diff --git a/MaterialLib/SolidModels/MFront/CMakeLists.txt b/MaterialLib/SolidModels/MFront/CMakeLists.txt
index 6facf3fc1416de3699a491ec8643f4b289a04838..d1e05c8f8508c73c071093d522d72bbb93b1f942 100644
--- a/MaterialLib/SolidModels/MFront/CMakeLists.txt
+++ b/MaterialLib/SolidModels/MFront/CMakeLists.txt
@@ -18,7 +18,9 @@ mfront_behaviours_check_library(OgsMFrontBehaviour
MohrCoulombAbboSloan
MohrCoulombAbboSloanOrtho
StandardElasticityBrick
- StandardElasticityBrickOrtho)
+ StandardElasticityBrickOrtho
+ Lubby2
+ Lubby2mod)
target_include_directories(MaterialLib_SolidModels_MFront
PUBLIC ThirdParty/MGIS/include)
diff --git a/MaterialLib/SolidModels/MFront/Lubby2.mfront b/MaterialLib/SolidModels/MFront/Lubby2.mfront
new file mode 100644
index 0000000000000000000000000000000000000000..a3d0048369d1d8d265e3086d1a41ae4ef0f86058
--- /dev/null
+++ b/MaterialLib/SolidModels/MFront/Lubby2.mfront
@@ -0,0 +1,99 @@
+
+@DSL Implicit;
+@Behaviour Lubby2;
+@Author Thomas Nagel, Tengfei Deng;
+@Description
+{Lubby2 model for stationary
+and transient creep based on Burgers
+rheological model
+};
+
+@Algorithm NewtonRaphson;
+@MaximumNumberOfIterations 100;
+
+@Brick StandardElasticity;
+
+@Epsilon 1.e-14;
+@Theta 1.0;
+@Parameter local_zero_tolerance = 1.e-14;
+
+@ModellingHypotheses{".+"};
+
+// Intercept of yield function
+@MaterialProperty real GK0;
+GK0.setEntryName("KelvinShearModulus");
+@MaterialProperty real etaK0;
+etaK0.setEntryName("KelvinViscosity");
+@MaterialProperty real etaM0;
+etaM0.setEntryName("MaxwellViscosity");
+@MaterialProperty real mK;
+mK.setEntryName("KelvinElasticParameter");
+@MaterialProperty real mvK;
+mvK.setEntryName("KelvinViscoParameter");
+@MaterialProperty real mvM;
+mvM.setEntryName("MaxwellViscoParameter");
+
+@StateVariable Stensor epsK;
+epsK.setEntryName("KelvinStrain");
+
+@StateVariable Stensor epsM;
+epsM.setEntryName("MaxwellStrain");
+
+//! Second Lamé coefficient
+@LocalVariable stress mu;
+
+@InitLocalVariables
+{
+ mu = computeMu(young, nu);
+ // Compute initial elastic strain
+ eel = 1. / (2. * mu) * sig - nu / young * trace(sig) * Stensor::Id();
+}
+
+@Integrator
+{
+ // Implicit system
+ constexpr auto id4 = Stensor4::Id();
+ constexpr auto Pdev = Stensor4::K();
+
+ const auto sigma_eff = std::max(sigmaeq(sig), local_zero_tolerance * mu);
+
+ const auto s = deviator(sig);
+ const auto k = deviator(epsK + depsK);
+
+ const auto etaK = etaK0 * std::exp(mvK * sigma_eff);
+ const auto etaM = etaM0 * std::exp(mvM * sigma_eff);
+ const auto GK = GK0 * std::exp(mK * sigma_eff);
+ const auto s_m_2G_eK = s - 2.0 * GK * k;
+
+ // residuals
+ feel += depsM + depsK;
+
+ // calculate Kelvin strain residual
