Mfront pk2 stress

dolfinx_materials/mfront.py

@@ -52,6 +52,7 @@ def __init__(
         parameters={},
         rotation_matrix=None,
         dt=0,
+        finite_strain_options=None,
     ):
         """
         Parameters
@@ -74,6 +75,13 @@ def __init__(
             a 3D rotation matrix expressing the rotation from the global
             frame to the material frame. The matrix can be spatially variable
             (either UFL matrix or function of Tensor type)
+        finite_strain_options: dict
+            A dictionary with {"stress": "PK1" | "PK2", "tangent": "DPK1_DF" | "DS_DEGL"}
+            specifying if we should work with 1st (PK1) or 2nd (PK2) Piola-Kirchhoff stress.
+            Attention: the tangent operator choice should match the corresponding stress choice,
+            if one wants to use automatic differentiation. Otherwise, wrong derivatives will be
+            calculated.
+            Default choice is PK1/F.
         """
         self.path = str(path)  # ensure string in case we use a PosixPath from pathlib
         self.name = name
@@ -84,6 +92,10 @@ def __init__(
         self.integration_type = (
             mgis_bv.IntegrationType.IntegrationWithConsistentTangentOperator
         )
+        if finite_strain_options is None:
+            self.finite_strain_options = {"stress": "PK1", "tangent": "DPK1_DF"}
+        else:
+            self.finite_strain_options = finite_strain_options
         self.dt = dt
         # Loading the behaviour
         self.load_behaviour(self.path)
@@ -95,9 +107,13 @@ def load_behaviour(self, path):
         if self.is_finite_strain:
             # finite strain options
             bopts = mgis_bv.FiniteStrainBehaviourOptions()
-            bopts.stress_measure = mgis_bv.FiniteStrainBehaviourOptionsStressMeasure.PK1
-            bopts.tangent_operator = (
-                mgis_bv.FiniteStrainBehaviourOptionsTangentOperator.DPK1_DF
+            bopts.stress_measure = getattr(
+                mgis_bv.FiniteStrainBehaviourOptionsStressMeasure,
+                self.finite_strain_options["stress"],
+            )
+            bopts.tangent_operator = getattr(
+                mgis_bv.FiniteStrainBehaviourOptionsTangentOperator,
+                self.finite_strain_options["tangent"],
             )
             self.behaviour = mgis_bv.load(bopts, path, self.name, self.hypothesis)
         else:

tests/mfront/LogarithmicStrainPlasticity.mfront

@@ -0,0 +1,27 @@
+@DSL Implicit;
+
+@Behaviour LogarithmicStrainPlasticity;
+@Author Thomas Helfer/Jérémy Bleyer;
+@Date 07 / 04 / 2020;
+
+@StrainMeasure Hencky;
+
+@Algorithm NewtonRaphson;
+@Epsilon 1.e-14;
+@Theta 1;
+
+@MaterialProperty stress s0;
+s0.setGlossaryName("YieldStress");
+@MaterialProperty stress H0;
+H0.setEntryName("HardeningSlope");
+
+@Brick StandardElastoViscoPlasticity{
+  stress_potential : "Hooke" {
+	young_modulus : 210e9,
+        poisson_ratio : 0.3
+        },
+  inelastic_flow : "Plastic" {
+    criterion : "Mises",
+    isotropic_hardening : "Linear" {H : "H0", R0 : "s0"}
+  }
+};

tests/mfront/test_finite_strain.py

@@ -0,0 +1,37 @@
+import pathlib
+import numpy as np
+import sys
+import pytest
+import ufl
+from dolfinx_materials.mfront import MFrontMaterial
+
+path = pathlib.Path(__file__).parent.absolute()
+
+sys.path.append(str(path.parent.absolute()))
+
+
+def test_mfront_finite_strain_options():
+    material = MFrontMaterial(
+        path / "src/libBehaviour.so",
+        "LogarithmicStrainPlasticity",
+    )
+    assert material.behaviour.getBehaviourType() == "StandardFiniteStrainBehaviour"
+    assert material.behaviour.getKinematic() == "F_CAUCHY"
+    assert material.gradient_names == ["DeformationGradient"]
+    assert material.flux_names == ["FirstPiolaKirchhoffStress"]
+    assert material.tangent_block_names == [
+        ("FirstPiolaKirchhoffStress", "DeformationGradient")
+    ]
+
+    material = MFrontMaterial(
+        path / "src/libBehaviour.so",
+        "LogarithmicStrainPlasticity",
+        finite_strain_options={"stress": "PK2", "tangent": "DS_DEGL"},
+    )
+    assert material.behaviour.getBehaviourType() == "StandardFiniteStrainBehaviour"
+    assert material.behaviour.getKinematic() == "F_CAUCHY"
+    assert material.gradient_names == ["DeformationGradient"]
+    assert material.flux_names == ["SecondPiolaKirchhoffStress"]
+    assert material.tangent_block_names == [
+        ("SecondPiolaKirchhoffStress", "GreenLagrangeStrain")
+    ]