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，人们一直推测声表面波会导致船舶螺旋桨空化产生的表面损伤、风力涡轮机叶片的高速冲击以及喷射流造成的岩石破碎。 在纳米脉冲碎石术等新兴医疗应用中，SAW 也被认为在确保患者肾结石成功无创崩解方面发挥着至关重要的作用。 尽管如此，声表面波引发材料表面断裂的基本机制仍然很大程度上未知。这并不是一个孤立的现象，因为无论加载类型如何，裂纹的成核和扩展几十年来一直是一个令人烦恼的问题。在此背景下，该奖项支持基础研究，以解释埋弧焊和其他动态载荷的重复应用如何导致脆性材料表面裂纹的成核并影响其随后的生长。该项目的见解将使科学家和工程师受益匪浅，他们试图理解和预测一个仍然难以捉摸的基本现象：脆性材料响应大机械载荷而发生损坏。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，充分探索此类问题。 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族裔学生开展材料力学研究的外展活动。 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向固体生长转变的科学理解仍然不完整且尚未得到充分探索。 这项研究的重点是脆性材料在各种条件下响应重复动态载荷时裂纹成核和扩展的实验、理论和计算研究。将研究两个典型系统：浸入水中并承受多次冲击载荷（也会引起 SAW）的材料，以及承受重复冲击载荷的干燥材料。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。这些实验将与基于新连续理论的模拟结合进行，该理论将惯性效应和低周疲劳纳入裂纹成核和扩展的统一模型中。这些研究的结果将揭示一个长期未解决的基本问题，即低周疲劳和惯性载荷如何降低材料系统的强度和韧性，并最终导致其在响应任意机械载荷时断裂和失效。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。