Tips & Tricks: Part 2 - What's the best value FEA approach for your business?
'CAD-embedded' Finite Element Analysis (FEA) codes like SolidWorks Simulation, or a dedicated high-end code like FEMAP with NX Nastran, Abaqus or similar?
It's no secret that CAD embedded (CE) FEA codes cop a fair amount of scorn in the analysis community and, seeing as we use both these codes as well as a high-end FEA package, we thought we would try to shed a bit of light on the issue. In Part 1 we looked at the accuracy of CAD embedded FEA versus that of dedicated FEA packages with a particular focus on the key sources of analysis error. In this part we'll address ease of use and functionality.
|So what's really going on in there?|
|A lot of the angst around the CAD Embedded (CE) FEA codes is their so called "black box" nature - analysts who are familiar with dedicated FEA codes which expose the "nuts and bolts" are often a bit miffed at the distinct lack of detail the C.E. FEA codes provide. Often this detail is listed in the help documentation but it can be frustrating having to search for this information as a second step. Experienced analysts will often undertake simple tests for projects to check the code is behaving as expected i.e. If a load is applied to two surfaces, is the load split between the two surfaces or applied to each surface? It is also very easy to miss a critical "tick box" with CE FEA as finding the option desired can be half the challenge.
On the other hand, the plethora of options and information that a dedicated FEA software often show can be confusing - the image below is one of eight screens a user is taken through when they run a linear static analysis in FEMAP with NX NASTRAN:
Solver options from FEMAP - options aplenty
|Flexibility and Power|
|There is no doubt that the dedicated FEA codes generally have much more flexibility and some powerful tools which can save a lot of time. Dedicated FEA codes tend to have better associativity to the various flavors of CAD whereas with a CE FEA software it may only be possible to analyze the CAD format it is embedded with resorting to using "dumb" CAD models such as STEP and Parasolid. However the CE codes usually have much better user interfaces and are easier to learn and use. To illustrate how much time can be saved by some of the extra functionality that a dedicated FEA code can provide, consider the wind turbine bearing shown below as an example:
Wind turbine pitch bearing courtesy of Windflow Technology
To setup the contact conditions (and other advanced aspects we cannot disclose) for all 124 balls literally took our client ~ two days using a CE FEA. Using a dedicated FEA code (FEMAP with NX NASTRAN) we setup the same conditions on a single sector (1/62nd) of the bearing then simply "arrayed" the mesh etc. around into a full bearing. The whole process only took a couple of hours which was an excellent time saving. You could imagine how you would feel though if you were an analyst who was familiar with this method but were well into your second day of monotonous setup on a CE FEA code!
|Most of the dedicated FEA codes also offer advanced modules which have capability that exceeds that of CE.FEA. For example, rare problems that involve extremely high strain rates and/or strain such as a car crash simulation are unlikely to be able to be solved using any CE FEA. However, we use Solidworks Simulation for consulting work on multimillion dollar projects and have been using the software since the 80's when it was called GeoSTAR. We also use "FEMAP with NX NASTRAN" which has a strong reputation as being a high-end FEA package but for 90% of projects the choice between FEMAP and Solidworks is one of convenience.|
|The analyst is the key to reliable results, not the FEA code|
|A competent analyst can produce accurate results using both CE FEA or a dedicated FEA code. The analyst may be frustrated that certain tools aren't available and they can't easily see what the code is doing if they have a background of dedicated FEA codes. Or, if they come from a CE FEA background, they may feel that the user interface is cumbersome and they are being swamped with unnecessary detail. Either way they will probably find a way to get a solution and validate that it is correct. The key is understanding the FEA code used, its limitations and validating the results.|
|So what's best? CE FEA or a dedicated code?|
|Unfortunately, the answer is: it depends; if you expect to be doing a lot of analysis and/or specialist work it would definitely be worth investigating the capabilities of a dedicated code - they all have reputations for strengths in different areas and it is sometimes possible to undertake analysis in a fraction of the time it would take with CE FEA. If you are undertaking analysis less frequently it can be difficult to remember what is happening in that 'black box' leading to more verification work and/or a greater chance of mistake. The CE FEA codes are probably easier to learn and appreciate how loads etc. are being applied simply due to (generally) better user interfaces and, in the case of SolidWorks Simulation, have more capability then people give them credit for. At Motovated we have the best of both worlds so if you would like a competitive price for some analysis work, please get in touch!
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