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Contributor
Posts: 12
Registered: ‎06-18-2008

mesh generated unwanted common nodes

217 Views, 3 Replies
01-28-2013 09:35 AM

fabricated frame interaction with pin

my initial model has holes without any edge chamfer in contact with pins
the results indicate very high edge stresses due to the high edge load that developed from the pin deflection as it

passes through the hole

the second model includes a small chamfer at the dege of the hole
this chamfer will cause the high edge load to be a a point inward from the surface of the plate
the edge will thus be better supported and hopefull i will be able to see a reduced level of stress in the high

pressure zone

problem:
when i mesh the model that includes the small chamfers some of the nodes are undesirably joined

this creates a connection between the rwo parts
how can i prevent the parts from connecting?

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Valued Mentor
Posts: 461
Registered: ‎08-30-2012

Re: mesh generated unwanted common nodes

01-28-2013 11:18 AM in reply to: jm74jensen

If I am understanding the image correctly, you need to change the tolerance that determines whether the mesh is stretched to bring nodes into contact or not. Going off of memory, it is under "Mesh > Mesh > 3D Mesh Settings > Option > Model". Then there are a couple of inputs for the tolerance. I suggest you change it to "absolute length dimension" or whatever the terminology is so that you can enter the actual separation at which you want nodes to be bonded or not.

 

It should not be necessary, but it might help if you set some of the surface pairs to "free/no contact" before meshing. See the attached image.

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16 years experience with Simulation Mechanical
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Contributor
Posts: 12
Registered: ‎06-18-2008

Re: mesh generated unwanted common nodes

01-29-2013 03:48 AM in reply to: AstroJohnPE

Thanks John,

 

I had tried a smaller mesh but that ended up with an unwieldy degree of fine element mesh. I went back and adjusted the absolute mesh size as suggested and was able to stop the node merge between the parts.

As an alternative, I'll keep in mind the idea of setting "free no contact" if this issue reappears.

 

Regards,

Jay May
Engineer

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Contributor
Posts: 12
Registered: ‎06-18-2008

Re: mesh generated unwanted common nodes

01-29-2013 06:13 AM in reply to: jm74jensen

My model now does not appear to have the unwanted connection(s) between the pin and frame bore. Another issue has developed that I don't understand.

There is surface contact defined where the pin meets the bore and deflection views show that they are not connected. Also the surface mesh of the pin in this area matches the surface mesh of the bore. All of the pin/bore connection have surface contact defined (zero friction). When the model was imported from Inventor I set the option to create surfaces where parts touch.

The problem that I have is a high stress development at a few nodes on the bore surface. I can not explain why this would occur.

Are there any recomendations of how to correct this sort of issue?

The first image gives a general idea of my assembly.

The second image shows the high  stress nodes in question.

 

Thanks,

Jay

 

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