Discussion Forum

Posted: 1 decade ago 16 janv. 2013, 04:39 UTC−5

Dear Steven, I am struggling with a similar problem (penetration of a metal tip into a plastacally deformable soil) using usind the Structural mechanics modul including the geotechnical part). But I saw that there was no answer to your question up to now. Is the problem solved in the meantime? If yes, I would appreciate to get some hints from you. In my modelling I also noted that the parametric solver (stationary) seems to work up to some point whem a prescribed displacement of the tip into the soil is specified. It fails when mesh distortions become to big, as might be expected. But the CONTACT PAIRS work in this case, at least in 2D geometry (not in 2Daxisymmetric, strangely enough). But for the time dependent calculation the contact pairs do not work, despite the definition of the geometry as "assembly" instead of "union". It appears that the moving body just crosses the soil without any stress interaction with the soil. (see attached example) Any explanation for this? Can you tell me where you found the statement that: "In the COMSOL manual I read that you cannot use contact pairs together with the transient solver. " ?? This was not mentioned in my recent communication with the COMSOL support team. Thanks! If anybody else knows an answer to the problem this is highly appreciated. Norbert [QUOTE] Dear, I would like to use contact pairs in a transient model. In the COMSOL manual I read that you cannot use contact pairs together with the transient solver. An alternative is to use the parametric solver with the time t as the parameter to solve the contact problem. However, I don't know how to set the solver settings in order to do this. I suppose you have to use the previous solution as ininital value for the calculation of the next time step, but I dont know how to do this in the Solver Manager. Also, what initial value has to be used for the calculation of the first time step (t=0)? Thx, Steven [/QUOTE]

Attachments:

• pen_support.mph

Posted: 1 decade ago 16 janv. 2013, 09:13 UTC−5

Hi Norbert, I have used contact with transient solvers before and it works. In some cases I found it better for transient problems to switch to a pure penalty contact formulation rather than the default Augmented Lagrange. You can find more details on that switch in this forum thread: http://www.comsol.com/community/forums/general/thread/30262/. Nagi Elabbasi Veryst Engineering

Posted: 1 decade ago 16 janv. 2013, 14:33 UTC−5

Hi and you might want to consider to exclude the inertial terms (2nd order time derivatives), see the main physics node, to avoid the ringing during the transient settling of your initial conditions, except if this is exactly what you are looking for. If so often its worth to consider a statioanry study to smoothen all initial conditions, and then ramp up force or penetration distance in the time domain -- Good luck Ivar