Connecting cohesive elements

[StevenJS]

Hi all,

I previously used a cohesive surface in a model to describe interface behaviour of my model.
However the cohesive surface gave inacurate results (peak stresses).

Therefore i want to create a model with cohesive elements instead of cohesive surfaces since the cohesive elements do not have these peak stresses.

I tried to connect 2 lineair-elastic parts with 1 cohesive parts (all of a single element).
However i can't figure out the correct way to create the connections between the parts.

I thought the most simple, and easiest way to do this, is with tie-constraints.
The tie-constraints do not pass on the stresses correctly.

When merging the parts together (and manually adjusting element numbering for the cohesive element in the .inp file) i get correct results. But i want to implent the cohesive elements in a more complicated model, thus merging the parts together (and manualy adjusting the element numbering) is actually not really a option for me.

Is there any special way to connect cohesive elements to other plane stress elements?
Does anyone have any experience with connecting the cohesive elements?


Thanks in advance,
Any help would be greatly appreciated!

Steven

 

[Mohcine]

To my understanding from reading Abaqus manual about connecting the tie constre aint is that:

If the mesh is the same as the parts and the cohesive elements, use the node tie constraint.
If the the mesh is different ( finer for the cohesive element), surface tie constraint is to be used.

What are you simulating? is it impact related?

 

[Mohcine]

*Constraint

 

[StevenJS]

Hi Mohicine,

Thank you for the reply.
This is my understanding as well.

For my simple model (see image) i found out the problem.
Abaqus does not always correctly provide the element numbering.
For cohesive elements: first the node numbers of the first "solid" edge should be definded, then the node numbers for the seccond edge.
Sometimes Abaqus does not define the element by this rule (i don't know when or why yet, still working on this), then calculation runs into troubles

In this image:
Element 1 and 3 are "solid" element (Lineair elastic, with very high E-module)
Element 2 is the cohesive element

Element 2 should be defined as: [3,2,5,8]
Sometimes Abaqus however defines it as: [2,5,8,3] which will not correctly run trough the processor.

This was why i thought my tie-constraints did not provide correct results.
They now seem to work just fine.


Steven