When the speckle pattern (laser or white light) of a corroded specimen surface is compared to that of a virgin surface, the difference can be quickly and clearly revealed by the cross-correlation coefficient of the two speckle patterns. This technique can reveal pitting corrosion areas as small as 5mm × 5mm wherein exists a cluster of pits of 0.3mm (diameter) and 0.1 mm (depth). An artificial stress-corrosion crack was used to demonstrate the validation of this method for detection of stress-corrosion cracking. For detection of crevice corrosion, laser illumination must be applied. Digital speckle correlation takes both the advantage of digital image correlation and laser speckle properties. The speckle decorrelation coursed by out-of-plane displacement in the region with a crevice corrosion underneath the specimen's surface is bigger than without defects. This different is calculated by digital correlation algorithm, which reveals the existence of crevice corrosion.

Subject
Pits, Nondestructive testing, Materials, Deformation, Correlation, Cameras, Structures, Inspection, Corrosion detection, Crevice corrosion, Lasers, Pitting, Stress corrosion cracking
Keywords:
pitting corrosion, stress-corrosion cracking, crevice corrosion, speckle, correlation, nondestructive inspection
© 1995 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1995
Association for Materials Protection and Performance (AMPP)
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