Learning Forum

[xhassanv]

I want to create a bilinear orthotropic model with different behaviour in tension and compression. is there any possibility to create this model? I know the Hill yield criterion has orthotropy plasticity ability but unfortunately, it doesn't differentiate between the tension and compression. I already used the APDL code but I want to know the better option, for example, are Granta, ACP(pre), or material designer have any abilities to create such a model?

[April Wang]

Hi.
To add anisotropic plasticity with bilinear hardening, you need to add a command object under geometry body.
Note that this law is only usable with some elements: PLANE42, SOLID45, SOLID92, SOLID95, LINK1, PLANE2, LINK8, PIPE20, BEAM23, BEAM24, SHELL43, SHELL51, PIPE60, SOLID62, SOLID65 PLANE82, SHELL91, SHELL93, and SHELL143

Here is an example of commands:

MP,EX,matid,200000000000, ! Pa, matid is the material id assigned to the body
MP,EY,matid,200000000000, ! Pa
MP,EZ,matid,200000000000, ! Pa

MP,PRXY,matid,0.3 MP,PRYZ,matid,0.3 MP,PRXZ,matid,0.3
MP,GXY,matid,76923076923.0769, ! Pa
MP,GYZ,matid,76923076923.0769, ! Pa
MP,GXZ,matid,76923076923.0769, ! Pa

TB,ANISO,matid
TBDATA,1,160000000,200000000,200000000,5100000000,4500000000,5300000000
!Tensile yield stresses in the material x, y, and z directions following by tangent moduli
TBDATA,7,160000000,200000000,200000000,5100000000,4500000000,5300000000 ! Compressive "" ""
TBDATA,13,160000000,200000000,200000000,5100000000,4500000000,5300000000 !Shear "" ""

et,matid,95 ! set element type to be solid95

You can find introduction of command TB, ANISO from ANSYS Help

[April Wang]

The above command allows different tensile and compression behavior, but the plasticity behavior is the same for the three orthotropicdirections.

[Sean Harvey]

Regarding the other tools. Granta, ACP. First Granta has material data, but in the end, it still has to write out a material model that Ansys can utilize. I have not seen any material with such behavior. Regarding ACP, it is just a pre/post tool and not a solver so it too won't have any material model. Material Designer is a pre/post to MAPDL as it runs RVE simulations in the background to compute material properties using homogenization. It does have a non-linear capability in beta, which can export stress-strain curves. This would be a micro-mechanical model representation, so if I put in plasticity or even damage, then the RVE model will use it, but note that convergence could be a problem especially when damage is included.. So in the end you may result in some stress-strain curves that you could potentially apply at the macro level via the material models such as Hill or ANISO or others. You can not take the curves and use them directly. We can for response function in hyperelasticity, but that is a digression. I just wanted to point this out. What are the materials if you can elaborate. Thank you.
Sean