Interpretation of finite element analysis results

[Fugro]

Hi,

Recently started with FEA - loving it, at least the modelling / load application part.

Interpreting the results is tricky - particularly around where loads are applied.

Got a project (no pics sorry) which has a drilled hole in a plate, and have applied the load as a a pressure, representatve of a bolt bearing on the face.

When doing a linear static solve, area around the contact point goes white (i.e. stress capped at yeild), then rest of region up to the closest edge goes to acceptable stress levels (using von mises).

Using hand cals for tearout and bearing, the plate is fine. Using FEA confuses things, and what do i write in a report to say that the lug won't fail (despite the yeild).

Should get some pics in a few days.

Thanks,

 

[afreiden]

Why would the FEA show failure if your hand calcs (usually conservative) do not?
Are you sure that your material properties and load application are correct in the FEA?

 

[davidm1732]

How is your load applied...on the geometry or on the mesh?
What is your mesh density in that area... do you have a fine enough mesh? If you've applied the load on the geometry (surface), and you have a very coarse mesh, you may have issues. What pre-processor & code are you using... some make it difficult to refine the mesh locally without affecting the entire mesh.
How are you viewing the results... are you looking at contours that are averaged at the element centroid?

 

[Vadar2012]

My guess is that you have applied the stress around the hole as a pressure, and when you look at the maximum it is giving you the stress at the hole, which will have a concentration factor. What you want is the stress on the plate outside of the area where this pressure is being applied. When I do this, I make the part of the plate that the bolt is acting on a different element to that of the rest of the plate so I can turn it off and it only shows me the outside results.

I think this will help you.

 

[alphy]

I understand the challenges of interpreting FEA results, especially when it comes to load application. It is important to remember that FEA is a tool and not a perfect representation of the real world. While it can provide valuable insights, it should not be the sole basis for design decisions. It is always a good idea to validate FEA results with hand calculations and physical testing.

In your case, with the drilled hole and applied load, it is not uncommon for the stress to be capped at yield in the area around the contact point. This could be due to the mesh size, material properties, or other factors. It is important to carefully review and understand the assumptions and limitations of the FEA model.

When reporting your results, it is important to clearly state the assumptions made and any limitations of the FEA model. You can also include a comparison with hand calculations and any physical testing that has been done. This will help to provide a more comprehensive understanding of the results and give confidence in the design.

In terms of the plate not failing despite the yield, it could be due to the material having a larger margin of safety or the applied load not being a worst-case scenario. Again, it is important to carefully review and understand the results and any potential factors that could affect the outcome.

I hope this helps in your interpretation of FEA results. Remember to always validate and verify your results and to use FEA as a tool, not the final decision-maker. Best of luck with your project!