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2 Questions about VUHARD and VUMAT

I am trying to implement an analytic formulae of dynamic flow stress in material plasticity in abaqus. The model is similar to FlowStress=K*(PlasticStrain^n)*(StrainRate^m). 

Could you provide help for these 2 questions?

1: Is it OK to define Young's modulus (E) and v in "Elastic" and choose "User" in "Plastic-->Hardening" with the subroutine "VUHARD", instead of by "VUMAT" with plasticity criterion and calculation of delta stress and strain?

2: Is it a must to define dyieldDeqps(nblock,2) (i.e.  the derivative of the yield stress with respect to the equivalent plastic strain and strain rate at the material points) in VUHARD? And how? Could we define dyieldDeqps(nblock,1)=K*n*(PlasticStrain^(n-1))*(StrainRate^m) and dyieldDeqps(nblock,2)=K*m*(PlasticStrain^n)*(StrainRate^(m-1))?

Thank you very much for your help!

Comments

shahram's picture

hey Stanley

 

I wonder if you get any answer for your question? bevause I have the same problem with vuhard :(. if you have got any progress writing this sub please let me know.

 

Thank you 

Hey Shahram,

 

I am having the same problem. Can you please let me know if you have figured out it yet.

 

Thanks.

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