Rubber - Model goes unstable - how to increase damping?.
Rubber - Model goes unstable - how to increase damping?.
(OP)
Dear all,
I am modeling rubber friction at high coefficients (bigger 1.0) and at some point of sliding friction, my model goes somehow unstable and bounces up and down, with waves on the surface. Looks a bit like I modeled a liquid.
Does anybody know how I can change the damping, or put additional damping to my model?
Thanks,
Phil
I am modeling rubber friction at high coefficients (bigger 1.0) and at some point of sliding friction, my model goes somehow unstable and bounces up and down, with waves on the surface. Looks a bit like I modeled a liquid.
Does anybody know how I can change the damping, or put additional damping to my model?
Thanks,
Phil





RE: Rubber - Model goes unstable - how to increase damping?.
However, I would start by changing the matrix storage to Unsymmetric because of the high friction.
I hope this helps.
Rob Stupplebeen
RE: Rubber - Model goes unstable - how to increase damping?.
thanks for the super fast answer. I guess "stabilization" and "matrix storage" all appear on the help manual, right?
I'll have a look for them tomorrow!
Thanks again,
Phil
RE: Rubber - Model goes unstable - how to increase damping?.
I am trying to change the critical damping factor (by default = 0.03) at the moment.
RE: Rubber - Model goes unstable - how to increase damping?.
Rob Stupplebeen
RE: Rubber - Model goes unstable - how to increase damping?.
I am not entirely sure how that damping works, as I dont want to change the behaviour of my model.
I used both, Mooney and Neo-hookean SEF for rubber, but I doubt that putting a visco-elastic term in the model will solve the progression of the wave, would it?
Picture:
The white elements on the picture are the CIN-elements. As they are only allowed to be linear, I defined them with same properties as rubber (E=1.6MPa, poisson ratio=0.495). They seem to distort a bit, which I guess is due to the nature of CIN elements if I get it right from the Abaqus manual:
"During dynamic response analysis the infinite elements hold the static stress on the boundary constant but do not provide any stiffness. Therefore, some rigid body motion of the region modeled will generally occur. This effect is usually small."
RE: Rubber - Model goes unstable - how to increase damping?.
Could you more fully explain your model. What are the boundary conditions? Is there contact? You might be going down a complex solution where a simple fix could suffice.
PS" the last post should have read YOUR model not OUR
Rob Stupplebeen
RE: Rubber - Model goes unstable - how to increase damping?.
As shown in figure "wave2" my 2D model consists of a block with rubbery properties and a rigid slider.
BC's:
The block is constrained in all DOF's on the bottom side, all other sides are unconstrained (as it would be in "real life"). The slider in step 1 is indenting into the block (contact is established, defined as "surface-to-surface contact)), after that the rigid body is displaced to the left hand side.
Would that be enough for the BC's?
I would like to damp my model so that the waves shown on the surface either disappear completely or are significantly damped out.
RE: Rubber - Model goes unstable - how to increase damping?.
Is there a reason you can not do this in Standard? I know the sliding contact could be an issue however this is such smooth geometry that I doubt it will be that difficult.
Have you tried playing with linear bulk viscosity?
Try having the indentor move significantly slower 1/10th.
Rob Stupplebeen