Surface Wave (Rayleigh Wave)
A surface wave (Rayleigh wave) is an ultrasonic mode that propagates along the surface of a solid with motion confined within roughly one wavelength of the surface, used for surface-crack detection on curved or complex surfaces.
Definition
Rayleigh surface waves travel along the free surface of a solid with elliptical particle motion confined to about one wavelength depth. They are highly sensitive to surface-breaking defects and follow contoured surfaces around corners.
When It Is Used
- Surface crack detection in welds and shafts
- Stress-corrosion crack inspection
- Aerospace fillet and radius inspection
The principle
A wave that travels along a free surface with elliptical particle motion, its energy confined to roughly one wavelength of depth. Generated beyond the second critical angle in a wedge.
How it shows up in practice
Highly sensitive to surface-breaking cracks and able to follow gentle contours, which suits it to blades, shafts and fillet regions. That same surface confinement makes it exquisitely sensitive to couplant, dirt and hand contact along its path.
Where the codes address it
Addressed within ASME Section V Article 4 technique options.
Where practitioners get caught
Letting couplant or a finger touch the surface between probe and target — the wave is absorbed there, and the resulting loss of signal can be mistaken for an absence of flaws.
Where Surface Wave fits in an inspection programme
A term is only useful when it connects to a decision. Surface Wave appears in written procedures, in technique sheets, and in the records an owner or accreditation body reviews afterwards — which means the way it is defined in your documentation has to match the way it is applied on site. Where the two drift apart, audits find it. Atlantis writes and reviews procedures against the governing codes, trains inspection personnel to apply them, and builds the record-keeping that makes the evidence retrievable years later. Procedure development and code consulting · NDT training and certification · Ask us about your programme.
Related terms
- Shear Wave — A shear wave is an ultrasonic mode in which particle motion is perpendicular to the direction of propagation; in steel, shear waves travel at ~3,250 m/s and are produced by mode conversion at angled wedges for weld inspection.
- Longitudinal Wave — A longitudinal (compression) wave is the ultrasonic mode in which particle motion is parallel to the direction of propagation; the fastest wave mode, used for thickness measurement and 0° flaw detection.
- Lamb Wave — A Lamb wave is a guided ultrasonic plate wave that propagates through the full thickness of a thin-walled plate or pipe with symmetric and antisymmetric modes, used in long-range guided-wave inspection and aircraft skin scanning.
More physics terms
Back-Wall Echo · Beam Spread · Near-Field · Far-Field · Dead Zone · Mode Conversion · Attenuation · Geometric Unsharpness · Radiographic Density · Radiographic Sensitivity
Where this comes up in practice
Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.
Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.