Learning Forum

[MFN]

Hi

I'm trying to do an analysis of timber in workbench.

I would like use a material model as shown below. However this is not possible to do in a Static Structural model as it does not account for the strain limits.

When I try to run it in Explicit Dynamics instead I get a problem because Hill yield criterion is not supported.

Do I have any other options?

[Erik Kostson]

Hi

Hill yield criteria is for mapdl, and can not thus be used with Explicit dynamics that uses the autodyn Explicit solver (autodyn does not have a Hill Yield Criterion).

As mentioned in previous post, I would recommend the mat_143 (*MAT_WOOD) model in ls dyna for modelling timber/wood. See the LS-DYNA_Keywords_Manual_Volume_volume_II, for more info on that. This model includes the softening you tried to illustrate in your last image (first original post), and is introduced via the material damage model that is included in this material model.


Thank you

Erik

[WolfgangNeil]

A quick question about your model.
As wood is an orthotropic material, which direction have you considered for defining the yield strength for the bilinear isotropic hardening model? And the reason?

[MFN]

The orthotropic strengths are very important in my model. Therefore I have used a static structural model where it is possible to define Hill yield criterion. This allows me to specify orthogonal strength parameters. However it is not possible to specify different strengths for compression and tension.
My main reason for trying an explicit model was to include strain limits. I have chosen to omit this from my model as it was more important to include the Hill criterion.

[WolfgangNeil]

@MFN
I agree with your physics of your model.
As yield strength can be defined for each principal directions, I'm interested in knowing which yield strength (2.1*e7 Pa) have entered while defining bilinear isotropic hardening and the reason why you have choose that value?
Regards

[MFN]

2.1e7 Pa corresponds to the compressive strength in the axial direction (parallel to grain) of my material.
In Hill criterion I have set the yield stress ratio in x-direction to 1. I have then inserted local coordinate systems in my model to align the x-direction with my grain direction.

[WolfgangNeil]

Thank you for the clarification!
Regards

[Mas Rosli]

Hi,

I also want to model 3D solid timber and cross-laminated timber using ANSYS with Hashin failure criteria. However, there few things that I'm not sure. I hope anyone can help me with this.

1) Which package I need to use to model timber with Hashin failure? ACP, AUTODYN or LS DYNA? I'm confused because I know ACP is for composite material, hence I can use to model laminated timber, AUTODYN has hashin failure criteria and LS DYNA has wood material model. But I'm still not sure which one to use.

2) Since I'm new user of ANSYS, can someone share me a guide/paper/video on how to model timber using ansys with hashin failure? I dont know which/what parameter to input in the software in order to get the failure that I want.

Thank you. Best regards