MSE Colloquium: George M. Pharr, Probing the Mechanical Behavior of Hard, Brittle Materials with Nanoindentation: Chapter II

Chancellor's Prof & McKamey Prof of Engineering; Un of Tennessee, Oak Ridge National Laboratory

Abstract

Since its development in the mid-1980's, nanoindentation has proven to be an important tool for measuring and characterizing the mechanical behavior of a wide variety of materials at the micron and submicron scales. Among the properties that are now routinely measured are hardness, elastic modulus, fracture toughness, yield strength, work hardening, residual stress, and the time-dependent parameters characteristic of viscoelasticity and creep. In this presentation, we continue a discussion we began last year (Chapter I) on how nanoindentation can be used to characterize the mechanical behavior of hard, brittle materials like ceramics, glasses, and semiconductors. Last year, the focus was primarily on: (1) understanding the mechanics of fracture during indentation with sharp pyramidal indenters, and (2) methods for measuring stress-strain behavior in materials that don't normally plastically flow when tested by conventional techniques. In this presentation, we will discuss new techniques for measuring fracture toughness in thin films and small volumes as well as new methods for exploring the fundamental origins of crack initiation at the smallest scales. We will also review the status of the "next generation nanomechanical testing platform" which is currently under design and development at the University of Tennessee. By providing for small-scale mechanical testing at temperatures up to 1100°C in very high vacuum and gaseous environments, this unique new system will facilitate the characterization of a variety of new ceramic coatings and composite materials for high temperature application. In addition, the system will use new laser-based methods for displacement measurement that will help to mitigate problems with thermal drift and provide for very high rates of data acquisition (up to 10 MHz) to study very fast deformation events such as indentation pop-in and unstable crack propagation. 

Work supported by the National Science Foundation under grant number DMR 1427812, and by the US Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division.

Bio

 

George M. Pharr is Chancellor's Professor and McKamey Professor of Engineering at the University of Tennessee, Knoxville (UT). He also holds a Joint Faculty position in the Materials Science and Technology Division at the Oak Ridge National Laboratory (ORNL). He received his BS in Mechanical Engineering at Rice University in 1975 and Ph.D. in Materials Science and Engineering from Stanford in 1979. After one year of postdoctoral study at the University of Cambridge, England, he returned to Rice in 1980 as a faculty member in the Department of Mechanical Engineering and Materials Science. He moved to his current joint position at UT and ORNL in 1998 and served as Head of the UT Materials Science and Engineering Department during the period 2006-2011. He is currently the Director of the UT/ORNL Joint Institute for Advanced Materials.

Dr. Pharr received ASM International’s Bradley Stoughton Award for Young Teachers of Metallurgy in 1985. His honors also include the Amoco Award for Superior Teaching at Rice University in 199, a Humboldt Senior Scientist Award in 2007, the Materials Research Society's inaugural Innovation in Materials Characterization Award in 2010, and the University of Tennessee Macebearer Award in 2015. He is a member of the National Academy of Engineering (2014), a Fellow of ASM International (1995), and a Fellow of the Materials Research Society (2012). Dr. Pharr has been an Associate Editor of the Journal of the American Ceramic Society since 1990 and Principal Editor of the Journal of Materials Research since 2012. He is an author or co-author of more than 200 scientific publications, including 4 book chapters. His research focuses on mechanisms of plasticity and fracture in solids, especially at small scales.