1 (edited by SaeidM 22-12-2021 07:48:40)

Topic: For lattice models is there any implimented method for Poisson effect?

Hi,

I was wondering if there have been any implementations for any of the lattice models that restores the Poisson's ratio of the materials or if anyone is interested in discussing this topic.

Thanks

Re: For lattice models is there any implimented method for Poisson effect?

To my knowledge, there is no method implemented yet. We use the lattice models mainly for concrete for which the range of Poisson's ratio predicted by the models was OK.
Many years ago, we worked on it for 2D lattice approaches.
http://petergrassl.com/tempFiles/grabazcus06.pdf
However, this is not implemented in OOFEM right now.

3 (edited by SaeidM 01-04-2022 04:29:44)

Re: For lattice models is there any implimented method for Poisson effect?

Dear Peter, thanks for the valuable information on your method. I wish I knew about this approach earlier!

Eventhough as you mention, the range of Poisson's ratio in some lattice models can be close to concrete-like material when using a lattice network, the following concerns remain:

1. Inaccurate internal stresses in the body due to the nature of the lattice network and the inability to incorporate Hooke's law. For example horizontal struts fall in tension in a vertically applied uniaxial compression.
https://ars.els-cdn.com/content/image/1-s2.0-S0266352X15001627-gr1.sml
figure adapted from Asahina et al. (2015)

It is shown that it can be fixed by some methods incorporating the Poisson effect (Asahina et al. (2015))

2. When it comes to mesoscopic modeling of the bodies with different PR values, such as steel, aggregates with different PR than the matrix or rubber inside the concrete, etc. (most lattice models can't be combined with FEM element like your approach does)

3. Some methods that fix the PR issue in lattice-like models have other side effects.

May I know if your method of coupled CST and Truss elements can fix the issue 1 above?

Re: For lattice models is there any implimented method for Poisson effect?

Yes, but you need to do something with the bulk element when damage starts in the lattice element.
We only tested the 2D case in the elastic regime.