Modal analysis of a base excited composite plate

[Kanza]

Hello,

I am doing modal analysis of a composite plate exposed to base excitation. The plate is fixed at the center with the nut and allowed to move in y-direction due to the vibrations. After designing my plate, if I don't put any boundary conditions, my mode shapes are coming very correct but the natural frequencies are very high. But if I constraint it from the center, natural frequencies come a bit down but mode shapes change completely.

Kindly advise me the correct boundary conditions after looking at the attachment pictures.(

http://files.engineering.com/getfil...-a8a2-37defcb58435&file=composite_plate.docx)

Thanking you in anticipation.

Regards,
Kanza

 

[GregLocock]

Lots of security warnings with that doc.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[Kanza]

http://files.engineering.com/getfil...-a2b8-f3d255d3ad23&file=FE_model_of_plate.jpg

http://files.engineering.com/getfil...4e-4a82-a029-810e959b702b&file=real_plate.jpg

I hope you will be able to see it now-

I am basically interested in getting the right boundary conditions for a base excited plate to do the modal analysis. plate has a hole in the center with which it is attached to the vibrator through a pin.

I want to get the solution as early as possible. I will be highly grateful to you if anyone of you can help me out in this problem.

Regards,
Kanza

 

[Shu Jiang PEng SE]

The high frequency is due to you do not apply any boundary condition and the model is free to move theoretically. A very weak restraints is added to your model by the program automatically. The modal shape may be not correct either. Applying restraint to the center of the plate is reasonable.

 

[Kanza]

But after apply the constraint I am not getting the correct mode shapes. Rather than bending, the plate is translating in x-z plane. Although I am applying boundary condition by constrainting the center nodes in 5 DOF and leaving it to translate only in y-direction