10-Marble

Question

Contact regions on adjacent tangent surfaces

Forum|Forum|12 years ago
December 17, 2013
7 replies
5197 views

Good day folks,

I have noticed something here that bugs me...I have created a contact
pairing of co-axial inside and outside rounds (filets) but want the outside
round to be able to "leave the area" if so inclined.

like this >

However, on at least one run it appeared the contact region was behaving
like a pin connection and would not let the one object leave the corner. Is
this the intended functionality? On another similar study this seemingly
didn't happen ?!?

To counter the former I made the inside round quite small and defined
contact between the outside round and the two planar surfaces. That did
allow the "point" to pull out of the corner. On the latter case this is a
less desirable solution.

My question is how are you handling the possible transfer of a contact
surface from a cylindrical contact region to a tangent planar surface? I
tried several modeling techniques to get one continuous surface to no
avail...yes, I knew better, but tried just the same J.

Thanks in advance,

Gavin B. Rumble, PE

Solid Engineering

336-224-2312

Surfacing

C

ChrisKaswer

16-Pearl

Gavin,

Did you create the contact region yourself? The first thing I would suggest is to check how your default behavior is set for contact - my guess is it may be set to "bonded". You can check for the behavior graphically using the command "Review Geometry" - this example has mine set to "Bonded" as I believe is the default:

[cid:image003.png@01CEFB3D.CD256580]

Hope this helps.

Chris

Christopher Kaswer
Principal Engineer, Manager
Advanced Computation & Methods Engineering Group
Covidien
Research and Development, Surgical Solutions
60 Middletown Avenue
North Haven, CT 06473
(203) 492-7167 (office)

[b18d9204b63b9ee99e4b458788049390ec68c7e372a861c3]

G

GavinBRumble

Author

10-Marble

Thanks Chris, but there is no way to have Bonded active when you create a
Contact region.

R

rgiles

1-Visitor

Hi Gavin,

You need to make sure that you have contact defined between the inner (convex) round and the flat on the opposing piece (horizontal line in the sketch). You may also need to add another contact to the vertical face as well, depending upon how the components move due to the applied load. Don't forget contact is only valid for 'small displacement', so if your parts have too much sliding motion, the results can be invalid, even if there is no unconstrained rigid-body motion present.

Anyone heard when contact with large displacement will be available in Mechanica?

Thanks,

Rod

Rod Giles
Principal Engineer - Powertrain CAE
Triumph Designs Ltd

C

ChrisKaswer

16-Pearl

Gavin,

What version are you using? Component interface behavior is detected automatically for you (for the last few versions), and defaults to "bonded" for surfaces that are in contact. Unfortunately, icons are never created to visually indicate this after the assembly is fully transferred into Mechanica - that's why you need to use the tool I showed in my previous e-mail to see how Mechanica/Simulate has handled components that are adjacent to each other. My images have been from Creo2 (see below). This is behavior that I'd like to see changed - create interface icons for everything automatically generated ... or at least create model tree entries for all interfaces, not just user created.

Rod brings up a very good point too about creating contact pairs for all possible surface combinations. Creo 3 or 4 will allow you to select multiple surfaces from each body in just one contact definition - this will be a huge help . My recommendation is to set the default behavior to "Free" and manually create every interface you require for all pairs of surfaces that may come into contact.

[cid:image008.png@01CEFCA6.E629E8C0][cid:image006.png@01CEFC98.20B45200]

Chris

G

GavinBRumble

Author

10-Marble

Rod, you bring up an important aspect I had not considered. I have used
cams in Mechanism and always figured I could use a Contact Region like a
cam...evidently not. Thanks!

Regarding the two planar surfaces you mention here, yes, that is what I did.
However, I didn't also keep the curved contact region, I deleted it and then
shrank (is that a real word?) the radius of the inside round to something
small that would never touch the outside round of the moving part and then
defined two contact regions...both curve to flat.

Thanks in advance,

Gavin B. Rumble, PE

Solid Engineering

336-224-2312

G

GavinBRumble

Author

10-Marble

Thanks Chris, yes, I did accept Bonded as the default Interface going in,
but then intentionally defined the individual Contact Regions as described.
That overrides the Default. But, I see what you're saying, if the Default
is Bonded, the interface doesn't show you anything that tells you that for
an individual surface pair. In my work things are almost always Bonded so I
have never considered the fact that it should tell you that. In full
disclosure, there is the reminder text at the bottom of the screen...

We use mostly Creo EP 5 (which is really WF5) for analysis...I should jump
to Creo 2, I know. The point you make below may well be just what I need to
make the move. Because, in WF5, the Contact Region dialog box specifically
says, "Pick a Surface", and does not allow multiple selections. Nice
improvement in Creo 2, ehh?

Now then, none of this really addresses the core of my question which is a
somewhat inconsistent behavior in these partial cylinder Contact
Regions...sometimes they act like a hinge pin and sometimes they do not.
Rod G. points out that adjacent surfaces SHOULD also be part of the contact
definition, and yet at least one time I still wound up with a "hinge".

Regards,

Gavin

P

ptc-468947

1-Visitor

Rod,

Contact with large displacements and other non-linarites is available in
Creo 2.0

Best regards,

Miroslaw Chamera

ARIADNE Engineering AB

Från: Rod Giles [

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