Modelling Stress softening behaviour in ABAQUS 1

[v0gue3]

Hi everyone,

I am modelling a material (Honeycomb) that exhibits stress-softening (reduction in yield stress with increasing strain after peak yield stress) behaviour when undergoing quasi-static compression.

I have tried to model this stress-softening behaviour in ABAQUS by trying both Plastic kinematic and isotropic hardening laws specifying the decrease in the yield stress.

However I fail to see the stress actually decrease when I run the simulation and often encounter convergence difficulties. Does anyone have an idea of where I am going wrong? If I have failed to mention something please let me know! This problem has been driving me nuts for a long time now!

Thanks!

 

[VzHache]

Hello,

Do you use the Newton-Raphson algorithm to solve your problem. Unless I'm wrong, I think this algorithm is suitable with a change of slope in the material behaviour.
You may have to use a continuation method like riks, Fried or Crisfield.

 

[v0gue3]

Hi VzHache,

Thank you for your reply. I was using the Newton-Raphson method previously. It seems that the Newton-Raphson method is unsuitable when there is a change in slope.

Of the continuation methods you mentioned, Rik's method seems the most promising. Seeing as I haven't used this method before, I am finding it a bit troubling that I cannot really control the loading magnitude. What I have seemed to notice is that the reduction in stress corresponds to a decrease in the loading factor (hence decrease in compressive displacement) and hence the behaviour is not true stress-softening behaviour or is it?

Thanks

 

[VzHache]

Hello,

I will not be very helpfull for your questions. What I user in the past was the risk's method to simulate the buckling and post-buckling behavior of a curve panel. In that case, the curve Load/displacement presented a change of slope (due to buckling) and the risk's method helped us to solve the calculation.