Press fit with glued contact in NX Nastran

[PietPeterson]

Hey guys,
Is it possible to model a pressfit in a contact using the face gluing?
With the Face contact there are the two options i know of (CAD modelling the interference and negative contact search or by numerical face offset). Is there a similar way with the face gluing? Not an option for my solution is the "adjusting-the-thermal-elongation-and-applying-temperatures-method"...

Thanks for any input.
Piet

Using Advanced Simulation with NX Nastran 7.5

 

[Helrezer]

You can not use glue since glue will not preform the iterative solution.

You would need to use the contact. NX has an option that will force the 2 faces to be identical and calculate the resultant displacements and stresses. In the contact parameters, set Initial Penetration to 3.

Good luck.

Marilyn Tomlin
Siemens PLM Software

 

[PietPeterson]

Hey Helrezer,

finally I came around to try your version, but it didn't quite get me there. With this option the interference is ignored and therefore no pressfit modeled.
I know (form previous analysis) that the faces will be in contact in all condition considered, so as I understand it theoretically no iteration would be necessary. If gluing had a offset option that would do the trick. Obviously no contact analysis is possible then.
The other thing is, that I am trying to validate a calculation done two decades ago and I am having some differences. My guess is, this is due to the contact modeling, since the option then were probably not so elaborate.
Thanks for your help though...
regards

 

[Helrezer]

Dear Piet,

I have done this type of analysis several times and it works. Make sure that you have a negative search distance that is larger then you interface. (I think I forogt that in the last email.) But it should work. Glue does not move the surfaces.

Actually all glue and contact have to have iterations because they are indeterminat equations. Even though most solvers include contact in the linear solve, under the covers the solvers all do some iterations.

Have you contacted the hotline? All of the CAE support people can help you do this.

In 10 years the contact solutions have improved, but they actual solve would be that different.

Good luck!

Marilyn Tomlin
Siemens PLM Software

 

[BlasMolero]

Dear Piet,
In NX NASTRAN the contact region parameters are defined using the BCRPARA bulk entry, and one of the contact region parameters allows you to play with OFFSET fields to be used in linear solutions SOL101.

Use the OFFSET field to account for a rigid layer which might occur between two faces coming into contact. For example, a model which has two metal surfaces coming into contact, and one of these has a ceramic coating. If the ceramic material stiffness is not significant enough to be included in the analysis, it may not have been specifically modeled, but the thickness it adds to the face of the metal may be important when considering the contact problem.

You can also use the OFFSET field to analyze an interference fit problem if unconnected elements are modeled coincident. The offset value in this example can represent the theoretical interference of these faces. In the following example I have used different methods to model the interference fit between a steel axis and a NYLON rim with an interference fit: the shaft radius is 0.05 mm bigger than the rim radius.
1.- EXPLICIT INTERFERENCE: Using Min. Contact Serach Distance = -0.5 + INIPENE=0 allows you to solve the interference problem (deformed exagerated!!)

2.- OFFSET METHOD: When defining the Source Contact Region one option available is OFFSET field.

This method is great because allows you to solve the interference fit problem using LOW COST but highly accurate CHEXA 8-nodes elements!!. In the attached published post I compare results using high order CHXA 20-nodes elements, CTETRA 10-nodes with "explicit" interference fit vs. linear CHEXA 8-nodes solid elements + OFFSET trick and as you may see by the comparison table the results are practically the same, but AT A FRACTION OF TIME & RAM MEMORY!!.

The comparison was done using FEMAP 10.3.1B & NX NASTRAN 8.1, but the philosopy is more or less the same uwing NX Advanced Simulation: in the BSURF card you have both SURFACE and OFFSET fields, use it and enjoy!!. Here you are the link to my blog:

http://iberisa.wordpress.com/2012/0...-lineales-de-zunchado-con-femap-y-nx-nastran/

Best regards,
Blas.

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

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/