Applying modified Weibull failure theory on a polysilicon MEMS Structure

Experiment on polysilicon, ultrananocrystalline diamond and single walled carbon nanotubes, micro/nanoscale specimens found the followings: (1) specimens are sensitive to flaws; (2) fracture occurs at the critical defect; and (3) Weibull analysis can be applied to predict successfully the failure stresses of these specimens. Weibull analysis for predicting failure induced by perforations in microtensile test based on Weibull parameter estimates from either uniform tensile bars or from a parametric estimate generated with other perforated tensile tests. Results from literature showed that the predictions based on uniform tensile data were better suited to predict failure in perforations with shallow stress gradients and less capable in situation where the stress-gradient was steep. Researchers highlighted the challenges that remain in the use of uniform tensile data in the Weibull failure theory to predict failure in the presence of notches or cracks. The overreaching goal of this study is to develop and verify a modified Weibull failure formulization to predict strength of polysilicon MEMS microtensile specimens with or without notch. To achieve this long term goal, the goal of this research was to design and simulate a microtensile test jig to measure the loading and notch shape effects on the fracture strength of a micro/nano scale fracture specimen.