Ultrasonic Defect Visualization in a Metal Block
A technique has been developed to produce a three-dimensional image of internal defects in a metal block. In the experiment, a rectangular block (approximately 9cm × 7cm × 7cm) with a hole drilled through it diagonally was inspected. The block was scanned with narrow beam, focused transducers and the time of flight (TOF) to the defect was measured.
The initial transducer position and scanning parameters were taken as input, and the TOF data were processed. The software used the position and orientation of the transducer to determine which surfaces of the block had been penetrated by the beam. The program assumed that the scanned block was rectangular. Knowing the surface of penetration allowed the angle of incidence to be found, and Snell’s Law was used to calculate the angle of refraction. If the flaw was located inside the block it was stored in a data file, otherwise it was considered to be noise and was eliminated.
The shape of the defect was mathematically reconstructed from the data file of the defect points and displayed on a 3-D colour graphics system.
KeywordsRectangular Block Flight Data Ultrasonic Beam Focus Transducer Transmission Tomography
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