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Stress Intensity Thresholds for Development of Reliable Brittle Materials

Rimsza, Jessica R.; Strong, Kevin T.; Buche, Michael R.; Jones, Reese E.; Nakakura, Craig Y.; Weyrauch, Noah M.; Brow, Richard; Duree, Jessica M.; Stephens, Kelly S.; Grutzik, Scott J.

Brittle material failure in high consequence systems can appear random and unpredictable at subcritical stresses. Gaps in our understanding of how structural flaws and environmental factors (humidity, temperature) impact fracture propagation need to be addressed to circumvent this issue. A combined experimental and computational approach composed of molecular dynamics (MD) simulations, numerical modeling, and atomic force microscopy (AFM) has been undertaken to identify mechanisms of slow crack growth in silicate glasses. AFM characterization of crack growth as slow as 10-13 m/s was observed, with some stepwise crack growth. MD simulations have identified the critical role of inelastic relaxation in crack propagation, including evolution of the structure during relaxation. A numerical model for the existence of a stress intensity threshold, a stress intensity below which a fracture will not propagate, was developed. This transferrable model for predicting slow crack growth is being incorporated into mission-based programs.

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TYPE SAND Report YEAR 2022
DOIOSTI

Photoluminescence Spectroscopy to Determine Residual Stresses in Glass-to-Metal Seals

Huntley, Emily H.; Strong, Kevin T.; Elisberg, Brenton E.; Meserole, Stephen M.; Diebold, Thomas W.

In components with two materials, such as glass-to-metal (GtM) seals, residual stress can reduce long-term reliability. Therefore, it is important to be able to accurately measure residual stress within these components. The residual stress can be from a large strain due to the mismatch of thermo-physical response of the two materials or a small strain due to stress and/or structural relaxation. Both modeling and experimental measurements were conducted on multiple GtM seals constructed with CGI 930 glass with purposely added alumina particles. The alumina particles have an established Cr fluorescence pattern and the shift in position of these peaks can accurately measure the strain of the alumina crystals. Photoluminescence spectroscopy (PLS) technique was utilized due to its non-destructive nature and high spatial resolution. PLS scans of these components were analyzed and compared to the models developed previously.

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TYPE Other Report YEAR 2019
DOIOSTI
Results 1–25 of 46
Results 1–25 of 46