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Title: Ultrasonic imaging of materials under unconventional circumstances

This paper reflects the contents of the plenary talk given by Nico Felicien Declercq. “Ultrasonic Imaging of materials” covers a wide technological area with main purpose to look at and to peek inside materials. In an ideal world one would manage to examine materials like a clairvoyant. Fortunately this is impossible hence nature has offered sufficient challenges to mankind to provoke curiosity and to develop science and technology. Here we focus on the appearance of certain undesired physical effects that prohibit direct imaging of materials in ultrasonic C-scans. Furthermore we try to make use of these effects to obtain indirect images of materials and therefore make a virtue of necessity. First we return to one of the oldest quests in the progress of mankind: how thick is ice? Our ancestors must have faced this question early on during migration to Northern Europe and to the America’s and Asia. If a physicist or engineer is not provided with helpful tools such as a drill or a device based on ultrasound, it is difficult to determine the ice thickness. Guided waves, similar to those used for nondestructive testing of thin plates in structural health monitoring can be used in combination with themore » human ear to determine the thickness of ice. To continue with plates, if an image of its interior is desired high frequency ultrasonic pulses can be applied. It is known by the physicist that the resolution depends on the wavelength and that high frequencies usually result in undesirably high damping effects inhibiting deep penetration into the material. To the more practical oriented engineer it is known that it is advantageous to polish surfaces before examination because scattering and diffraction of sound lowers the image resolution. Random scatterers cause some blurriness but cooperating scatters, causing coherent diffraction effects similar to the effects that cause DVD’s to show rainbow patterns under sunlight, can cause spooky images and erroneous measurements of material properties. However when properly understood, diffraction effects, for instance if one has no other options but to work with frequencies that are fortuitously very effectively diffracted by the surface structure of a material under investigation, can be used to obtain high contract images or to obtain information that would normally be hidden from standard C-scan techniques. Similar contrast enhancement is also obtained for oblique C-scans of composites.« less
Authors:
; ; ;  [1] ;  [2]
  1. Georgia Institute of Technology, UMI Georgia Tech - CNRS 2958, George W. Woodruff School of Mechanical Engineering, Georgia Tech Lorraine, Laboratory for Ultrasonic Nondestructive Evaluation, 2 rue Marconi, 5070 Met-technopole (France)
  2. Institut de Soudure, 4 Bvd Henri Becquerel, Espace Cormontaigne, 57937 Yutz (France)
Publication Date:
OSTI Identifier:
22391245
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1650; Journal Issue: 1; Conference: 41. Annual Review of Progress in Quantitative Nondestructive Evaluation, Boise, ID (United States), 20-25 Jul 2014; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BUILDING MATERIALS; COMPOSITE MATERIALS; DIFFRACTION; ICE; IMAGES; MONITORING; PLATES; RANDOMNESS; RESOLUTION; SHIELDING MATERIALS; SURFACES; THICKNESS; ULTRASONIC TESTING; ULTRASONIC WAVES