Contact Pressure diverges when mesh on slave surface is refined
Contact Pressure diverges when mesh on slave surface is refined
(OP)
Hello everyone,
I am trying to solve one contact problem of two axisymmetric geometries. The (zipped) .cae file of the model is attached. Issue is: stresses in the direction normal to applied load are under-predicted in the subsurface region just below the contact. Also, the contact pressure values diverge from true analytical solution as mesh on slave surface is refined. Can somebody please guide me on where am I going wrong? Any suggestions would be highly appreciated.
Thanks in advance,
Nik
I am trying to solve one contact problem of two axisymmetric geometries. The (zipped) .cae file of the model is attached. Issue is: stresses in the direction normal to applied load are under-predicted in the subsurface region just below the contact. Also, the contact pressure values diverge from true analytical solution as mesh on slave surface is refined. Can somebody please guide me on where am I going wrong? Any suggestions would be highly appreciated.
Thanks in advance,
Nik





RE: Contact Pressure diverges when mesh on slave surface is refined
I don't have CAE installed so I cannot look at the model.
Do you have surface smoothing active? It could help.
If you haven't seen this document yet, have a look. It might give you some ideas.
http://marketing.intrinsys.co.uk/CONTACT_SEMINAR.pdf
RE: Contact Pressure diverges when mesh on slave surface is refined
RE: Contact Pressure diverges when mesh on slave surface is refined
What elements are you using? If you send an input file I can maybe have a look.
/S
RE: Contact Pressure diverges when mesh on slave surface is refined
RE: Contact Pressure diverges when mesh on slave surface is refined
But then you must make sure that the energy disipated is under 5% more or less. ALLIE vs ALLSE
RE: Contact Pressure diverges when mesh on slave surface is refined
Also, I tried contact controls approach (with very little damping factor so as not to alter the Physics of the model) it was of very little help.
Any guidance on this issue would be highly appreciated,
Thank you in advance,
Nik
RE: Contact Pressure diverges when mesh on slave surface is refined
b) Increasing the load for a certain spatial discretization is changing the problem at hand. You might want to read about mesh convergence.
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RE: Contact Pressure diverges when mesh on slave surface is refined
Some recomendations i have learned working hard xDDD:
Change initial incremet size to 0,01 and maximun to 0,1.
I don´t know which units are you using, but i thing that you have chosen distance in milimeters and force in N. So... the mass would be in Tons and the pressure in MPa. Corect me if i´m wrong.
The density of the steel is 7,8E-9, not 7,8 E-6, put for the static analysis i think that it is useless and the energy is mJ.
I have achieved the convergence very easily with those changes. I think that your problem is nummerical, due to a very big time increment.
RE: Contact Pressure diverges when mesh on slave surface is refined
can you please tell how much contact pressure did you achieve? In the analysis that I am doing accuracy is more important.
Thanks again,
RE: Contact Pressure diverges when mesh on slave surface is refined
RE: Contact Pressure diverges when mesh on slave surface is refined
RE: Contact Pressure diverges when mesh on slave surface is refined
RE: Contact Pressure diverges when mesh on slave surface is refined
Also improving element quality at the contact boundary (close to perfect squares).
Contact adjustment might remove some numerical problems (initial overclosure), or even better, separate contacts at analysis start and then move them into contact.
Please report back if you find the answer! :)
RE: Contact Pressure diverges when mesh on slave surface is refined
Thanks for your suggestions!
I tried equally dense mesh on both contact surfaces and close to perfect square elements. I also automatically adjusted slave surface for initial over closures. But I am not familiar with the last approach that is to separate contact at analysis start and then move them into contact. Is there any specific control/option for this? Please let me know.
Dear kukogoba,
I am referring to Model with the name: 2mm_Q=4500_Run_57
Thanks to both for your assistance in this matter,
Cheers!
RE: Contact Pressure diverges when mesh on slave surface is refined
I was just thinking that you could move the part in the assembly and then use a boundary condition to move them into contact. Overclosure adjustment might change the shape a little. It was just a suggestion.
This is an interesting topic. Let me/us know of your findings. A certain error is to be expected. Your results aren't that bad imo.
Just a thought: Were you using a symmetry boundary condition? I know contact pressures are strange at the symmetry boundary. I tried once and I got really confused and started doing an averaging of a small area instead. Are you looking at the contour plot or nodal values? In CAE you can change the results averaging (default 75%). Anyway, good luck!