Checking stress value in LS-DYNA user-defined material (UMAT) by hsv?

- July 13, 2023 at 8:47 pm
  
  Tuan Nguyen
  Subscriber
  
  Hello everyone, I am using UMAT in LS-DYNA for my simulation. I have a curiosity that why the value of stresses that I have computed in umat subroutine does not give me the exactly value in the fringe of stress output. I tried to use history variable to compare, but the value of results is quite different. Anyone have the experience in that issue? Please, see the attached picture below.
- July 14, 2023 at 6:22 pm
  
  Andreas Koutras
  Ansys Employee
  
  Hello,
  Have you set NHV = 4 on the *MAT_USER_DEFINED_MATERIAL_MODELS card?
  You can include a write statement in the subroutine to print the sig and hsv values in an ascii file and compare them directly.
  - July 14, 2023 at 6:37 pm
    
    Tuan Nguyen
    Subscriber
    
    Thanks for your answer. I have set NHV =4 on the *MAT_USER_DEFINED_MATTERIAL_MODELS card and also set on EXTEND_BINARY card but the value also different. The values I write in ASCII are also differrent. I can share my model and my subroutine in UMAT since I got stuck with that problem and it is quite wierd.