QUESTION:
I get the error shown below when I use the ANISO material model. My tensile yield in the x, y, and z directions is 102,000 psi and my compressive yield in all 3 directions is 72,000 psi. Satisfaction of the consistency equation only appears to allow for very small differences between tensile and compressive yield strength. For instance, a difference of 15 psi would satisfy it, but that small difference would be useless to me, and to most others for that matter.
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*** ERROR *** CP= 2.125 TIME= 18:02:13
TheTB,ANISO table for material 1 has anisotropic yield stresses that do not satisfy the consistency equation requirement. Consistency equation equals 1.058823529E05 which must be less that 1.883239171E09. Improve the accuracy of the input yield stresses.
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Are there any other material models that can handle real differences between the tensile and compressive response for materials with a history of cold rolling?
ANSWER:
Unless one is willing to accept the different value of yield stress in one of the directions, the consistent condition will never be met.
If both the elastic and plastic responses of the material are completely isotropic, and the only is difference is yield stress in tension and compression, then use the cast iron option to mimic the behavior by using
TB,CAST,1
tbdata,1,0.5
TB,uniaxil,1,,,TENSION
tbpt,,,,
TB,uniaxil,1,,,COMPRESSION
tbpt,,,,
ADDITIONAL DETAILS:
The option of using tb,cast option was suggested as the properties of this material are very close to isotropic in both elasticity and plasticity. The only special thing here is that they have difference yield stress and tension and compression. It is actually not really an orthotropic material, which is why it was suggested to use the cast option with plastic Poisson's to 0.5. This will ignore the Ra
QUESTION: I get the error shown below when I use the ANISO material model. My tensile yield in the x, y, and z directions is 102,000 psi and my compressive yield in all 3 directions is 72,000 psi. Satisfaction of the consistency equation only appears to allow for very small differences between tensile and compressive yield strength. For instance, a difference of 15 psi would satisfy it, but that small difference would be useless to me, and to most others for that matter. ***************************** *** ERROR *** CP= 2.125 TIME= 18:02:13 TheTB,ANISO table for material 1 has anisotropic yield stresses that do not satisfy the consistency equation requirement. Consistency equation equals 1.058823529E05 which must be less that 1.883239171E09. Improve the accuracy of the input yield stresses. ***************************** Are there any other material models that can handle real differences between the tensile and compressive response for materials with a history of cold rolling? ANSWER: Unless one is willing to accept the different value of yield stress in one of the directions, the consistent condition will never be met. If both the elastic and plastic responses of the material are completely isotropic, and the only is difference is yield stress in tension and compression, then use the cast iron option to mimic the behavior by using TB,CAST,1 tbdata,1,0.5 TB,uniaxil,1,,,TENSION tbpt,,,, TB,uniaxil,1,,,COMPRESSION tbpt,,,, ADDITIONAL DETAILS: The option of using tb,cast option was suggested as the properties of this material are very close to isotropic in both elasticity and plasticity. The only special thing here is that they have difference yield stress and tension and compression. It is actually not really an orthotropic material, which is why it was suggested to use the cast option with plastic Poisson's to 0.5. This will ignore the Rankin yield surface assumption in cast iron and is a purely VonMises yield surface in tension and compression. The cast iron option allows different tension and compression behavior, and it is what we want here. The cast iron option in ANSYS 8.0 does not work for this, as we have completely reimplement the cast iron model in 8.1 and dropped support for plane stress, shell and beam. So if a user has an isotropic material but with different yields in tension and compression, they should use TB,CAST with Poisson=0.5. 

