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ComputeMultiPlasticityStress.C
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ComputeMultiPlasticityStress.C
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//* This file is part of the MOOSE framework
//* https://www.mooseframework.org
//*
//* All rights reserved, see COPYRIGHT for full restrictions
//* https://github.com/idaholab/moose/blob/master/COPYRIGHT
//*
//* Licensed under LGPL 2.1, please see LICENSE for details
//* https://www.gnu.org/licenses/lgpl-2.1.html
#include "ComputeMultiPlasticityStress.h"
#include "MultiPlasticityDebugger.h"
#include "MatrixTools.h"
#include "MooseException.h"
#include "RotationMatrix.h" // for rotVecToZ
#include "libmesh/utility.h"
registerMooseObject("TensorMechanicsApp", ComputeMultiPlasticityStress);
template <>
InputParameters
validParams<ComputeMultiPlasticityStress>()
{
InputParameters params = validParams<ComputeStressBase>();
params += validParams<MultiPlasticityDebugger>();
params.addClassDescription("Base class for multi-surface finite-strain plasticity");
params.addRangeCheckedParam<unsigned int>("max_NR_iterations",
20,
"max_NR_iterations>0",
"Maximum number of Newton-Raphson iterations allowed");
params.addRequiredParam<Real>("ep_plastic_tolerance",
"The Newton-Raphson process is only deemed "
"converged if the plastic strain increment "
"constraints have L2 norm less than this.");
params.addRangeCheckedParam<Real>(
"min_stepsize",
0.01,
"min_stepsize>0 & min_stepsize<=1",
"If ordinary Newton-Raphson + line-search fails, then the applied strain increment is "
"subdivided, and the return-map is tried again. This parameter is the minimum fraction of "
"applied strain increment that may be applied before the algorithm gives up entirely");
params.addRangeCheckedParam<Real>("max_stepsize_for_dumb",
0.01,
"max_stepsize_for_dumb>0 & max_stepsize_for_dumb<=1",
"If your deactivation_scheme is 'something_to_dumb', then "
"'dumb' will only be used if the stepsize falls below this "
"value. This parameter is useful because the 'dumb' scheme is "
"computationally expensive");
MooseEnum deactivation_scheme("optimized safe dumb optimized_to_safe safe_to_dumb "
"optimized_to_safe_to_dumb optimized_to_dumb",
"optimized");
params.addParam<MooseEnum>(
"deactivation_scheme",
deactivation_scheme,
"Scheme by which constraints are deactivated. (NOTE: This is irrelevant if there is only "
"one yield surface.) safe: return to the yield surface and then deactivate constraints with "
"negative plasticity multipliers. optimized: deactivate a constraint as soon as its "
"plasticity multiplier becomes negative. dumb: iteratively try all combinations of active "
"constraints until the solution is found. You may specify fall-back options. Eg "
"optimized_to_safe: first use 'optimized', and if that fails, try the return with 'safe'.");
params.addParam<RealVectorValue>(
"transverse_direction",
"If this parameter is provided, before the return-map algorithm is "
"called a rotation is performed so that the 'z' axis in the new "
"frame lies along the transverse_direction in the original frame. "
"After returning, the inverse rotation is performed. The "
"transverse_direction will itself rotate with large strains. This "
"is so that transversely-isotropic plasticity models may be easily "
"defined in the frame where the isotropy holds in the x-y plane.");
params.addParam<bool>("ignore_failures",
false,
"The return-map algorithm will return with the best admissible "
"stresses and internal parameters that it can, even if they don't "
"fully correspond to the applied strain increment. To speed "
"computations, this flag can be set to true, the max_NR_iterations "
"set small, and the min_stepsize large.");
MooseEnum tangent_operator("elastic linear nonlinear", "nonlinear");
params.addParam<MooseEnum>("tangent_operator",
tangent_operator,
"Type of tangent operator to return. 'elastic': return the "
"elasticity tensor. 'linear': return the consistent tangent operator "
"that is correct for plasticity with yield functions linear in "
"stress. 'nonlinear': return the full, general consistent tangent "
