Help Forums

Elastic and Plastic deformation gradients in AB Viscoplastic model  

Page 2 / 2

Jorgen
Posts: 3835
Moderator
(@jorgen)
Member
Joined: 2 months ago

At first sight, your code looks reasonable. Unfortunately it is very time consuming to carefully review code, and my schedule is too busy to spend hours reviewing the code. I'm happy to answer any questions, however 😀

-Jorgen

Reply
1 Reply
Melly
(@melly)
Joined: 1 month ago

Active Member
Posts: 19

@jorgen

I understand. Thank you. 

I have narrowed down the problem. Both the F and Fp turn out to be identity matrices leading to zero Hencky strains and zero Cauchy stresses. Eventually, the plastic deformation rate Dp and the time rate change of Fp(dot) including the plastic deformation gradient at t+dt turns out to be NaN

I am probably missing out on how to properly define the total deformation gradient at the beginning and  end of the increment. Also on the plastic deformation gradient at the beginning of the increment.

Importantly, how to define the beginning of plastic deformation? using the totalTime or stepTime

 

Many thanks, 

Melly

Reply
Jorgen
Posts: 3835
Moderator
(@jorgen)
Member
Joined: 2 months ago

I'm not quite sure I understand. The plastic deformation at the start of an increment needs to be obtained from the state variables. Similarly, you need to save the new plastic deformation at the end of an increment as the state variables.

-Jorgen

Reply
1 Reply
Melly
(@melly)
Joined: 1 month ago

Active Member
Posts: 19

@jorgen

Many thanks.

My code is now working perfectly. I made numerous mistakes in the previous code that I posted to you. For instance, I was saving the plastic flow stress instead of the Total(Cauchy) stress as the new stress at the end of the increment. 

Now, I will be comparing my simulation results with some published experimental work to check the accuracy of the code. 

Soon, I will be inquiring about the MCalibration software. 

I appreciate your guidance. 

Warm regards, 

Melly

 

Reply
Jorgen
Posts: 3835
Moderator
(@jorgen)
Member
Joined: 2 months ago

That is very impressive! 👍 

Writing a functioning user-material model is not easy.

-Jorgen

Reply
1 Reply
Melly
(@melly)
Joined: 1 month ago

Active Member
Posts: 19

@jorgen

Thank you for your compliment. 

All this is possible courtesy of your book and your answers to my questions. 

With thanks, 

Melly

Reply
Page 2 / 2
Share:

Please Login or Register