Ultrasonic flaw detection is a powerful nondestructive testing (NDT) technology and a well-established test method in Ngofa Inspection Services Limited.
Ultrasonic flaw detectors can be used in a variety of applications where nondestructive flaw detection and analysis is required. The type of tests performed varies depending on the application, but will be either straight-beam inspection or angle-beam inspection.
Straight-beam testing is generally employed to find cracks or delamination’s parallel to the surface of a test piece, as well as voids and porosity, such as those found in plates, bars, forgings, castings, and so forth. It may use contact, delay line, dual element, or immersion transducers, all of which launch longitudinal waves on a straight path into the test piece. Straight-beam testing is also commonly employed in testing fiberglass and composites.
Although straight-beam techniques can be highly effective at finding laminar flaws, they are not effective when testing many common welds, where discontinuities are typically not oriented parallel to the surface of the part. The combination of weld geometry, the orientation of flaws, and the presence of the weld crown or bead require inspection from the side of the weld using a beam generated at an angle. Angle-beam testing is by far the most commonly used technique in ultrasonic flaw detection. Angle-beam probes consist of a transducer and a wedge, which may be separate parts or built into a single housing. They use the principle of refraction and mode conversion at a boundary to produce refracted shear or longitudinal waves in a test piece.