+ fepsK = depsK - dt / (2.0 * etaK) * s_m_2G_eK;
+
+ // calculate Maxwell strain residual
+ fepsM = depsM - dt / (2.0 * etaM) * s;
+
+ // Pdev * D
+ const auto Pdev_D = 2 * mu * Pdev;
+
+ // Jacobian
+ const auto dsigma_eff_ddeel = 3. / (2. * sigma_eff) * s | (Pdev_D);
+ const auto detaK_ddeel = etaK * mvK * dsigma_eff_ddeel;
+ const auto detaM_ddeel = etaM * mvM * dsigma_eff_ddeel;
+ const auto dGK_ddeel = GK * mK * dsigma_eff_ddeel;
+
+ // dfeel_ddeel = id4; //initialized as such
+ dfeel_ddepsK = id4;
+ dfeel_ddepsM = id4;
+
+ dfepsK_ddeel = (dt / (2.0 * etaK * etaK) * s_m_2G_eK ^ detaK_ddeel) -
+ (dt / (2.0 * etaK) * Pdev_D) + (dt / etaK * k ^ dGK_ddeel);
+ dfepsK_ddepsK = (1. + dt * GK / etaK) * id4;
+ // dfepsK_ddepsM is all zero --> nothing to do
+
+ dfepsM_ddeel = (dt / (2.0 * etaM * etaM) * s ^ detaM_ddeel) -
+ (dt / (2.0 * etaM) * Pdev_D);
+ // dfepsM_ddepsK is all zero --> nothing to do
+ dfepsM_ddepsM = id4;
+}
diff --git a/MaterialLib/SolidModels/MFront/Lubby2.py b/MaterialLib/SolidModels/MFront/Lubby2.py
new file mode 100644
index 0000000000000000000000000000000000000000..92905601e5f54ca233b32983912ba916a0696810
--- /dev/null
+++ b/MaterialLib/SolidModels/MFront/Lubby2.py
@@ -0,0 +1,69 @@
+import mtest
+import numpy as np
+import matplotlib.pyplot as plt
+
+
+GM0 = 9.54e3
+KM0 = 2.78e4
+GK0 = 6.27e4
+mK = -0.254
+mvK = -0.327
+mvM = -0.267
+etaK0= 1.66e5
+etaM0= 4.03e7
+tmax = 15.
+
+
+m = mtest.MTest()
+mtest.setVerboseMode(mtest.VerboseLevel.VERBOSE_QUIET)
+m.setMaximumNumberOfSubSteps(10)
+m.setBehaviour('generic', 'src/libBehaviour.so', 'Lubby2')
+m.setExternalStateVariable("Temperature", 293.15)
+m.setImposedStress('SXX', 0.0)
+m.setImposedStress('SYY', 0.0)
+m.setImposedStress('SZZ', 0.0)
+m.setImposedStress('SXZ', 0.0)
+m.setImposedStress('SYZ', 0.0)
+m.setImposedStress('SXY', {0: 0, 1.e-5 : 5 * np.sqrt(2.), 15 : 5 * np.sqrt(2.)}) #Kelvin Mapping of shear components!!
+
+m.setMaterialProperty('YoungModulus', (9 * GM0 * KM0) / (3 * KM0 + GM0)) #this was the wrong equation
+m.setMaterialProperty('PoissonRatio', (3 * KM0 - 2 * GM0) / (2 * GM0 + 6 * KM0)) #this was the wrong equation
+m.setMaterialProperty('KelvinShearModulus', GK0)
+m.setMaterialProperty('KelvinViscosity', etaK0)
+m.setMaterialProperty('MaxwellViscosity', etaM0)
+m.setMaterialProperty('KelvinElasticParameter', mK)
+m.setMaterialProperty('MaxwellViscoParameter', mvM) #these were switched
+m.setMaterialProperty('KelvinViscoParameter', mvK) #these were switched
+
+sig_xy = 5.
+sig_eff = np.sqrt(3.)*sig_xy
+
+GK=GK0*np.exp(mK*sig_eff)
+etaK=etaK0*np.exp(mvK*sig_eff)
+etaM=etaM0*np.exp(mvM*sig_eff)
+
+
+eps_xy = lambda t: ((1./GM0 + t/etaM)*sig_xy + 1./GK*(1.-np.exp(-GK/etaK*t))*sig_xy)/2.
