PSI - Issue 52

Ruben I. Erives et al. / Procedia Structural Integrity 52 (2024) 600–610 Ruben Erives et al./ Structural Integrity Procedia 00 (2019) 000–000

605

6

10 5

10 5

3

Cum. Amp. Ch 1 Cum. Amp. Ch 2

Cum. Energy Ch 1 Cum. Energy Ch 2 t 0

2.5

dA/dt Ch 1 dA/dt Ch 2 t 0

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1

0.5

0

0

0

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80

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120

140

160

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80

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a)

b)

Fig. 3. Delamination onset time identification using a) the cumulative amplitude and its derivative, and b) the cumulative energy

Although only the cumulative amplitude and energy plots are shown, all the AE features provided with approximately the same onset time 0 . Furthermore, it can be noted that using the derivative of the cumulative amplitude plot provides a good visualisation of the transition from region I to region II. A plot where the combination of AE features namely the Energy normalised by the amplitude, and the Energy per hit are shown. It can be observed that both quantities show a rapid drop at crack initiation ( 0 =247 ), however, this would be difficult to observe without the previous knowledge of 0 .

2

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1.5

0.6

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0.5

Initiation t 0 =247s

0.2

0

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a)

b)

Fig. 4. Delamination onset time identification using a) the cumulative amplitude and its derivative, and b) the cumulative energy

4.2. Deviation from linearity Three plots where the deviation from linearity (in a moment versus end-opening plot) is visualised are shown in Fig. 4 for; a) (near) pure normal opening displacement, b) mixed mode, and c) (near) pure shear opening