PSI - Issue 61

10

Rachid Azzi and Farid Asma / Structural Integrity Procedia 00 (2023) 000 – 000

Rachid Azzi et al. / Procedia Structural Integrity 61 (2024) 241–251

250

To investigate the effect of damage position, the response of the intact blade and those of the damaged blades for different damage positions is show in Fig. 17. The damage length equal to 3mm. It is seen that the response of a damaged blade is different from that of an intact blade. When the defect approaches to the base of the blade the amplitude of vibration increases. Fig. 18 shows the displacement of blade tip as function of time for the two geometrical damage forms and for two damage positions S8 and S12. We notice that the effect of the damage form on the dynamic response of blade tip is not significant.

Detail in interval [0.00195-0.00203 s]

L=3 mm, S5 L=3 mm, S8 L=3 mm, S17 Intacte

0,03

0,0215

0,02

L=3 mm, S5 L=3 mm, S8 L=3 mm, S17

0,01

0,021

0

0,0205

-0,01

0,02

-0,02 Displacement in Y- direction (mm)

0,0195

Displacement in Y -direction (mm)

-0,03

0,019

0 0,001 0,002 0,003 0,004 0,005 0,006 0,007

0,001950,001960,001970,001980,00199 0,002 0,002010,002020,00203

Times (S)

Times (S)

Fig. 17. Tip blade displacement with time for damaged and undamaged blade for different damage positions, L=3mm, V.

L=3, S8, V L=3, S8, I L=3mm, S12, I L=3, S12, V Intacte

Detail in interval [0.00195-0.00203 s]

0,03

0,02

0,0215

L=3, S8, V L=3, S8, I L=3mm, S12, I L=3, S12, V

0,01

0,021

0

0,0205

-0,01

0,02

-0,02 Displacement in Y- direction (mm)

0,0195

Displacement in Y-direction (mm)

-0,03

0,019

0 0,001 0,002 0,003 0,004 0,005 0,006 0,007

0,001950,001960,001970,001980,00199 0,002 0,002010,002020,00203

Times (S)

Times (S)

Fig. 18. Tip blade displacement with time for V and I damage shapes, L=3mm, S8 and S12.

4. Conclusion In this study, the effects of the defect on the modal and dynamic behaviors of marine propeller blades has been studied. The damage modelled by an empty gap has two shapes, and varied lengths and takes several positions along the length of the leading edge. A modal analysis of both damaged and healthy propeller blades has been performed in rotating and non-rotating conditions. Then, a dynamic analysis is also carried out for healthy and damaged blades. The obtained natural frequencies, mode shapes, and dynamic responses for healthy and damaged blades have been compared and discussed. The presence of a defect on the leading edge of the blade decreases the natural frequencies. The more the defect length increases, the frequency reduction increases. This is because the more the defect length increases, the more the deformations become important. The more the damage approaches from the embedded base, the more the percentage frequency reduction; this is because the bending moment is very important near the base of the blade.