How can define material in Abaqus

[gatre]

Hi friends

I am newcomer in abaqus, I spent 2 weeks to read documentation but I can not image how can I define a material model like Newton-Hoff or Swiff. Abaqus is so differrent with other fem sofware about defining material model. For Plastic behaviour, it only show a table with Yield stress and strain. Anybody can tell me a basic way to define a material model like Newton-Hoff or Swiff with constitutive law
Newton-Hoff model sigma = K.epsilon^n . epsilon_dot^m . exp(beta\T)
Swiff model: sigma = a(esilon_0 + epsilon)^n

I am greatly appreciate any suggestions.
Regards
Gatre

 

[barney75]

Hi Gatre,
I'm not very used with CAE so my advice, even if it may seem rough, is to make the CAE to write the input file. Edit the .inp file and find the rows where the material specs. are written and then just use the option to give the material charcteristic s-e curve through a text input file that u have already compiled with each sigma epsilon (plastic-true) point u want in accordance to your law.

I hope this can help u

Regards
Barney

 

[gatre]

Thanks for your explainations. So I only need to input directly the values which took from tensile test. Is this true. We dont need to fit the constitutive equation?
Please explain me, it would be nice if you show me an example of Swift model in input file format (if you dont you CAE)
Thanks in advance
Regards

 

[vumat721]

The only way to specify an equation is to write a user material subroutime (VUMAT or UMAT). Other than that, you have two choices:

1) Input your Mises yield data using the *Plastic option. This is a table of: true stress, true plastic strain
For perfect plasticity, you would enter:
100, 0.0
(where 100 is your yield stress)
for hardening, you enter additional rows.

or

2) Try using Johnson-Cook in place of your equation 1. See Section 19.2.7 of the Abauqus 6.8 Analysis User Manual