
Re: Nonlinear analysis
Ryan Enos Jul 14, 2015 3:37 PM (in response to Mustafa Bgr)Send a picture of the Model and a picture of the Study properties



Re: Nonlinear analysis
Ryan Enos Jul 14, 2015 4:12 PM (in response to Mustafa Bgr)what solver are you using

Re: Nonlinear analysis
Mustafa Bgr Jul 15, 2015 2:20 AM (in response to Ryan Enos)Hi Ryan,
I'm using Iterative solver.
By the way, 4 of the components have elastic properties and 1 has viscoelastic .

Re: Nonlinear analysis
Ryan Enos Jul 15, 2015 2:47 AM (in response to Mustafa Bgr)did you try direct sparse

Re: Nonlinear analysis
Mustafa Bgr Jul 15, 2015 3:13 AM (in response to Ryan Enos)No , I haven't tried it.

Re: Nonlinear analysis
Ryan Enos Jul 16, 2015 1:33 AM (in response to Mustafa Bgr)what have you tried doing to fix it

Re: Nonlinear analysis
Mustafa Bgr Jul 16, 2015 4:36 AM (in response to Ryan Enos)Dear Ryan
Since geometry and problem's condition(nonlinear analysis), time required for analysis to complete takes too much. I changed the solver as you said but this time another text is written in the warning part and it is : "Incremental creep strain is too large..."

Re: Nonlinear analysis
Andrei Popov Jul 16, 2015 5:56 AM (in response to Mustafa Bgr)Your model is over restricted, so you get the error in the firts step because of that.
you'll get same or similar error with any solver so don't bother with that.
you have to fix one face and the other you have to let it slide or you don't fix it at all. Jist give it freedom to move.
and I don't understand what is the purpose of your simulation? Because you basically use compressive force on a knob, what do you want to find? The stresses in the knob neck? if this is what you want you can cut the whole part with a plane perpendicular to the forces and apply the fixture there on one surface, this will make the solution more stable, but still the solver will stop when the buckling instability occurs Which is what really happens. Which means that after the final step the solution is not real anymore, it is complex which means that there is a bifurcation point just after the last step which is the limit of stability. And this is given by the magnitude of the force and the characteristics of the material that reached the Euler buckling limit, has nothing to do with the solver. I mean any solver will reach the same limit sooner or later.
also in the solver menu you have an option there that you can check "Use large strain model for creep" or something similar.
CHeck this link is a course about the instability of the compressed columns:
because you have creep you may have this elasticplastic behaviour:

Re: Nonlinear analysis
Mustafa Bgr Jul 16, 2015 6:06 AM (in response to Andrei Popov)Dear Andrei
Thanks for your response. This is a human's tooth model and I wanna know the regions with maximum stress and strain under cyclic loading. the reason that I fixed two sides is that in reality they're fixed. If I leave one side unfixed, results may be unreal and unreliable. So is there a way to fix it?
Thanks

Re: Nonlinear analysis
Andrei Popov Jul 16, 2015 12:46 PM (in response to Mustafa Bgr)Well in that case if that is a jaw then to me it makes more sense to fix only one side and let the other side free, this is how the jaw is fixed by the face anyways.

Re: Nonlinear analysis
Mustafa Bgr Jul 16, 2015 1:50 PM (in response to Andrei Popov)But in reality they are both fixed and researches done in this field consider both sides fixed and t seems reasonable.

Re: Nonlinear analysis
Ryan Enos Jul 16, 2015 2:15 PM (in response to Mustafa Bgr)Andrei is right, the resultant moment would occur on the head side of the section in reality, but with both sides fixed you have a bending moment in the middle of the section













Re: Nonlinear analysis
Stephen White Jul 17, 2015 8:02 AM (in response to Mustafa Bgr)Hi Mustafa,
A stiffness matrix with negative values would actually suggest that the model is underrestrained,
I wonder what contact sets you have between the components? Do you have no penetration contacts etc?
Cheers
Steve

Re: Nonlinear analysis
Mustafa Bgr Jul 17, 2015 2:32 PM (in response to Stephen White)Hi Steve
I haven't define any contact sets.
thanks
