Surface Regions and Contact Connections

[marksummers]

I am trying to model a simple assembly for a static analysis in Pro/Mechanica. It consists of two SST shafts and two aluminum tubes. The tubes run front-to-back, and at the end of each tube are two holes on each side with pressed in bushings. In between the tubes, and running perpendictular to the length of the tubes are my shafts. Each end of the shafts rides on two tube bushings.

Looking from the top:

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To transfer the loads (direction down in my lame picture above) at the middle of the shafts to the tubes, I simplifed the model such that the bushings are gone, and the hole size in the tubes are exactly the same size as the shaft diameters. I figured I would create surface regions on the shafts to coincide with the surface of the holes in the tubes.

However, I can't seem to generate surface regions on the shaft surfaces. I can generate datum curves on the shafts using the xref option, but when I try to generate surface regions, it will only let me select one datum curve, and then immediately asks for the surface(s). Once I select the surfaces, it generates a surface region starting at the selected datum curve, but instead of stopping at the second unselectrwed datum curve, it continues until the surface ends at the end of the shaft.

Any ideas? It seems as if creating sufface regions and using them to define contact connections (and automatically created measures to extract surface contact pressures) was an ideal way to model this assembly, but maybe not. I am used to Split Faces in Solidworks and Inventor, but Pro/E does not seem to have such a feature.

Any and all comments are appreciated.

 

[marksummers]

Let me try this again. Maybe my lame effort at the top view of my assembly from teh last post using ASCII characters scared many of you off!

Basic question is how do contact connections work? When modeling mating surface pairs, should I have a gap between the surfaces or no gap? On a cylindrical surface, does it use only the half of the cylindrical selected? What happens if the mating surfaces are off 90° from one another? Would using surface regions and/or volume regions be a better approach?

Any help would be appreciaated.

-Mark

 

[adnanh]

Hallo Mark,

I have been reading your post and I recognize the problem very well. I do not have that much experience with Pro/M and certainly when it comes to contact analysis I seem to have similar problems. My understanding so far is that when choosing a surface of a cylinder, Pro/M assumes that you have defined the proper surface. If not, the program returns the error "pair of surfaces do not form a valid contact region" or "invalid contact region due to unconstrained tangential motion". The latter error has to do with the fact that Pro/M only works with frictionless contact. And defining contact with mating surfaces with off 90° one from one another usually results in either error messages or uncorrect results.

Can you add an attachement of the assembly, so those who want can take a closer look at it?

 

[marksummers]

Attached is the assembly model and related parts for those interested in helping me out with some suggestions.