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Modal analysis of a base excited composite plate

Modal analysis of a base excited composite plate

(OP)
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/getfile.aspx?folder=f...)

Thanking you in anticipation.

Regards,
Kanza

RE: Modal analysis of a base excited composite plate

(OP)
http://files.engineering.com/getfile.aspx?folder=d...
http://files.engineering.com/getfile.aspx?folder=a...

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

RE: Modal analysis of a base excited composite plate

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.

RE: Modal analysis of a base excited composite plate

(OP)
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

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