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.

非技术概要应力腐蚀开裂 (SCC) 是一种材料退化现象，易受影响的材料在存在拉伸载荷（拉型载荷）的情况下可能会发生应力腐蚀开裂，而盐溶液等腐蚀环境是导致应力腐蚀开裂的原因。飞机、桥梁和管道发生灾难性故障，造成重大经济损失和人员伤亡，因此，详细研究和了解SCC对于防止桥梁和管道等结构发生故障至关重要。在该项目中，通过调整用于研究时间依赖性塑性变形（蠕变）的方法，提出了一种研究 SCC 的新方法。通过稳定地拉动形状像狗骨头的样品，该研究旨在了解裂纹是如何开始和扩散的。在 SCC 实验期间，测试会定期中断，以使用先进的显微镜捕获微观尺度（微观结构）的结构演变。SCC 测试数据和微观结构是相关的，特别是在二级区域。 （三个阶段之一观察到的 SCC 变形），最终促进仅在二级状态下进行 SCC 测试，以预测 SCC 机制和断裂。这种新方法还有助于根据实验室的短期实验预测材料的长期行为。该项目提出的活动与学生培训、SCC 新课程、SCC 研讨会以及让 K-12 学生、教育工作者和公众了解 SCC 现象的外展活动完美结合。研究与整合的直接成果很少技术摘要更好、更安全的材料对于提高生产力、安全性和国家安全至关重要的先进工程结构至关重要。虽然对 SCC 的理解有所扩展，但它仍然基于经验数据；SCC 测试速度缓慢，有时会忽略早期裂纹阶段，从而限制了机械测试的机械见解。实验室测试结果的方法不足，通常是从加速条件到实际使用场景。拟议的工作旨在开发新的测试方法，以更好地理解并预测遭受 SCC 的结构的长期寿命，从而实现更安全和稳健的负载。 -通过分析从承受恒定载荷的简单光滑狗骨形拉伸样本获得的测试数据，正在研究具有更高抗应力腐蚀开裂能力的轴承设计。电化学环境，这种创新方法可以帮助提高对 SCC 机制（例如裂纹萌生和扩展机制）的理解，还可以确定断裂时间、变形率和各种其他参数。所提出的研究与教育和推广活动很好地结合在一起。该项目为研究生和本科生提供了精通 SCC 相关实验技能的机会。涉及理论和实践活动的 SCC 新课程为学生提供了解决 SCC 相关问题所需的理论和实践知识。 SCC 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 领域的最新进展。此外，展示腐蚀、SCC 影响和预防措施的外展活动使学生和社区受益匪浅。该项目是该奖项由金属和金属纳米结构计划 (MMN) 和刺激竞争性研究既定计划 (EPSCoR) 共同资助。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力评估进行评估，认为值得支持优点和更广泛的影响审查标准。