7. Basic Principles of Ultrasonic Testing Sound is transmitted in the material to be tested The sound reflected back to the probe is displayed on the Flaw Detector
8. Basic Principles of Ultrasonic Testing The distance the sound traveled can be displayed on the Flaw Detector The screen can be calibrated to give accurate readings of the distance Bottom / Backwall Signal from the backwall
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10. Basic Principles of Ultrasonic Testing The presence of a Defect in the material shows up on the screen of the flaw detector with a less distance than the bottom of the material Defect The BWE signal Defect signal
11. The depth of the defect can be read with reference to the marker on the screen 60 mm 0 10 20 30 40 50 60
12. Thickness / depth measurement A A B B C C The THINNER the material the less distance the sound travel The closer the reflector to the surface, the signal will be more to the left of the screen The thickness is read from the screen 68 46 30
17. Velocity 4 times What is the velocity difference in steel compared with in water? If the frequency remain constant, in what material does sound has the highest velocity, steel, water, or air? Steel If the frequency remain constant, in what material does sound has the shortest wavelength, steel, water, or air? Air Remember the formula = v / f
18. DRUM BEAT Low Frequency Sound 40 Hz Glass High Frequency 5 K Hz ULTRASONIC TESTING Very High Frequency 5 M Hz
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20. Acoustic Spectrum 0 10 100 1K 10K 100K 1M 10M 100m Sonic / Audible Human 16Hz - 20kHz Ultrasonic > 20kHz = 20,000Hz Ultrasonic Testing 0.5MHz - 50MHz Ultrasonic : Sound with frequency above 20 KHz
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23. Sound waves are the vibration of particles in solids, liquids or gases. Particles vibrate about a mean position. One cycle Displacement The distance taken to complete one cycle wavelength wavelength Wavelength Wavelength is the distance required to complete a cycle.
25. Frequency & Wavelength 1 M Hz 5 M Hz 10 M Hz 25 M Hz Which probe has the smallest wavelength? SMALLEST LONGEST Which probe has the longest wavelength? = v / f F F
26. Wavelength is a function of frequency and velocity. 5MHz compression wave probe in steel Therefore: or or f V V f V f
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30. The Sound Beam NZ FZ Main Beam Distance Intensity varies Exponential Decay
31. Main Lobe Side Lobes Near Zone Main Beam The main beam or the centre beam has the highest intensity of sound energy Any reflector hit by the main beam will reflect the high amount of energy The side lobes has multi minute main beams Two identical defects may give different amplitudes of signals