+
+s = mtest.MTestCurrentState()
+wk = mtest.MTestWorkSpace()
+m.completeInitialisation()
+m.initializeCurrentState(s)
+m.initializeWorkSpace(wk)
+
+ltime = np.append(np.linspace(0,1e-5,10),np.linspace(2.e-5,tmax,200))
+
+numerical = np.array([0.])
+
+#run sim
+for i in range(len(ltime)-1):
+ m.execute(s, wk, ltime[i], ltime[i + 1])
+ numerical = np.append(numerical,s.e1[3]/np.sqrt(2.)) #Kelvin mapping backwards!
+
+fig,ax = plt.subplots()
+ax.plot(ltime,numerical*100.,label='numerical')
+ax.plot(ltime,eps_xy(ltime)*100.,label='analytical')
+ax.set_xlabel('$t$ / d')
+ax.set_ylabel('$\\epsilon_{xy}$ / %')
+fig.legend()
+fig.savefig('lubby_mfront.pdf')
diff --git a/MaterialLib/SolidModels/MFront/Lubby2mod.mfront b/MaterialLib/SolidModels/MFront/Lubby2mod.mfront
new file mode 100644
index 0000000000000000000000000000000000000000..42ee281d0e32029f5c6c57ec36219fed97ffba44
--- /dev/null
+++ b/MaterialLib/SolidModels/MFront/Lubby2mod.mfront
@@ -0,0 +1,94 @@
+
+@DSL Implicit;
+@Behaviour Lubby2mod;
+@Author Thomas Nagel, Thomas Helfer;
+@Description
+{Lubby2 model for stationary
+and transient creep based on Burgers
+rheological model.
+Reduced implementation.
+};
+
+@Algorithm NewtonRaphson;
+@MaximumNumberOfIterations 100;
+
+@Epsilon 1.e-14;
+@Theta 1.0;
+
+@ModellingHypotheses{".+"};
+@Brick StandardElasticity;
+
+// Intercept of yield function
+@MaterialProperty real GK0;
+GK0.setEntryName("KelvinShearModulus");
+@MaterialProperty real etaK0;
+etaK0.setEntryName("KelvinViscosity");
+@MaterialProperty real etaM0;
+etaM0.setEntryName("MaxwellViscosity");
+@MaterialProperty real mK;
+mK.setEntryName("KelvinElasticParameter");
+@MaterialProperty real mvK;
+mvK.setEntryName("KelvinViscoParameter");
+@MaterialProperty real mvM;
+mvM.setEntryName("MaxwellViscoParameter");
+
+@AuxiliaryStateVariable Stensor epsK;
+epsK.setEntryName("KelvinStrain");
+
+//! increment of the Kelvin strain
+@LocalVariable Stensor depsK;
+//! increment of the Maxwell strain
+@LocalVariable Stensor depsM;
+
+//! Second Lamé coefficient
+@LocalVariable stress mu;
+
+@InitLocalVariables
+{
+ mu = computeMu(young, nu);
+ // Compute initial elastic strain
+ eel = 1. / (2. * mu) * sig - nu / young * trace(sig) * Stensor::Id();
+}
+
+@Integrator
+{
+ const auto seq = sigmaeq(sig);
+ const auto iseq = 1. / std::max(seq, 1.e-14 * mu);
+ const auto s = deviator(sig);
+ constexpr auto Pdev = Stensor4::K();
+
+ const auto etaK = etaK0 * std::exp(mvK * seq);
+ const auto etaM = etaM0 * std::exp(mvM * seq);
+ const auto GK = GK0 * std::exp(mK * seq);
+
+ // calculate Kelvin strain residual
+ const auto etaK_impl = etaK + dt * GK * theta;
+ depsK = dt / (2. * etaK_impl) * (s - 2 * GK * epsK);
+
+ // calculate Maxwell strain residual
+ depsM = dt / (2 * etaM) * s;
+
+ // residuals
+ feel += depsM + depsK;
+
+ // Jacobian
+ // Pdev_D
+ const auto Pdev_D = 2 * mu * Pdev;
+ const auto dseq_ddeel = 3. * iseq / 2. * s | (Pdev_D);
+ const auto detaK_ddeel = etaK * mvK * dseq_ddeel;
+ const auto detaM_ddeel = etaM * mvM * dseq_ddeel;