"operator. The calculations assume the hardening potentials are "
"independent of stress and hardening parameters.");
params.addParam<bool>("perform_finite_strain_rotations",
true,
"Tensors are correctly rotated in "
"finite-strain simulations. For "
"optimal performance you can set "
"this to 'false' if you are only "
"ever using small strains");
params.addClassDescription("Material for multi-surface finite-strain plasticity");
return params;
}
ComputeMultiPlasticityStress::ComputeMultiPlasticityStress(const InputParameters & parameters)
: ComputeStressBase(parameters),
MultiPlasticityDebugger(this),
_max_iter(getParam<unsigned int>("max_NR_iterations")),
_min_stepsize(getParam<Real>("min_stepsize")),
_max_stepsize_for_dumb(getParam<Real>("max_stepsize_for_dumb")),
_ignore_failures(getParam<bool>("ignore_failures")),
_tangent_operator_type((TangentOperatorEnum)(int)getParam<MooseEnum>("tangent_operator")),
_epp_tol(getParam<Real>("ep_plastic_tolerance")),
_dummy_pm(0),
_cumulative_pm(0),
_deactivation_scheme((DeactivationSchemeEnum)(int)getParam<MooseEnum>("deactivation_scheme")),
_n_supplied(parameters.isParamValid("transverse_direction")),
_n_input(_n_supplied ? getParam<RealVectorValue>("transverse_direction") : RealVectorValue()),
_rot(RealTensorValue()),
_perform_finite_strain_rotations(getParam<bool>("perform_finite_strain_rotations")),
_elasticity_tensor_name(_base_name + "elasticity_tensor"),
_elasticity_tensor(getMaterialPropertyByName<RankFourTensor>(_elasticity_tensor_name)),
_plastic_strain(declareProperty<RankTwoTensor>("plastic_strain")),
_plastic_strain_old(getMaterialPropertyOld<RankTwoTensor>("plastic_strain")),
_intnl(declareProperty<std::vector<Real>>("plastic_internal_parameter")),
_intnl_old(getMaterialPropertyOld<std::vector<Real>>("plastic_internal_parameter")),
_yf(declareProperty<std::vector<Real>>("plastic_yield_function")),
_iter(declareProperty<Real>("plastic_NR_iterations")), // this is really an unsigned int, but
// for visualisation i convert it to Real
_linesearch_needed(declareProperty<Real>("plastic_linesearch_needed")), // this is really a
// boolean, but for
// visualisation i
// convert it to Real
_ld_encountered(declareProperty<Real>(
"plastic_linear_dependence_encountered")), // this is really a boolean, but for
// visualisation i convert it to Real
_constraints_added(declareProperty<Real>("plastic_constraints_added")), // this is really a
// boolean, but for
// visualisation i
// convert it to Real
_n(declareProperty<RealVectorValue>("plastic_transverse_direction")),
_n_old(getMaterialPropertyOld<RealVectorValue>("plastic_transverse_direction")),
_strain_increment(getMaterialPropertyByName<RankTwoTensor>(_base_name + "strain_increment")),
_total_strain_old(getMaterialPropertyOldByName<RankTwoTensor>(_base_name + "total_strain")),
_rotation_increment(
getMaterialPropertyByName<RankTwoTensor>(_base_name + "rotation_increment")),
_stress_old(getMaterialPropertyOld<RankTwoTensor>(_base_name + "stress")),
_elastic_strain_old(getMaterialPropertyOld<RankTwoTensor>(_base_name + "elastic_strain")),
// TODO: This design does NOT work. It makes these materials construction order dependent and it
// disregards block restrictions.
_cosserat(hasMaterialProperty<RankTwoTensor>("curvature") &&
hasMaterialProperty<RankFourTensor>("elastic_flexural_rigidity_tensor")),
_curvature(_cosserat ? &getMaterialPropertyByName<RankTwoTensor>("curvature") : nullptr),
_elastic_flexural_rigidity_tensor(
_cosserat ? &getMaterialPropertyByName<RankFourTensor>("elastic_flexural_rigidity_tensor")
: nullptr),
_couple_stress(_cosserat ? &declareProperty<RankTwoTensor>("couple_stress") : nullptr),
_couple_stress_old(_cosserat ? &getMaterialPropertyOld<RankTwoTensor>("couple_stress")
: nullptr),
_Jacobian_mult_couple(_cosserat ? &declareProperty<RankFourTensor>("couple_Jacobian_mult")
: nullptr),
_my_elasticity_tensor(RankFourTensor()),
_my_strain_increment(RankTwoTensor()),
_my_flexural_rigidity_tensor(RankFourTensor()),
_my_curvature(RankTwoTensor())
{
if (_epp_tol <= 0)
mooseError("ComputeMultiPlasticityStress: ep_plastic_tolerance must be positive");
