Department of Mechanical Engineering Fall Seminar Series
“Multiscale Process-Structure Simulations for Additive Manufacturing in Metals”
Presented by Professor Greg Wagner
Mechanical Engineering, Northwestern University
Additive manufacturing (AM) brings advantages for the fabrication of metal parts compared with traditional techniques, including the ability to create complex geometries with reduced production lead time and less material waste. However, the intricacy of the additive process and the extreme thermal environments involved can lead to material defects, heterogeneous microstructures, and wide variation in properties, leading to unpredictable and sometimes inferior performance of AM-built parts. Computational simulation can be used to understand and predict the effects of various process parameters on the resulting material, and to suggest strategies to optimize ultimate part performance. In this talk, I present modeling approaches at several length scales that are important in predicting material structure in AM. These include the part scale, where geometry and build strategy affect the thermal history throughout the material; the melt pool scale, where fluid flow and phase change dictate the heat transfer in the solidifying material; and the material microscale, where repeated re-melting and the competition between grain growth and nucleation can lead to unusual grain structures. Novel computational methods and tools are used at each scale, and to couple across scales. Finally, I discuss ideas for developing reduced order models to more efficiently material structure for a given set of process parameters.
Greg Wagner received his Ph.D. in Mechanical Engineering from Northwestern University in 2001. He spent over 12 years as a staff member and later manager in the Thermal/Fluid Science and Engineering department at Sandia National Laboratories in Livermore, CA, where his work included multiscale and multi-physics computational methods, multiphase and particulate flow simulation, extended timescale methods for atomistic simulation, and large-scale engineering code development. In January 2015 he joined the faculty of the Mechanical Engineering department at Northwestern. His current research focuses on applying novel simulation methods and high performance computing to multiphase flows and flows with complex and moving geometries. He is the author or co-author of over 50 journal articles, and his awards include the Zienkiewicz Prize for Numerical Methods in Engineering. He is an associate editor for Computer Modeling in Engineering & Sciences and Journal of Micromechanics and Molecular Physics.