# Metafor

ULiege - Aerospace & Mechanical Engineering

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commit:2016:10_09

# Commit 2016-10-09

## Lode parameter

Introduction of the Lode parameter ($\overline{\theta}$) as a new field available at Gauss points, which has been denoted as IF_LODE_PARAMETER. This variable is defined as: $$\overline{\theta} = 1 - \frac{6\theta}{\pi} = 1 - \frac{2}{\pi}\arccos{\left( \frac{J_3}{\overline{\sigma}} \right)^3}$$ where $\theta$ is the Lode angle, $J_3$ is the third invariant of the deviatoric stress tensor and $\overline{\sigma}$ is the equivalent stress. The range of values of the Lode angle ($\theta$) is $[0,\pi /3]$. The Lode paramater ($\overline{\theta}$), which values always lie in the interval $[-1,1]$, is a normalized version of the Lode angle ($\theta$). This stress state variable will permit the definition of more advanced fracture criteria and damage models.

The respective documentation page has been updated: Doc Fields at Gauss Points.

## Rupture Criterion Field

• The IF_RUPT_CRIT field has been added to the ElastHypoMaterial, EvpIsoHHypoMaterial and EvpMixtHHypoMaterial materials in order to transfer them when the ALE or remeshing methods are used.
Do not forget to ignore this field if you are not considering fracture in your test.
For ALE: region.ignore(IF_RUPT_CRIT)
For Remeshing: cell.addFieldToIgnore(IF_RUPT_CRIT)

## LemaitreChabocheContinuousDamage

• Introduction of a new constant threshold value for damage accumulation. The parameter is called LEMAITRE_TRIAX_THRESHOLD and its depends solely on the stress triaxiality ratio ($\eta = p/\overline{\sigma}$).
It is now mandatory to include this parameter when using the isotropic version of the Lemaitre-Chaboche continuous damage model.
• Accordingly to the previous point, the toolbox/createMaterialLaw.py file has been modified in order to include the LEMAITRE_TRIAX_THRESHOLD parameter.
• Minor corrections of the inequalities defining damage accumulation thresholds. According to [Lemaitre 1987], damage develops when $\overline{\varepsilon}^p {\color{red}{>}} \overline{\varepsilon}^p_0$ instead of $\overline{\varepsilon}^p {\color{red}{\ge}} \overline{\varepsilon}^p_0$ (former version), where $\overline{\varepsilon}^p_0$ is the threshold value which depends on the equivalent plastic strain. The same condition is considered for the new threshold parameter.
• The respective documentation page has been updated: Doc Continuous Damage.

## ContinuousDamageEvpIsoHHypoMaterial

• Introduction of the Micro-Crack Closure Effect (MCCE) by means of the DAMAGE_MCCE parameter. This new parameter makes the distinction of the weakening effect of damage under compressive ($\eta<0$) and tensile ($\eta\ge 0$) stress states. In this first attempt, the distinction between stress states depends solely on the stress triaxiality ratio. It is no mandatory to include this parameter when using the ContinuousDamageEvpIsoHHypoMaterial and it takes a default value equal to $1.0$ (no MCCE).
• The respective documentation page has been updated: Doc Traditional Materials.

## Fracture criteria

• BaiRuptureCriterion: Fracture criterion that takes into account $\eta$ and $\overline{\theta}$ into its formulation.
• LouRuptureCriterion: Fracture criterion that takes into account $\eta$ and $\overline{\theta}$ into its formulation. Specially developed for shear-dominated fracture.
• OneParameterRuptureCriterion: Family of simple fracture criteria i.e., Cockroft and Latham, Brozzo, Ayada and Rice and Tracey models.
• The respective documentation page has been updated (including a Reference section with external links to relevant papers): Doc Failure Criteria.

## Tests mtParasolid

• A new repository (mtParasolid/tests/numisheet) has been created to include recently developed Numisheet benchmark tests. Two tests have been included by the moment: Square Cup Deep-drawing (Numisheet1993) and Cross-shaped Cup Deep-drawing (Numisheet2011).

## Test Blanking

• The tests that I used to simulate the sheet metal blanking process has been included in apps.remeshing2.baseTests and apps.remeshing2.fullAuto. The information related to the geometry and material parameters can be found in our publication: Article.

## Fichiers ajoutés/supprimés

[a]: mtElements\rupture\BaiRuptureCriterion.cpp
[a]: mtElements\rupture\BaiRuptureCriterion.h
[a]: mtElements\rupture\LouRuptureCriterion.cpp
[a]: mtElements\rupture\LouRuptureCriterion.h
[a]: mtElements\rupture\OneParameterRuptureCriterion.cpp
[a]: mtElements\rupture\OneParameterRuptureCriterion.h
[r]:

## Cas tests ajoutés/supprimés

[a]: apps\monosMaterials2\EvpIsoDamageLemaitreTriax.py
[a]: apps\monosMaterials2\EvpIsoDamageLemaitreTriaxMCCE.py
[a]: apps\remeshing2\baseTests\blanking.py
[a]: apps\remeshing2\fullAuto\blankingS01.py
[a]: apps\rupture\ruptureCont2AllLemaitre.py
[a]: apps\rupture\ruptureCont2AllLemaitreTriax.py
[a]: apps\rupture\ruptureCont2AllLemaitreTriaxMCCE.py
[a]: mtParasolid\tests\numisheet\numisheet1993BM1.py
[a]: mtParasolid\tests\numisheet\numisheet1993BM1_blankholder.xmt_txt
[a]: mtParasolid\tests\numisheet\numisheet1993BM1_die.xmt_txt
[a]: mtParasolid\tests\numisheet\numisheet1993BM1_punch.xmt_txt
[a]: mtParasolid\tests\numisheet\numisheet2011BM2.py
[a]: mtParasolid\tests\numisheet\numisheet2011BM2_blankholder.xmt_txt
[a]: mtParasolid\tests\numisheet\numisheet2011BM2_die.xmt_txt
[r]: