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ABAQUS cohesive elements - damage for traction separation problem

ABAQUS cohesive elements - damage for traction separation problem

ABAQUS cohesive elements - damage for traction separation problem

(OP)
Hi everyone. I’m modeling a fiber reinforced concrete notched beam, 550 mm long; it’s a three point bending test and I have to plot the CMOD (crack mouth opening displacement)-force diagram in order to compare it with those obtained from laboratory tests. I modeled the beam as a 2D planar part with shell elements. The model is composed of three parts: the left portion of the specimen, the right one, and a cohesive interface. The interface is made of cohesive elements ( COH2D4 type ) and its material is defined by the following parameters:

ELASTIC, type=traction, E=G1=G2=400000 MPa
DAMAGE FOR TRACTION SEPARATION LAWS >MAXS DAMAGE, nominal stress normal –only mode=3.5 MPa, nominal stress first direction = 100 MPa, nominal stress second direction = 100 MPa

My problem is related to the DAMAGE EVOLUTION parameters. I’d like to model it with a displacement, tabular type; but the analysis responds well only when I model it with a displacement, linear type. If I use the tabular type, the cohesive elements don’t deform at all, even if the model is a displacement –control analysis (it’s a Riks step: the stopping criterion is that of the maximum vertical displacement of 50 mm).

With a linear damage evolution and a displacement at failure of 5 mm all is ok, but if I try to model the same softening branch with tabular data, the cohesive elements don’t deform. The tabular data that I tried are the following:
First line: damage variable = 0, displacement = 0;
Second line: damage variable = 1, displacement = 5.

Can anyone help me? Thanks a lot!

Luca

RE: ABAQUS cohesive elements - damage for traction separation problem

I was also interested in using this option (*Damage evolution, type=DISPLACEMENT, softening=TABULAR). In 6.12 it doesn't seem to work as I would expect. I ran some single element models and found that the behavior is strange... Also noticed that from 6.11 to 6.12 the Analysis manual goes from a brief description of this feature to no description, so it seems like Abaqus might be aware that something is wrong here. I've since moved on to other issues and have not checked to see if it's fixed in 6.13 or if it's a known bug.

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