Hello friends,
In the scope of my master thesis I am developing a numerical model for a steel connection under cyclic loading. I already calibrated the plastic and damage properties of the material. I applied ductile damage concept with fracture energy damage evolution.
The problem i have is that on the unloading phases the response is very stiff, even after the damage initiation. You can see on the image that the lines corresponding to unloading are almost vertical and i wanted for them to be more in a curve like the experimental test.
(Numerical test: grey, Experimental test: Black)
How can I define this stifness degradation for unloading phases?
Thank you, if you have any question regarding the problem I will be glad to answer, Diogo Cabrita.
Hi Diogo
This is outside of what I do, so take anything I say with a grain of salt.
For what it’s worth, looking at your experimental data, it reminds me a bit about cycling of rubber, where you have the Mullins effect.
As opposed to your problem, rubber does not show damage, as internal sliding between molecule chains and friction is the probable mechanism.
Still, they look similar.
The best model I have come across for rubber is the Bergström-Boyce model. It uses a two network model. Perhaps you can borrow some ideas from this work?
You might also want to take a look at the work on seabed soils made by Tomas Sabaliauskas.
Hope this helps
Claes
Claes Richard Fredö I dont think those models are worth applying but it was helpful to have that similarity in mind.
Al Mouayed Bellah Nafeh , I forgot to mention, i am using general static analysis on Abaqus. You right this degradation results in pinching, and a decreasing of dissipation energy capacity, so I think its really important to capture this behaviour in my case. I thank you for your insight and python tool, it seems interesting but I need more practical help because i have limited time to solve this problem.
Thank you both I am still trying to solve the question
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