+ const auto dGK_ddeel = GK * mK * dseq_ddeel;
+ //
+ dfeel_ddeel +=
+ -(dt / (2 * etaK_impl * etaK_impl) * (s - 2 * GK * epsK) ^
+ detaK_ddeel) +
+ (dt / (2 * etaK_impl) * Pdev_D) - dt / etaK_impl * (epsK ^ dGK_ddeel) -
+ dt / (2 * etaK_impl * etaK_impl) * dt * theta *
+ ((s - 2 * GK * epsK) ^ dGK_ddeel) -
+ (dt / (2 * etaM * etaM) * s ^ detaM_ddeel) + (dt / (2 * etaM) * Pdev_D);
+}
+
+@UpdateAuxiliaryStateVariables
+{
+ epsK += depsK;
+} // end of @UpdateAuxiliaryStateVariables
diff --git a/ProcessLib/SmallDeformation/Tests.cmake b/ProcessLib/SmallDeformation/Tests.cmake
index fbaf77f9c9adad00495a86df9fbf259625fb94c9..a804d38feb6f380f150d5d64368a7507e83e187a 100644
--- a/ProcessLib/SmallDeformation/Tests.cmake
+++ b/ProcessLib/SmallDeformation/Tests.cmake
@@ -60,6 +60,8 @@ if (OGS_USE_MFRONT)
OgsTest(PROJECTFILE Mechanics/Linear/MFront/square_1e0_orthotropic_xyz.prj)
OgsTest(PROJECTFILE Mechanics/Linear/MFront/square_1e0_orthotropic_45xy_z.prj)
OgsTest(PROJECTFILE Mechanics/Linear/MFront/square_1e0_orthotropic_y-xz.prj)
+ OgsTest(PROJECTFILE Mechanics/Burgers/cube_1e0_mfront.prj)
+ OgsTest(PROJECTFILE Mechanics/Burgers/cube_1e0_mfront_mod.prj)
# Linear elastic, no internal state variables, no external state variables.
AddTest(
NAME Mechanics_SDL_disc_with_hole_mfront
@@ -224,4 +226,4 @@ AddTest(
DIFF_DATA
output_pcs_0_ts_1_t_1.000000.vtu output_pcs_0_ts_1_t_1.000000.vtu displacement displacement 0 1e-12
output_pcs_0_ts_1_t_1.000000.vtu output_pcs_0_ts_1_t_1.000000.vtu principal_stress_values principal_stress_values 0 1e-10
-)
\ No newline at end of file
+)
diff --git a/Tests/Data/Mechanics/Burgers/cube_1e0_mfront.prj b/Tests/Data/Mechanics/Burgers/cube_1e0_mfront.prj
new file mode 100644
index 0000000000000000000000000000000000000000..b62fb50945ecb3ea95d3fa45030080f13bc6228d
--- /dev/null
+++ b/Tests/Data/Mechanics/Burgers/cube_1e0_mfront.prj
@@ -0,0 +1,251 @@
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<OpenGeoSysProject>
+ <mesh>cube_1x1x1_hex_1e0.vtu</mesh>
+ <geometry>cube_1x1x1.gml</geometry>
+ <processes>
+ <process>
+ <name>SD</name>
+ <type>SMALL_DEFORMATION</type>
+ <integration_order>2</integration_order>
+ <constitutive_relation>
+ <type>MFront</type>
+ <behaviour>Lubby2</behaviour>
+ <material_properties>
+ <material_property name="YoungModulus" parameter="YoungModulus"/>
+ <material_property name="PoissonRatio" parameter="PoissonRatio"/>
+ <material_property name="KelvinShearModulus" parameter="GK0"/>
+ <material_property name="KelvinViscosity" parameter="etaK0"/>
+ <material_property name="MaxwellViscosity" parameter="etaM0"/>
+ <material_property name="KelvinElasticParameter" parameter="mK"/>
+ <material_property name="MaxwellViscoParameter" parameter="mvM"/>
+ <material_property name="KelvinViscoParameter" parameter="mvK"/>
+ </material_properties>
+ </constitutive_relation>
+ <solid_density>rho_sr</solid_density>
+ <specific_body_force>0 0 0</specific_body_force>
+ <process_variables>
+ <process_variable>displacement</process_variable>
+ </process_variables>
+ <secondary_variables>
+ <secondary_variable internal_name="sigma" output_name="sigma"/>
+ </secondary_variables>
+ </process>
+ </processes>
+ <time_loop>
+ <processes>
+ <process ref="SD">
+ <nonlinear_solver>basic_newton</nonlinear_solver>
+ <convergence_criterion>
+ <type>DeltaX</type>
+ <norm_type>NORM2</norm_type>
+ <abstol>1e-15</abstol>
+ </convergence_criterion>
+ <time_discretization>
+ <type>BackwardEuler</type>
+ </time_discretization>
+ <time_stepping>
+ <type>FixedTimeStepping</type>
+ <t_initial>0</t_initial>
+ <t_end>1</t_end>
+ <timesteps>
+ <pair>
+ <repeat>1</repeat>
+ <delta_t>0.0001</delta_t>
+ </pair>
+ <pair>
+ <repeat>100</repeat>
+ <delta_t>0.01</delta_t>
+ </pair>
+ </timesteps>
+ </time_stepping>
+ </process>
+ </processes>
+ <output>
+ <type>VTK</type>
+ <prefix>cube_1e0_mfront</prefix>
+ <timesteps>
+ <pair>
+ <repeat>1</repeat>
+ <each_steps>1</each_steps>
+ </pair>
+ <pair>
+ <repeat>1</repeat>
+ <each_steps>10000000</each_steps>
+ </pair>
+ </timesteps>
+ <variables>
+ <variable>displacement</variable>
+ <variable>sigma</variable>
+ </variables>
+ </output>
+ </time_loop>
+ <parameters>
+ <parameter>
+ <name>GK0</name>
+ <type>Constant</type>
+ <value>0.8</value>
+ </parameter>
+ <parameter>
+ <name>etaK0</name>
+ <type>Constant</type>
+ <value>0.5</value>
+ </parameter>
+ <parameter>
+ <name>YoungModulus</name>
+ <type>Constant</type>
+ <value>1.8</value>
+ </parameter>
+ <parameter>
+ <name>PoissonRatio</name>
+ <type>Constant</type>
+ <value>0.125</value>
+ </parameter>
+ <parameter>
+ <name>etaM0</name>
+ <type>Constant</type>
+ <value>0.5</value>
+ </parameter>
+ <parameter>
+ <name>mK</name>
+ <type>Constant</type>
+ <value>-0.2</value>
+ </parameter>
+ <parameter>
+ <name>mvK</name>
+ <type>Constant</type>
+ <value>-0.2</value>
+ </parameter>
+ <parameter>
+ <name>mvM</name>
+ <type>Constant</type>
+ <value>-0.3</value>
+ </parameter>
+ <parameter>
+ <name>rho_sr</name>
+ <type>Constant</type>
+ <value>1</value>
+ </parameter>
+ <parameter>
+ <name>displacement0</name>
+ <type>Constant</type>
+ <values>0 0 0</values>
+ </parameter>
+ <parameter>
+ <name>neumann_force</name>
+ <type>Constant</type>
+ <values>0.01</values>
+ </parameter>
+ <parameter>
+ <name>dirichlet0</name>
+ <type>Constant</type>
+ <value>0</value>
+ </parameter>
+ </parameters>
+ <process_variables>
+ <process_variable>
+ <name>displacement</name>
+ <components>3</components>
+ <order>1</order>
+ <initial_condition>displacement0</initial_condition>
+ <boundary_conditions>
+ <!-- fixed boundaries -->
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>left</geometry>
+ <type>Dirichlet</type>
+ <component>1</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>back</geometry>
+ <type>Dirichlet</type>
+ <component>1</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>front</geometry>
+ <type>Dirichlet</type>
+ <component>0</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>front</geometry>
+ <type>Dirichlet</type>
