You need JavaScript to view this

A circular aperture array for ultrasonic tomography and quantitative NDE

Abstract

The main topics of this thesis are ultrasonic tomography and ultrasonic determination of elastic stiffness constants. Both issues are based on a synthetic array with transducer elements distributed uniformly along a circular aperture, i.e., a circular aperture array. The issues are treated both theoretically and experimentally by broadband pulse techniques. Ultrasonic tomography, UCT, from a circular aperture is a relatively new imaging technique in Non-destructive Evaluation (NDE) to acquire cross sectional images in bulk materials. A filtered back-projection algorithm is used to reconstruct images in four different experiments and results of attenuation, velocity and reflection tomograms in Plexiglas of AlSi-alloy cylinders are presented. Two kinds of ultrasonic tomography are introduced: bistatic and monostatic imaging. Both techniques are verified experimentally by Plexiglas cylinders. Different reconstruction artifacts are discussed and theoretical resolution constraints are discussed for various configurations of the circular aperture array. The monostatic technique is used in volumetric imaging. In the experimental verification artificial and real discontinuities in a cylindrical AlSi-alloy are compared with similar discontinuities in a Plexiglas specimen. Finally, some limitations to UCT are discussed. The circular aperture array is used to determine five independent elastic stiffness constants of a unidirectional glass/PET (Poly Ethylene Teraphtalate) laminate. Energy flux  More>>
Authors:
Publication Date:
Aug 01, 1998
Product Type:
Thesis/Dissertation
Report Number:
RISO-R-1057(EN)
Reference Number:
SCA: 360602; 360603; 420500; PA: DK-99:001015; EDB-99:030688; SN: 99002047380
Resource Relation:
Other Information: TH: Thesis (ph.d.); PBD: Aug 1998
Subject:
36 MATERIALS SCIENCE; 42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES; ULTRASONIC TESTING; TOMOGRAPHY; POLYETHYLENES; ELASTICITY; SHEAR PROPERTIES; PLEXIGLAS; APERTURES; CIRCULAR CONFIGURATION; ACOUSTIC MEASUREMENTS; COMPOSITE MATERIALS; FIBERS; REINFORCED MATERIALS
OSTI ID:
321654
Research Organizations:
Risoe National Lab., Roskilde (Denmark). Materials Research Dept.; Danmarks Tekniske Univ., Lyngby (Denmark)
Country of Origin:
Denmark
Language:
English
Other Identifying Numbers:
Other: ON: DE99721506; ISBN 87-550-2400-9; TRN: DK9901015
Availability:
OSTI as DE99721506
Submitting Site:
DK
Size:
167 p.
Announcement Date:
Mar 30, 1999

Citation Formats

Nielsen, S A. A circular aperture array for ultrasonic tomography and quantitative NDE. Denmark: N. p., 1998. Web.
Nielsen, S A. A circular aperture array for ultrasonic tomography and quantitative NDE. Denmark.
Nielsen, S A. 1998. "A circular aperture array for ultrasonic tomography and quantitative NDE." Denmark.
@misc{etde_321654,
title = {A circular aperture array for ultrasonic tomography and quantitative NDE}
author = {Nielsen, S A}
abstractNote = {The main topics of this thesis are ultrasonic tomography and ultrasonic determination of elastic stiffness constants. Both issues are based on a synthetic array with transducer elements distributed uniformly along a circular aperture, i.e., a circular aperture array. The issues are treated both theoretically and experimentally by broadband pulse techniques. Ultrasonic tomography, UCT, from a circular aperture is a relatively new imaging technique in Non-destructive Evaluation (NDE) to acquire cross sectional images in bulk materials. A filtered back-projection algorithm is used to reconstruct images in four different experiments and results of attenuation, velocity and reflection tomograms in Plexiglas of AlSi-alloy cylinders are presented. Two kinds of ultrasonic tomography are introduced: bistatic and monostatic imaging. Both techniques are verified experimentally by Plexiglas cylinders. Different reconstruction artifacts are discussed and theoretical resolution constraints are discussed for various configurations of the circular aperture array. The monostatic technique is used in volumetric imaging. In the experimental verification artificial and real discontinuities in a cylindrical AlSi-alloy are compared with similar discontinuities in a Plexiglas specimen. Finally, some limitations to UCT are discussed. The circular aperture array is used to determine five independent elastic stiffness constants of a unidirectional glass/PET (Poly Ethylene Teraphtalate) laminate. Energy flux propagation and attenuation of ultrasonic waves are considered and velocity surfaces are calculated for different planes of interest. Relations between elastic stiffness constants and engineering constants (i.e., Young`s moduli, shear moduli and Poisson`s ratios) are discussed for an orthotropic composite. Six micromechanical theories are reviewed, and expressions predicting the elastic engineering constants are evaluated. The micromechanical predicted elastic stiffness constants for the unidirectional glass/PET laminate are compared with ultrasonic and mechanical test results. Finally, the capabilities and limitations of the applied ultrasonic method are discussed. (au) 15 tabs., 103 ills., 203 refs.}
place = {Denmark}
year = {1998}
month = {Aug}
}