[MatL] Solids; Extract elasticTangentStiffness().

Same function is used in Ehlers and in the LinearElasticIsotropic.

MaterialLib/SolidModels/Ehlers.cpp

@@ -9,9 +9,10 @@
 
 #include "Ehlers.h"
 #include <boost/math/special_functions/pow.hpp>
-
 #include "MathLib/LinAlg/Eigen/EigenMapTools.h"
 
+#include "LinearElasticIsotropic.h"
+
 /**
  * Common convenitions for naming:
  * x_D              - deviatoric part of tensor x
@@ -53,19 +54,6 @@ template <int DisplacementDim>
 MathLib::KelvinVector::KelvinMatrixType<DisplacementDim> sOdotS(
     MathLib::KelvinVector::KelvinVectorType<DisplacementDim> const& v);
 
-template <int DisplacementDim>
-MathLib::KelvinVector::KelvinMatrixType<DisplacementDim>
-elasticTangentStiffness(double const K, double const G)
-{
-    using KelvinMatrix =
-        MathLib::KelvinVector::KelvinMatrixType<DisplacementDim>;
-
-    KelvinMatrix tangentStiffness = KelvinMatrix::Zero();
-    tangentStiffness.template topLeftCorner<3, 3>().setConstant(K - 2. / 3 * G);
-    tangentStiffness.noalias() += 2 * G * KelvinMatrix::Identity();
-    return tangentStiffness;
-}
-
 template <int DisplacementDim>
 struct PhysicalStressWithInvariants final
 {
@@ -527,7 +515,8 @@ SolidEhlers<DisplacementDim>::integrateStress(
              calculateIsotropicHardening(mp.kappa, mp.hardening_coefficient,
                                          state.eps_p.eff)) < 0))
     {
-        tangentStiffness = elasticTangentStiffness<DisplacementDim>(mp.K, mp.G);
+        tangentStiffness = elasticTangentStiffness<DisplacementDim>(
+            mp.K - 2. / 3 * mp.G, mp.G);
     }
     else
     {

MaterialLib/SolidModels/LinearElasticIsotropic.cpp

@@ -47,12 +47,8 @@ LinearElasticIsotropic<DisplacementDim>::getElasticTensor(
     double const t, ProcessLib::SpatialPosition const& x,
     double const /*T*/) const
 {
-    KelvinMatrix C = KelvinMatrix::Zero();
-
-    C.template topLeftCorner<3, 3>().setConstant(_mp.lambda(t, x));
-    C.noalias() += 2 * _mp.mu(t, x) * KelvinMatrix::Identity();
-
-    return C;
+    return elasticTangentStiffness<DisplacementDim>(_mp.lambda(t, x),
+                                                    _mp.mu(t, x));
 }
 
 template class LinearElasticIsotropic<2>;

MaterialLib/SolidModels/LinearElasticIsotropic.h

@@ -133,5 +133,20 @@ protected:
 extern template class LinearElasticIsotropic<2>;
 extern template class LinearElasticIsotropic<3>;
 
+template <int DisplacementDim>
+MathLib::KelvinVector::KelvinMatrixType<DisplacementDim>
+elasticTangentStiffness(double const first_lame_parameter,
+                        double const shear_modulus)
+{
+    using KelvinMatrix =
+        MathLib::KelvinVector::KelvinMatrixType<DisplacementDim>;
+
+    KelvinMatrix tangentStiffness = KelvinMatrix::Zero();
+    tangentStiffness.template topLeftCorner<3, 3>().setConstant(
+        first_lame_parameter);
+    tangentStiffness.noalias() += 2 * shear_modulus * KelvinMatrix::Identity();
+    return tangentStiffness;
+}
+
 }  // namespace Solids
 }  // namespace MaterialLib