Glenn S. Daehn

 Map to 347 Fontana Labs (Office)

Professor

  

Ph.D. Stanford University, 1988

  

Tel. (614) 292-6779

  
daehn .1@osu.edu  
 
National Science Foundation Young Investigator
Robert Lansing Hardy Gold Medal of TMS recipient-1992
Grossman Young Author Award of ASM -1990
Mars G. Fontana Professor of Metallurgical Engineering

Prof. Daehn has been on the Faculty since 1988 when he completed his formal education at Northwestern University (B.S.) and Stanford University (M.S. and Ph.D.) He maintains wide interests in problems related to mechanical behavior, plasticity and mechanical processing in manufacturing. His research is in areas where fundamental principles can be applied in new ways to solve practical problems:

  Hyperplasticity and High Velocity Metal Forming  
Recent work in Daehn's group has shown that high velocity sheet metal forming can dramatically improve material formability (the amount of stretch available without tearing) and wrinkling can be greatly suppressed. Electromagnetic forming is a very convenient way of flexibly producing very high velocity deformation (see example at right of non-contact launch of an aluminum sheet). Presently Daehn's group is working with automotive, aluminum and aerospace companies and the National Science Foundation to develop this process.

Details are available at www.osu.edu/hyperplasticity.

2  
Electromagnetic launch of an aluminum plate. 30µs between images.
Our Concept of a hybrid press
  Rate Dependent Plastic Deformation  
Daehn has long-standing interests in creep, plasticity and superplasticity. His group has carefully considered how thermal expansion mismatch in composites can accelerate plastic deformation when temperature is changed. This understanding has been applied to life assessment in high temperature composites and to thermal-cycling superplastic forming. More recently activities are centered on modeling rate dependent deformation considering how many obstacles and load shedding act together. The figure at the left comes from some of that work and shows the variation in slip activity in varied parts of a microstructure resulting from local 'hard' and 'soft' spots.

 

  Powder Consolidation in Metal Matrix Composites
 

Motivated by the studies of thermal expansion mismatch induced superplastic deformation discussed above, we postulated that metal matrix composites may be compacted more effectively under cyclic pressure than static pressure, and found this was indeed the case. For moderate to large volume fractions of reinforcement with different compressibility than the matrix, compaction with cyclic pressure yields significantly higher compacted density, improved uniformity of density and dramatically improved strength.


. 5µm . static consolidation (left) cyclic (right).


Ceramic-Based Composites

While studying as an undergraduate, Michael Breslin made the surprising discovery that if dense silica is immersed in liquid aluminum at a temperature around 1100 C the stable oxide, alumina, will form in a porous morphology and aluminum will fill the pores. This reaction takes place replicating the shape of the silica precursor. With Hamish Fraser, we have studied the kinetics, structure (right) and mechanical properties of these composites.



Some Recent Publications

See more complete publication list 

"A Model for Creep Based on Microstructural Length Scale Evolution",  G. S Daehn, H. Brehm H. Lee and B-S Lim, Proceedings of ICSMA Conference, Budapest, Hungary, August 25-30, 2003, in press. (see preprint)

"Formability of Sheet Steel in High Velocity Impact” M. Seth, V.J. Vohnout and G.S. Daehn,  J Mater. Proc. Tech., submitted October, (2003). (see preprint)

"Effect of Velocity on Flow Localization in Tension", X. Hu and G. S. Daehn ,Acta Mater., 44 , 1021-33 (1996).

"Co-Continuous Composite Materials from Net-Shape Displacement Reactions" , G. S. Daehn, in Frontiers of Engineering: Reports on Leading Edge Engineering from the 1996 NAE Symposium on Frontiers of Engineering, National Academy Press, pp. 91-94 (1997).

"Spot Impact Welding of Sheet Aluminum", A. Turner, P. Zhang, V.J. Vohnout and G.S. Daehn, submitted to 8th International Conference on Aluminum Alloys, Cambridge, UK, July 2-5, 2002.

"A Framework for Modeling Creep in Pure Metals", H. Brehm and G. S. Daehn, Materials Transactions A, 33, 363-371, (2002).

"Modeling Thermally Activated Deformation with a Variety of Obstacles and its Application to Creep Transients", G.S. Daehn ,Acta Mater, 49, 2017-2026 (2001).

"Effect of Cyclic Compaction on the Uniformity of Metal Matrix Composites", Y. Fu, J. J. Lannutti, R. H. Wagoner and G. S. Daehn, Materials and Metallurgical Transactions, 33A, 183-191, (2002).

"Thermal Cycling and Related Strain Mismatch in Metal Matrix Composites", G. S. Daehn , Volume 3, Chapter 15 Comprehensive Composite Materials, edited by A. Kelly and C. Zweben, Elsevier, 419-445 (2000).