Rodney Clifton
Professor:
Engineering
Phone: +1 401 863 2855
Phone 2: +1 401 863 3034
clifton@engin.brown.edu
Professor Clifton's primary research is on the mechanical response of materials at very high loading rates. Applications include: high speed machining, armor penetration, shear band formation, martensitic phase transformations, elastohydrodynamic lubrication, and dynamic fracture. Principal experimental approach is pressure-shear plate impact. A second research focus involves the measurement of the high frequency, viscoelastic response of soft, biological tissues, especially vocal folds.
Interests
Beginning with Harry Kolsky (deceased) and continuing with Jacques Duffy (deceased) and Rod Clifton, Brown investigators have led the development of the experimental methodologies for studying the mechanical behavior of materials at high strain rates. The torsional Kolsky bar and the pressure-shear plate impact experiment developed at Brown are widely used to study the deformation and failure of materials at the high strain rates that occur in high speed machining, terminal ballistics, and explosive loading. Professor Clifton's group conducts research on the mechanical response of materials subjected to very high loading rates. This research is motivated by the need for better understanding of such processes as high speed machining, armor penetration, shear band formation, martensitic phase transformations, elastohydrodynamic lubrication, and dynamic fracture. The research involves combined experimental and computational investigations in which the experimental component makes use of plane wave loading to provide the most direct interpretation of the experimental results in terms of the response of the material.
Pressure shear plate impact: Plane waves are generated in a plate impact facility, which is designed to produce the impact of parallel plates. In order to subject the impacting plates to combined pressure and shear loading, the impacting plates are inclined relative to the direction of approach. The motion of the rear surface of the impacted plate is recorded using a variety of laser interferometers. Computer simulation of the experiment is used to relate the recorded velocity-time profiles to the response of the material being studied. Scope: Studies have been conducted on a wide variety of materials including metals, metal alloys, glasses, ceramics, ceramic powders, lubricants, and shape memory alloys. In addition, studies have been conducted on the dynamic friction of sliding interfaces, such as the interface between a machine tool and the stock being machined. Recently, an induction heater has been added that makes it possible to conduct the experiments at temperatures up to 700 degrees C. Experiments can also be conducted in a so-called "soft recovery" configuration in which the specimen is recovered after being subjected to a single plane pulse -- thereby making it possible to relate the dislocation motion or microcracking that occurred to the action of a known stress pulse.
Current projects: Current research projects are concerned with the modeling of martensitic phase transformation, dynamics failure of steel welds, dynamics plasticity of refractory metals, dislocation mobility in Ni3Al, and the competition between shear banding and shear fracture in the dynamic failure of materials.
Awards
Member Phi Kappa Phi, Pi Mu Epsilon, Sigma Tau, Sigma Xi
NDEA Fellow - 1960-63
National Science Foundation Science Faculty Fellow - 1971-72
Fellow, American Academy of Mechanics (AAM) (elected in l980)
Melville Medal, American Society of Mechanical Engineers (ASME) - l98l (with K.S. Kim)
Prager Medal, Society of Engineering Science (SES) - l986
Best Paper, Tribology, American Society of Mechanical Engineers (ASME) - 1987 (with K.T. Ramesh)
Member, National Academy of Engineering (NAE) – (elected in 1989)
Distinguished Alumni Award, Carnegie Mellon University - 1992
Murray Medal, Society for Experimental Mechanics (SEM) – 1997
Fellow, American Society of Mechanical Engineers (ASME)─ 1999
Timoshenko Medal, American Society of Mechanical Engineers (ASME) ─ 2000
Distinguished Civil Eng. Alumnus Award, Univ. Nebr. ─ 2001
Member, American Academy of Arts and Sciences (AAAS) (elected in 2005)
Affiliations
Associate Editor, J. Applied Mechanics - 1981 - 1988
Society of Engineering Science, President - 1982-83.
Editorial Advisor, J. Mechs. Phys. Solids - 1982-present
Member: American Society of Mechanical Engineers (ASME), American Society of Civil Engineers (ASCE), Society for Industrial and Applied Mathematics (SIAM), American Physical Society (APS)
Member, NRC Committee on Material Response to Ultra High Loading Rates - 1977
Panelist, National Committee for Rock Mechanics Workshop - 1977
NRC Committee for Dynamics of Continuous Media
Committee on U.S. Army Basic Scientific Research - 1976-79
Co-Organizer, National Science Foundation Workshop on Nonlinear Waves in Solids - 1977
Board of Directors, Society of Engineering Science - 1977-1983
Panelist for Review of National Science Foundation Research Initiation Grants
Panelist for Review of National Science Foundation Specialized Research Equipment Grants
Member, American Society of Mechanical Engineers (ASME) Committee on Research Directions in Solid Mechanics - l984 - l985.
Member, Department Of Energy Panel on Solid Mechanics, Structural Mechanics and Dynamics - l985.
Member, Board of Governors, Institute for Mechanics and Materials, UCSD, 1992- 1998
Vice-Chair, Mechanical Engineering Peer Committee, National Academy of Engineering, 1995
Member, Armor and Armaments Panel, Army Research Laboratory, 2001-
Chair, Visiting Committee, Graduate Program in Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, 2005
