What is Classical FEA and How Does It Differ?

[Observables]

Hi all,

I was speaking to a design engineer and he mentioned that he uses Classical Finite Element Analysis in his work designing valves and cylinders.

Can someone explain to me what is Classical FEA, and how does it differ from FEA that you use in a computer program (Ansys, abaqsus,...), or am I being dumb, and they are the same thing.

thanks

 

[Mech_Engineer]

"Classical FEA" probably means he either uses old software, does it by hand, or uses old methods. In any case, it's a nonsensical term.

 

[xxChrisxx]

The only think I can think of is Ansys Classic. Now known as Mechanical APDL in Workbench.

 

[AlephZero]

Finite element methods have been developing/evolving ever since they were invented, not least because of the steady increase in computer power over the past 50 years or so.

I have never heard the term "Classic FE" used to describe anything definite, beyond a general nostalgia for the "good old days".

 

[nvn]

(1) Classical FEA uses geometry that generally is not exactly the same as the CAD (computer-aided design) solid model part geometry, and generally uses h-version finite elements, which means detailed features are simulated by decreasing the mesh size at details.

(2) "Modern" FEA uses the actual CAD part geometry (isogeometric analysis), and either uses mesh-free (meshless) analysis methods, or perhaps uses a p-version finite element mesh, which means detailed features are simulated by automatically increasing the mesh polynomial order at details, instead of decreasing the mesh size.

Both of the above categories of FEA are used in computer programs.

 

[Mech_Engineer]

nvn, I don't think any of your post is really true, sorry...

(1) Classical FEA uses geometry that generally is not exactly the same as the CAD (computer-aided design) solid model part geometry,

Standard practice for any analysis engineer. Removing features that do not affect the solution redudces mesh size and solve time. Standard examples would be removing holes from low stress-gradient areas, and removing fillets/chamfers from external corners.

and generally uses h-version finite elements, which means detailed features are simulated by decreasing the mesh size at details.

This doesn't make sense to me. Deacreasing mesh size at details would just give you lower resolution at a detail feature (unless you correspondingly increase element order), this has been true ever since FEA was first invented.

(2) "Modern" FEA uses the actual CAD part geometry (isogeometric analysis),

It's true that you can use geometry straight out of a CAD model. Additionally less simplification is required these days due to more powerful computers. Still, I don't think this is really a fundamental difference between your two examples...

and either uses mesh-free (meshless) analysis methods, or perhaps uses a p-version finite element mesh, which means detailed features are simulated by automatically increasing the mesh polynomial order at details, instead of decreasing the mesh size.

I would consider ANSYS to be a state-of-the-art FEA package, and it utilizes standard meshing techniques at least for structural models (differences in the FLUENT vs. CFX world are more subtle). What "modern" FEA packages are you referring to, considering "Finite Element Analysis" basically requires the use of finite elements in a mesh?

Additionally, increasing mesh density in detailed features has been practice in FEA since day 1.

 

[Unrest]

(1) Classical FEA... uses h-version

Isn't it the other way round? Very old software used high order (above quadratic) elements. That's nothing new. While very new software uses local mesh refinement.

(2) "Modern" FEA ... mesh-free (meshless)

I'm curious what software applications in practical use use mesh-free methods. It sounded exciting when it became popular a few years ago, but I wonder if it actually offered any advantages in common situations.

I tend to agree with other posters that "classic" doesn't have any clear definition. I've heard it used (and use it myself) to refer to older applications where you build the mesh directly, or generate it from CAD geometry and work on it from there - meaning if you make changes to the CAD geometry you have to reapply a lot of the boundary conditions etc. That's in contrast to something like ANSYS Workbench or Solidworks Simulation where you hardly have to think about the mesh at all.

 

[CFDFEAGURU]

ANSYS has two different interfaces. One is the "Classical" Ansys, that has been around for many years. WorkBench is the newer interface that is easier to use but is limited. The reason the word "classical" came about was that companies wanted to be able to differentiate between the two for bidding purposes and hiring purposes.

Thanks
Matt