if (_n_supplied)
{
// normalise the inputted transverse_direction
if (_n_input.norm() == 0)
mooseError(
"ComputeMultiPlasticityStress: transverse_direction vector must not have zero length");
else
_n_input /= _n_input.norm();
}
if (_num_surfaces == 1)
_deactivation_scheme = safe;
}
void
ComputeMultiPlasticityStress::initQpStatefulProperties()
{
ComputeStressBase::initQpStatefulProperties();
_plastic_strain[_qp].zero();
_intnl[_qp].assign(_num_models, 0);
_yf[_qp].assign(_num_surfaces, 0);
_dummy_pm.assign(_num_surfaces, 0);
_iter[_qp] = 0.0; // this is really an unsigned int, but for visualisation i convert it to Real
_linesearch_needed[_qp] = 0;
_ld_encountered[_qp] = 0;
_constraints_added[_qp] = 0;
_n[_qp] = _n_input;
if (_cosserat)
(*_couple_stress)[_qp].zero();
if (_fspb_debug == "jacobian")
{
checkDerivatives();
mooseError("Finite-differencing completed. Exiting with no error");
}
}
void
ComputeMultiPlasticityStress::computeQpStress()
{
// the following "_my" variables can get rotated by preReturnMap and postReturnMap
_my_elasticity_tensor = _elasticity_tensor[_qp];
_my_strain_increment = _strain_increment[_qp];
if (_cosserat)
{
_my_flexural_rigidity_tensor = (*_elastic_flexural_rigidity_tensor)[_qp];
_my_curvature = (*_curvature)[_qp];
}
if (_fspb_debug == "jacobian_and_linear_system")
{
// cannot do this at initQpStatefulProperties level since E_ijkl is not defined
checkJacobian(_elasticity_tensor[_qp].invSymm(), _intnl_old[_qp]);
checkSolution(_elasticity_tensor[_qp].invSymm());
mooseError("Finite-differencing completed. Exiting with no error");
}
preReturnMap(); // do rotations to new frame if necessary
unsigned int number_iterations;
bool linesearch_needed = false;
bool ld_encountered = false;
bool constraints_added = false;
_cumulative_pm.assign(_num_surfaces, 0);
// try a "quick" return first - this can be purely elastic, or a customised plastic return defined
// by a TensorMechanicsPlasticXXXX UserObject
const bool found_solution = quickStep(rot(_stress_old[_qp]),
_stress[_qp],
_intnl_old[_qp],
_intnl[_qp],
_dummy_pm,
_cumulative_pm,
rot(_plastic_strain_old[_qp]),
_plastic_strain[_qp],
_my_elasticity_tensor,
_my_strain_increment,
_yf[_qp],
number_iterations,
_Jacobian_mult[_qp],
computeQpStress_function,
true);
// if not purely elastic or the customised stuff failed, do some plastic return
if (!found_solution)
plasticStep(rot(_stress_old[_qp]),
_stress[_qp],
_intnl_old[_qp],
_intnl[_qp],
rot(_plastic_strain_old[_qp]),
_plastic_strain[_qp],
_my_elasticity_tensor,
_my_strain_increment,
_yf[_qp],
number_iterations,
linesearch_needed,
ld_encountered,
constraints_added,
_Jacobian_mult[_qp]);
if (_cosserat)
{
(*_couple_stress)[_qp] = (*_elastic_flexural_rigidity_tensor)[_qp] * _my_curvature;
(*_Jacobian_mult_couple)[_qp] = _my_flexural_rigidity_tensor;
}
postReturnMap(); // rotate back from new frame if necessary
_iter[_qp] = 1.0 * number_iterations;
_linesearch_needed[_qp] = linesearch_needed;
_ld_encountered[_qp] = ld_encountered;
_constraints_added[_qp] = constraints_added;
// Update measures of strain
_elastic_strain[_qp] = _elastic_strain_old[_qp] + _my_strain_increment -
(_plastic_strain[_qp] - _plastic_strain_old[_qp]);
// Rotate the tensors to the current configuration
if (_perform_finite_strain_rotations)
{
_stress[_qp] = _rotation_increment[_qp] * _stress[_qp] * _rotation_increment[_qp].transpose();
_elastic_strain[_qp] =
_rotation_increment[_qp] * _elastic_strain[_qp] * _rotation_increment[_qp].transpose();
_plastic_strain[_qp] =
_rotation_increment[_qp] * _plastic_strain[_qp] * _rotation_increment[_qp].transpose();
}
}
RankTwoTensor
ComputeMultiPlasticityStress::rot(const RankTwoTensor & tens)
{
if (!_n_supplied)
return tens;
return tens.rotated(_rot);
}
void
ComputeMultiPlasticityStress::preReturnMap()
{
if (_n_supplied)
{
// this is a rotation matrix that will rotate _n to the "z" axis
_rot = RotationMatrix::rotVecToZ(_n[_qp]);
// rotate the tensors to this frame
_my_elasticity_tensor.rotate(_rot);
_my_strain_increment.rotate(_rot);
if (_cosserat)
{
_my_flexural_rigidity_tensor.rotate(_rot);
_my_curvature.rotate(_rot);
}
}
}
void
