CAREER: Elucidating the fundamental mechanisms of stress corrosion cracking from smooth tensile specimens under constant load for quantitative life-prediction

职业：阐明恒定载荷下光滑拉伸样品应力腐蚀开裂的基本机制，以进行定量寿命预测

• 批准号: 2339696
• 负责人: Nilesh Kumar
• 金额: $ 54.6万
• 依托单位: University of Alabama Tuscaloosa
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-07-01 至 2029-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2339696&HistoricalAwards=false
• 关键词: CAREER; Elucidating; fundamental; mechanisms; stress

NON-TECHNICAL SUMMARYStress corrosion cracking (SCC) is a type of material degradation phenomenon. A susceptible material can undergo SCC in the presence of a tensile load (pull type loading) and a corrosive environment such as a salt solution. SCC has been responsible for catastrophic failures in aircraft, bridges, and pipelines, resulting in significant economic losses and casualties. Therefore, it is crucial to study and understand SCC in detail to prevent failures in structures like bridges and pipelines. In this project, a new and simple method to study SCC is suggested by adapting methods used to study time dependent plastic deformation (creep). By steadily pulling on a sample shaped like a dog bone, the study aims to understand how cracks start, spread, and finally cause a break. During SCC experiments, the test is interrupted at regular intervals to capture the evolution of the structure at a microscopic scale (microstructure) using advanced microscopes. The SCC test data and microstructure are correlated, particularly in the secondary regime (one of three stages of SCC deformation observed), which eventually promote conducting SCC tests only up to the secondary regime to predict the SCC mechanism and fracture. This new method also helps predict how materials behave over a long period based on short-term experiments in the lab. Several research activities proposed in the project are well integrated with educational and outreach activities. Training of students, a new course on SCC, a workshop on SCC, and outreach activities to expose K-12 students, educators, and the public to the SCC phenomenon are a few direct outcomes of the integration of research and education, benefitting a wide spectrum of stakeholders with a focus on society’s underserved. TECHNICAL SUMMARYBetter and safer materials are critical to advanced engineering structures essential in increasing productivity, safety, and national security. A better understanding of deformation processes during stress corrosion cracking (SCC) leads to better design of metallic materials. While the understanding of SCC has expanded, it remains based on empirical data; testing for SCC is slow and sometimes overlooks early crack stages, limiting mechanistic insights from mechanical tests. Moreover, there is a deficiency in methods to adapt lab test outcomes, often from accelerated conditions to actual service scenarios. The proposed work aims to develop novel test methods to have a better mechanistic understanding and predict long-term life for structures undergoing SCC, leading to safer and robust load-bearing designs with higher resistance to SCC. The SCC phenomenon is being studied following the concepts and procedures developed to understand creep deformation behavior of metallic materials. By analyzing test data obtained from simple smooth dog-bone-shaped tensile specimens subjected to constant loads in an electrochemical environment, this innovative approach can help improve understanding of the mechanisms of SCC (for example, crack initiation and propagation mechanisms). It also allows for the determination of fracture time, deformation rate, and various other parameters. The proposed research is well integrated with educational and outreach activities. The project provides opportunities for graduate and undergraduate students to become proficient in experimental skills related to SCC. The new course on SCC involving theory and hands-on activities equips students with the necessary theoretical and practical knowledge to solve SCC-related problems. Moreover, the summer workshop on SCC brings together students, engineers, scientists, and researchers to share and learn about the latest advancements in the field of SCC. Additionally, outreach activities to showcase the effects of corrosion, SCC, and prevention measures significantly benefit students and communities from underrepresented populations.This project is jointly funded by the Metals and Metallic Nanostructures Program (MMN) and the Established Program to Stimulate Competitive Research (EPSCoR).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.

非技术摘要应力腐蚀破裂（SCC）是一种物质定义现象。易感材料可以在有拉伸负荷（拉型负荷）和腐蚀性环境（例如盐溶液）的情况下进行SCC。 SCC一直导致飞机，桥梁和管道中的灾难性故障，从而造成了巨大的经济损失和人员伤亡。因此，详细研究和理解SCC至关重要，以防止桥梁和管道等结构中的故障。在该项目中，通过用于研究时间依赖性塑性变形（蠕变）的适应方法提出了一种新的研究SCC方法。通过安静地拉动形状像狗骨头的样本，该研究旨在了解裂缝如何开始，传播并最终导致休息。在SCC实验期间，使用高级显微镜以微观尺度（微结构）捕获结构的演变，以定期中断测试。 SCC测试数据和微观结构是相关的，特别是在次级状态（观察到的SCC变形的三个阶段之一）中，这有时仅促进进行SCC测试，直到二级制度才能预测SCC机制和断裂。这种新方法还有助于预测基于实验室中短期实验的长期行为。该项目中提出的几项研究活动与教育和外展活动充分融合。培训学生，有关SCC的新课程，有关SCC的研讨会以及外展活动，以使K-12学生，教育工作者和公众接触到SCC现象，这是研究和教育整合的一些直接成果，使广泛的利益相关者受益于社会贫乏。技术摘要和安全材料对于提高生产率，安全性和国家安全至关重要的先进工程结构至关重要。更好地了解应力腐蚀破裂（SCC）期间的变形过程，从而更好地设计了金属材料。尽管对SCC的理解已经扩展，但它仍然基于经验数据。 SCC的测试缓慢，有时会忽略早期的裂纹阶段，从而限制了机械测试的机械见解。此外，通常从加速条件到实际服务方案的方法来调整实验室测试结果的方法不足。拟议的工作旨在开发新型的测试方法，使其具有更好的机械理解并预测经历SCC的结构的长期寿命，从而导致更安全，强大的承重设计具有对SCC的耐药性。 SCC现象正在研究遵循为了解金属材料的蠕变开发行为而开发的概念和程序。通过分析在电化学环境中受到恒定载荷的简单平滑狗形拉伸标本获得的测试数据，这种创新的方法可以帮助提高对SCC机制的理解（例如，裂纹引发和传播机制）。它还允许确定断裂时间，变形率和各种参数。拟议的研究与教育和外展活动充分融合。该项目为研究生和本科生提供了熟练与SCC相关的实验技能的机会。涉及理论和动手活动的SCC的新课程使学生拥有必要的理论和实践知识，以解决与SCC相关的问题。此外，SCC的夏季研讨会汇集了学生，工程师，科学家和研究人员分享和了解SCC领域的最新进步。此外，展示腐蚀，SCC和预防措施的影响的外展活动极大地使学生和社区受益于代表性不足的人群。该项目由金属和金属纳米结构计划（MMN）共同资助（MMN），并已建立的计划以及既定的竞争性研究（EPSCOR）的启发，并反映了NSF的规定，并以此为基础。优点和更广泛的影响审查标准。