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dustins
Posts: 3
Registered: ‎03-01-2008
Message 1 of 2 (201 Views)

Stress analysis, how to constrain.

201 Views, 1 Replies
12-31-2012 09:53 AM

I am trying to determine how to properley constrain the assembly below, so that the compression of the rubber gasket will be properly indicated.

 

Currently I am seeing the deflection of the shelf in the downward direction, but I do not see any indication of stress in the gasket behind...

 

Currently the gasket is "bonded" to the steel tube

 

the screws are bonded to the shelf bracket and the steel tube.

 

I put in "work axis" at the center line of the shelf bracket and the CL of the gasket, but I can't find a way to constrain to a work axis..

 

The file is too large to upload here, but I can make it availible to anyone interested..

Horizontal overview.jpg

Deflection.jpg

Compression.jpg

Active Contributor
rhinterhoeller
Posts: 41
Registered: ‎08-07-2002
Message 2 of 2 (186 Views)

Re: Stress analysis, how to constrain.

12-31-2012 12:45 PM in reply to: dustins

Based upon your description the high loads are likely happening in the bolts in bending.  There is some compression happening in the gasket but because it is likely a more compliant material than the metal parts, the stress is low.  If it were a few hundred psi it would be blue by comparison to the 132,000 elsewhere.

 

In reality I would expect that you are applying a pre-load to the bolts sufficient to pre-stress the gasket.  When the 300# downward load is added the compression in the gasket changes to counter-act the moment due to this load.  I would also expect the downward shear load to be resisted by friction betwen the shelf base and the gasket.

 

My first approach would be to:

1/ bond the shelf to the gasket

2/ remove the screws from the analysis

3/ sketch circles to represent the contact surface of the bolt heads

4/ split each circle

5/ apply a load to the pseudo bolt heads representing the pre-load from each bolt

6/ analyse

 

There is some interaction happening with the bolts taking some shear but I'd have to dwell on how to model that accurately.

 

Richard

 

 

 

 

 

IV 2013 Product Design Suite 64 Bit
Win 7 64 bit

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