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.
Definition
Shear (transverse) waves vibrate perpendicular to the propagation direction. They cannot propagate in liquids or gases. In metals, shear-wave velocity is roughly half the longitudinal velocity (e.g., 3,250 m/s versus 5,920 m/s in carbon steel).
Technical Context
Most weld inspection uses shear waves refracted from a plastic wedge at 45°, 60°, or 70°.
The principle
A wave mode whose particle motion is perpendicular to travel. It propagates only in solids, at roughly half the longitudinal velocity in steel — which halves the wavelength at a given frequency and sharpens resolution.
How it shows up in practice
Angle-beam weld examination is shear-wave work: beyond the first critical angle only the shear mode remains in the part, giving a clean single-mode beam at the standard 45/60/70-degree wedge angles.
Where the codes address it
ASME Section V Article 4 and ISO 17640 angle-beam techniques are built on it.
Where practitioners get caught
Sizing a shear-wave path with a longitudinal velocity setting. The factor-of-two velocity difference puts the reflector at twice its true depth, and the error looks entirely plausible on screen.
Where Shear Wave fits in an inspection programme
A term is only useful when it connects to a decision. Shear 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
- 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.
- Mode Conversion — Mode conversion is the partial conversion of an ultrasonic wave from one mode (longitudinal, shear, surface) to another at a refracting or reflecting interface, governed by Snell's law and the angle of incidence.
- Angle-Beam Probe — An angle-beam probe couples ultrasonic energy through a plastic wedge to produce a refracted shear or longitudinal wave at a fixed angle (typically 45°, 60°, or 70°) in the test piece, used primarily for weld inspection.
- 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.
Further reading
shear wave ut for thick section inspection · compression wave vs shear wave technical differences
More physics terms
Back-Wall Echo · Beam Spread · Near-Field · Far-Field · Dead Zone · Lamb Wave · 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.