Update ElectrostaticContactCondition to calculate conductance.

Refs idaholab#25

modules/electromagnetics/include/interfacekernels/ElectrostaticContactCondition.h

@@ -2,6 +2,12 @@
 
 #include "ADInterfaceKernel.h"
 
+/**
+ *  This ADInterfaceKernel object calculates the electrostatic potential value
+ *  and gradient relationship as a result of contact between two dissimilar,
+ *  homogeneous materials.
+ */
+
 class ElectrostaticContactCondition : public ADInterfaceKernel
 {
 public:
@@ -12,7 +18,30 @@ class ElectrostaticContactCondition : public ADInterfaceKernel
 protected:
   virtual ADReal computeQpResidual(Moose::DGResidualType type) override;
 
+  /// Electrical conductivity property for the primary side
   const MaterialProperty<Real> & _conductivity_master;
+
+  /// Electrical conductivity property for the secondary side
   const MaterialProperty<Real> & _conductivity_neighbor;
-  const Real & _contact_resistance;
+
+  /// Geometric mean of the hardness from both sides of the boundary, taken in as a material property
+  const ADMaterialProperty<Real> & _mean_hardness;
+
+  /// Mechanical pressure uniformly applied at the contact surface area (user-supplied for now)
+  const Real & _mechanical_pressure;
+
+  /// User-provided electrical contact resistance constant value
+  const Real & _user_contact_resistance;
+
+  /// Experimental proportional fit parameter for contact resistance parameter (set using Cincotti et al DOI:10.1002/aic.11102)
+  const Real _alpha_electric;
+
+  /// Experimental power fit parameter for contact resistance parameter (set using Cincotti et al DOI:10.1002/aic.11102)
+  const Real _beta_electric;
+
+  /// Check parameter for user-provided electrical contact resistance value
+  bool _resistance_was_set;
+
+  /// Check parameter for material-provided mean hardness value
+  bool _mean_hardness_was_set;
 };

modules/electromagnetics/src/interfacekernels/ElectrostaticContactCondition.C

@@ -10,35 +10,74 @@ ElectrostaticContactCondition::validParams()
       "master_conductivity", "electrical_conductivity", "Conductivity on the master block.");
   params.addParam<MaterialPropertyName>(
       "neighbor_conductivity", "electrical_conductivity", "Conductivity on the neighbor block.");
-  params.addRequiredParam<Real>("electrical_contact_resistance",
-                                "Electrical contact resistance coefficient.");
+  params.addParam<MaterialPropertyName>(
+      "mean_hardness",
+      "mean_hardness",
+      "Geometric mean of the hardness of each contacting material.");
+  params.addParam<Real>("user_electrical_contact_resistance",
+                        "User-supplied electrical contact resistance coefficient.");
+  params.addParam<Real>("mechanical_pressure",
+                        "Mechanical pressure uniformly applied at the contact surface area "
+                        "(Pressure = Force / Surface Area).");
   params.addClassDescription(
       "Interface condition that describes the current continuity and contact resistance across a "
-      "boundary formed between two dissimilar materials (resulting in a potential discontinuity), "
-      "as described in Cincotti, et al (https://doi.org/10.1002/aic.11102). Conductivity on each "
-      "side of the boundary is defined via the material peoperties system.");
+      "boundary formed between two dissimilar materials (resulting in a potential discontinuity). "
+      "Conductivity on each side of the boundary is defined via the material peoperties system.");
   return params;
 }
 
 ElectrostaticContactCondition::ElectrostaticContactCondition(const InputParameters & parameters)
   : ADInterfaceKernel(parameters),
     _conductivity_master(getMaterialProperty<Real>("master_conductivity")),
     _conductivity_neighbor(getNeighborMaterialProperty<Real>("neighbor_conductivity")),
-    _contact_resistance(getParam<Real>("electrical_contact_resistance"))
+    _mean_hardness(isParamValid("user_electrical_contact_resistance")
+                       ? getGenericZeroMaterialProperty<Real, true>("mean_hardness")
+                       : getADMaterialProperty<Real>("mean_hardness")),
+    _mechanical_pressure(isParamValid("mechanical_pressure") ? getParam<Real>("mechanical_pressure")
+                                                             : _real_zero),
+    _user_contact_resistance(isParamValid("user_electrical_contact_resistance")
+                                 ? getParam<Real>("user_electrical_contact_resistance")
+                                 : _real_zero),
+    _alpha_electric(64.0),
+    _beta_electric(0.35)
 {
+  _resistance_was_set = parameters.isParamSetByUser("user_electrical_contact_resistance");
+  _mean_hardness_was_set = parameters.isParamSetByUser("mean_hardness");
 }
 
 ADReal
 ElectrostaticContactCondition::computeQpResidual(Moose::DGResidualType type)
 {
   ADReal res = 0.0;
+  ADReal contact_resistance = 0.0;
+
+  ADReal mean_conductivity = 2 * _conductivity_master[_qp] * _conductivity_neighbor[_qp] /
+                             (_conductivity_master[_qp] + _conductivity_neighbor[_qp]);
+
+  if (_resistance_was_set && !_mean_hardness_was_set)
+  {
+    contact_resistance = _user_contact_resistance;
+  }
+  else if (_mean_hardness_was_set && !_resistance_was_set)
+  {
+    contact_resistance = _alpha_electric * mean_conductivity *
+                         std::pow((_mechanical_pressure / _mean_hardness[_qp]), _beta_electric);
+  }
+  else
+  {
+    mooseError("In ",
+               _name,
+               ", both user-supplied electrical contact resistance and mean hardness values (for "
+               "calculating contact resistance) have been provided. Please only provide one or the "
+               "other!");
+  }
 
   switch (type)
   {
     case Moose::Element:
       res = 0.5 *
             (_conductivity_neighbor[_qp] * _grad_neighbor_value[_qp] * _normals[_qp] -
-             _contact_resistance * (_neighbor_value[_qp] - _u[_qp])) *
+             contact_resistance * (_neighbor_value[_qp] - _u[_qp])) *
             _test[_i][_qp];
       break;
 

modules/electromagnetics/test/tests/interfacekernels/contact_resistance.i

@@ -79,7 +79,7 @@
     variable = potential_stainless_steel
     neighbor_var = potential_graphite
     boundary = ssg_interface
-    electrical_contact_resistance = 1.47e5 # as described in Cincotti et al (https://doi.org/10.1002/aic.11102)
+    user_electrical_contact_resistance = 1.47e5 # as described in Cincotti et al (https://doi.org/10.1002/aic.11102)
   [../]
 []