A step forward in TOFD technique
TOFD technique requires analyzing the acquired image. The UT-TOFD software provided with DASEL equipments includes several digital processing algorithms that improve defects detection and sizing:
“Lateral Wave Straightening”, image with the lateral wave aligned. The algorithm automatically recognizes the lateral wave within a pre-defined gate.
(Left) Original image (Right) Lateral wave aligned.
“Linearization”: provides an image in which the time scale is converted to scan depth into the material.
In a raw TOFD image, the acquisition range is measured and represented in time unites (usually microseconds). To convert this vertical scale to depth into the material (usually in millimeters) a process called “linearization” is necessary. The distance between transducers (PCS) and the time of flight of the lateral wave are also needed for calculation.
“S.A.F.T.”: provides an image with increased lateral resolution, in which each line is corrected based on the information of the adjacent ones.
Synthetic Aperture Focusing Technique (SAFT) is used to correct the distortion in the flaw indications (hyperboles) when the ultrasound beam is wider than the defect in the direction of movement. Furthermore, SAFT processing increases lateral resolution, improving detection of near defects.
“Hyperbolic cursors”
Hyperbolic cursors allow measuring a defect location taking into account the distortion effects produced by the beam width. When the shape of the echo matches that of the cursor, the reflector is located at the coordinates shown by the display.