Differences in Ultrasonic Indications –Thermal Fatigue Cracks and EDM Notches

18th WCNDT 2012Ari KoskinenVTT Technical Research Centre of Finland

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Different flaw types

a) EDM-notchb) Welded crack simulationc) Grown crackd) Service-induced crack

1G 2G 3G Service-induced

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EDM vs. TF

Indicication from EDM notch Indication from TF crack

Both measurements done with same setup (probe, angle, gain, etc.)

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Trueflaw pipe

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Crack Characteristics – Thermal Fatigue

More information than just lenght and detphSurface microscopySurface opening Surface roughness

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C-mode scanning acoustic microscope

Immersion tank with manipulatorsRotation and movement in x, y and z directions

Ultrasonic unit with pulser-receiver cardsControl and data acquisition unit

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C-SAM setup

Longitudinal wave in water is transformed to transverse wave (45°) in steel when the probe angle is:

With this setup about 11 % of the longitudinal wave hitting the surface is transformed in to transverse wave in steel.

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C-SAM setup

Probe: 5 MHz frequency, 3” focus, 0.5” diameterAngle: ~20° in water = ~45° in steel Scanning (X): 123..0.25..146mm Scanning (R): -30..0.24..450mm (360° is 0..530mm)Gain: +7dBVoltage: 100VLine scanning

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1

3 4

2

5

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SAM measurements

1 2 3 4 5

# Type Size (mm) Max amplitude1 EDM 16.6*4.5 62.4%

2 EDM 6.4*2.2 67.8%

3 Thermal 6.4*2.2 47.1%

4 Thermal 3.8*?? 34.5%

5 Thermal 16.5*4.5 53.7%

Amp(5)/Amp(1) = -1.30 dBAmp(3)/Amp(2) = -3.16 dB

”During production secondary cracking appeared. Productionwas discontinued and the depth of this crack is unknown”

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SAM measurements

0%

10%

20%

30%

40%

50%

60%

70%

EDM 16.6*4.5mm

thermal 16.5*4.5mm

EDM 6.4*2.2mm

thermal 6.4*2.2 mm

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Future plans

Sample will be measured also with PATOFD method will be appliedUltrasonic simulations will be compared to measurement resultsDifferent types of modern artificial flaws will be compared

TOFDPAC-SAMSimulation

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