Johnson-Cook Parameters

proudbrown

Hello guys,

I would like to know how i can determine the johnson-cook parameters using my stress-strain curve?

Is there any formula or method?

Thanks

Pranav Hari

Hi irwinp

 

I think if you have a stress- strain  curve you can use MAT Law 36, which is similar to MAT Law 2( johnson-cook).  This law models an isotropic elasto-plastic material using user-defined functions for the work-hardening portion of the stress-strain curve (for example, plastic strain vs. stress) for different strain rates.

or

you can use the option IFLAG =1 in MAT Law 2(  johnson-cook) which will automatically extract all the parameters.

Check Radioss theory manual from online help also for MAT Law 2 and 36.

 

 

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Thanks

proudbrown

Hi Pranav,

 

Thank you for your reply.

I am using MAT LAW 36 but i want to consider crack/fractures on my analysis.

For that I will need the D1, D2 and D3 parameters.

Is there any way to calculate those parameters from the Stress-Strain curve?

 

thanks,

Irwinp

Altair Forum User

Hi,

You can simulate crack propagation with Law36 using extended finite element method (XFEM) in which you can select the enrichment zones and can provide the failure criteria. Please check the Help on /FAIL/XFEM. 

Another option is assigning damage property cards where user should have all the damage parameters (D1,D2,D3). These need to be experimentally found, and there is nothing to do with stress strain curve for these. Many open web resources are available for finding these parameters. Please check for the same.

Another easy method is to assign failure plastic strain directly in material card (EPS_Max). Elements reaching this failure strain value will be deleted from the model.

 

Best Regards,

.