Fracture Mechanics In the Presence of Reversible Martensitic Transformation in High Temperature Shape Memory Alloys

该奖项的研究目标是对纳米沉淀硬化高温形状记忆合金（HTSMA）在热机械诱导可逆马氏体相变过程中致动期间的断裂响应进行系统的实验和理论研究。负担得起的纳米沉淀硬化HTSMA具有极其稳定的循环致动响应，并且可以用作高功率输出#8722;一个数量级高于任何其他致动器材料可用的#8722;固态致动器在与航空、能量转换和存储、消费产品和汽车相关的应用中。 将对这些材料进行热机械实验，以测量断裂韧性，研究热机械引起的裂纹扩展，并确定形状，尺寸和沉淀物的一致性对断裂机制的影响。与此同时，分析工作将致力于理解热机械诱导马氏体相变对裂纹尖端附近的机械场、裂纹扩展起始的驱动力和裂纹扩展阻力的影响。如果成功，这些研究将提供有价值的信息的影响，形状记忆性能指标和微观，结构特征，以改善这些指标的断裂行为的HTSMA。这些信息最终可以用于它们的设计和优化，并允许它们最终插入应用程序。 从这些努力中获得的知识将有助于一个新的断裂力学领域，需要探索的全球各向异性相变得到妥善处理，并有望导致新的理论表征疲劳裂纹扩展和寿命的SMA执行器。 该教育计划的重点是开发教学模块，以纳入智能材料和断裂力学的本科生和研究生课程，以及通过与NSF国际材料研究所（IIMEC）和德克萨斯州A M大学的NSF - I/UCRC合作，为参与的学生提供丰富的国际和工业经验。 这两项举措都将涉及传播通过演讲、出版物、SMART网站和SMA研究技术促进联合会（CASMART）产生的知识。

The research objective of this award is a systematic experimental and theoretical investigation of the fracture response of nano-precipitation hardened high temperature shape memory alloys (HTSMAs) during actuation in the course of thermo-mechanically-induced reversible martensitic transformation. Affordable nano-precipitation hardened HTSMAs have extremely stable cyclic actuation response and can be used as high power output − an order of magnitude higher than any other actuator material available − solid state actuators in applications related to aeronautics, energy conversion and storage, consumer products, and automotive. Thermo-mechanical experiments will be performed on these materials to measure fracture toughness, investigate thermo-mechanically-induced crack growth, and identify the effect of shape, size and coherency of the precipitates on the fracture mechanisms. In parallel, the analytical efforts will be directed towards the understanding of the effect of thermo-mechanically-induced martensitic transformation on the mechanical fields near the crack tip, driving force for initiation of crack growth, and crack growth resistance.If successful, these studies would provide valuable information on the effects of shape memory performance metrics and micro-structural features to improve those metrics on the fracture behavior of HTSMAs. This information can eventually be used in their design and optimization, and permit their ultimate insertion into applications. The knowledge gained from these efforts will contribute to a new field of fracture mechanics that needs to be explored for global anisotropic phase transformation to be treated properly, and is expected to result in new theories for characterizing fatigue crack growth and lifetime in SMA actuators. The educational plan focuses on the development of teaching modules for incorporation into undergraduate and graduate courses on smart materials and fracture mechanics as well as on enriched international and industrial experiences for the students involved via the partnership with the NSF International Materials Institute (IIMEC) and the NSF - I/UCRC at Texas A&M University. Both initiatives will involve disseminating the knowledge generated through presentations, publications, the SMART website and the Consortium for the Advancement of SMA Research Technologies (CASMART).