use full strain rate when computing the viscoelastic strain rate

Author: YiminJin

source/material_model/rheology/elasticity.cc

@@ -858,7 +858,7 @@ namespace aspect
         const double timestep_ratio = calculate_timestep_ratio();
 
         const SymmetricTensor<2, dim>
-        edot_deviator = Utilities::Tensors::deviator(strain_rate) + 0.5 * stress_0_advected / elastic_viscosity
+        edot_deviator = strain_rate + 0.5 * stress_0_advected / elastic_viscosity
                         + 0.5 * (1. - timestep_ratio) * (1.  - creep_viscosity/elastic_viscosity) * stress_old / creep_viscosity;
 
         return edot_deviator;

source/material_model/rheology/visco_plastic.cc

@@ -306,7 +306,8 @@ namespace aspect
                            ExcMessage("Invalid strain_rate in the MaterialModelInputs. This is likely because it was "
                                       "not filled by the caller."));
 
-                    const SymmetricTensor<2, dim> effective_strain_rate = elastic_rheology.calculate_viscoelastic_strain_rate(in.strain_rate[i],
+                    const SymmetricTensor<2, dim> effective_strain_rate = 
+                      elastic_rheology.calculate_viscoelastic_strain_rate(Utilities::Tensors::deviator(in.strain_rate[i]),
                                                                           stress_0_advected,
                                                                           stress_old,
                                                                           non_yielding_viscosity,

source/simulator/assemblers/newton_stokes.cc

@@ -452,7 +452,7 @@ namespace aspect
                                    * JxW;
 
               if (enable_elasticity)
-                data.local_rhs(i) += ( Utilities::Tensors::deviator(elastic_out->elastic_force[q])
+                data.local_rhs(i) += ( elastic_out->elastic_force[q]
                                        * scratch.grads_phi_u[i]
                                      ) * JxW;