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

Krautkramer NDT Ultrasonic Systems Examples of oscillation ball on a spring pendulum rotating earth Krautkramer NDT Ultrasonic Systems

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

Krautkramer NDT Ultrasonic Systems Oscillation Krautkramer NDT Ultrasonic Systems

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

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

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

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

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

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

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

Krautkramer NDT Ultrasonic Systems 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

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

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

Krautkramer NDT Ultrasonic Systems 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 waves travel at lower speeds. Sound velocity mainly depends on the density and E-modulus of the material. Air Water Steel, long Steel, trans 330 m/s 1480 m/s 3250 m/s 5920 m/s Krautkramer NDT Ultrasonic Systems

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

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

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

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

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

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

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

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

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

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

Krautkramer NDT Ultrasonic Systems 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

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

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

Krautkramer NDT Ultrasonic Systems RF signal (medium) Krautkramer NDT Ultrasonic Systems

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

Ultrasonic Instrument 2 4 8 10 6 Krautkramer NDT Ultrasonic Systems

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

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

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

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

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

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

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

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

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

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

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