I’ve been using FEA for 25 years; I worked in many industry sectors with different software for numerous companies.
I’m working towards becoming an expert but I’m not there yet because there’s stuff I still need to learn.
You see becoming an expert in FEA is like becoming an expert in mechanical engineering.
To be an expert in mechanical engineering requires all of these;
Then for each category, there is a subcategory, let’s pick solid mechanics. To be an expert in solid mechanics requires all of these;
Then there are more subcategories, let’s pick plasticity. To be an expert in plasticity requires all of these;
Then there are different general FEA commercial software packages thrown into the mix.
Not to mention specialist FEA packages for pressure vessels, pipework, structural steel, dynamics and more.
Don’t get me started on design codes, that’s for another day.
Oh boy, I need another 25 years to learn all of that lot!
I hope by now, I’ve mastered a few things though.
Here are my top ten tips to master FEA like a pro.
1. Read a good book
This is the best place to start in my opinion. When I first started, I bought the book Building Better Products with Finite Element Analysis and read every single page.
The best books teach you how to understand FEA, not how to operate the software.
Another good book is Practical Finite Element Analysis for Mechanical Engineers by Dominique Madier.
2. Try going through a tutorial using commercial FEA software
You can get trial software licences or student licences for free or quite cheaply. They often come with tutorials. It doesn’t matter which commercial software package you choose; they are all similar and will produce more or less the same result.
This will give you a basic understanding of the process applied for FEA.
3. Go on some training courses
There are some great training courses available, a good place to start is NAFEMS.
4. Start with small simple models like a cantilever beam, then check it with hand calculations
Forget FEA, learn the hand calculations. If you can replicate hand calculation results with FEA, you’re halfway there. This allows you to check if you are using the FEA software correctly.
Don’t expect the FEA results to be exactly the same as the hand calculation, but the FEA results should be fairly close, maybe to within a few percent.
There are some great examples for checking FEA results with hand calculations on the Value Design Ltd website under the heading Finite Element Analysis.
5. Identify stress that is real and stress that is spurious (or fake)
There are many opportunities for FEA to report stress that is not real. Boundary conditions, contacts, load application and singularities.
FEA cannot find stress on a corner, or point/edge constraint; this is because they have no area and stress is basically force divided by area. This type of stress is called a singularity and most solid or shell models are riddled with singularities.
So, the FEA peak stress on a corner, point/edge constraint or geometry is not really the peak stress at all, it’s just some random number.
6. Learn about ductility and how to interpret the results for ductile and brittle materials
As a rule of thumb brittle materials have an elongation of less than 5% and ductile materials are over 5%.
Von Mises stress is great for ductile materials and maximum principal stress is good for brittle materials.
Stress concentrations are important for very brittle materials, even for static loading.
7. Learn how to handle fatigue
Fatigue is generally for components that are doing a lot of cycles. Learn about the difference between nominal stress and peak stress.
The nominal stress on a component is magnified by a stress concentration factor (kt) of about 3 for a hole.
Learn about SN curves and endurance limits. If the stress is low enough, steel components just keep going for infinite life.
8. Try nonlinear materials, buckling, thermal, dynamics and vibration
Once you know what you’re doing, there are other more advanced types of analysis you can try such as nonlinear FEA. One thing to bear in mind, the more advanced the analysis is, the more likely it is that errors will creep in.
There is a reason they do physical tests on an aircraft wing before flying the aeroplane!
Check out the article on nonlinear FEA on the Value Design Ltd website.
9. Correlate FEA with physical testing
This is by far the best way to learn FEA but it is not usually possible very often.
When you predict the exact failure spot on a component and then see it fail in the very same spot. There’s no better endorsement of your FEA skills than that. You’ll see for yourself how good your FEA predictions really are.
Sometimes non-linear FEA or dynamic analysis is a necessity to match physical test results, and it’s not always easy to get it right.
10. Don't get stressed
Are you enjoying it?
You will learn over time that there is no such thing as a perfect FEA model and the best you will ever achieve is to build models that are good enough to predict what you need them to predict.
So, relax, enjoy yourself and don’t get stressed.