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Basic Principles of Ultrasonic Testing Theory and Practice

Basic Principles of Ultrasonic Testing Theory and Practice. Examples of oscillation. ball on a spring. pendulum. rotating earth. Pulse. The ball starts to oscillate as soon as it is pushed. Oscillation. Movement of the ball over time. Frequency. Time. One full oscillation T.

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Basic Principles of Ultrasonic Testing Theory and Practice

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  1. Basic Principles of Ultrasonic Testing Theory and Practice Krautkramer NDT Ultrasonic Systems

  2. Examples of oscillation ball ona spring pendulum rotatingearth Krautkramer NDT Ultrasonic Systems

  3. Pulse The ball starts to oscillate as soon as it is pushed Krautkramer NDT Ultrasonic Systems

  4. Oscillation Krautkramer NDT Ultrasonic Systems

  5. Movement of the ball over time Krautkramer NDT Ultrasonic Systems

  6. Frequency Time One full oscillation T From the duration of one oscillation T the frequency f (number of oscillations per second) is calculated: Krautkramer NDT Ultrasonic Systems

  7. The actual displacement a is termed as: a Time 0 90 180 270 360 Phase Krautkramer NDT Ultrasonic Systems

  8. Spectrumofsound Example Frequency range Hz Description Infrasound 0 - 20 Earth quake 20 - 20.000 Audible sound Speech, music > 20.000 Ultrasound Bat, Quartz crystal Krautkramer NDT Ultrasonic Systems

  9. Atomic structures liquid gas solid • low density • weak bonding forces • medium density • medium bonding forces • high density • strong bonding forces • crystallographic structure Krautkramer NDT Ultrasonic Systems

  10. Understanding wave propagation: Ball = atom Spring = elastic bonding force Krautkramer NDT Ultrasonic Systems

  11. start of oscillation T distance travelled Krautkramer NDT Ultrasonic Systems

  12. During one oscillation T the wave front propagates by the distance : T Distance travelled From this we derive: Wave equation or Krautkramer NDT Ultrasonic Systems

  13. Sound propagation Longitudinal wave Direction of propagation Direction of oscillation Krautkramer NDT Ultrasonic Systems

  14. Direction of propagation Sound propagation Transverse wave Direction of oscillation Krautkramer NDT Ultrasonic Systems

  15. 330 m/s AirWaterSteel, longSteel, trans 1480 m/s 5920 m/s 3250 m/s Wave propagation Longitudinal waves propagate in all kind of materials. Transverse waves only propagate in solid bodies. Due to the different type of oscillation, transverse wavestravel at lower speeds. Sound velocity mainly depends on the density and E-modulus of the material. Krautkramer NDT Ultrasonic Systems

  16. Reflection and Transmission As soon as a sound wave comes to a change in material characteristics ,e.g. the surface of a workpiece, or an internal inclusion, wave propagation will change too: Krautkramer NDT Ultrasonic Systems

  17. Behaviour at an interface Medium 1 Medium 2 Incoming wave Transmitted wave Reflected wave Interface Krautkramer NDT Ultrasonic Systems

  18. Reflection + Transmission: Perspex - Steel 1,87 1,0 Transmitted wave Incoming wave 0,87 Reflected wave Perspex Steel Krautkramer NDT Ultrasonic Systems

  19. Reflection + Transmission: Steel - Perspex Transmitted wave Incoming wave 1,0 0,13 -0,87 Reflected wave Steel Perspex Krautkramer NDT Ultrasonic Systems

  20. Amplitude of sound transmissions: Copper - Steel Steel - Air Water - Steel • Strong reflection • Double transmission • No reflection • Single transmission • Strong reflection with inverted phase • No transmission Krautkramer NDT Ultrasonic Systems

  21. + Piezoelectric Effect Battery Piezoelectrical Crystal (Quartz) Krautkramer NDT Ultrasonic Systems

  22. + Piezoelectric Effect The crystal gets thicker, due to a distortion of the crystal lattice Krautkramer NDT Ultrasonic Systems

  23. + Piezoelectric Effect The effect inverses with polarity change Krautkramer NDT Ultrasonic Systems

  24. Piezoelectric Effect Sound wave withfrequency f U(f) An alternating voltage generates crystal oscillations at the frequency f Krautkramer NDT Ultrasonic Systems

  25. Piezoelectric Effect Short pulse ( < 1 µs ) A short voltage pulse generates an oscillation at the crystal‘s resonant frequency f0 Krautkramer NDT Ultrasonic Systems

  26. Reception of ultrasonic waves A sound wave hitting a piezoelectric crystal, induces crystal vibration which then causes electrical voltages at the crystal surfaces. Electrical energy Piezoelectrical crystal Ultrasonic wave Krautkramer NDT Ultrasonic Systems

  27. Delay / protecting face socket Electrical matching crystal Cable Damping Straight beam probe TR-probe Angle beam probe Ultrasonic Probes Krautkramer NDT Ultrasonic Systems

  28. 100 ns RF signal (short) Krautkramer NDT Ultrasonic Systems

  29. RF signal (medium) Krautkramer NDT Ultrasonic Systems

  30. Focus Angle of divergence Crystal Accoustical axis 6 D0 N Near field Far field Sound field Krautkramer NDT Ultrasonic Systems

  31. 0 2 4 6 8 10 Ultrasonic Instrument Krautkramer NDT Ultrasonic Systems

  32. - + U h 6 10 0 2 4 8 Ultrasonic Instrument Krautkramer NDT Ultrasonic Systems

  33. - + U h 0 2 4 6 8 10 Ultrasonic Instrument Krautkramer NDT Ultrasonic Systems

  34. + U v - - + U h 0 2 4 6 8 10 Ultrasonic Instrument Krautkramer NDT Ultrasonic Systems

  35. amplifier screen horizontal sweep IP BE clock pulser probe work piece Block diagram: Ultrasonic Instrument Krautkramer NDT Ultrasonic Systems

  36. Sound reflection at a flaw s Probe Sound travel path Flaw Work piece Krautkramer NDT Ultrasonic Systems

  37. IP BE F 0 2 4 6 8 10 delamination plate IP = Initial pulse F = Flaw BE = Backwall echo Plate testing Krautkramer NDT Ultrasonic Systems

  38. Wall thickness measurement s s Corrosion 0 2 4 6 8 10 Krautkramer NDT Ultrasonic Systems

  39. Through transmission signal 1 T R 1 2 T R 2 0 2 4 6 8 10 Flaw Through transmission testing Krautkramer NDT Ultrasonic Systems

  40. a = s sinß F a' = a - x ß = probe angle s = sound path a = surface distance a‘ = reduced surface distance d‘ = virtual depth d = actual depth T = material thickness s d' = s cosß 0 20 40 60 80 100 d = 2T - t' a x a' d ß Lack of fusion s Work piece with welding Weld inspection Krautkramer NDT Ultrasonic Systems

  41. Direct contact, single element probe Direct contact, dual element probe Fixed delay Through transmission Immersion testing Straight beam inspection techniques: Krautkramer NDT Ultrasonic Systems

  42. IP IP 1 2 IE IE BE BE F 2 4 6 8 10 0 2 4 6 8 10 0 Immersion testing 1 2 surface = sound entry water delay backwall flaw Krautkramer NDT Ultrasonic Systems

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