Motivation and Objectives This 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 Merit The 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 Impacts The 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 to applications in ceramic-to-metal bonds, thin-film coatings, and thermal loading of ceramic turbines.
