Characterization of nuclear graphite elastic properties using laser ultrasonic methods

Fan W. Zeng, Karen Han, Lauren R. Olasov, Nidia C. Gallego, Cristian I. Contescu, James B. Spicer

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

Laser ultrasonic methods have been used to characterize the elastic behaviors of commercially-available and legacy nuclear graphites. Since ultrasonic techniques are sensitive to various aspects of graphite microstructure including preferred grain orientation, microcrack orientation and porosity, laser ultrasonics is a candidate technique for monitoring graphite degradation and structural integrity in environments expected in high-temperature, gas-cooled nuclear reactors. Aspects of materials texture can be assessed by studying ultrasonic wavespeeds as a function of propagation direction and polarization. Shear wave birefringence measurements, in particular, can be used to evaluate elastic anisotropy. In this work, laser ultrasonic measurements of graphite moduli have been made to provide insight into the relationship between the microstructures and the macroscopic stiffnesses of these materials. In particular, laser ultrasonic measurements have been made using laser line sources to produce shear waves with specific polarizations. By varying the line orientation relative to the sample, shear wave birefringence measurements have been recorded. Results from shear wave birefringence measurements show that an isostatically molded graphite, such as PCIB, behaves isotropically, while an extruded graphite, such as H-451, displays significant ultrasonic texture. Graphites have complicated microstructures that depend on the manufacturing processes used, and ultrasonic texture in these materials could originate from grain orientation and preferred microcrack alignment. Effects on material isotropy due to service related microstructural changes are possible and the ultimate aim of this work is to determine the degree to which these changes can be assessed nondestructively using laser ultrasonics measurements.

Original languageEnglish
Title of host publicationThermosense
Subtitle of host publicationThermal Infrared Applications XXXVII
EditorsJoseph N. Zalameda, Sheng-Jen Hsieh
PublisherSPIE
ISBN (Electronic)9781628416015
DOIs
StatePublished - 2015
EventSPIE ThermoSense Conference: Thermal Infrared Applications XXXVII - Baltimore, United States
Duration: Apr 20 2015Apr 23 2015

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume9485
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X

Conference

ConferenceSPIE ThermoSense Conference: Thermal Infrared Applications XXXVII
Country/TerritoryUnited States
CityBaltimore
Period04/20/1504/23/15

Funding

Keywords

  • Anisotropy
  • Graphite
  • Laser ultrasonics
  • Shear modulus
  • Shear wave birefringence
  • Texture

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