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Autumn 2009 Seminar Series
Friday, September 25, at 3:30 p.m.
Room 264 MacQuigg Labs
Thomas Buchheit
Materials Modeling and Simulation
Sandia National Laboratories
Albuquerque, NM
Extracting Material Properties using Instrumented Indentation:
Two case studies
Abstract
There are many well-known hurdles to extracting fundamental materials properties from indentation experiments. However, depending on the approach to a specific problem, relevant material properties information beyond a hardness and modulus measurement can be extracted from an instrumented indentation experiment (Instrumented meaning that load, displacement, and contact stiffness data are collected continuously throughout the experiment). Two cases, relevant to specific engineering applications, will be considered in this presentation. The first, measuring the properties of individual powder particles sized between 25 µm and 100 µm of four common very hard ceramic materials: tungsten carbide, alumina, boron carbide, and silicon carbide. The second, using instrumented indentation to measure residual stress in a film, specifically glass, although this case will be considered from a more general perspective. In both cases, a similar approach using a modified expanding cavity model (ECM) and direct simulation-experiment comparisons is applied. The approach is similar but each case provides complementary results. Those to be discussed include the influence of residual stress on elastic-plastic deformation within a substrate during an indentation experiment and the plausibility of a relationship between the hardness of the individual powder particles, strength, and the high rate deformation behavior of compacts fabricated from these hard ceramic powders. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.
Bio
Thomas Buchheit earned his Ph. D. in Materials Science and Engineering from the University of Virginia in 1995, his dissertation was entitled "Modeling the Stress-Induced Transformation on Shape Memory Alloy Single Crystals". He was hired by Sandia National Laboratories in 1995 as a post-doc to work on micromechanical modeling related to formability problems. He joined the technical staff at Sandia in 1998 as a metallurgist/material scientist. Over the years, his research direction has shifted toward micromechanical testing and modeling on materials relevant to microsystems applications and component reliability. A few of his recent projects include microstructure-properties characterization of candidate LIGA materials, properties characterization of silicon for MEMS applications, local measurement of residual stress in glass and LTCC assemblies, and polycrystal deformation modeling for microsystems materials.
Please join our speaker for light refreshments in 479 Watts Hall following the talk.
