Non Linear Contact NX Nastran

[thecadguy]

Dear All,

I am having a gard time getting contact with 601,106 non linear. It is basically a shaft that rotates with an ear that hits inside of a machined pocket on a casting. I can get the linear contact to solve with no problem. However, the non linear is not wokring correctly. When the model does converge and work it ignores the contact all together. I have tried all the settings:

slow steps
MSTAB
Damping
ATS & TLA
Weak SPrings

Currently i am fixing the housing and constraining the shaft with a pin contraint and y direction axially. I apply a torue on the shaft. The parts are steel. An thoughts would be appreciated the contact just is not taking.

Thanks

 

[dwallace1971]

Try reversing the source/target relationship of the contacts. That's worked for me in the past.

"On the human scale, the laws of Newtonian Physics are non-negotiable"

 

[ZeroExperience]

thecadguy, I saw in your post history made in the Marc forum.

Why not use SOL 600 in MD Nastran for this? It's easier.

 

[BlasMolero]

Dear TheCadguy,
Remember that the CONTACT LINEAR properties defined for NX NASTRAN solver are not the same as for the NX Nastran Advanced ADINA nonlinear solver, then is not comparable.
Also, without the model in hands is difficult to realize what you are doing wrong.
You don't mention if the parts in contact are meshed with SHELL or SOLID elements, it you use solids I strongly suggest to always use CHEXA 20-nodes elements, forget at all TETRA elements, if possible.
Some suggestions:
• Use the same mesh density in both SOURCE & TARGET regions.
• For some contact problems, the contactor and target surfaces in a contact pair can be interchanged without much effect on the solution.
• If one surface is significantly stiffer than the other, it should preferably be the target.
• In general it is recommended that the lengths of segments on the contactor and target surfaces be approximately equal. This is particularly important if multiple contact surface pairs are considered in the analysis or if the contact surface geometries are complex.
• It is recommended that the ATS method to be used in contact analysis. It can also be effective to use the low-speed dynamics option of the ATS method (ATSLOWS parameter of the NXSTRAT entry).
• Line search can sometimes be beneficial for contact problems.
• Geometric and material nonlinearities can highly depend on the sequence of load application. Thus, for problems involving such features, the load steps should be small. The time step Δt should also be small in dynamic analysis and when time dependent material constitutive relations are used.

Best regards,
Blas.

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

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