AE faculty members Ioannis Chasiotis and John Lambros, along with recent PhD graduate Krishna Jonnalagadda and current graduate student Sivakumar Yagnamurty, are the 2012 winners of the M. Hetényi Award from the Society for Experimental Mechanics (SEM).
The award is bestowed for the Best Research Paper published in 2010 inExperimental Mechanics, the journal SEM has produced the past 51 years. The four AE scientists’ paper, “Experimental Investigation of Strain Rate Dependence of Nanocrystalline Pt Films,” was produced with collaborators from the Army Research Laboratory in Adelphi, Maryland.
Chasiotis said the team was able to make a breakthrough in microscale measurement methods to study the mechanical behavior of nanocrystalline thin metal films used in micromachines, such as radio frequency switches, mechanical capacitors and cell phones.
AE Prof. Ioannis Chasiotis
He explained that, when loaded, nanocrystalline metallic films tend to creep and stretch over time. The rate of this mechanical behavior depends upon how quickly the specimens are loaded. Complicating the issue is that the samples are very small, at 100 to 500 times thinner than a human hair, and so their behavior is difficult to measure.
For years, other researchers had tried to decorate the films with fine particles and had used elaborate measurement techniques, Chasiotis said. His group designed a method to filter then deposit fine particles on the miniature and fragile specimens’ surface without having an intrusive effect upon them or damaging them. By using this technique, the group was able to show for the first time that the mechanical behavior of nanocrystalline thin metal films varies dramatically with the loading time even at room temperature.
“An important part of the experimental method was the development of a testing apparatus that could measure the behavior of these films with nanometer resolution and at time scales that vary from a 1/1000th of a second to hours long,” Chasiotis said.
The award-winning paper resulted from research that began in 2006. The National Science Foundation and the Army Research Office have supported the work.
This is the second Best Paper Award for Jonnalagdda, who also won for a paper published in 2007 in the Journal of Fatigue & Fracture of Engineering Materials & Structures. Jonnalagdda, who earned his PhD in AE in 2008, is now on faculty at the India Institute of Technology in Bombay.
The Hetényi Award was established in 1967 in honor of Dr. Miklos Hetényi, one of SEM’s four founders. Hetényi wrote over 70 scientific papers on analytical and experimental mechanics and on the theory of structures.