Scalar trial stress update (#173)

* Scalar trial stress update (#173)
* Modify the input file slightly so that the gold file can be reused
* Add unit tests for the two new objects

---------

Co-authored-by: Gary Hu <[email protected]>

tests/include/J2FlowDirection.h → include/neml2/models/solid_mechanics/AssociativeJ2FlowDirection.h

@@ -28,13 +28,13 @@
 
 namespace neml2
 {
-/// The plastic flow direction assuming J2 flow.
-class J2FlowDirection : public Model
+/// The plastic flow direction assuming an associative J2 flow.
+class AssociativeJ2FlowDirection : public Model
 {
 public:
   static OptionSet expected_options();
 
-  J2FlowDirection(const OptionSet & options);
+  AssociativeJ2FlowDirection(const OptionSet & options);
 
 protected:
   virtual void set_value(bool, bool, bool) override;

include/neml2/models/solid_mechanics/LinearIsotropicElasticJ2TrialStressUpdate.h

@@ -0,0 +1,67 @@
+// Copyright 2024, UChicago Argonne, LLC
+// All Rights Reserved
+// Software Name: NEML2 -- the New Engineering material Model Library, version 2
+// By: Argonne National Laboratory
+// OPEN SOURCE LICENSE (MIT)
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+#pragma once
+
+#include "neml2/models/Model.h"
+
+namespace neml2
+{
+/**
+ * @brief Update the trial stress under the assumptions of J2 plasticity and isotropic linear
+ * elasticity
+ *
+ * This allows the construction of fully scalar return mapping models for
+ * isotropic materials.
+ */
+class LinearIsotropicElasticJ2TrialStressUpdate : public Model
+{
+public:
+  static OptionSet expected_options();
+
+  LinearIsotropicElasticJ2TrialStressUpdate(const OptionSet & options);
+
+protected:
+  /// compute updated trial stress
+  virtual void set_value(bool out, bool dout_din, bool d2out_din2) override;
+
+  /// input trial stress (i.e., assuming a purely elastic step)
+  const Variable<Scalar> & _elastic_trial_stress;
+
+  /// input inelastic strain
+  const Variable<Scalar> & _inelastic_strain;
+
+  /// input old inelastic strain
+  const Variable<Scalar> & _inelastic_strain_old;
+
+  /// output (updated) trial stress
+  Variable<Scalar> & _updated_trial_stress;
+
+  /// Young's modulus
+  const Scalar & _E;
+
+  /// Poisson's ratio
+  const Scalar & _nu;
+};
+} // namespace neml2

tests/src/J2FlowDirection.cxx → src/neml2/models/solid_mechanics/AssociativeJ2FlowDirection.cxx

@@ -22,31 +22,37 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
-#include "J2FlowDirection.h"
+#include "neml2/models/solid_mechanics/AssociativeJ2FlowDirection.h"
 #include "neml2/tensors/SSR4.h"
 
 namespace neml2
 {
-register_NEML2_object(J2FlowDirection);
+register_NEML2_object(AssociativeJ2FlowDirection);
 
 OptionSet
-J2FlowDirection::expected_options()
+AssociativeJ2FlowDirection::expected_options()
 {
   auto options = Model::expected_options();
+  options.doc() = "The plastic flow direction assuming an associative J2 flow.";
+
   options.set<VariableName>("mandel_stress") = VariableName("state", "M");
+  options.set("mandel_stress").doc() = "Mandel stress";
+
   options.set<VariableName>("flow_direction") = VariableName("state", "NM");
+  options.set("flow_direction").doc() = "Flow direction";
+
   return options;
 }
 
-J2FlowDirection::J2FlowDirection(const OptionSet & options)
+AssociativeJ2FlowDirection::AssociativeJ2FlowDirection(const OptionSet & options)
   : Model(options),
     _M(declare_input_variable<SR2>("mandel_stress")),
     _N(declare_output_variable<SR2>("flow_direction"))
 {
 }
 
 void
-J2FlowDirection::set_value(bool out, bool dout_din, bool d2out_din2)
+AssociativeJ2FlowDirection::set_value(bool out, bool dout_din, bool d2out_din2)
 {
   neml_assert_dbg(!d2out_din2, "Second derivatives not implemented");
 
