Issue 63

T. G. Sreekanth et alii, Frattura ed Integrità Strutturale, 63 (2023) 37-45; DOI: 10.3221/IGF-ESIS.63.04

Coordinates (mm)

Delamination Size (mm 2 )

NF 1 (Hz)

NF 2 (Hz)

NF 3 (Hz)

NF 4 (Hz)

NF 5 (Hz)

X axis (mm) X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60 X= 60

Y axis (mm) Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60 Y=60

Z axis (mm) Z=0.6 Z=0.6 Z=0.6 Z=0.6 Z=0.6 Z=1.5 Z=1.5 Z=1.5 Z=1.5 Z=1.5 Z=2.40 Z=2.40 Z=2.40 Z=2.40 Z=2.40 Z=3.3 Z=3.3 Z=3.3 Z=3.3 Z=3.3 Z=4.1 Z=4.1 Z=4.1 Z=4.1 Z=4.1

25 50 75

258.5

814.45 867.58

1849.3 1839.9 1834.7 1831.2 1847.1 1839.2 1834.2 1821.6 1809.4 1846.5 1839.8 1835.2 1830.8 1819.7 1846.2 1838.5 1834.4 1829.4 1824.6 1845.5 1838.4 1834.4

1894.2 1889.3 1884.2 1879.6 1874.1 1892.6 1879.9 1874.5 1870.2 1859.6 1892.5 1878.9 1873.5 1868.2 1860.6 1892.6 1890.12 1885.6 1881.2 1877.6 1892.1 1889.92 1885.6

254.46 810.39 863.57 250.41 806.37 859.51 246.26 802.28 855.48

100 125

241.85 798.13 851.48 18519.6

25 50 75

256.49 812.42 865.15

254.4

809.6

862.2

250.32 805.26 858.16

100 125

245.26 800.84

853.1

240.25 796.25 848.48

25 50 75

256.3 253.8

812.24 865.01 810.21 862.15

249.22 803.84 858.14

100 125

245.2 240.9

799.4

847.9

794.54 843.47

25 50 75

256.25 812.22 865.62 254.16 810.26 863.54 249.24 805.46 859.25 245.12 801.03 855.05

100 125

241.1

796.95 850.47

25 50 75

256.12

812.2

865.25

253.24 809.46 863.14 249.16 805.03 858.25

100 125

245.1

800.95 854.05 1829.31 1881.15

241

795.69 849.47

1824.5

1876.6

Table 1: Dataset for the location X=60 mm Y=60 mm.

D ATABASE GENERATION

database of shifts in frequencies (due to known delaminations) is required to train the inverse algorithm. With the aid of finite element analysis, the appropriate database is created. A significant number of composite plate samples with various sizes and locations of delaminations were subjected to numerical analysis. The database size required to train ANN is important for properly diagnosing delaminations. Two hundred and twenty five distinct delamination scenarios were created numerically for this study by combining delaminations at nine different places (combinations of x = 60, 120, 180; and Y = 60, 120, 180; where x and y are distance of delaminations location from bottom left end.), five different sizes (25, 50, 75, 100, 125 mm 2 ) and five different layers (Layer 2, 5, 8, 11 & 14). Fig. 5 shows an example of one of the delaminations scenarios, with delaminations at x=60, y=60 and a delaminations area of 25 mm 2 on layer 5. Tab. 1 shows the first five natural frequencies of the plate sample with delaminations at X=60, Y=60, and Z=0.6, for five delamination areas. A similar dataset is created for the remaining eight locations. Fig. 6 (a) and (b) illustrate the bending modes for the same sample delaminated plate with delamination size of 25 mm 2 . A

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