PSI - Issue 61

Rachid Azzi et al. / Procedia Structural Integrity 61 (2024) 241–251 Rachid Azzi and Farid Asma / Structural Integrity Procedia 00 (2023) 000 – 000

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Fig. 9. Geometric model of an intact propeller blade with boundary condition in a rotating frame.

a

b

c

0,1

0

0

0

-0,1

-0,5

-0,1

-0,2

-0,2

S2, 2500 RPM S5, 2500 RPM S8, 2500 RPM S12, 2500 RPM

S2, 2500 RPM S5, 2500 RPM S8, 2500 RPM S12, 2500 RPM

-1

-0,3

S2, 2500 RPM S5, 2500 RPM S8, 2500 RPM S12, 2500 RPM

-0,3

S2, Fixed S5, Fixed S8, Fixed S12, Fixed

S2, Fixed S5, Fixed S8, Fixed S12, Fixed

-0,4

-0,4

-0,5 S2, Fixed S5, Fixed S8, Fixed S12, Fixed Frequency reduction for the first mode (%)

-1,5

-0,5

Frequency reduction for the fourth mode (%)

Frequency reduction for the second mode (%)

-0,6

-2

-0,6

0

1

2

3

4

5

6

0

1

2

3

4

5

6

0

1

2

3

4

5

6

Damage length (mm)

Damage length (mm)

Damage length (mm)

Fig. 10. Frequency reduction versus damage length for rotating and fixed blade. (a) First mode, (b) Second mode, (c) Fourth mode.

The mode shapes obtained for the intact propeller blade for a rotational speed of 2500 RPM are shown in Fig. 11 and those obtained for the damaged blade with the same rotational speed of 2500 RPM are shown in Fig. 12. The damage is inserted at position S12 with “I” geometrical shape and 5 m m of length. The comparison of the mode shapes of the undamaged blade with those of the damaged blade shows no significant change. Therefore, detecting damages by analyzing the pictures of the displacement mode shapes will be difficult.

a

b

c

Fig. 11. Mode shapes of an intact propeller blade in a rotating frame. (a) First mode, (b) Second mode, (c) Fourth mode.