Faculty Awards for Women Scientists and Engineers

NSF女性科学家和工程师学院奖表彰获奖者在教学和学术方面的高质量记录，以及潜在的研究、学术专业和未来科学家和工程师的教育。Faber博士在该奖项下的研究旨在了解脆性材料的机械行为。复相陶瓷和陶瓷-金属系统的一个普遍特征是残余应力。这种应力的存在是由于热膨胀失配应变，而热膨胀失配应变在加工过程中无法通过变形来调节。根据应力的符号、位置和大小，这种极端的应力可以作为失效的来源，或者也可以增强材料的抗断裂性。考虑到残余应力的关键作用，了解这些应力的大小和分布对于我们理解多相材料中的断裂和增韧是至关重要的。这项研究的目的是表征两种陶瓷基系统中的残余应力，特别是通过施加外部应力或热处理来改变残余应力的系统。提出了两个系统：(1)最近观察到的应力诱导微裂纹和微裂纹消除的碳化硅-二硼化钛复合材料；(2)金属衬底上的氧化锆热障涂层，其高温暴露后残余应力发生变化。X射线衍射法和必要时的中子衍射法将是测量残余应力的主要工具。残余应力分布及其在应力或热处理后的变化将与所测量的力学性能相关联。

The NSF Faculty Awards for Women Scientists and Engineers recognizes the high quality of the awardee's record in teaching and scholarship, as well as potential research, the academic profession, and the education of future scientists and engineers. Dr. Faber's research under this award is directed at understanding the mechanical behavior of brittle materials. A ubiquitous feature of multiphase ceramics and ceramic- metal systems is residual stress. Such stresses are present due to thermal expansion mismatch strains that cannot be accommodated by deformation during processing. Such stresses in the extreme may serve as a source of failure, or alternatively, may enhance the fracture resistance of the material depending on the sign, the locale, and the magnitude of the stress. Given the pivotal role of residual stresses, it is essential to know both the magnitude and the profile of these stresses to aid in our understanding of fracture and toughening in multiphase materials. It is the aim of this study to characterize residual stresses in two ceramic-based systems, in particular, systems where residual stresses are altered through the application of an external stress or a thermal treatment. Two systems are proposed: (1) a silicon carbide - titanium diboride composite in which stress-induced microcracking and stress-relief on microcracking has recently been observed; and (2) zirconia thermal barrier coatings on metallic substrates in which the residual stresses change after high temperature exposure. X-ray diffraction and, when necessary, neutron diffraction will be the primary tools used to measure residual stresses. The residual stress profile and its change after stressing or heat treatment will be correlated to measured mechanical properties.