+ <component>1</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>right</geometry>
+ <type>Dirichlet</type>
+ <component>1</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ <!-- force -->
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>back</geometry>
+ <type>Neumann</type>
+ <component>0</component>
+ <parameter>neumann_force</parameter>
+ </boundary_condition>
+ <!-- fix front for the 3d case -->
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>top</geometry>
+ <type>Dirichlet</type>
+ <component>2</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>bottom</geometry>
+ <type>Dirichlet</type>
+ <component>2</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ </boundary_conditions>
+ </process_variable>
+ </process_variables>
+ <nonlinear_solvers>
+ <nonlinear_solver>
+ <name>basic_newton</name>
+ <type>Newton</type>
+ <max_iter>4</max_iter>
+ <linear_solver>general_linear_solver</linear_solver>
+ </nonlinear_solver>
+ </nonlinear_solvers>
+ <linear_solvers>
+ <linear_solver>
+ <name>general_linear_solver</name>
+ <lis>-i cg -p jacobi -tol 1e-16 -maxiter 10000</lis>
+ <eigen>
+ <solver_type>CG</solver_type>
+ <precon_type>DIAGONAL</precon_type>
+ <max_iteration_step>10000</max_iteration_step>
+ <error_tolerance>1e-16</error_tolerance>
+ </eigen>
+ <petsc>
+ <prefix>sd</prefix>
+ <parameters>-sd_ksp_type cg -sd_pc_type bjacobi -sd_ksp_rtol 1e-16 -sd_ksp_max_it 10000</parameters>
+ </petsc>
+ </linear_solver>
+ </linear_solvers>
+ <test_definition>
+ <vtkdiff>
+ <file>cube_1e0_mfront_pcs_0_ts_1_t_0.000100.vtu</file>
+ <field>displacement</field>
+ <absolute_tolerance>1e-16</absolute_tolerance>
+ <relative_tolerance>1e-16</relative_tolerance>
+ </vtkdiff>
+ <vtkdiff>
+ <file>cube_1e0_mfront_pcs_0_ts_101_t_1.000000.vtu</file>
+ <field>displacement</field>
+ <absolute_tolerance>1e-16</absolute_tolerance>
+ <relative_tolerance>1e-16</relative_tolerance>
+ </vtkdiff>
+ </test_definition>
+</OpenGeoSysProject>
diff --git a/Tests/Data/Mechanics/Burgers/cube_1e0_mfront_mod.prj b/Tests/Data/Mechanics/Burgers/cube_1e0_mfront_mod.prj
new file mode 100644
index 0000000000000000000000000000000000000000..5f9963108631360c8b07f69c617932b63a27b420
--- /dev/null
+++ b/Tests/Data/Mechanics/Burgers/cube_1e0_mfront_mod.prj
@@ -0,0 +1,251 @@
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<OpenGeoSysProject>
+ <mesh>cube_1x1x1_hex_1e0.vtu</mesh>
+ <geometry>cube_1x1x1.gml</geometry>
+ <processes>
+ <process>
+ <name>SD</name>
+ <type>SMALL_DEFORMATION</type>
+ <integration_order>2</integration_order>
+ <constitutive_relation>
+ <type>MFront</type>
+ <behaviour>Lubby2mod</behaviour>
+ <material_properties>
+ <material_property name="YoungModulus" parameter="YoungModulus"/>
+ <material_property name="PoissonRatio" parameter="PoissonRatio"/>
+ <material_property name="KelvinShearModulus" parameter="GK0"/>
+ <material_property name="KelvinViscosity" parameter="etaK0"/>
+ <material_property name="MaxwellViscosity" parameter="etaM0"/>
+ <material_property name="KelvinElasticParameter" parameter="mK"/>
