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# Random vibration with contact problem

## Random vibration with contact problem

(OP)
Hi guys,

I am quite new with random vibration, I have been reading some material but everything is kind of a mess in my head. It would be great if you can help me with some questions or recommend me a relevant book, thank you.

If I have a plate subjected to a random excitation PSD (eg 0.1 g^2/Hz), what does it really mean? Should I treat it like a forced vibration problem or a base excitation problem?

If the plate has one support leg at each corner, they are not bonded but in contact due to a pretension force at the center of plate, is there any way that I can tell if they will stay in contact? I am thinking if the RMS displacement value calculated from response PSD is less than the displacement introduced by pretension force, they will stay in contact within 68% of time. Is that true?

### RE: Random vibration with contact problem

(OP)
Hi Greg,

There is one leg at each corner of the plate so four in total. The pretension force is applied at the center of plate.

### RE: Random vibration with contact problem

So you've got an indeterminate structure. As such the exact answer will be highly dependent on your real boundary conditions, including the stiffness of the 'floor'.

Cheers

Greg Locock

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### RE: Random vibration with contact problem

(OP)
Hi Greg,

Thank you for your reply. I would like to assume the boundary condition is simply supported along four edges of the plate (since I don't think I can solve more realistic one like four point supported and free edge elsewhere).

But I am not quite sure what do you mean regarding the stiffness of the floor? I would say it is a rigid body and we don't need to include a spring or so in the model to represent the floor. Would this make the problem more simple?

### RE: Random vibration with contact problem

(OP)
Hi Greg,

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