Short pulses of high frequency ultrasound are propagated by a transducer along a narrow beam into the test piece. Where the pulses strike the opposite side of the test piece, some of the ultrasound is reflected back to the transducer. These echoes are detected and their flight times are measured electronically. Sound propagates through a medium at a constant velocity which is a characteristic of that material. Echo flight-times can therefore be calibrated directly for distance. Multiple echoes are then displayed as a digital read-out, which allows for a quick measurement. The instrument employed also allows us to take measurements through fairing materials and coatings up to 12mm.
Steel
Thickness gauging of coated plating.
Aluminium
Thickness gauging of coated plating.
Ultrasonic Thickness Gauging has some limitations in that it is not generally capable of detecting localized pitting corrosion, slag inclusions and other such localized defects under surface finishes.
Coatings exceeding approximately 12mm in thickness make readings on these areas impossible. Coatings thinner than 12mm but including extremely low-density fillers (or featuring large inconsistency in the density of the different layers of coatings) and/or with poor adhesion between coatings layers may also negatively affect the performance of the instrument.
