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Spring 2008 Seminar Series

Wednesday, May 21, at 3:30 p.m.
Room 264 MacQuigg Labs

Craig S. Hartley

Consultant, El Arroyo Enterprises LLC
Emeritus Professor of Mechanical Engineering, Florida Atlantic University
Program Manager Emeritus, Air Force Research Laboratory

Deformation Textures and Mechanical Properties of FCC and HCP Metals Predicted by Crystal Plasticity Codes

Abstract

Dr. Craig S. Hartley

Three crystal plasticity codes, the Material Particle Simulator (MPS) developed at Cornell, the crystal plasticity codes developed at Drexel University and the ViscoPlastic Self-Consistent code (VPSC7b) developed at LANL, were compared by simulating the isochoric, free upsetting of a face-centered cubic (FCC) alloy, Type 304 Stainless Steel, and a hexagonal close-packed (HCP) material, unalloyed Ti. Deformation of an initially random sample of 5000 grains was carried out in compression at a constant true strain rate of 0.001 s-1 using strain increments of 0.02 to a true strain of 1.0. In all cases hardening on active slip planes was modeled by a Voce-type equation, and calculations were performed for non-hardening and linear hardening conditions. Deformation conditions appropriate to elevated temperature deformation were modeled by selecting a strain-rate sensitivity of 0.25 on all active slip systems. The Taylor linking hypothesis was employed for all codes, giving an upper bound calculation for the results. In addition, the MPS code was employed to calculate a lower bound for the same deformation conditions and the Affine mode of the VPSC7b code was employed to model grain interactions.

Results of the calculations are expressed as von Mises effective stress-effective strain curves, normalized to the critical resolved shear stress (CRSS) on the slip plane, in the case of the FCC material. In the case of the HCP material, slip on basal <a>, prismatic <a> and pyramidal <c+a> systems was permitted, with the ratio of the CRSS on the three systems equal to 1.0, 0.7 and 3.0, respectively. For these calculations the effective stress-strain curve was normalized to the CRSS on the basal <a> system. Pole figures of two or three principal crystallographic directions at the end of the deformation process are presented for all simulations. The effective Taylor Factor is also calculated as a function of strain using two different methods. The results demonstrate the equivalence of calculations performed with all codes using the Taylor hypothesis and the sensitivity of the calculations to the choice of linking hypothesis in other cases.


Dr. Hartley's bio info available at "mse.osu.edu/department/seminars/"

Authors: C. S. Hartley, El Arroyo Enterprises, Sedona, AZ; P. R. Dawson and D. Boyce, Sibley School of Mechanical and Aerospace; Engineering, Cornell University, Ithaca, NY; S. R. Kalidindi and M, Knezevic, Department of Materials Science and Engineering, Drexel University, Philadelphia, PA; C. Tomé and R. Lebensohn, Los Alamos National Laboratory, Los Alamos, NM; S.L. Semiatin, T.J. Turner, Air Force Materials and Manufacturing Directorate, AFRL, Wright-Patterson AFB, OH; A. A. Salem, Universal Energy Systems, Dayton, OH

Bio

Dr. Hartley received the degree Bachelor of Metallurgical Engineering from Rensselaer Polytechnic Institute in 1958. While working for Nuclear Metals, Inc. in Concord, MA he was called to active duty as a lieutenant in the US Air Force, and stationed at Wright-Patterson AFB, OH, where he served as an officer and civilian employee from 1959 until 1965. During that time he earned the M.S. and Ph.D. degrees in Metallurgical Engineering from the Ohio State University. His graduate advisors were Joseph Spretnak for the M.S. and John P. Hirth for the Ph.D.

Following an NSF postdoctorate appointment in 1965-66 at Birmingham University in England, where he worked with Professor Ray Smallman, he was appointed Assistant Professor of Metallurgical and Materials Engineering and Engineering Science and Mechanics at the University of Florida. He remained at UF for fourteen years, one of which was a sabbatical at Imperial College, London, where he worked with Professor John Alexander on metal forming by co-extrusion. During the summers of this period he held visiting summer positions at UKAEA, Harwell in England (3 summers); Savannah River Laboratory, Westinghouse Research Laboratory, Lockheed Palo Alto Laboratory and Sandia Laboratories, Albuquerque, NM. He left the University of Florida to become department head of Materials Science at SUNY-Stony Brook in 1980.

Dr. Hartley became Associate Dean for Research and Graduate Affairs and Director of the Division of Engineering Research in the College of Engineering at Louisiana State University in 1982. In 1986-87 he served for one year as Program Manager for the Metals program in the Division of Materials Research at NSF. In 1987 he was appointed Department Head of Materials Engineering at the University of Alabama at Birmingham, where he served until he became Dean of Engineering at Florida Atlantic University in 1990. In 1996 Dr. Hartley was appointed Program Manager for Materials in the Mechanics and Materials Program at NSF, where he served for one year before taking a sabbatical in the Metallurgy Division at NIST. From 1998-2000 he was an IPA Program Manager for Materials Science in the Metal and Ceramic Sciences program, Division of Materials Science, Office of Basic Energy Sciences, Department of Energy in Germantown, MD. In May, 2000 Dr. Hartley retired from academe to accept appointment as Program Manager for Metallic Materials with AFOSR, Arlington, VA. He retired from this position in February, 2005 and relocated to Sedona, AZ, where he continues his professional activities as a consultant in materials research and education. Dr. Hartley is Emeritus Professor of Mechanical Engineering at Florida Atlantic University and Program Manager Emeritus in the Air Force Research Laboratory, AFOSR. He is a Fellow of the American Association for the Advancement of Science, ASM International and ASME and an Eminent Engineer of Tau Beta Pi.

Dr. Hartley's principal research areas are in the mechanics and mechanical behavior of metallic materials from the scale of crystal defects through deformation processing. He has made contributions in the areas of dislocation theory and the mechanics of metal deformation processing. He formerly served on the Shaping and Forming Committee of TMS, including one term as chair. He has also served on the TMS Education and Professional Affairs Committee, serving a term as chair, as well as the Governmental Affairs Committee and Continuing Education chair for the MDMD. He has been organizer or co-organizer of many conferences and symposia and has served on the scientific committee of several international conferences.


Please join our speaker for light refreshments in 479 Watts Hall following the talk.