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Stack, Han Win Best Presentation Awards at 12th Annual Dayton Engineering Sciences Symposium

The Department of Mechanical and Aerospace Engineering was well represented at the 12th Dayton Engineering Sciences Symposium (DESS), held November 1st by the ASME Dayton section.  Doctoral students Cory Stack and Tianyang (Tyler) Han both received Best Presentation Awards during the symposium. Cory Stack is a graduate research associate in the High Fidelity Computational Multi-Physics Laboratory (HFCMPL), headed by Dr. Datta Gaitonde. Tianyang (Tyler) Han is a graduate research associate in the Ultrasonic Additive Manufacturing (UAM) Lab and is advised by Dr. Marcelo Dapino.

Stack completed his undergraduate degree in Aerospace Engineering in May 2014 from The Ohio State University before joining the HFCMPL immediately thereafter as a PhD student in Aerospace Engineering. For his graduate research, he uses supercomputers maintained by the Department of Defense to study fundamental turbulence mechanisms in complex jet engine nozzles, specifically a supersonic, rectangular, multistream nozzle with an extended surface below the streams. Such a configuration represents a potential airframe integrated propulsion system for a supersonic vehicle.

His simulations generate massive amounts of data, which facilitate detailed analysis of the flowfield, but are also very challenging to interrogate.  He has therefore developed new tools and techniques that have helped clarify the rich physics that arises in these flows.

Stack’s presentation characterized the primary unsteady mechanism in the flow responsible for a sharp peak in the noise spectra thus complementing a companion experimental campaign being performed at Syracuse University. This unsteady mechanism was also found to have significant ramifications on pressure fluctuations induced on the extended surface, presenting a concern from unsteady structural loading in real-world applications, while also providing insight into techniques to avoid such unsteadiness in future nozzle designs.

Before joining UAM lab in 2015, Tianyang Han completed his undergraduate degree in 2013 from Xi’an Jiaotong Univeristy, China and the M.S. degree in 2015 from University of Michigan, both in mechanical engineering. The focus of Han’s doctoral research is to develop fundamental understanding of the UAM process toward implementing UAM in new material combinations, especially steel alloys, and to investigate new methods to characterize UAM builds at scales ranging from the microstructure to structural macroscale.

Ultrasonic additive manufacturing (UAM) is an emerging additive manufacturing technology that combines solid-state additive ultrasonic welding and CNC subtractive machining to produce metal components and structures. The UAM process takes place at very low temperature on the order of 125 °C which enables the joining of dissimilar metals without the formation of brittle intermetallics or melting of the materials. UAM has been demonstrated to create robust metal structures involving Al-Al, Al-Ti, Al-steel, Cu-Cu, Al-Cu, and Al- NiTi. However, builds including high-strength steels have not been consistently manufactured with the UAM process due to a lack of fundamental understanding of the process as well as certain equipment limitations. In Han’s ASME DESS presentation, a laminated steel structure made with OSU’s UAM system was discussed along with supporting mechanical and microstructural test data.