SGER: Weibull Failure Criterion for MEMS Component with Stress Singularity

项目摘要：具有应力奇点的MEMS元件的Weibull失效准则动机和目标本提案涉及微机电系统（MEMS）的概率分析和设计，特别是将Weibull失效准则应用于具有应力奇点或高应力梯度的元件。提出的研究解决了MEMS可靠性的一个关键方面。这是一个重要的问题，因为MEMS正在广泛应用于可靠性至关重要的关键领域：医疗领域和国土安全。MEMS材料表现出脆性和尺寸效应，因此选择基于脆性材料尺寸效应的威布尔理论。此外，蚀刻工艺和MEMS材料的性质通常会导致制造的部件出现尖锐的缺口。此外，许多MEMS元件由多层组成。尖锐的缺口和多层界面都会产生应力奇点，从而产生奇点问题。这些力学问题分别得到了广泛的研究，但对威布尔理论和奇点的结合问题进行了稀疏的研究。事实上，人们已经注意到，在高应力梯度的情况下应用传统的威布尔理论可能会低估构件的临界缺陷尺寸（从而低估强度）。因此，提出研究的动机是需要一种可用的（对于工程师）方法，以威布尔理论为基础，解决整个工程问题中出现的奇点。因此，拟议工作的目标是双重的；也就是说，开发初步的理论结果（这将是具有应力奇点的MEMS组件的鲁棒威布尔失效准则的基础），并提出一种新型测试设备的初步设计（用于在后期研究阶段验证理论结果）。提出的研究将通过发展强大的威布尔理论来描述由于材料界面和尖锐缺口引起的应力奇点的脆性部件的失效概率，从而推进知识。在拟议的研究中获得的结果将是一个基本上未经检验的想法的初步工作。这使得提议的工作成为SGER资助的理想候选人。此外，PI打算使用从SGER拨款中获得的结果作为更广泛项目的催化剂，该项目将涉及使用新型MEMS材料测试仪器验证开发的理论。更广泛的影响拟议的研究将研究活动完全整合到本科生和研究生的工程概率方面的教学中。该计划规定本科生和研究生（特别是来自代表性不足群体的学生）在研究活动的各个阶段和各级积极参与研究。学生们将被鼓励在专业会议上展示他们的成果。PI引入并创造了“泛指导”的教学方法，涉及到大学水平的工程教学。他将继续开发和采用有效的教学技术来教授工程。该研究计划旨在加强与德克萨斯理工大学代表性不足群体的学生和/或教师的合作。此外，还与Prairie View a&m大学（历史上的黑人学院之一）和德克萨斯大学圣安东尼奥分校（西班牙裔服务机构之一）的教师进行了接触。在与政府的合作方面，美国宇航局格伦研究中心，特别是生命预测部门对拟议的研究活动非常感兴趣。拟议的研究活动的结果将不仅限于MEMS应用，而且可以扩展到陶瓷-金属键，薄膜涂层和陶瓷涡轮机热负载的应用。

0411844PI - Okwaro-Osire, Texas Tech UniversityPROJECT SUMMARYSGER: Weibull Failure Criterion for MEMS Component with Stress SingularityMotivation and ObjectivesThis proposal is concerned with the probabilistic analysis and design of microelectromechanical systems (MEMS), specifically with the application of the Weibull failure criterion to components with stress singularities or high stress gradients. The proposed research addresses a critical aspect of MEMS reliability. This is an important issue since MEMS are finding extensive use in the critical areas where reliability is paramount: the medical field and homeland security. MEMS materials have been shown to behave in a brittle manner and to exhibit the size effect , thus the choice of the Weibull theory, which is based on the size effect of brittle materials. Additionally, the etching process and the nature of MEMS materials often result in sharp notches in the manufactured components. Furthermore, many MEMS components consist of multi-layers. Both the sharp notches and multi-layer interfaces create stress singularities thus the singularity problem. Separately, each of these Mechanics problems has been researched extensively, but sparse work has been conducted on the combined problem of Weibull theory and singularity. In fact, it has been noted that applying the traditional Weibull theory in situations of high stress gradients can underestimate the critical flaw size (consequently the strength) in the component. Thus, the motivation of the proposed research is the need for a useable (for an engineer) approach anchored in the Weibull theory to address singularity that occurs in a whole class of engineering problems. Thus the objective of the proposed work is twofold; namely, develop preliminary theoretical results (that will be a basis for a robust Weibull failure criterion for MEMS component with stress singularity) and to present a preliminary design of a novel testing apparatus (to be used in verifying the theoretical results at a later phase of research).Intellectual MeritThe proposed research will advance knowledge by developing a robust Weibull theory to describe the probability of failure of brittle components with stress singularities due to material interfaces and sharp notches. The results obtained in the proposed research will be preliminary work in a largely untested idea. This makes the proposed work an ideal candidate for an SGER grant. Furthermore, the PI intends to use the results obtained from the SGER grant as a catalyst for a more extensive project, which will involve verifying the developed theory using a novel testing instrumentation on MEMS materials.Broader ImpactsThe proposed research fully integrates research activities into the teaching of probabilistic aspects of engineering to undergraduate and graduate students. The plan provides for the active research participation of both undergraduate and graduate students (particularly those from underrepresented groups) at the various stages and the level of the research activities. The students will be encouraged to present their results at professional meetings. The PI introduced and coined the pedagogic approach "Pan-mentoring" which relates to engineering instruction at college level. He will continue developing and adopting effective pedagogic techniques for teaching engineering. This research plan provides for the strengthening of collaboration with students and/or faculty who are members of underrepresented groups at Texas Tech University. Furthermore, contacts have been initiated with faculty at Prairie View A&M University (one of Historically Black Colleges & Universities) and at the University of Texas at San Antonio (one of Hispanic Serving Institutions). In regard to collaboration with the government, the proposed research activity is of immense interest to NASA Glenn Research Center, specifically the Life Prediction Branch.The results of the proposed research activity will not be limited to MEMS applications, but could extend toapplications in ceramic-to-metal bonds, thin-film coatings, and thermal loading of ceramic turbines.