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Using eigenmodes to perform the inverse problem associated with resonant ultrasound spectroscopy
Farhad Farzbod1, David H Hurley
1Materials Science and Engineering Department, Idaho National Laboratory, Idaho Falls, ID, USA. farzbod@ieee.org
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
|November 30, 2012
Summary
Laser-based resonant ultrasound spectroscopy (LRUS) offers a novel approach to material characterization. This method utilizes eigenmodes to determine crystallographic orientation with high accuracy, outperforming traditional eigenfrequency analysis.
Area of Science:
- Materials Science
- Solid State Physics
- Acoustics
Background:
- Resonant ultrasonic spectroscopy (RUS) traditionally characterizes materials via elastic constants, dimensions, and crystal orientation.
- Parameter extraction in RUS typically involves iterative inverse problem-solving comparing calculated and measured eigenfrequencies.
Purpose of the Study:
- To introduce and demonstrate laser-based resonant ultrasound spectroscopy (LRUS) as an alternative method for material characterization.
- To utilize sample eigenmodes, rather than just eigenfrequencies, for determining crystallographic orientation.
Main Methods:
- LRUS employs a pulsed laser for thermoelastic ultrasound excitation.
- An interferometer detects out-of-plane displacements associated with ultrasonic resonances.
- Raster scanning the probe generates images of displacement patterns (eigenmodes).
Main Results:
- A technique for calculating crystallographic orientation using experimental and theoretical eigenmodes was developed.
- The LRUS-derived orientation for a single-crystal copper sample showed excellent agreement with electron backscatter diffraction (EBSD).
- Eigenmode analysis demonstrated superior sensitivity to crystal orientation compared to eigenfrequency analysis for this application.
Conclusions:
- LRUS provides a powerful, non-contact method for material characterization.
- Eigenmode analysis using LRUS offers enhanced sensitivity for determining crystallographic orientation.
- This technique has potential applications in materials science and solid-state physics.
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