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Tips & Tricks: Part 1 - Which FEA Simulation Software Is Best?

FEA Simulation Software.

For most engineering problems there is no difference in accuracy between FEA codes, even CAD Embedded FEA vs. dedicated FEA codes. In fact nearly all of the error is related to factors apart from the code itself. Far more relevant sources of error include:

  • Geometry errors - how well does my CAD/FEM model match the real-world component/s?
  • Load errors - how well are the loads (magnitude, distribution) really understood?
  • Boundary conditions - It takes a good analyst to get realistic results near constraints and to achieve realistic deformations (and hence, stresses)
  • Mesh errors - Is the mesh fine enough that "convergence" is achieved and element quality checks are acceptable?
  • Element and solver selection - Can the element and solver chosen capture the mechanics of materials present in the real world? For example a linear-static solver will not assess the tendency to buckle i.e. a 1m long, 5mm diameter rod will record exactly the same von Misses stress whether in compression or tension, and give no indication that the rod would buckle at a fraction of the tensile load when loaded in compression. This often trips people up when analysing sheetmetal parts...
  • The human factor – while it is surprisingly easy to get a load, constraint, material or contact definition incorrect, interpretation of results is another area where there are some hidden traps and a good understanding of mechanics of materials, material science and FEA go along way if realistic results are desired.

Knowing the Loads

How well do you really know the loads?

Validation is Critical

The errors listed above affect all FEA codes alike – the point being that any errors relating to the code itself are usually fairly insignificant in comparison to these. With any software there will always be bugs that can trip you up – particularly when new features are added. For this reason and the aforementioned error sources it is absolutely critical that the FEA results are verified in some way. We put a lot of focus and systems around this as it is very easy to produce a “pretty picture” that, when stared at for long enough, appears to be correct! Some methods of validation include reviewing deformed shape vs. expected, hand calculations, physical testing, FEA mesh quality and reaction load checks. If you are outsourcing analysis work we think this should be one of the key criteria you assess of your provider – be warned, there are cowboys out there!

The analyst is the key to reliable results, not the FEA code
A competent analyst can produce accurate results using both almost any FEA code. In fact Motovated often highlights to clients how to get correct enough answers out of the free limited functionality embedded FEA tools available in most CAD packages. An analyst doesn’t need a PhD in material science or 40 years' experience to get useful results – the key is having at least a diploma level mechanics of material course under your belt and understanding the FEA code used, its limitations and validating the results. Unfortunately getting quality results is not enough for robust engineering; the bigger question is: are you analysing the right things and making good decisions based on the results? This requires engineering judgment but that’s a topic for another newsletter!

So can you rely on results from “CAD-embedded” Finite Element Analysis (FEA) codes like Solidworks Simulation, Solid Edge Simulation and Autodesk Multiphysics Simulation? Insofar as you can rely on the results from any FEA code and provided you validate the results; yes! We’ll talk more in our next newsletter about whether CAD Embedded or dedicated FEA codes might be better for your application, but the simple truth is both will be accurate enough as long as you know how to use them...

Interested in learning more about FEA?

Drop me a line for a free copy of our new "Introduction To FEA - How To Guide"

Leon Daly
Analysis Manager (Chch Office)
leon@motovated.co.nz

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