# Anisotropic plastic deformation

**URL:** <https://calculix.discourse.group/t/anisotropic-plastic-deformation/1648>\
**Category:** Uncategorized\
**Created:** [May 9, 2023, 2:05pm UTC](https://calculix.discourse.group/t/anisotropic-plastic-deformation/1648 "2023-05-09T14:05:58Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![thodec](https://avatars.discourse-cdn.com/v4/letter/t/9de0a6/32.png) [@thodec](https://calculix.discourse.group/u/thodec)\
**Post date:** [May 9, 2023, 2:05pm UTC](https://calculix.discourse.group/t/anisotropic-plastic-deformation/1648/1 "2023-05-09T14:05:58Z")

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Hello everyone,

I just started learning CalculiX and need help.  
I want to simulate the deformation of paper.  
Paper consists of fibers and is anisotropic. Is there any way to calculate plastic deformations of an anisotropic Material wird CalculiX?

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**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\
**Post date:** [May 9, 2023, 3:21pm UTC](https://calculix.discourse.group/t/anisotropic-plastic-deformation/1648/2 "2023-05-09T15:21:19Z")

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Unfortunately, there’s no anisotropic plasticity (Hill potential) in CalculiX, you would need UMAT subroutine for that. But layered composites with different ply orientations and anisotropic elasticity are supported. By the way, paper is considered to be auxetic.

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**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\
**Post date:** [May 10, 2023, 2:53pm UTC](https://calculix.discourse.group/t/anisotropic-plastic-deformation/1648/3 "2023-05-10T14:53:18Z")

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Also TFEL/Mfront is not deal to implemented, however an orthotropic plasticity is available [there](https://thelfer.github.io/tfel/web/orthotropiclinearhardeningplasticity.html).

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**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\
**Post date:** [November 16, 2024, 4:45am UTC](https://calculix.discourse.group/t/anisotropic-plastic-deformation/1648/4 "2024-11-16T04:45:27Z")

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only an update: latest version of CalculiX is capable of anisotropic plasticity material, but use Mises instead of Hill criterion.

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**Author:** ![rsmith](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/rsmith/32/1684_2.png) [@rsmith](https://calculix.discourse.group/u/rsmith)\
**Post date:** [November 16, 2024, 8:49pm UTC](https://calculix.discourse.group/t/anisotropic-plastic-deformation/1648/5 "2024-11-16T20:49:34Z")

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Most of my work is in fiber reinforced plastics, which have some similarity to paper in that both are fibrous materials bound by another material, the matrix.

I’m not sure about paper, but in general FRPs do not exhibit plastic deformation.

What I look for in the analysis is first whether the vectors of the worst principal stress align with the fibers.  
Second, I check that the worst principal strain does not exceed the failure strain of the fibers in question.

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<div class="post-metadata">

**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\
**Post date:** [November 16, 2024, 9:26pm UTC](https://calculix.discourse.group/t/anisotropic-plastic-deformation/1648/6 "2024-11-16T21:26:02Z")

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some test reported, behavior of paper materials share similarity with wood, it can exhibit plastic deformation.

 ![paper_material_elastic_plastic](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/6/6bb04ac495080c6bcdac689f958e3de505172206.png)

image from Yujun Li etal, 2016