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Reduce grain size due to plastic strain #5915

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Reduce grain size due to plastic strain #5915

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14 changes: 14 additions & 0 deletions include/aspect/material_model/grain_size.h
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Original file line number Diff line number Diff line change
Expand Up @@ -198,6 +198,7 @@ namespace aspect
*/
std::vector<double> grain_boundary_energy;
std::vector<double> boundary_area_change_work_fraction;
std::vector<double> yielding_work_fraction;
std::vector<double> geometric_constant;

/**
Expand Down Expand Up @@ -352,6 +353,19 @@ namespace aspect
const double diffusion_viscosity,
const double viscosity_guess = 0) const;

Rheology::DruckerPragerParameters compute_drucker_prager_inputs (MaterialUtilities::PhaseFunctionInputs<dim> &phase_inputs) const;

double get_pressure_for_yielding (const double pressure,
const double adiabatic_pressure) const;

double compute_yield_stress (const double pressure_for_yielding,
const Rheology::DruckerPragerParameters &drucker_prager_parameters) const;

double plastic_viscosity (const double pressure_for_yielding,
const double second_strain_rate_invariant,
const double viscous_viscosity,
const Rheology::DruckerPragerParameters &drucker_prager_parameters) const;

double density (const double temperature,
const double pressure,
const std::vector<double> &compositional_fields,
Expand Down
186 changes: 137 additions & 49 deletions source/material_model/grain_size.cc
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Expand Up @@ -320,20 +320,47 @@ namespace aspect
const double dislocation_strain_rate = second_strain_rate_invariant
* current_viscosity / current_dislocation_viscosity;

double stress = 2.0 * second_strain_rate_invariant * std::min(std::max(min_eta,current_viscosity),max_eta);

// If material is yielding, all strain rate is plastic strain rate (the rock is breaking).
bool is_yielding = false;
if (enable_drucker_prager_rheology)
{
const double gravity_norm = this->get_gravity_model().gravity_vector(in.position[i]).norm();
const double depth = this->get_geometry_model().depth(in.position[i]);
const double rho_g = density(in.temperature[i], pressures[i], in.composition[i], in.position[i]) * gravity_norm;

// We do not fill the phase function index, because that will be done internally in the get_phase_index() function
MaterialUtilities::PhaseFunctionInputs<dim> phase_inputs(in.temperature[i], pressures[i], depth, rho_g, numbers::invalid_unsigned_int);

const Rheology::DruckerPragerParameters drucker_prager_parameters = compute_drucker_prager_inputs(phase_inputs);

// We use the adiabatic pressure for grain size evolution, so we also use it for plasticity here.
const double yield_stress = compute_yield_stress(pressures[i], drucker_prager_parameters);
stress = std::min(stress, yield_stress);
is_yielding = true;
Comment on lines +340 to +341
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wouldnt you need to check for if (stress > yield_stress) before these two lines? At the moment it looks like it is always yielding.

}

double grain_size_reduction_rate = 0.0;

if (grain_size_evolution_formulation == Formulation::paleowattmeter)
{
double strain_rate_for_reduction = boundary_area_change_work_fraction[phase_indices[i]] * dislocation_strain_rate;
if (is_yielding)
strain_rate_for_reduction = yielding_work_fraction[phase_indices[i]] * second_strain_rate_invariant;

// paleowattmeter: Austin and Evans (2007): Paleowattmeters: A scaling relation for dynamically recrystallized grain size. Geology 35, 343-346
const double stress = 2.0 * second_strain_rate_invariant * std::min(std::max(min_eta,current_viscosity),max_eta);
grain_size_reduction_rate = 2.0 * stress * boundary_area_change_work_fraction[phase_indices[i]] * dislocation_strain_rate * grain_size * grain_size
grain_size_reduction_rate = 2.0 * stress * strain_rate_for_reduction * grain_size * grain_size
/ (geometric_constant[phase_indices[i]] * grain_boundary_energy[phase_indices[i]]);
}
else if (grain_size_evolution_formulation == Formulation::pinned_grain_damage)
{
double strain_rate_for_reduction = partitioning_fraction * second_strain_rate_invariant;
if (is_yielding)
strain_rate_for_reduction = yielding_work_fraction[phase_indices[i]] * second_strain_rate_invariant;

