Pros/Cons of Pro/Mechanica 5

I understand that Pro Mechanica from Parametric Technologies Corporation doesn't compare to Ansys or other high end software. But I'd like to know what it's downfalls and benefits are. Thanks for your time.

hydrogen

 

[DRDearth]

Over the years, I've become fluent in every commercially available FEA code, Algor, Cosmos, Ansys, Nastran, Mechanica. The single biggest problem (or limitation is a better word) with Mechanica, is one is limited in what one can do with Mechanica. I wrote my masters thesis on the P-method (Polynominal) technology so I beat this approach up for a long time, even writing my own custom code from the ground up.

In general some of the reasons I prefer FEA codes like Nastran over the Mechanica type codes are:
(a.) Mechanica is not as comprehensive as all the other FEA codes.
(b.) Mechanica isn't very flexible in what one can do with regard to auto-meshing and element formulation; for example one has more control over Rigid Links I don't believe even the current Mechanica code could handle the Rigid Links as eloquently as say Nastran.
(c.) Nastran is the defacto standard for FEA analysis results {can be a factor when working with large aerospace companies (Boeing & Lockheed) or auto manufactures (Ford & GM) }. Now I'm not suggesting Mechanica isn't accurate, but in my consulting business I typically end up having to supply solutions to these companies in the Nastran code as well as in Mechanica or any other code my clients might be using.
(d.) The solution times for a fine grid meshed H-Method (like Nastran) is probably an order of magnitude faster than an equivalent Mechanica P-Method coded model.
(e.) I can recall several Pro-E CAD models that even experienced users were not able to get Mechanica to develop an auto-mesh. With more comprehensive software tools like the ones found in Nastran we are able idealized these CAD models in a relatively short period of time. I had to due some tune-up of the idealizations but I got them.

Some of the More Obvious Downsides of Mechanica:
(a.) Pretty much stuck with Linear analysis only.
(b.) I don't think the current release of Mechanica can do either Large Deflections, Non-Linear Stress/Strain, or Resonant Vibrations with Load Stiffening. Maybe they can do that now, I would have to check.
(b.) Base Excitation for Dynamic Response [ Random & Sinusoidal ] - Not a big deal for most problems but there are many cases where one would like to subject models to variable input excitation at different points instead of *shaking* the entire model on it's supports {or Boundary Conditions}.
(c.) Mechanica's claim to fame when it was called Rasna was that one didn't need to develop detailed meshes. One only had to crudely mesh regions and Mechanica by virtue it's P-method internally updates the order of polynomials until convergence of the solution is achieved One Downside here is that one still needs to define proper patches [2-D] and hyper-patches [3-D] for the models to converge. Another downside is the length of processing time. Today's automeshing tools make the meshing aspects a moot point. With Nastran one can still do a lot more when it come to manipulating the idealization.
(d.) One aspect of the Mechanica code that I've witnessed is that some users take the idea of not needing to develop proper meshes too far and end up with solutions that aren't as good as they should be. The solution to this problem is to do lots of sample problems and spend a lot of time using the software. [Same with any other code.]
(e.) On the more practical ends, the Mechanica code has a limited element library - Nastran has a lot of flexibility in this area.
(f.) One interesting note is that when Mechanica P-Method [and the other FEA codes as well] list comparisons of their solution accuracy they compare to Nastran H-Method. Typically though every FEA code today gives good results if used properly.

The types of analysis most companies perform are typically -Linear Static's, Resonant Vibrations, and Dynamic Response to Sinusoidal Excitation. Every FEA code can do this. Mechanica included. I suppose the most attractive aspect of Nastran over Mechanica is the Comprehensive Modeling capability [ I know that word *comprehensive* covers a lot of ground], more Flexible modeling tools and Defacto industry standard.

That's about all I can come up with on the spur of the moment. Give me a call if you have any specific questions. I think this might be a good topic for one of my articles for Machine Design's FEA Update Column.

Regards,

David Dearth
Applied Analysis & Technology
"AppliedAT@aol.com"