Modeling Kinematic hardening model for steel in Cyclic analysis

[Wonder_Women]

Hi

I am modelling a steel tube filled with concrete under cyclic loading. For concrete, I am using the Concrete damage plasticity model with damage parameters. and for steel, I am using the Kinematic hardening (KH) model. But with the KH model, I am getting weird results, which I cannot figure out how to resolve. To check whether FE model is right or not. I have used Isotropic Harding, and it worked (I have attached a hysteretic graph for the same). But when I used Kinematic hardening my hysteresis graph is weird (watched the graph). I am also attaching material properties as well as cyclic loading for your reference.

Can anyone help me understand why my displacement in the hysteresis curve with the KH model differs from what I defined? Both hysteresis curves are for the same cyclic loading (excel sheet attached).

loading protocol??

 

[FEA way]

Do you mean those irregularities (since the overall shape is similar) ? To account for the Bauschinger effect you need at least linear kinematic hardening but for fully realistic results under cyclic loading, you may want to use nonlinear combined hardening if you can provide sufficient input data. Check the documentation chapter "Models for Metals Subjected to Cyclic Loading" for more details.

 

[Wonder_Women]

I read the documentation.. So for the first equation constant can be automatically calculated in abaqus. (under half cyclic I will be defining my stress strain I got from uniaxial coupon test).

But for the second equation isotro[ic hardening.. How i will get Q infinity and b values?? That i am not able to understand.
I am attaching graph from my experiments that I am trying to simulate. How to define steel material properties? If you could guide a bit it will be huge help.

 

[FEA way]

Those constants need to be calibrated from test data. But it's also possible to define this type of hardening by specifying the equivalent stress-strain test data directly. According to the documentation, the easiest way is to perform a symmetric strain-controlled cyclic experiment with a proper strain range.