DEFLECTION OF CIRCULAR STEEL PLATE

[samstreet101]

My problem is this:

A simple circular steel plate with a hole in the middle. OD=225mm ID-58mm Thickness=3mm

I did a hand calculation to check the deflection and with a load of 2079 N the plate should deflect around 3.5mm at the edge of the ID.

We did a practical experiment too in order to verify the hand calculations. A plate of the same dimensions as above was supported by a ring underneath (very near to, but not on the outer edge) and a load was applied (using a hydraulic press and load cell) to the centre, an area just outside the inner edge. We measured deflection with a dial test indicator and the result agreed remarkably well with the hand calculated result.

Needless to say; the FEA version did not. I set up the constrains as follows: mild steel material, same dimensions as above. FIxed constraint at the out edge, a load of 2079 N at the inner edge. Deflection was 1.5mm. I then did a similar simulation but with the fixed constraint as an area on the underside of the plate and the load applied to an area around the inner edge. Almost the same result as before. I've attached pictures (in 2 posts) so you can see for yourselves.

Any advice would be much appreciated.

[samstreet101]

Here's the remainder of the attachments

[JDMather]

Your description of your digital set-up for constraints and loads doesn't match what you describe for your physical experiment.

Can you attach the ipt file here?

Make sure the file you attach is the one with the two Split faces that match the actual constraint and load faces.

[samstreet101]

Hmmm although it's a simple part, it's a big file..4MB. Perhaps due to multiple simulations on it. Anywhere else that you recommend I upload it to?

[torbjorn]

I would suspect that you have used fixed(in all directions) as your constraint. This is stiffer than the support you describes in your practical experiment.

Make sure that you only fix in one direction - normal to the flat surface. This will allow the edge to flex.

[JDMather]

You should be able to right click in the browser and delete the extra stuff, or that part looks so simple - surely you can remodel in 5 minutes or less.

[samstreet101]

I've just tried doing this (by using the vector components in the fixed constrain dialogue box and only ticking the Y option) however, once I've done this I get an error when running the simulaiton saying 'not enough constrains'...

[samstreet101]

Here's a copy of the model with just one simulation...only the inital constrains.

[JDMather · Accepted solution]

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@samstreet101 wrote:

My problem is this:

A simple circular steel plate with a hole in the middle. OD=225mm ID-58mm Thickness=3mm

I did a hand calculation to check the deflection and with a load of 2079 N the plate should deflect around 3.5mm at the edge of the ID.

 ...

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The file you attached had a different load than the 2079N you state in the problem description.

I set the Fixed constraint on the outer circle by components and fixed only the Y DOF.

Changed the load on the inner circle (or on the inner cylindrical face - I ran both ways).

Set the Simulation Properties to Detect and Eliminate Rigid Body Modes (since the Fixed Constraint is underconstrained).  Result image of deflection attached.

In your physical test was the part permanently distorted (not completely flat) after the test?  (SF<1)

Note:  I suspect the Thin Bodies analysis tools should be used, but I do not have experience with that functionality.

Hopefully Hugh will come by and add his comments.

[samstreet101]

Thanks JD that worked a treat!

Have also checked the plate again with differing dimensions against my hand calculations...they agree almost exactly now. Many thanks for your help

Sam