Cohesive behaviour - stiffness vs displacement inconsistent

[DJStatics]

Hi there

I am testing the use of surface-to-surface contact interaction with a cohesive behaviour contact property. However, I find that my model is not matching a theoretical calculation and the behaviour is not consistent across different stiffness values(Knn, Kss, Ktt).

Model description: (CAE file also attached)
- Two plates (100mm x 100mm x 5 mm) with very large E modulus. Plates separated by 5mm.
- Bottom plate fixed in translation and rotation. Top plate fixed in Z and Y.
- S4R elements with 5mm seed size.
- Body force of 0.1 applied to top plate in X direction.
- Interaction setup: Type = Surface-to-surface. Top plate master, bottom slave. Discretization method = surface to surface. Sliding formulation = small sliding. Slave adjustment = 'Adjust only to remove overclosure' (not sure about this one).
- Interaction property: Cohesive behaviour

Results of interest:
Displacement of top plate for different K values (with Knn=Kss=Ktt).

Theoretical calculation:
Displacement of top plate = (Total force across top plate / Area of plate) / K. -> This follows from Shear stress = Shear strain*G, assuming bond thickness = 1.

For K = 10, the model matches the theory near exact. With increasing values of K, the error with the theory also increases. For K=20, 65% error, K=100, 256% error,..)


Perhaps my theory calculation is wrong, but if someone has some insight into these results, I would be grateful.

 

[Li01]

Hi,

I suggest you try using "Discretization method = node to surface" instead of "Discretization method = surface to surface".

Best regard,
Li

 

[FEA way]

Your problem sound like a typical case from the Verification Guide in Abaqus documentation. Have you checked there for similar examples ?

 

[DJStatics]

Thank you for the replies.


The problem is indeed the discretization method and my apparent lack of understanding the differences in the methods. Node-to-surface results in expected displacements.

Thanks FEA way for referring me to the Verification Guide, this I have not used before.