// pinned_grain_damage: Mulyukova and Bercovici (2018) Collapse of passive margins by lithospheric damage and plunging grain size. Earth and Planetary Science Letters, 484, 341-352.
const double stress = 2.0 * second_strain_rate_invariant * std::min(std::max(min_eta,current_viscosity),max_eta);
grain_size_reduction_rate = 2.0 * stress * partitioning_fraction * second_strain_rate_invariant * grain_size * grain_size
grain_size_reduction_rate = 2.0 * stress * strain_rate_for_reduction * grain_size * grain_size
* roughness_to_grain_size
/ (geometric_constant[phase_indices[i]] * grain_boundary_energy[phase_indices[i]] * phase_distribution);
}
Expand Down Expand Up @@ -523,6 +550,88 @@ namespace aspect



template <int dim>
Rheology::DruckerPragerParameters
GrainSize<dim>::
compute_drucker_prager_inputs (MaterialUtilities::PhaseFunctionInputs<dim> &phase_inputs) const
{
// The following handles phases
std::vector<unsigned int> n_phases = {n_phase_transitions+1};
std::vector<double> phase_function_values(n_phase_transitions, 0.0);

for (unsigned int k=0; k<n_phase_transitions; ++k)
{
phase_inputs.phase_index = k;
phase_function_values[k] = phase_function.compute_value(phase_inputs);
}

// In the grain size material model, viscosity does not depend on composition,
// so we set the compositional index for the Drucker-Prager parameters to 0.
return drucker_prager_plasticity.compute_drucker_prager_parameters(0,
phase_function_values,
n_phases);
}


template <int dim>
double
GrainSize<dim>::
get_pressure_for_yielding (const double pressure,
const double adiabatic_pressure) const
{
return use_adiabatic_pressure_for_yielding
?
adiabatic_pressure
:
std::max(pressure,0.0);
}


template <int dim>
double
GrainSize<dim>::
compute_yield_stress (const double pressure_for_yielding,
const Rheology::DruckerPragerParameters &drucker_prager_parameters) const
{
return drucker_prager_plasticity.compute_yield_stress(drucker_prager_parameters.cohesion,
drucker_prager_parameters.angle_internal_friction,
pressure_for_yielding,
drucker_prager_parameters.max_yield_stress);
}



template <int dim>
double
GrainSize<dim>::
plastic_viscosity (const double pressure_for_yielding,
const double second_strain_rate_invariant,
const double viscous_viscosity,
const Rheology::DruckerPragerParameters &drucker_prager_parameters) const
{
// Calculate non-yielding (viscous) stress magnitude.
const double non_yielding_stress = 2. * viscous_viscosity * second_strain_rate_invariant;
const double yield_stress = compute_yield_stress (pressure_for_yielding, drucker_prager_parameters);

double effective_viscosity = viscous_viscosity;

// Apply plastic yielding:
// If the non-yielding stress is greater than the yield stress,
// rescale the viscosity back to yield surface
if (non_yielding_stress >= yield_stress)
{
effective_viscosity = drucker_prager_plasticity.compute_viscosity(drucker_prager_parameters.cohesion,
drucker_prager_parameters.angle_internal_friction,
pressure_for_yielding,
second_strain_rate_invariant,
drucker_prager_parameters.max_yield_stress,
effective_viscosity);
}
return effective_viscosity;
}



template <int dim>
double
GrainSize<dim>::
Expand Down Expand Up @@ -817,8 +926,6 @@ namespace aspect

if (in.requests_property(MaterialProperties::viscosity))
{
double effective_viscosity;
double disl_viscosity = std::numeric_limits<double>::max();
Assert(std::isfinite(in.strain_rate[i].norm()),
ExcMessage("Invalid strain_rate in the MaterialModelInputs. This is likely because it was "
"not filled by the caller."));
Expand All @@ -842,62 +949,31 @@ namespace aspect
second_strain_rate_invariant,
phase_indices[i]);

double effective_viscosity = diff_viscosity;
double disl_viscosity = std::numeric_limits<double>::max();

if (std::abs(second_strain_rate_invariant) > 1e-30)
{
disl_viscosity = dislocation_viscosity(in.temperature[i], adiabatic_temperature, adiabatic_pressures[i], in.strain_rate[i], phase_indices[i], diff_viscosity);
effective_viscosity = disl_viscosity * diff_viscosity / (disl_viscosity + diff_viscosity);
}
else
effective_viscosity = diff_viscosity;
const double non_yielding_stress = 2. * effective_viscosity * second_strain_rate_invariant;

if (enable_drucker_prager_rheology)
{
// Calculate non-yielding (viscous) stress magnitude.
const double non_yielding_stress = 2. * effective_viscosity * second_strain_rate_invariant;

// The following handles phases
std::vector<unsigned int> n_phases = {n_phase_transitions+1};
std::vector<double> phase_function_values(n_phase_transitions, 0.0);

for (unsigned int k=0; k<n_phase_transitions; ++k)
{
phase_inputs.phase_index = k;
phase_function_values[k] = phase_function.compute_value(phase_inputs);
}

// In the grain size material model, viscosity does not depend on composition,
// so we set the compositional index for the Drucker-Prager parameters to 0.
const Rheology::DruckerPragerParameters drucker_prager_parameters = drucker_prager_plasticity.compute_drucker_prager_parameters(0,
phase_function_values,
n_phases);
const double pressure_for_yielding = use_adiabatic_pressure_for_yielding
?
adiabatic_pressures[i]
:
std::max(in.pressure[i],0.0);

const double yield_stress = drucker_prager_plasticity.compute_yield_stress(drucker_prager_parameters.cohesion,
drucker_prager_parameters.angle_internal_friction,
pressure_for_yielding,
drucker_prager_parameters.max_yield_stress);

// Apply plastic yielding:
// If the non-yielding stress is greater than the yield stress,
// rescale the viscosity back to yield surface
if (non_yielding_stress >= yield_stress)
{
effective_viscosity = drucker_prager_plasticity.compute_viscosity(drucker_prager_parameters.cohesion,
drucker_prager_parameters.angle_internal_friction,
pressure_for_yielding,
second_strain_rate_invariant,
drucker_prager_parameters.max_yield_stress,
effective_viscosity);
}
const Rheology::DruckerPragerParameters drucker_prager_parameters = compute_drucker_prager_inputs(phase_inputs);
const double pressure_for_yielding = get_pressure_for_yielding (in.pressure[i], adiabatic_pressures[i]);
effective_viscosity = plastic_viscosity (pressure_for_yielding,
second_strain_rate_invariant,
effective_viscosity,
drucker_prager_parameters);

PlasticAdditionalOutputs<dim> *plastic_out = out.template get_additional_output<PlasticAdditionalOutputs<dim>>();

if (plastic_out != nullptr)
{
const double yield_stress = compute_yield_stress(pressure_for_yielding, drucker_prager_parameters);

plastic_out->cohesions[i] = drucker_prager_parameters.cohesion;
plastic_out->friction_angles[i] = drucker_prager_parameters.angle_internal_friction;
plastic_out->yield_stresses[i] = yield_stress;
Expand Down Expand Up @@ -1113,6 +1189,11 @@ namespace aspect
"The fraction $\\chi$ of work done by dislocation creep to change the grain boundary area. "
"List must have one more entry than the Phase transition depths. "
"Units: \\si{\\joule\\per\\meter\\squared}.");
prm.declare_entry ("Work fraction for boundary area change when yielding", "0.2",
Patterns::List (Patterns::Double (0.)),
"The fraction $\\chi$ of work done by plastic tielding to change the grain boundary area. "
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Suggested change
"The fraction $\\chi$ of work done by plastic tielding to change the grain boundary area. "
"The fraction $\\chi$ of work done by plastic yielding to change the grain boundary area. "

"List must have one more entry than the Phase transition depths. "
"Units: \\si{\\joule\\per\\meter\\squared}.");
prm.declare_entry ("Geometric constant", "3.",
Patterns::List (Patterns::Double (0.)),
"The geometric constant $c$ used in the paleowattmeter grain size reduction law. "
Expand Down Expand Up @@ -1396,6 +1477,8 @@ namespace aspect
(Utilities::split_string_list(prm.get ("Average specific grain boundary energy")));
boundary_area_change_work_fraction = Utilities::string_to_double
(Utilities::split_string_list(prm.get ("Work fraction for boundary area change")));
yielding_work_fraction = Utilities::string_to_double
(Utilities::split_string_list(prm.get ("Work fraction for boundary area change when yielding")));
geometric_constant = Utilities::string_to_double
(Utilities::split_string_list(prm.get ("Geometric constant")));

Expand Down Expand Up @@ -1567,6 +1650,11 @@ namespace aspect

std::vector<unsigned int> n_phases = {n_phase_transitions+1};
drucker_prager_plasticity.parse_parameters(prm, std::make_unique<std::vector<unsigned int>> (n_phases));

if (enable_drucker_prager_rheology)
AssertThrow(n_phases[0] == yielding_work_fraction.size(),
ExcMessage("Error: The list of ``Work fraction for boundary area change when yielding'' "
"does not have the correct length! It needs to have one entry per phase."));
}
prm.leave_subsection();
}
Expand Down
1 change: 1 addition & 0 deletions tests/grain_size_yield.prm
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Expand Up @@ -19,6 +19,7 @@ subsection Material model
set Reference temperature = 293
set Grain growth rate constant = 0
set Work fraction for boundary area change = 0
set Work fraction for boundary area change when yielding = 0
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So when setting the new parameter to 0 nothing changes, which is good. But we also need a test that uses the new feature.


# Diffusion creep
# new scaled prefactors to match vertical viscosity profile
Expand Down
1 change: 1 addition & 0 deletions tests/gs_drucker_prager.prm
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Expand Up @@ -90,6 +90,7 @@ subsection Material model
set Reference temperature = 1600
set Grain growth rate constant = 0
set Work fraction for boundary area change = 0
set Work fraction for boundary area change when yielding = 0

# Faul and Jackson 2007
# Diffusion creep
Expand Down