Calculate Damage parameter: Cohesive softening

[StevenJS]

Hi all,

For my research i want to model a bi-lineair softening curve of a cohesive element (see image below).
This should be able to be modelled in Abaqus CAE with a tabular damage evolution.

However the Abaqus user manual gives a formula to calculate the damage parameter for lineair softening, and another formula for exponential softening.
But not how to calculate the damage paramter for a given traction-separation diagram.

So how can i for a given set of points in the bi-linair softening curve, find the damage paramter (D)?
So that i can use these to model the damage evolution in Abaqus.

The points in this traction-separation diagram are the following:

d	            e	              t
0.008082904	    0	              0
0.043118013	    0.00112986	      13.43787122
0.051200917	    0.001996947	      4.847601852
0.123627852	    0.002230329	      2.814681189
0.247255704	    0.002463712	      2.814681189

Thanks in advance for any help.

 

[isyhadh]

dear steven
if you don't mind
can you share the pull out test simulation model? if possible

http://www.eng-tips.com/viewthread.cfm?qid=343838

many thanks

 

[StevenJS]

Hi,

The pull-out data from the image above is the pull-out stress for a concrete-reinforcement interface.
I calculated the values for concrete C30/35 based on the analytical pull-out model of Den Uijl and Bigaj (1996).

Den Ujil, J. and Bigaj, A.J., (1996) A bondmodel for ribbed bars based on concrete loaded in compression. Heron nr. 41 (3), p.201–226

Hope this will help you!



However do you maybe have a suggestion how to find the damage parameters that are needed to model this softening behavior?

 

[Chen1]

Hello StevenJS,

I am working on Rock samples, i have the stress-strain curve from the uni-axial compression test. the stress-strain curve for my rock sample is similar to yours.

I need to know how to calculate the damage variables, Actually i read the manual, but i did not find answer for my question. I wish you could help me.

Thank you in advance