Learning Forum

[Jimmy_Yang_NCKU]

Hello all,

I want to define a plasticity model with different yield stress in tension and compression, and I refer the example from 1.1. Generalized Hill.

! Define generalized Hill model
/prep7

! Define elastic material properties
mp,ex,1,210
mp,nuxy,1,0.3

! Define anisotropic material properties 
tb,aniso,1         
tbdata,1,0.33,0.33,0.495         ! Tensile yield stress (x,y & z)
tbdata,4,0.21,0.21,0.315         ! Tangent moduli (tensile)
tbdata,7,0.33,0.33,0.495         ! Compressive yield stress (x,y & z)
tbdata,10,0.21,0.21,0.315        ! Tangent moduli (compressive)
tbdata,13,0.1905,0.1905,0.1905   ! Shear yield stress (xy,yz,xz)
tbdata,16,0.105,0.07,0.07        ! Tangent moduli (shear)

I got error, when I defined the yield stress in different value.

I want to know how to solve this error, or have better way to solve my problem.

Thanks for your answer.

Best regards,

Jimmy

[John Doyle]

You did not mention what the error message was. Is it a reference to yield stresses that do not satisfy the consistency equation requirements?
Two problems commonly arise in the definition of ANISO:
The yield surface must always represent a closed yield surface throughout loading.Otherwise, the yield surface would not make physical sense (elastic domain would not be definable).


The consistency equation must always be satisfied.This is a requirement of plastic incompressibility ÔÇô recall that plastic strains are incompressible and do not contribute to volumetric change.


This means that the anisotropic yield stresses and slopes are not independent.You must ensure the above criteria, otherwise a warning/error message will be printed in ANSYS