Cohesive surfaces and tangential displacement

[erolsson]

Dear!

I'm trying to model the bonding strength between two spherical particles using cohesive surfaces in ABAQUS 6.11
Firstly, the particles are pressed together using controlled displacement, giving a planar circular contact area, thereafter sheared apart (also with controlled displacement) with the aim to get shear strength of the bond given a known fracture energy (and maximum cohesive stresses). I'm using NODE-TO-SURFACE contact with finite sliding. In the future, the particles with be elastic-plastic.

The problem is that during the compression step, I get a tangential slip, (CSLIP1, CSLIP2) for nodes that are not yet in contact. Eventually, when the node come into contact, the relative tangential displacement is so large that damage in the cohesive surface is initiated and a too low or zero bonding strength is predicted.

I wonder if it is possible in some way or another to count the tangential displacement relative the start of the second step or when the nodes start to make contact. Due to the symmetry of the problem, the relative tangential displacement during compression should be negligible and thus damage in the cohesive surface during the compression is nonsense.

I attach my python script that generates the model and runs the simulation. The contact definition with cohesive surfaces starts at line 594.

Any comments and suggestions are really much appreciated!

Thanks in advance!
Erik Olsson

 

[afgbikes]

I have tried to run your model
but it appeared the error in the simulation as
line 213 size growth rate, keyword error?