Scanning laser source and scanning laser detection techniques for different surface crack geometries
| Autor: | M. H. Rosli, Rachel S. Edwards, B. Dutton, A. R. Clough |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2012 |
| Předmět: |
Surface (mathematics)
Materials science business.industry 020502 materials Detector 02 engineering and technology 021001 nanoscience & nanotechnology Laser law.invention Cracking symbols.namesake Optics 0205 materials engineering law Surface wave symbols Ultrasonic sensor Rayleigh wave 0210 nano-technology business Normal QC |
| Zdroj: | AIP Conference Proceedings |
| ISSN: | 0094-243X |
| Popis: | Standard test samples typically contain simulated defects such as slots machined normal to the surface. However, real defects will not always propagate in this manner; for example, rolling contact fatigue on rails propagates at around 25o to the surface, and corrosion cracking can grow in a branched manner. Therefore, there is a need to understand how ultrasonic surface waves interact with different crack geometries. We present measurements of machined slots inclined at an angle to the surface normal, or with simple branched geometries, using laser ultrasound. Recently, Rayleigh wave enhancements observed when using the scanning laser source technique, where a generation laser is scanned along a sample, have been highlighted for their potential in detecting surface cracks. We show that the enhancement measured with laser detector scanning can give a more significant enhancement when different crack geometries are considered. We discuss the behaviour of an incident Rayleigh wave in the region of an angled defect, and consider mode-conversions which lead to a very large enhancement when the detector is close to the opening of a shallow defect. This process could be used in characterising defects, as well as being an excellent fingerprint of their presence. |
| Databáze: | OpenAIRE |
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