Node Face Constraint List extension

Discuss new capabilities you would like to have in MARS.

Node Face Constraint List extension

Postby rwendner » Tue Jul 26, 2016 10:04 am

For a new research application it would be important to add a stress slip feature to the
TrngFaceNodeBondList{}
where the stress slip relationship would be given in a similar fashion as used on the fictitious surface of the RebarConcreteInteraction Model.

Is it possible to prepare the framework so that we can implement the material (stress slip law)?
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Re: Node Face Constraint List extension

Postby zhouxinwei » Thu Jul 28, 2016 3:56 pm

After careful assessment, we find this work to be not trivial. If you need this feature, please send us a quote request so we can implement it at a cost.
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Re: Node Face Constraint List extension

Postby rwendner » Thu Jul 28, 2016 5:01 pm

thanks for the information - I will talk to my collaborators to evaluate the situation and get back to you at a later point.
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Re: Node Face Constraint List extension

Postby zhouxinwei » Thu Aug 04, 2016 1:20 am

We have discussed possible implementations for a more general triangle face - node constraint. The complexity of these implementations depends on what we are trying to accomplish. So we some questions.

For clarity, let's assume that we are dealing with
1. a general surface consisting of triangular facets
2. the node numbering of the facets is such that we can define a positive normal direction for each facet and the normal are consistent
3. if there is material on one side of the surface, the normals are oriented away from the material
4. the 'slave' node is initially bonded to the surface, but that bond can degrade during a simulation.

Here are the questions:

1. Are we dealing with large deformations? In other words, do we want the 'slave' node to move from one facet to an adjacent facet, when it 'gets out' of the facet is on.

2. Are we forcing the 'slave' node to move on the surface with a bilateral constraint, or do we also want to handle the case where the constraint is unilateral (it can never penetrate the surface but it can move away from it once the bond is broken) ?

3. In the second scenario of 2., do we want to address the condition that a node that has moved away from the surface may come into contact with the surface later on in the simulation?

The level of effort for this task depends on how general we want to make this formulation.
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Re: Node Face Constraint List extension

Postby rwendner » Thu Aug 04, 2016 7:29 am

ad(1) Ability to handle large deformations would be nice but is of lower priority for the beginning. Similar to rebar concrete interaction for most practical problems, large deformations are not an issue.

ad(2) The two connected bodies should be able to separate once the bond is broken but can not penetrate each other.

ad(3) For the time being we can assume that after bond failure there will not be another contact.
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Re: Node Face Constraint List extension

Postby weixinli » Fri Jun 16, 2017 10:13 pm

In addition to Roman's request on Node Face Constraint List, we want to seek the possibility to have different constraint models in tension and compression. Here is an application in direct shear simulation (see sketch on the attachment):
Because of asymmetric loads applied on two off-set half platens, the bonding forces between the platen and the sample are not uniform. Detachment between the platens and the sample can be observed at the outer part of the sample due to the rotation of the sample. Ideally, the problem can be solved by using Contact algorithm rather than constraint list at a higher computational cost.
To be able to simulate this, the Node Face Constraint List should have the following features:
(1) The two connected bodies can be detached without any bonding force (in tension);
(2) Under compression, either master-slave or penalty model can be activated.
(3) Sliding with friction between two bodies is enabled.

Beyond the case described above, it may not be trivial to have general constraint constitutive model which enable user-defined features.
Attachments
DirectShear.png
DirectShear.png (9.85 KiB) Viewed 22028 times
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