Shell Off-sets in NX Linear and Advanced Nonlinear Contact Analyses

[jerzy]

Hello forum members,

I have been running test cases using shell-to-shell contacts where the shells are off-set from the
contact surface. The NX linear contact solution 101 behaves as I expect: it will compensate for shell thickness
and also for the shell offset using the Z-offset setting. Advanced non-linear compensates for shell thickness,
but I can't find any settings that will recognize the shell offset from contact surface, I have experimented with the many settings in the Advanced Nonlinear Contact Property screen in FEMAP, but can't get feasible results.
Will the Advanced Nonlinear Solution handle shells only when the shell midsurface is not offset?

Jerzy

 

[BlasMolero]

Dear Jerzy,
NX NASTRAN Advanced Nonlinear solver support OFFSET in surface-to-surface contact (SOL601):

• Contact surface offsets
Penetration of a contact surface occurs when the plane or line
defined by the contact segment nodes is penetrated. However, an
offset distance can be specified which causes the actual contact
surface to be offset from the plane defined by the contact surface
nodes. In the case of double-sided contact, the offset creates two
separate surfaces above and below the reference surface. Note that
if the contact surface is on a shell then half the shell thickness can
automatically be used as the offset (OFFTYPE=2 in the BCTPARA
entry). Fig. 4.4-1 shows the possibilities for single and double
sided contact. Note that the offset distance should be small
compared to the contact surface length.

Offsets for a whole contact set are specified via the OFFSET
parameter in the BCTPARA entry, while offsets for a specific
contact surface are set via the OFFSET parameter in the
BCRPARA entry. If one of the contact surfaces has a defined
offset, it will overwrite the contact set offset.
The use of contact surface offsets in double-sided contact is not
recommended.

Best regards,
Blas.

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

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

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[jerzy]

Hello Blas,

Thank you for the reply. I had read the contact information from the Modeling Guide before posting
my question and posted only after I could not get results that allowed for shell thickness and for
shell offset from the meshing surface. I had run analyses using linear contact that handled this but I wanted to
run large displacemnt non-linear solution 601.

I run a lot of problems in which I receive geometry in the form of thin wall solids which I analyze using
shells. The contact distance between walls is important in some of these problems. I think I can use solution 601
if I mesh my models with no shell offset.

It seems that NX solution 101 linear contact handles shell offset differently from solution 601.

Best regards

Jerzy

 

[jerzy]

Hello forum members,

I wanted to follow up my question. I submitted the problem to Siemens GTAC support and received a prompt reply:

"The NX Nastran 8.5 Quick Reference Guide bulk data entry for CQUAD4 lists a remark as follows:
Remarks related to SOLs 601 and 701:
1.ZOFFS is ignored."

I had not checked this part of the documentation.

I can work around this. I just have to treat solution 101 and 601 contact problems differently.


Best regards

Jerzy