Assemblies in MECHANICA?

[cyrilcroun]

I just got my hands on Pro/MECHANICA and Mechanism Design(MDX, not MDO). I was wondering, is there a way run run stress tests on an entire assembly? The few tutorials I've found only let me run one part at a time. I've already found out that I can't add myloads and constraints in Mechanism because I've got the wrong module, so I need some good news!

 

[sezerserhan]

Hi, Why dont you try to run the analysis integrated Pro/Mechanica which is in Pro/E. You shouldn't have any problem analyzing assemblies with it.


Regards,


SS
Edited by: sezerserhan

 

[cyrilcroun]

How do I go about doing that? I'm new to FEA.

 

[mechlad311]

you have not provided enough info.


what type of "stress tests" are you after?


there is a limitation in MDO in that it will only let you transfer one part into a structural analysis after doing a motion. My tip to you is to carefully watch how and where you set up the jointsthis will ultimately effect which pieces of the assembly you can run structure on.


Tech support says this will be addressed inWF3.


If you are new to FEA, find a mentor. SDC also has some good beginner level tutorials.

 

[cyrilcroun]

Well, what I'm essentially trying to do is test how much weight a scissor jack can safely hold. So far, I've got thisjack assembly held together with basic constraints (align, mate, etc.). Now that I've received Mechanica and Mechanism MDX (last Thursday), I need to learn which moduledoes what and perform the aforementioned tests as soon as possible.


So far all that I've learned is that I can't transfer loads from MDX to Mechanica (it's missing a lot of the features of MDO). So what I'm wondering is, can I run the weight tests on my old basic assembly? Or do I need a Mechanism assemblywhere the parts will bend and slide the way they're s'posed to? Or will neither work - do I need to test my parts piece by piece (as I think you were saying)? It seems that all I know is that I don't even know enough to know what questions to ask! (Say THAT three times fast!)

So obviouslyany help, tutorials (free, of course - my company won't let me purchase anything), or generic words of wisdom would be greatly appreciated!


Thanks much!

 

[KurtStark]

Hi,


You can perform stress test to standard assemblies, there is no influence whether they are done with or wothout MDX. But it only makes sense for one body of your MDX assembly, because Mechanica cant model your MDX Connections. For this body of MDX you have to calculate the external forces externaly (for exemple in MDO).


Every part and the whole assembly must be set to the correct units for Mechanica (mm/N/s).


You must be aware, that mechanica calculates all the touching surfaces as fix connected. For getting realistic results you have to modify the interfaces between the parts for getting the right strength/stiffness of the constraint. this is a lot of estimation work, with the danger of getting results far from the truth.


Good luck

 

[cyrilcroun]

So - does this mean thatas long asthe parts that need to pivot don't have surfaces thattouch, I can run Mechanica on my basic assembly without using Mechanism at all?

 

[KurtStark]

Yes , you can. But you have to define enough constraints and forces of your joints (pivot). This will be the same as making a Mechanica run for every body (assembly of fix connected parts).


Mechanica you can use for calculating stiffness, stress, and modes of a part or an assembly of parts which are fix connected. You can't directly calculate the whole assembly and define the pivot as "rotation allowed" and "actio = reactio". Perhaps there is a way with a special arrangement of beams added to the model, but this is above my knoledge.


Either you calculate your force in the pivot externaly or you have to use MDO for that.

 

[sezerserhan]

You can reach the integrated Mechanica in Pro/E under applications. When you are in that, the assembly you created will be recognized as whole. You can apply your loads and B.C. and run your stress analysis for entire assembly. However, you have to take care of contacts between the parts in your assembly otherwise you will get an error. If you are to solve a problem that you need to create mechanisms, then it is another story and it then will depend on what you want to calculate. Your loads and B.C. will decide that. For stress calculations,I don't see why you need to mess with mechanism.I might not have understood your problem thorougly. But, as far as how you can run an analysis for entire assembly is concerned i tried to explain and i hope it helps.


SS