# Define material with anisotropic yield surface in Calculix

**URL:** <https://calculix.discourse.group/t/define-material-with-anisotropic-yield-surface-in-calculix/371>\
**Category:** Uncategorized\
**Created:** [December 30, 2020, 1:14pm UTC](https://calculix.discourse.group/t/define-material-with-anisotropic-yield-surface-in-calculix/371 "2020-12-30T13:14:43Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![paffins](https://avatars.discourse-cdn.com/v4/letter/p/a88e57/32.png) [@paffins](https://calculix.discourse.group/u/paffins)\
**Post date:** [December 30, 2020, 1:14pm UTC](https://calculix.discourse.group/t/define-material-with-anisotropic-yield-surface-in-calculix/371/1 "2020-12-30T13:14:43Z")

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Ive performed a FE analysis on a microscale RVE and determined the elastoplastic behaviour with Hills yield criterium [1950]

I want to assign that material law in CalculiX for FE simulation on a macroscale level. From what Ive read so far a umat subroutine has to be defined in order to do that.

In Abaqus the Hill Yield is already implemented and can be used for that.

My question is if someone can give me a suggestion or hint if it is possible to define anisotropic plasticity without creating a umat subroutine?

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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:** [December 31, 2020, 12:38am UTC](https://calculix.discourse.group/t/define-material-with-anisotropic-yield-surface-in-calculix/371/2 "2020-12-31T00:38:52Z")

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hi @paffins

seems the material laws has much different load response (tensile, compression, transverse, shear) and some are limited/damage. may it look similar to glulam wood materials were i’m interested too.

i did not see any possibilities using CalculiX without user subroutine, also did not try using available ANISO\_PLAS materials unfortunately.

you could try to post the questions at TFEL/MFront forum which it can be integrated to the solver. it has richest libraries and hope you found there.

best,

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**Author:** ![paffins](https://avatars.discourse-cdn.com/v4/letter/p/a88e57/32.png) [@paffins](https://calculix.discourse.group/u/paffins)\
**Post date:** [January 4, 2021, 2:17pm UTC](https://calculix.discourse.group/t/define-material-with-anisotropic-yield-surface-in-calculix/371/3 "2021-01-04T14:17:07Z")

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hello @xyont happy new year and thank you very much for your response.

yes the material i am analysing is wood and iam trying to get it done with mfront. ANISO\_PLAS is only able to describe anisotropic behaviour in the elastic range. as far as i see the BARLAT yield criterion is available in TFEL. Have you used it already?

best regards