Add dynamic critical stretch

src/CabanaPD_Types.hpp

@@ -40,5 +40,9 @@ struct LinearLPS
 {
 };
 
+struct DynamicCriticalStretch
+{
+};
+
 } // namespace CabanaPD
 #endif

src/force/CabanaPD_ForceModels_PMB.hpp

@@ -91,10 +91,75 @@ struct ForceModel<PMB, Fracture, TemperatureIndependent>
         bond_break_coeff = ( 1.0 + s0 ) * ( 1.0 + s0 );
     }
 
+    // No-op.
+    template <class NeighListType, class PosType>
+    KOKKOS_INLINE_FUNCTION auto
+    minLocalStretch( const int, const NeighListType&, const PosType&,
+                     const PosType& ) const
+    {
+        return s0;
+    }
+
+    KOKKOS_INLINE_FUNCTION
+    bool criticalStretch( const int, const int, const double r, const double xi,
+                          const double ) const
+    {
+        return r * r >= bond_break_coeff * xi * xi;
+    }
+};
+
+template <>
+struct ForceModel<PMB, Fracture, TemperatureIndependent, DynamicCriticalStretch>
+    : public ForceModel<PMB, Fracture, TemperatureIndependent>
+{
+    using base_type = ForceModel<PMB, Fracture>;
+    using base_model = typename base_type::base_model;
+    using fracture_type = Fracture;
+    using thermal_type = base_type::thermal_type;
+
+    // Purposely not using the (static) base class bond_break_coeff
+    using base_type::c;
+    using base_type::delta;
+    using base_type::G0;
+    using base_type::K;
+    using base_type::s0;
+    double alpha = 0.25;
+
+    ForceModel() {}
+    ForceModel( const double delta, const double K, const double G0 )
+        : base_type( delta, K, G0 )
+    {
+    }
+
+    template <class NeighListType, class PosType>
+    KOKKOS_INLINE_FUNCTION auto
+    minLocalStretch( const int i, const NeighListType& neigh_list,
+                     const PosType& x, const PosType& u ) const
+    {
+        std::size_t num_neighbors =
+            Cabana::NeighborList<NeighListType>::numNeighbor( neigh_list, i );
+        double s_min = DBL_MAX;
+        for ( std::size_t n = 0; n < num_neighbors; n++ )
+        {
+            std::size_t j = Cabana::NeighborList<NeighListType>::getNeighbor(
+                neigh_list, i, n );
+
+            double xi, r, s;
+            double rx, ry, rz;
+            getDistanceComponents( x, u, i, j, xi, r, s, rx, ry, rz );
+            if ( s < s_min )
+                s_min = s;
+        }
+        return s0 - alpha * s_min;
+    }
+
+    // Use the dynamic s0 from the minLocalStretch function, reused through the
+    // neighbor loop.
     KOKKOS_INLINE_FUNCTION
-    bool criticalStretch( const int, const int, const double r,
-                          const double xi ) const
+    bool criticalStretch( const int, const int, const double r, const double xi,
+                          const double s0_i ) const
     {
+        double bond_break_coeff = ( 1.0 + s0_i ) * ( 1.0 + s0_i );
         return r * r >= bond_break_coeff * xi * xi;
     }
 };
@@ -231,7 +296,7 @@ struct ForceModel<PMB, Fracture, TemperatureDependent, TemperatureType>
 
     KOKKOS_INLINE_FUNCTION
     bool criticalStretch( const int i, const int j, const double r,
-                          const double xi ) const
+                          const double xi, const double ) const
     {
         double temp_avg = 0.5 * ( temperature( i ) + temperature( j ) ) - temp0;
         double bond_break_coeff =

src/force/CabanaPD_Force_PMB.hpp

@@ -214,6 +214,8 @@ class Force<ExecutionSpace, ForceModel<PMB, Fracture, ModelParams...>>
 
         auto force_full = KOKKOS_LAMBDA( const int i )
         {
+            auto s_min = model.minLocalStretch( i, neigh_list, x, u );
+
             std::size_t num_neighbors =
                 Cabana::NeighborList<NeighListType>::numNeighbor( neigh_list,
                                                                   i );
@@ -235,8 +237,8 @@ class Force<ExecutionSpace, ForceModel<PMB, Fracture, ModelParams...>>
                 model.thermalStretch( s, i, j );
 
                 // Break if beyond critical stretch unless in no-fail zone.
-                if ( model.criticalStretch( i, j, r, xi ) && !nofail( i ) &&
-                     !nofail( j ) )
+                if ( model.criticalStretch( i, j, r, xi, s_min ) &&
+                     !nofail( i ) && !nofail( j ) )
                 {
                     mu( i, n ) = 0;
                 }