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March 30, 2021

5 Essential Steps For Verifying FEA Results

FEA Result Verification

Whatever we design, Mother Nature will verify it in the end… but I would rather know if my design has a fighting chance before any major collapse occurs!

This is why FEA results verification is a very important thing.

When you are solving a known problem (i.e. as a benchmark) this is easy to do. You just compare the outcome of your model with the correct known results… and that is all (or you have some tweaking to do, which is more likely!).

But usually, you won’t know the correct answer right? This is when things become a bit tricky.

Here’s our process for verifying a FEA design.

1. Check the shape of deformations

The shape of the deformation is more important than its value! Checking how the deformed shape looks like gives you a chance to see whether the model behaves as intended! Use a large magnification, but also a factor of 1.0 to make sure nothing is poking out where it shouldn’t.

FEA deformations

Checking the shape of deformations

2. Check deformation values

Once you’re satisfied that the shape is expected, look at the values. Ensure they are within serviceability limits under the appropriate load combinations.

3. Check reaction forces

It seems obvious, but reactions tell a lot about the model’s accuracy. Look for large opposing reactions, tension where compression should be, etc.

> Check the force – reaction balance

The sum of the reactions should equal the sum of the applied loads.

> Check the “soft springs” (aka the “air hooks”)

From time to time, you will analyse a problem that is “a bit” unstable. You will most likely stabilise it with a very soft spring (sometimes called an “air hook”). This is a completely fake support but it helps with numerical calculation of the problem.

When you finish the analysis you need to check the reaction forces in those soft springs… Since there is no real support there, the reaction force should be minimal!

> Consider boundary conditions you have chosen

If you have doubts about what boundary conditions to use, use both sets and compare outcomes. This way you will see if the assumption you are uncertain about will play any significant role in design.

4. Take a look at stresses

Not specifically, but generally, to ensure they make sense.

By default, your software will most likely show you the average stress. Turn it off. You will be surprised how much the outcomes may change!

If the differences in stresses are big for adjacent elements, you should consider refining mesh in that region!

FEA Stress analysis

Design analysis

5. Do hand calculations!

Just as you should be able to predict the rough result from a calculator operation, you should be able to predict a rough result from a first principles hand calc.

In our quest to finish our projects on time, it’s easy to skip these steps and accept the results of computer analysis.

Don’t. Verification is a key element of design, to be carried out by the designer, not left to the checker (who would also do these 5 steps).

Hand Calculations

Example hand calculation

The Takeaway Here

In our quest to finish our projects on time, it’s easy to skip these steps and accept the results of computer analysis.

Don’t. Verification is a key element of design, to be carried out by the designer, not left to the checker (who would also do these 5 steps).

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