Drs. Owen Kingstedt’s, and John Lambros’ paper entitled, “Ultra-high speed imaging of laser-induced spallation” was recently recognized with the M. Hetenyi award as the best research paper published in the journal Experimental Mechanics at the 2017 annual meeting of the Society for Experimental Mechanics. Pictured left to right: Peter Avitable (SEM President), Drs. John Lambros and Owen Kingstedt.

Kingstedt is an assistant professor in the Department of Mechanical Engineering, and Lambros is a professor of Aerospace Engineering at the University of Illinois at Urbana-Champaign.

Under high rate impact, failure processes occur through the interaction of elastic and plastic waves in solids.  These waves travel at material dependent speeds on the order of a few thousand meters per second. As result, failure events occur over tens of nanoseconds (~10-9 s).  As shown, the spallation failure process captured occurs over 40ns in time, which requires frame rates on the order of 200 million frames per second. Visualizing processes occurring at these extreme rates has been a long standing technological and experimental challenge. The paper published by Profs. Kingstedt and Lambros presents a systematic approach to capturing events at extreme time scales, and novel approaches for generating sufficient light to achieve a well exposed image.

Captured images of a spallation event using a laser energy of 0.174 J/mm2 (a) stationary image, (b) time delay of 20 ns showing the initiation of the spallation event, (c) time delay of 25 ns, (d) time delay of 30 ns, (e) time delay of 35 ns showing the complex failure outline that develops during spallation, and (f) post mortem image of a failed Silicon wafer substrate and reflective aluminum film.
Captured images of a spallation event using a laser energy of 0.174 J/mm2 (a) stationary image, (b) time delay of 20 ns showing the initiation of the spallation event, (c) time delay of 25 ns, (d) time delay of 30 ns, (e) time delay of 35 ns showing the complex failure outline that develops during spallation, and (f) post mortem image of a failed Silicon wafer substrate and reflective aluminum film.