MLAW2 Plas Johns

Nancy Jewel Mcdonie

Hi all experts, 

I use material Law2 plas johns for my simulation, there are 2 ways to input parameters: Iflag = 0 or Iflag = 1.

with Iflag = 1, johnson cook parameters, b and n are calculated by radioss: 

My question is: If Iflag = 0, a, b,n are defined, so can i use above formula to calculate UTS ?

Polyvios Romanidis

Hi Nancy,

The 2 different Iflag formulations are used in order to help the user set up his model faster. 

If the user knows the σy, σu and εUTS, the Iflag = 1 formulation should be used.  In the other hand if the Johnson Cook model parameters a, b and n are known, the Iflag = 0 formulation should be used.

You can use the equations you have shared to calculate a, b and n from σy, σu and εUTS and vice versa.  If you use these equations and try to set up the material with the other Iflag formulation, the 2 material laws will be identical.

To sum up, if you have the a, b and n parameters known for your material, then you can solve the above equations to find the σu (UTS), σy and εUTS for your material model.

Thanks in advance for your time!

Polyvios