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Quantitative Mapping of Pore Fraction Variations in Silicon Nitride Using an Ultrasonic Contact Scan TechniqueAn ultrasonic scan procedure using the pulse-echo contact configuration was employed to obtain maps of pore fraction variations in sintered silicon nitride samples in terms of ultrasonic material properties. Ultrasonic velocity, attenuation coefficient, and reflection coefficient images were obtained simultaneously over a broad band of frequencies (e.g., 30 to 110 MHz) by using spectroscopic analysis. Liquid and membrane (dry) coupling techniques and longitudinal and shear-wave energies were used. The major results include the following: Ultrasonic velocity (longitudinal and shear wave) images revealed and correlated with the extent of average through-thickness pore fraction variations in the silicon nitride disks. Attenuation coefficient images revealed pore fraction nonuniformity due to the scattering that occurred at boundaries between regions of high and low pore fraction. Velocity and attenuation coefficient images were each nearly identical for machined and polished disks, making the method readily applicable to machined materials. Velocity images were similar for wet and membrane coupling. Maps of apparent Poisson's ratio constructed from longitudinal and shear-wave velocities quantified Poisson's ratio variations across a silicon nitride disk. Thermal wave images of a disk indicated transient thermal behavior variations that correlated with observed variations in pore fraction and velocity and attenuation coefficients.
Document ID
19940008583
Acquisition Source
Legacy CDMS
Document Type
Technical Publication (TP)
Authors
Roth, Don J.
(NASA Lewis Research Center Cleveland, OH, United States)
Kiser, James D.
(NASA Lewis Research Center Cleveland, OH, United States)
Swickard, Suzanne M.
(NASA Lewis Research Center Cleveland, OH, United States)
Szatmary, Steven A.
(Cleveland State Univ. Cleveland, OH, United States)
Kerwin, David P.
(Cleveland State Univ. Cleveland, OH, United States)
Date Acquired
September 6, 2013
Publication Date
August 1, 1993
Subject Category
Quality Assurance And Reliability
Report/Patent Number
E-7558
NASA-TP-3377
NAS 1.60:3377
Accession Number
94N13056
Funding Number(s)
PROJECT: RTOP 506-43-11
TASK: Y0H-2044
Distribution Limits
Public
Copyright
Public Use Permitted.
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