@@ -60,10 +66,12 @@ J2FlowDirection::set_value(bool out, bool dout_din, bool d2out_din2)
   }
 
   if (dout_din)
-  {
-    auto I = SSR4::identity_sym(options());
-    auto J = SSR4::identity_dev(options());
-    _N.d(_M) = 3.0 / 2.0 * (I - 2.0 / 3.0 * dvm_dM.outer(dvm_dM)) * J / vm;
-  }
+    if (_M.is_dependent())
+    {
+      auto I = SSR4::identity_sym(options());
+      auto J = SSR4::identity_dev(options());
+
+      _N.d(_M) = 3.0 / 2.0 * (I - 2.0 / 3.0 * dvm_dM.outer(dvm_dM)) * J / vm;
+    }
 }
 } // namespace neml2

src/neml2/models/solid_mechanics/LinearIsotropicElasticJ2TrialStressUpdate.cxx

@@ -0,0 +1,97 @@
+// Copyright 2024, UChicago Argonne, LLC
+// All Rights Reserved
+// Software Name: NEML2 -- the New Engineering material Model Library, version 2
+// By: Argonne National Laboratory
+// OPEN SOURCE LICENSE (MIT)
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+#include "neml2/models/solid_mechanics/LinearIsotropicElasticJ2TrialStressUpdate.h"
+
+namespace neml2
+{
+register_NEML2_object(LinearIsotropicElasticJ2TrialStressUpdate);
+
+OptionSet
+LinearIsotropicElasticJ2TrialStressUpdate::expected_options()
+{
+  OptionSet options = Model::expected_options();
+
+  options.doc() = "Update the trial stress under the assumptions of J2 plasticity and isotropic "
+                  "linear elasticity";
+
+  options.set_input("elastic_trial_stress") = VariableName("forces", "s");
+  options.set("elastic_trial_stress").doc() = "Initial trial stress assuming a purely elastic step";
+
+  options.set_input("equivalent_plastic_strain") = VariableName("state", "ep");
+  options.set("equivalent_plastic_strain").doc() =
+      "Current guess for the equivalent plastic strain";
+
+  options.set_output("updated_trial_stress") = VariableName("state", "s");
+  options.set("updated_trial_stress").doc() =
+      "Trial stress corrected for the current increment of plastic deformation";
+
+  options.set_parameter<CrossRef<Scalar>>("youngs_modulus");
+  options.set("youngs_modulus").doc() = "Young's modulus";
+
+  options.set_parameter<CrossRef<Scalar>>("poisson_ratio");
+  options.set("poisson_ratio").doc() = "Poisson's ratio";
+
+  return options;
+}
+
+LinearIsotropicElasticJ2TrialStressUpdate::LinearIsotropicElasticJ2TrialStressUpdate(
+    const OptionSet & options)
+  : Model(options),
+    _elastic_trial_stress(declare_input_variable<Scalar>("elastic_trial_stress")),
+    _inelastic_strain(declare_input_variable<Scalar>("equivalent_plastic_strain")),
+    _inelastic_strain_old(declare_input_variable<Scalar>(_inelastic_strain.name().old())),
+    _updated_trial_stress(declare_output_variable<Scalar>("updated_trial_stress")),
+    _E(declare_parameter<Scalar>("E", "youngs_modulus", /*allow_nonlinear=*/false)),
+    _nu(declare_parameter<Scalar>("nu", "poisson_ratio", /*allow_nonlinear=*/false))
+{
+}
+
+void
+LinearIsotropicElasticJ2TrialStressUpdate::set_value(bool out, bool dout_din, bool d2out_din2)
+{
+  const auto three_shear = 3.0 * _E / (2.0 * (1.0 + _nu));
+
+  if (out)
+    _updated_trial_stress =
+        _elastic_trial_stress - three_shear * (_inelastic_strain - _inelastic_strain_old);
+
+  if (dout_din)
+  {
+    if (_elastic_trial_stress.is_dependent())
+      _updated_trial_stress.d(_elastic_trial_stress) = Scalar::identity_map(options());
+
+    if (_inelastic_strain.is_dependent())
+      _updated_trial_stress.d(_inelastic_strain) = -three_shear;
+
+    if (_inelastic_strain_old.is_dependent())
+      _updated_trial_stress.d(_inelastic_strain_old) = three_shear;
+  }
+
+  if (d2out_din2)
+  {
+    // zero
+  }
+}
+} // namespace neml2

tests/regression/solid_mechanics/viscoplasticity/misc/polynomial/model.i

@@ -145,7 +145,7 @@
     stress = 'forces/S'
   []
   [trial_flow_direction]
-    type = J2FlowDirection
+    type = AssociativeJ2FlowDirection
     mandel_stress = 'forces/S'
     flow_direction = 'forces/N'
   []

tests/regression/solid_mechanics/viscoplasticity/misc/torch_script/model.i

@@ -103,7 +103,7 @@ nbatch = 20
     stress = 'forces/S'
   []
   [trial_flow_direction]
-    type = J2FlowDirection
+    type = AssociativeJ2FlowDirection
     mandel_stress = 'forces/S'
     flow_direction = 'forces/N'
   []