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Ultra Sonic Measurement And Computation Of Elastic Constants

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Conference

2006 Annual Conference & Exposition

Location

Chicago, Illinois

Publication Date

June 18, 2006

Start Date

June 18, 2006

End Date

June 21, 2006

ISSN

2153-5965

Conference Session

Building a Community in Materials

Tagged Division

Materials

Page Count

11

Page Numbers

11.1356.1 - 11.1356.11

DOI

10.18260/1-2--1286

Permanent URL

https://peer.asee.org/1286

Download Count

497

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Paper Authors

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Kathleen Stair Northwestern University

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Kathleen Stair received a B.S. in Engineering and a Ph.D. in Materials Science and Engineering from Northwestern University. She spent seven years as a Research Engineer with the Amoco Technology Company in Naperville, Illinois, where she was responsible for growth of GaAs-based materials using Molecular Beam Epitaxy. She has been a senior lecturer in Materials Science and Engineering at Northwestern since 1996, and is responsible for many of the undergraduate laboratories.

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Jefferson Z. Liu Northwestern University

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Zhe Liu is a Ph.D. candidate in the Department of Materials Science and Engineering, Northwestern University. He received his B.E. and M.E. in Engineering Mechanics from Tsinghua University, P.R. China. His research interests are in application of atomistic and first-principle methods for simulating thermodynamic, mechanical, and kinetic properties of complex multiphase bulk materials and nano-structures.

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Mark Asta Northwestern University

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Prof. Asta received his Ph. D. degree in an interdisciplinary Materials Physics program from the University of California, Berkeley, in 1993, and subsequently joined Sandia National Laboratories at Livermore, CA. He joined the faculty of the Department of Materials Science and Engineering, Northwestern University, as an Associate Professor
in 2000. In 2005 he joined the University of California, Davis, where he is a Professor in the Department of Chemical Engineering and Materials Science and also a member of the Computational Science and Engineering Center. Prof. Asta's research interests are in computational materials science, focusing on the development and application of atomistic and first-principles methods for simulating thermodynamic and kinetic properties of complex multiphase bulk materials, surfaces and interfaces.

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Abstract
NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

Ultra-sonic Measurement and Computation of Elastic Constants

Abstract

We have developed a laboratory exercise using an ultrasonic test system to measure elastic constants in copper single crystals, as well as moduli in polycrystalline samples. This laboratory is coordinated with the Introduction to Physics of Materials class taught to junior-level Materials Science and Engineering majors. Students in the class have usually taken a course in Mechanical Behavior of Solids, and are familiar with macroscopic (and destructive) testing of elastic moduli. This exercise provides an excellent basis for a discussion of the propagation of phonons in solids, the relationship between microscopic and macroscopic properties, destructive vs. non-destructive test methods, and an application of matrix algebra. We have recently added a computational component to the lab: use of density functional theory (using the program Plane Wave Self- Consistent Field, PWSCF) to calculate the elastic constants and compare to the measured values. The free software is part of the Quantum-ESPRESSO package.1 The use of DFT also allows the demonstration of the nature of the approximations that must be made to solve the many-body Schrödinger equation for electrons in a condensed phase. This follows discussions in the first half of the course about the hydrogen atom and how extending such calculations require approximations due to the many-body problem.

Introduction and Motivation

Materials Scientists and Engineers are increasingly using computational tools to predict material properties, in addition to using analytical tools to measure them. We feel it is essential to incorporate some of these tools, as well as knowledge of the theories on which they are based, into our undergraduate curriculum. One opportunity to do so is in our junior-level Introduction to Physics of Materials course. This is a two-quarter sequence, required by MSE majors, that introduces quantum mechanics and applications to materials and engineering, band structures, cohesive energy, thermal behavior, electrical conduction, etc. The first quarter emphasizes an introduction to quantum mechanics; the second quarter emphasizes applications, and is taught with a weekly two-hour laboratory. One of the lab exercises we have used for several years is the measurement of elastic constants using ultrasonic testing. Most of the students in the class have already taken a course in Mechanical Behavior of Solids, in which they use destructive testing (compression or tension), to measure elastic properties. They have familiarity with moduli, stiffness and compliance from this course, but they have not previously used non- destructive testing (ultrasound). This lab offers an excellent opportunity to expose students to a second method that yields some of the same information they obtained with conventional mechanical testing. We have recently written a follow-up exercise which uses computational free-ware to calculate these same constants. These computations rely heavily on approximations, and students see the limitations of the program when calculating their results that often differ from “book values” by 10-20 percent. This is underscored by the comparison with their measured values, which are much closer to the literature.

Stair, K., & Liu, J. Z., & Asta, M. (2006, June), Ultra Sonic Measurement And Computation Of Elastic Constants Paper presented at 2006 Annual Conference & Exposition, Chicago, Illinois. 10.18260/1-2--1286

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