PSI - Issue 12

V. Dattoma et al. / Procedia Structural Integrity 12 (2018) 9–18 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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Immersion method seems to offer best results, with the 2.25MHz probe. From the graphs it showed that the 1MHz probe is slightly better than 2.25MHz in contact technique. Figure 11c shows the amplitude trend versus defect thickness for low range depth to 10 mm defect diameter; the general trend of all Probes is similar for two analyzed techniques. Probe 1÷6 in Contact UT and Probe 2.25 in Water Stream UT present different behavior.

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(c) Figure 10. (a) – (b) – (c) Influence of depth on signal amplitude for 5 mm defect size using different UT methods in GFRP plates.

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(b) (c) Figure 11. (a) – (b) – (c) Influence of depth and defect thickness on signal amplitude for different UT methods for 10 mm defects.

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(b) Figure 12. (a) – (b) Influence of depth on signal amplitude for different UT methods for 20 mm defects in GFRP plates.

A statistical analysis is also performed in order to verify the repeatability and validity of the acquired values for automated UT scans using special tool D. Several ultrasonic inspections are recorded for example as associated to linear B-scan on Ø 10 mm on plate 1. Repeated acquisition of signal amplitude are recorded along two orthogonal X and Y directions using 0.5, 1 and 2 mm / s scan velocity and inspection diagrams are shown in Figure 13a and 13b, both for the defect and Back Wall echo. Scanning gain of 50 dB value is fixed for each amplitude detection.