Random vibration with contact problem

[YCL]

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?

Thank you in advance.

 

[GregLocock]

with regard to the second part of your question, how many legs?

Cheers

Greg Locock


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[YCL]

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.

 

[GregLocock]

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


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

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[YCL]

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?

 

[GregLocock]

It would certainly simplify the problem, by turning it into a SDOF model. It may be useful, but it won't be accurate.



Cheers

Greg Locock


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

http://eng-tips.com/market.cfm?

 

[YCL]

Hi Greg,

I understand, thank you so much for your reply!