of kidney stones in patients. Despite this, the fundamental mechanisms by which SAWs trigger fracture on the surface of materials remain largely unknown. This is not an isolated phenomenon as the nucleation and propagation of cracks regardless of the loading type has been a vexing problem for decades. In this context, this award supports fundamental research to explain how the repeated application of SAWs and other dynamic loadings can give rise to the nucleation of cracks on the surface of brittle materials and affect their subsequent growth. Insights from this project will significantly benefit scientists and engineers seeking to understand and predict a fundamental phenomenon that has remained elusive: the onset of damage in brittle materials in response to mechanical loads at large. The proposed research is interdisciplinary, bringing together engineers and computational scientists to fully explore this class of problems. Importantly, it also includes outreach activities designed to encourage under-represented minority students in STEM fields at the high school and undergraduate levels to pursue research in mechanics of materials. Despite recent theoretical progress in the field of fracture, the current scientific understanding of crack nucleation and its transition to growth in solids remains incomplete and under-explored. This research is focused on the experimental, theoretical, and computational study of crack nucleation and growth in brittle materials in response to repeated, dynamic loadings under a wide range of conditions. Two prototypical systems will be studied: materials that are submerged and subjected to multiple shock loadings that also cause SAWs, and dry materials that are subjected to repeated impact loads. New experiments will be conducted on both glass and Begostone, an engineered material whose elasticity, strength, and toughness properties can be conveniently varied over a substantial range. The experiments will be carried out in conjunction with simulations based on a new continuum theory that will incorporate inertial effects and low-cycle fatigue into a unified model of crack nucleation and growth. The results of these studies will shed light on the fundamental yet long-unresolved question of how low cycle fatigue and inertial loads can degrade the strength and toughness of material systems and ultimately result in their fracture and failure in response to arbitrary mechanical loads.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.

声表面波（SAW）在许多自然发生的破坏性现象中普遍存在，例如地震和海啸。此外，长期以来，人们一直认为SAW会导致船舶螺旋桨上的气穴现象、风力涡轮机叶片上的高速冲击以及喷射流造成的岩石破碎所产生的表面损坏。 在新兴的医疗应用中，如纳米脉冲碎石术，SAW也被认为在确保患者肾结石的非侵入性崩解成功方面发挥着至关重要的作用。 尽管如此，SAW在材料表面上触发断裂的基本机制在很大程度上仍然未知。这不是一个孤立的现象，因为无论载荷类型如何，裂纹的成核和扩展都是几十年来令人烦恼的问题。在这种情况下，该奖项支持基础研究，以解释SAW和其他动态载荷的重复应用如何引起脆性材料表面裂纹的成核并影响其随后的生长。该项目的见解将使寻求理解和预测一个仍然难以捉摸的基本现象的科学家和工程师受益匪浅：脆性材料在机械载荷作用下发生损伤。拟议的研究是跨学科的，将工程师和计算科学家聚集在一起，充分探索这类问题。 重要的是，它还包括旨在鼓励高中和本科阶段STEM领域代表性不足的少数民族学生从事材料力学研究的外联活动。 尽管最近在断裂领域取得了理论进展，但目前对裂纹成核及其在固体中过渡到生长的科学认识仍然不完整，并且未得到充分探索。 本研究的重点是在广泛的条件下，响应于重复的动态载荷的脆性材料中的裂纹成核和生长的实验，理论和计算研究。两个原型系统将被研究：材料被淹没，并受到多重冲击载荷，也会导致SAW，和干燥的材料，受到反复的冲击载荷。新的实验将在玻璃和Begostone上进行，Begostone是一种工程材料，其弹性，强度和韧性特性可以在很大范围内方便地变化。实验将结合基于新的连续理论的模拟进行，该理论将惯性效应和低周疲劳纳入裂纹成核和生长的统一模型。这些研究的结果将揭示基本的，但长期-一个尚未解决的问题，即低周疲劳和惯性载荷如何降低材料系统的强度和韧性，并最终导致其在任意机械载荷下的断裂和失效。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查进行评估，被认为值得支持的搜索.