UGNX Nastran 7.5 2D Axis Symmetry Contact Problem

[thecadguy]

Hello All,

I am trying to simulate the compression of a square seal (EPDM) in a groove of an iron casting. I set the model up using sol 601 and used Mooney Rivlin material properties for the seal. In the mesh model I am trying to use the contact mesh (PGAP) which seems to match up fairly well with the nodes. I apply a forced displacement to compress the seal with a tool into the groove. However when I simulate some areas contact and some blow thru the mesh. I tried both a continuous gap and also breaking them into smaller individual gaps. This is very frustrating because of the lack of control. I am constantly tweaking the gap stiffness’s which helps in one direction and hurts another direction.

I have read about a slide line contact but cannot seem to find this. Ironically I can still create a region and then an advanced axis symmetrical nonlinear contact (similar to 3d contacts functionality). This seems to apply to the model correctly and solve correctly. However, the result show that it does nothing to the model and the contacts are completely ignored. Why is this functionality option available if it does not work?

Now I am going back and tweaking the PGAP elements again and this is very painful. Any suggestions on how to effectively use the contact mesh method?

Thanks,

The CAD GUY

 

[BlasMolero]

Hello!,
Better use 3-D SLIDE-LINE CONTACT. Also take a look to FEMAP EXAMPLES Manual Examples 28 & 29.

[b]Remarks related to SOL 601 edge contact:[/b]
1.BLSEG defines a flexible or rigid 2D contact region on axisymmetric elements CQUADX4, CQUADX8, CTRAX3 and CTRAX6, 
plane stress elements CPLSTS3, CPLSTS4, CPLSTS6 and CPLSTS8, plane strain elements CPLSTN3, CPLSTN4, CPLSTN6 and CPLSTN8, 
or a rigid 2D contact target region when the grid points are not attached to any elements.
2.The grid points in a BLSEG entry must either be all attached to elements or all not attached to elements. 
3.For a rigid target region, it is important to note that the top surface is on the left side of the line from Gi to Gi+1. 
By default, contact is expected to occur from the top surface. SURF=’BOT’ in BCRPARA entry may be used to change the contact side.
4.Grid points in BLSEG entry must lie in the basic XZ plane. 
5.The BWIDTH bulk entry is ignored.
6.Contact set pairs are defined by BCTSET entry instead of BCONP entry.
7.Contact region properties are defined by BCRPARA entry and contact set properties are defined by BCTPARA entry in a similar way as for 3-D contact. 
In addition, global contact settings may be specified in the NXSTRAT entry.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

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