Grad student wins ASTM best paper award

In Fall 2012, MechSE PhD candidate Garrett J. Pataky was awarded a Best Student Paper Award by the American Society for Testing and Materials (ASTM) for his presentation on fatigue crack growth.

Pataky was among 12 competitors from academia in the running for best research presentation at ASTM's conference in Atlanta, Georgia. Pataky presented on his dissertation project research on slip irreversibility in fatigue crack growth and the high temperature properties of nickel-based superalloy Haynes 230.

"Fatigue is when you have a cyclic load on a material, and it will start to weaken at certain points and crack due to strain and stress build-up," Pataky said.

With advising from MechSE professor Huseyin Sehitoglu, Pataky used digital image correlation (DIC) to test Haynes 230's fatigue crack growth at room temperature and 900˚C.

"My work that I presented was looking at how the strain builds up between cycles," Pataky said. "I was also trying to characterize the material and see if it's able to be used at high temperatures."

To contrast fatigue growth at different temperatures, Pataky found the DIC strain fields. Then, he measured the slip irreversibility–the quantitative difference between forward and reversed strains at tip of the crack–and found that 900˚C produced an order of magnitude higher amount of slip irreversibility than room temperature did.

As anticipated, results showed that fatigue crack growth rates were faster at higher temperatures than at room temperature. Yet, DIC analysis also showed that crack closure levels were alike in both scenarios.

Among the project's applications is the potential to use the nickel-based superalloy Haynes 230 in the next generation of nuclear reactors and intermediate heat exchangers.

"It is one of the candidate materials for the intermediate heat exchanger, which is going to see temperatures up to 1,000˚C," Pataky said. "They are trying to push as high as the reactor can go in temperature in order to increase the efficiency. Once you increase the efficiency, you can also pull out hydrogen from the system."

With help from MechSE professor Petros Sofronis, Pataky hopes to model the disposition of Haynes 230 to deform when exposed to 800˚C on account of stress, using a physically based model.

Pataky received his undergraduate degree in Mechanical Engineering at the University of Florida in 2009. He completed his master’s degree at Illinois in 2011.