Stress-strain curve field definition

[Rubendv]

Hello!
I am currently working on a material non-linear analysis and it would be so helpful to have your tips.
My doubts come while defining the stress-strain curve by using a material property field.
As far as I know, the steps should be the following:

1- Define material property field, tabular input of stress vs strain curve:
How should I define the first row of the table? I guess it should be strain=0 and stress=yield stress, but I don't really understand why strain=0. Acc to my understanding it should be the elastic strain when reaching the yield stress. Could someone explain this? Then, for the next rows, if I started with strain=0, what strain values should I introduce in the table?

2- Define Linear Elastic constitutive model:
This is clear, Young modulus and Yield stress must be defined.

3- Define Elastoplastic constitutive model:
Define plastic behaviour by using the previously defined field.

Please find attached the stress-strain curve I am using. You may use it to explain what values should be defined in the material property field.

Thanks a lot in advance!

 

[JBlack68]

1. total strain = elastic + plastic
the young's modulus give you the elastic strain (ee) at yield Y = Eee --> Y/E = ee
There is no plastic strain until the yield (stress) is reached

 

[Wazy01]

Hi Rubendv,

There are different model for non-linearity and they defined in different ways in different software

Based on your questions, it seem you are adopting plasticity model which is common to be used for metal
in this case the input for stress=strain data will be (stress vs plastic strain)
and the first point should be (0,Sy) which is the zero plastic strain at the yield stress.

so it is a cut of the plasticity part from the general stress-strain you have from the tensile test

The software automatically calculate the elastic strain from E,Sy ...and need the second plasticity part mentioned above to do incremental analysis
You have to check if the input of your values are Engineering or True values ..based on the software manual
for example Nx Nastran asking to input Engineering stress-strain
Hope this help
Regards

 

[Wazy01]

I just saw your attachmed file
I will not add new thing except that this curve seems did not produced correctly
You may move the (0,0) to the top point of the first small line (at stress of 25Mpa. so you will get one straight and one polynomial lines
Then start the procedure as described above