Non-contact ultrasonic detection of angled surface defects

Non-destructive testing is an important technique, and improvements are constantly needed. Surface defects in metals are not necessarily confined to orientations normal to the sample surface; however, much of the previous work investigating the interaction of ultrasonic surface waves with surface-br...

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Bibliographic Details
Published in:NDT & E international : independent nondestructive testing and evaluation 2011-07, Vol.44 (4), p.353-360
Main Authors: Dutton, B., Clough, A.R., Rosli, M.H., Edwards, R.S.
Format: Article
Language:English
Subjects:
Cracks
Defect characterization
Defects
Flaw detection
Laser ultrasound
Mathematical models
Nondestructive testing
Rayleigh wave
Reflection
SAW
Surface defects
Three dimensional
Ultrasound modelling
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Summary:Non-destructive testing is an important technique, and improvements are constantly needed. Surface defects in metals are not necessarily confined to orientations normal to the sample surface; however, much of the previous work investigating the interaction of ultrasonic surface waves with surface-breaking defects has assumed cracks inclined at 90° to the surface. This paper explores the interaction of Rayleigh waves with cracks which have a wide range of angles and depths relative to the surface, using a non-contact laser generation and detection system. Additional insight is acquired using a 3D model generated using finite element method software. A clear variation of the reflection and transmission coefficients with both crack angle and length is found, in both the out-of-plane and in-plane components. The 3D model is further used to understand the contributions of different wavemodes to B-Scans produced when scanning a sample, to enable understanding of the reflection and transmission behaviour, and help identify angled defects. Knowledge of these effects is essential to correctly gauge the severity of surface cracking.
ISSN:0963-8695
1879-1174
DOI:10.1016/j.ndteint.2011.02.001