+ <material_property name="MaxwellViscoParameter" parameter="mvM"/>
+ <material_property name="KelvinViscoParameter" parameter="mvK"/>
+ </material_properties>
+ </constitutive_relation>
+ <solid_density>rho_sr</solid_density>
+ <specific_body_force>0 0 0</specific_body_force>
+ <process_variables>
+ <process_variable>displacement</process_variable>
+ </process_variables>
+ <secondary_variables>
+ <secondary_variable internal_name="sigma" output_name="sigma"/>
+ </secondary_variables>
+ </process>
+ </processes>
+ <time_loop>
+ <processes>
+ <process ref="SD">
+ <nonlinear_solver>basic_newton</nonlinear_solver>
+ <convergence_criterion>
+ <type>DeltaX</type>
+ <norm_type>NORM2</norm_type>
+ <abstol>1e-15</abstol>
+ </convergence_criterion>
+ <time_discretization>
+ <type>BackwardEuler</type>
+ </time_discretization>
+ <time_stepping>
+ <type>FixedTimeStepping</type>
+ <t_initial>0</t_initial>
+ <t_end>1</t_end>
+ <timesteps>
+ <pair>
+ <repeat>1</repeat>
+ <delta_t>0.0001</delta_t>
+ </pair>
+ <pair>
+ <repeat>100</repeat>
+ <delta_t>0.01</delta_t>
+ </pair>
+ </timesteps>
+ </time_stepping>
+ </process>
+ </processes>
+ <output>
+ <type>VTK</type>
+ <prefix>cube_1e0_mfront_mod</prefix>
+ <timesteps>
+ <pair>
+ <repeat>1</repeat>
+ <each_steps>1</each_steps>
+ </pair>
+ <pair>
+ <repeat>1</repeat>
+ <each_steps>10000000</each_steps>
+ </pair>
+ </timesteps>
+ <variables>
+ <variable>displacement</variable>
+ <variable>sigma</variable>
+ </variables>
+ </output>
+ </time_loop>
+ <parameters>
+ <parameter>
+ <name>GK0</name>
+ <type>Constant</type>
+ <value>0.8</value>
+ </parameter>
+ <parameter>
+ <name>etaK0</name>
+ <type>Constant</type>
+ <value>0.5</value>
+ </parameter>
+ <parameter>
+ <name>YoungModulus</name>
+ <type>Constant</type>
+ <value>1.8</value>
+ </parameter>
+ <parameter>
+ <name>PoissonRatio</name>
+ <type>Constant</type>
+ <value>0.125</value>
+ </parameter>
+ <parameter>
+ <name>etaM0</name>
+ <type>Constant</type>
+ <value>0.5</value>
+ </parameter>
+ <parameter>
+ <name>mK</name>
+ <type>Constant</type>
+ <value>-0.2</value>
+ </parameter>
+ <parameter>
+ <name>mvK</name>
+ <type>Constant</type>
+ <value>-0.2</value>
+ </parameter>
+ <parameter>
+ <name>mvM</name>
+ <type>Constant</type>
+ <value>-0.3</value>
+ </parameter>
+ <parameter>
+ <name>rho_sr</name>
+ <type>Constant</type>
+ <value>1</value>
+ </parameter>
+ <parameter>
+ <name>displacement0</name>
+ <type>Constant</type>
+ <values>0 0 0</values>
+ </parameter>
+ <parameter>
+ <name>neumann_force</name>
+ <type>Constant</type>
+ <values>0.01</values>
+ </parameter>
+ <parameter>
+ <name>dirichlet0</name>
+ <type>Constant</type>
+ <value>0</value>
+ </parameter>
+ </parameters>
+ <process_variables>
+ <process_variable>
+ <name>displacement</name>
+ <components>3</components>
+ <order>1</order>
+ <initial_condition>displacement0</initial_condition>
+ <boundary_conditions>
+ <!-- fixed boundaries -->
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>left</geometry>
+ <type>Dirichlet</type>
