From the suburbs of Salt Lake City, mechanical engineering Ph.D. student Karen DeMille, advised by assistant professor Ashley Spear, has been awarded the highly competitive National Defense Science and Engineering Graduate (NDSEG) Fellowship. NDSEG Fellowships last for three years and pay for full tuition and all mandatory fees, a monthly stipend, and up to $1,000 a year in medical insurance. DeMille will also spend her summers at the Air Force Research Laboratory.

DeMille said, “This fellowship will support my research in establishing guidelines on the minimum amount of heterogeneous material needed around microstructurally small cracks (MSCs) to ensure that crack behavior can be studied accurately.”

“I can’t remember not having an interest in building things and understanding how they worked. In my junior high shop class, I was just as interested in watching the machines work as I was in building my projects. By the time I finished the class, I knew that I wanted to pursue a career that involved building things. Although I considered pursuing carpentry, my drive to understand how things worked, combined with an enjoyment of math and science pushed me to mechanical engineering.”

“Once in the mechanical engineering program,” added DeMille, “I learned how to code and found that coding was just another way that I enjoyed building things. My interest in coding, as well as my experience in working with wood and metal in shop class attracted me to research in computational solid mechanics. Doing research in the Multiscale Mechanics and Materials Lab, I am able to explore how things work, just on a much smaller scale than I ever imagined as a junior high school shop student.”

The formation and growth of MSCs, or cracks whose sizes are on the order of the size of microstructural features, is not well understood. This lack of understanding contributes to uncertainty in the prediction of part failure times, especially since a significant portion of a crack’s life is spent as a small crack. To account for the uncertainty, the “useful life” of the part, or the time the part can safely be used, is underestimated. However, with a better understanding of MSC behavior, the time to failure of a part can be predicted more accurately and the useful lives of parts can be extended.

Various methods, both experimental and computational, are being used to explore MSC behavior. These methods require the measurement and/or modeling of the microstructure surrounding a crack, since MSCs are highly sensitive to local microstructure. To study MSC behavior accurately, all of the microstructure that has a significant influence on the crack must be included in the measurements or models.

However, the measurement and modeling of microstructures becomes intractable as the volume of microstructure increases, limiting the amount of microstructure that can reasonably be considered. So, establishing guidelines on the minimum amount of material that is needed to capture accurate MSC behavior ensures that the mechanisms governing crack behavior can be captured, while maintaining tractability.

DeMille received her B.S. in mechanical engineering from Utah State University. Her future plans are to pursue a career in the defense industry developing the next generation of aircraft technology. “The progress made in aircraft technology over the last century is fascinating to me and I look forward to seeing where it goes next,” concludes DeMille.