Cohesive Elements Simcenter CHEXCZ

[martin555]

I have created a model in which in contains two shell elements and a layer of cohesive elements CHEXCZ in between the shell elements.

I am looking to know if I need to merge all the nodes between the three layers or how does the cohesive layer work.

 

[BlasMolero]

Dear Martin,
With the solver Simcenter NASTRAN Multi-Step Nonlinear (SOL401/402) we can use cohesive elements to model adhesively bonded interfaces. The advantages of cohesive elements over traditional glue connections are that with cohesive elements, you can account for:
• Compliance in the connection.
• Damage in the material.

You can define cohesive elements with the CHEXCZ and CPENTCZ elements. You can define these elements as occupying a solid volume or a planar area. To define the element geometry such that it occupies a planar area, define coincident grid points on each edge that connects the top and bottom faces.

In you case, you have to merge all coincident nodes between the 3-D HEX 8-nodes cohesive solid element and the two top & bottom shell elements.

Also you know that Simcenter Nastran does not use the physical thickness of cohesive elements as defined by the geometric coordinates of the grids to determine the stiffness of the cohesive element.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[SWComposites]

Blas - if you merge the top and bottom shell nodes into one node, how does the cohesive element work? Or do you mean just merge the coincident shell and cohesive solid element nodes, separately for top and bottom shells?

 

[BlasMolero]

Yes, of course, you need to merge the coincident nodes between the two 2-D shell elements and the 3-D solid CHEXCZ 8-nodes element, like in the picture above.
Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[martin555]

Hi Blas

Thank you for this information.

In regards to the merging of the nodes, what of the top and bottom shells did not have the same number of nodes ?

 

[BlasMolero]

Dear Martin,
If the two neighboring parts do not have matched meshes I will have to check with an small pilot study if we can use glue surface-to-surface effect.
In the list of capabilities of GLUE effect I do not see support specifically for solid CHEXCZ, I will check.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/