+ <component>1</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>back</geometry>
+ <type>Dirichlet</type>
+ <component>1</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>front</geometry>
+ <type>Dirichlet</type>
+ <component>0</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>front</geometry>
+ <type>Dirichlet</type>
+ <component>1</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>right</geometry>
+ <type>Dirichlet</type>
+ <component>1</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ <!-- force -->
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>back</geometry>
+ <type>Neumann</type>
+ <component>0</component>
+ <parameter>neumann_force</parameter>
+ </boundary_condition>
+ <!-- fix front for the 3d case -->
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>top</geometry>
+ <type>Dirichlet</type>
+ <component>2</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ <boundary_condition>
+ <geometrical_set>cube_1x1x1_geometry</geometrical_set>
+ <geometry>bottom</geometry>
+ <type>Dirichlet</type>
+ <component>2</component>
+ <parameter>dirichlet0</parameter>
+ </boundary_condition>
+ </boundary_conditions>
+ </process_variable>
+ </process_variables>
+ <nonlinear_solvers>
+ <nonlinear_solver>
+ <name>basic_newton</name>
+ <type>Newton</type>
+ <max_iter>4</max_iter>
+ <linear_solver>general_linear_solver</linear_solver>
+ </nonlinear_solver>
+ </nonlinear_solvers>
+ <linear_solvers>
+ <linear_solver>
+ <name>general_linear_solver</name>
+ <lis>-i cg -p jacobi -tol 1e-16 -maxiter 10000</lis>
+ <eigen>
+ <solver_type>CG</solver_type>
+ <precon_type>DIAGONAL</precon_type>
+ <max_iteration_step>10000</max_iteration_step>
+ <error_tolerance>1e-16</error_tolerance>
+ </eigen>
+ <petsc>
+ <prefix>sd</prefix>
+ <parameters>-sd_ksp_type cg -sd_pc_type bjacobi -sd_ksp_rtol 1e-16 -sd_ksp_max_it 10000</parameters>
+ </petsc>
+ </linear_solver>
+ </linear_solvers>
+ <test_definition>
+ <vtkdiff>
+ <file>cube_1e0_mfront_mod_pcs_0_ts_1_t_0.000100.vtu</file>
+ <field>displacement</field>
+ <absolute_tolerance>5e-16</absolute_tolerance>
+ <relative_tolerance>1e-16</relative_tolerance>
+ </vtkdiff>
+ <vtkdiff>
+ <file>cube_1e0_mfront_mod_pcs_0_ts_101_t_1.000000.vtu</file>
+ <field>displacement</field>
+ <absolute_tolerance>5e-16</absolute_tolerance>
+ <relative_tolerance>1e-16</relative_tolerance>
+ </vtkdiff>
+ </test_definition>
+</OpenGeoSysProject>
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+++ b/Tests/Data/Mechanics/Burgers/cube_1e0_mfront_mod_pcs_0_ts_101_t_1.000000.vtu
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diff --git a/Tests/Data/Mechanics/Burgers/cube_1e0_mfront_mod_pcs_0_ts_1_t_0.000100.vtu b/Tests/Data/Mechanics/Burgers/cube_1e0_mfront_mod_pcs_0_ts_1_t_0.000100.vtu
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diff --git a/Tests/Data/Mechanics/Burgers/cube_1e0_mfront_pcs_0_ts_1_t_0.000100.vtu b/Tests/Data/Mechanics/Burgers/cube_1e0_mfront_pcs_0_ts_1_t_0.000100.vtu
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