Jeffrey Kysar

Department Chair
248 S.W. Mudd, Mail Code 4703
Tel: (212) 854-7432
Fax: (212) 854-3304
Fall '16 office hours: Fri 9-10am

Jeffrey W. Kysar is a professor of mechanical engineering at Columbia University. His current research interests include understanding the fracture process from the atomic length scale to the macroscopic length scale, especially in materials that exhibit an elastic-plastic constitutive behavior such as ductile metals. The past 15 years have seen an intense effort to try to understand and numerically simulate the physical and chemical phenomena within the region close to the tip of a crack, where large deformations and fracture mechanisms render the constitutive and geometric assumptions of continuum fracture mechanics theories invalid. This task is made very difficult because this so-called fracture process zone spans many different length scales. At its most basic level, fracture involves the separation of atoms so that simulations are performed at the sub-atomic length scale (10-11 to 10-10 m) to determine the interatomic forces and potentials using quantum mechanics calculations. Once the potentials are known, fracture simulations at the atomic length scale (10-10 to 10-7 m) are performed in which the individual atoms around a crack tip are treated discretely in order to investigate the interactions between dislocation structures and the crack tip. However, only a very small volume of atoms can be directly simulated, so at some length scale, it becomes desirable to treat the underlying atomic structure as a continuum and to keep track only of the dislocations and dislocation structures at the microscopic length scale (10-7 to 10-5 m) using so-called discrete dislocation plasticity analyses. Eventually, the number and complexity of the dislocation structures becomes overwhelming and it is necessary to resort to a continuum-based description of elastic-plastic deformation using physics-based constitutive relationships at the mesoscopic length scale (10-5 to 10-3 m). Above this length scale, at the macroscopic length scale, conventional engineering techniques can be used to design the systems and structures that we encounter in our daily lives. In this way, a hierarchy of simulations is performed, with information passed successively from simulations at smaller length scales to simulations at larger length scales to eventually provide a coherent material description across all length scales. These efforts have been termed multiscale simulations.

Recent Publications

Y. Saito, M.S. Oztop, J.W. Kysar “Wedge Indentation into Elastic-Plastic Single Crystals, 2: Simulations for Face-Centered Cubic Crystals,” International Journal of Plasticity, 28(1):70–87 (2012)

X. Wei, J.W. Kysar “Residual Plastic Strain Recovery Driven by Grain-Boundary Diffusion in Nanocrystalline Thin Films,” Acta Materialia, 59(10):3937–3945 (2011)

S. Vukelic, I.C. Noyan, J.W. Kysar, Y.L. Yao “Characterization of Heterogeneous Response of Al Bicrystal Subject to Micro Scale Laser Shock Peening,” Experimental Mechanics, 51(5):793–796 (2011)

Y. Saito, J.W. Kysar “Wedge Indentation into Elastic-Plastic Single Crystals, 1: Asymptotic Fields for Nearly-Flat Wedge,” International Journal of Plasticity, 27(10):1640–1657 (2011)

 O. Okman, J.W. Kysar “Fabrication of Crack-Free Blanket Nanoporous Gold Thin Films by Galvanostatic Dealloying,” Journal of Alloys and Compounds, 509(22):6374–6381 (2011)

 C.J. Gardner, J. Kacher, J. Basinger, B.L. Adams, M.S. Oztop, J.W. Kysar “Techniques and Applications of the Simulated Pattern Adaptation of Wilkinson’s Method for Advanced Microstructure Analysis,” Experimental Mechanics, 51(8):1379–1393 (2011)

 O. Okman, D. Lee, J.W. Kysar “Fabrication of Crack-Free Nanoporous Gold Blanket Thin Films by Potentiostatic Dealloying,” Scripta Materialia, 63(10):1005–1008 (2010)

 J.W. Kysar, Y. Saito, M.S. Oztop, D. Lee, and W.T. Huh “Experimental Lower Bounds on Geometrically Necessary Dislocation Density,” International Journal of Plasticity, 26(8):1097–1123 (2010)

 X.D. Wei, B. Fragneaud, C.A. Marianetti, J.W. Kysar “Nonlinear Elastic Behavior of Graphene: Ab initio Calculations to Continuum Description,” Physical Review B, 80(20):205407 (2009)

J. Weissmüller, R.C. Newman, H.J. Jin, A.M. Hodge, J.W. Kysar. Nanoporous Metals by Alloy Corrosion: Formation and Mechanical Properties,” MRS Bulletin, 34(8):577–586 (2009)

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