CAREER: Understanding Micromechanisms of Fatigue in Shape Memory Alloys

该学院早期职业发展（CAREER）计划奖的研究目标是调查形状记忆合金（SMA）疲劳失效的基本机制，重点是微观结构长度尺度上的变形和相变。将研究低周疲劳（SMA在高应力幅下经历相对低的循环次数）和极高周疲劳（SMA在低应力幅下经历非常高的循环次数）。将在晶粒水平上定量表征使SMA具有独特性能的固-固相变，并将其与这些合金的介观响应和宏观应力-应变行为联系起来。由此产生的独特的，定量的相变信息将用于提高寿命和性能预测的准确性，以及这些材料的最佳设计。理解微观结构和宏观行为之间的联系是材料设计和使用中的一个基本挑战。SMA组件-例如，在军事，航空航天，生物医学和汽车应用中-越来越多地在疲劳条件下使用，并且定量了解微观结构对其疲劳行为的影响至关重要。该项目采用了一些教育的努力，是密切联系到拟议的研究，包括本科生暑期实习，研究生丰富涉及与数学系在布里斯托大学的合作努力，研究成果纳入课程，并通过公开研讨会系列和电视节目的研究成果的传播。

The research objective of this Faculty Early Career Development (CAREER) Program award is to investigate the fundamental mechanisms that are responsible for fatigue failure in shape memory alloys (SMAs), with a focus on deformation and phase transformation at the microstructural length scale. Low cycle fatigue, where the SMA undergoes a relatively low number of cycles at high stress amplitudes, and very high cycle fatigue, where the SMA undergoes a very high number of cycles at low stress amplitudes, will be studied. The solid-to-solid phase transformation that enables the unique properties of SMAs will be quantitatively characterized at the grain level, and linked to the mesoscopic response and macroscopic stress-strain behavior of these alloys. The resulting unique, quantitative information on phase transformations will be used to improve the accuracy of lifetime and performance predictions, as well as the optimal design, of these materials. Understanding the links between microstructure and macroscopic behavior is a fundamental challenge in the design and use of materials. SMA components - for example, in military, aerospace, biomedical, and automotive applications - are being increasingly used under fatigue conditions, and a quantitative understanding of the effect of microstructure on their fatigue behavior is critically necessary. This project incorporates a number of educational efforts that are closely tied to the proposed research, including undergraduate summer internships, graduate student enrichment involving a collaborative effort with the Department of Mathematics at the University of Bristol, incorporation of research results into coursework, and dissemination of research findings through a public seminar series and television show.