Ultrasound

Ultrasonic Testing

Ultrasound testing is a nondestructive method in which beams of high-frequency sound waves are introduced into materials for the detection of surface, subsurface or internal flaws in the material. The sound waves travel through the material with some attendant loss of energy (attenuation) and are reflected at interfaces (as described here). The reflected beam is displayed and then analyzed to define the presence and location of flaws or discontinui ties.

Depending on the fabrication process of the part, there’s a myriad of discontinuities that can be detected. Examples such as cracks, laminations, shrinkage cavities, bursts, flakes, pores, disbonds, and other discontinuities that produce reflective interfaces are well within the range of ultrasonic testing. Inclusions and other inhomogeneities can also be detected by causing partial reflection or scattering of the ultrasonic waves or by producing some other detectable effect on the ultrasonic waves.

Ultrasonic inspection is one of the most widely used methods of nondestructive inspection. Its primary application in the inspection of metals is the detection and characterization of internal flaws; it is also used to detect surface flaws, to define bond characteristics, to measure the thickness and extent of corrosion, and (much less frequently) to determine physical properties, structure, grain size, and elastic constants.

Phased Array

Multi-element technology (a.k.a. phased array) allows creating acoustic beams that will have the same characteristics as a beam produced by the conventional technology (a.k.a. mono-channel or mono-transducer): width, depth of field, half-angle divergence, etc. However, the multi-element technology allows changing the beam properties by fast electronic reprogramming. This is why we call a multi-element system a « beamformer ». We typically change 4 things with electronic means: aperture size, aperture position, transmit angle, and focus depth.