ComputeMultiPlasticityStress::postReturnMap()
{
if (_n_supplied)
{
// this is a rotation matrix that will rotate "z" axis back to _n
_rot = _rot.transpose();
// rotate the tensors back to original frame where _n is correctly oriented
_my_elasticity_tensor.rotate(_rot);
_Jacobian_mult[_qp].rotate(_rot);
_my_strain_increment.rotate(_rot);
_stress[_qp].rotate(_rot);
_plastic_strain[_qp].rotate(_rot);
if (_cosserat)
{
_my_flexural_rigidity_tensor.rotate(_rot);
(*_Jacobian_mult_couple)[_qp].rotate(_rot);
_my_curvature.rotate(_rot);
(*_couple_stress)[_qp].rotate(_rot);
}
// Rotate n by _rotation_increment
for (unsigned int i = 0; i < LIBMESH_DIM; ++i)
{
_n[_qp](i) = 0;
for (unsigned int j = 0; j < LIBMESH_DIM; ++j)
_n[_qp](i) += _rotation_increment[_qp](i, j) * _n_old[_qp](j);
}
}
}
bool
ComputeMultiPlasticityStress::quickStep(const RankTwoTensor & stress_old,
RankTwoTensor & stress,
const std::vector<Real> & intnl_old,
std::vector<Real> & intnl,
std::vector<Real> & pm,
std::vector<Real> & cumulative_pm,
const RankTwoTensor & plastic_strain_old,
RankTwoTensor & plastic_strain,
const RankFourTensor & E_ijkl,
const RankTwoTensor & strain_increment,
std::vector<Real> & yf,
unsigned int & iterations,
RankFourTensor & consistent_tangent_operator,
const quickStep_called_from_t called_from,
bool final_step)
{
iterations = 0;
unsigned num_plastic_returns;
RankTwoTensor delta_dp;
// the following does the customized returnMap algorithm
// for all the plastic models.
unsigned custom_model = 0;
bool successful_return = returnMapAll(stress_old + E_ijkl * strain_increment,
intnl_old,
E_ijkl,
_epp_tol,
stress,
intnl,
pm,
cumulative_pm,
delta_dp,
yf,
num_plastic_returns,
custom_model);
// the following updates the plastic_strain, when necessary
// and calculates the consistent_tangent_operator, when necessary
if (num_plastic_returns == 0)
{
// if successful_return = true, then a purely elastic step
// if successful_return = false, then >=1 plastic model is in
// inadmissible zone and failed to return using its customized
// returnMap function.
// In either case:
plastic_strain = plastic_strain_old;
if (successful_return && final_step)
{
if (called_from == computeQpStress_function)
consistent_tangent_operator = E_ijkl;
else // cannot necessarily use E_ijkl since different plastic models may have been active
// during other substeps
consistent_tangent_operator =
consistentTangentOperator(stress, intnl, E_ijkl, pm, cumulative_pm);
}
return successful_return;
}
else if (num_plastic_returns == 1 && successful_return)
{
// one model has successfully completed its custom returnMap algorithm
// and the other models have signalled they are elastic at
// the trial stress
plastic_strain = plastic_strain_old + delta_dp;
if (final_step)
{
if (called_from == computeQpStress_function && _f[custom_model]->useCustomCTO())
{
if (_tangent_operator_type == elastic)
consistent_tangent_operator = E_ijkl;
else
{
std::vector<Real> custom_model_pm;
for (unsigned surface = 0; surface < _f[custom_model]->numberSurfaces(); ++surface)
custom_model_pm.push_back(cumulative_pm[_surfaces_given_model[custom_model][surface]]);
consistent_tangent_operator =
_f[custom_model]->consistentTangentOperator(stress_old + E_ijkl * strain_increment,
intnl_old[custom_model],
stress,
intnl[custom_model],
E_ijkl,
custom_model_pm);
}
}
else // cannot necessarily use the custom consistentTangentOperator since different plastic
// models may have been active during other substeps or the custom model says not to use
// its custom CTO algorithm
consistent_tangent_operator =
consistentTangentOperator(stress, intnl, E_ijkl, pm, cumulative_pm);
}
return true;
}
else // presumably returnMapAll is incorrectly coded!
mooseError("ComputeMultiPlasticityStress::quickStep should not get here!");
}
bool
ComputeMultiPlasticityStress::plasticStep(const RankTwoTensor & stress_old,
RankTwoTensor & stress,
const std::vector<Real> & intnl_old,
std::vector<Real> & intnl,
const RankTwoTensor & plastic_strain_old,
RankTwoTensor & plastic_strain,
const RankFourTensor & E_ijkl,
const RankTwoTensor & strain_increment,
std::vector<Real> & yf,
unsigned int & iterations,
bool & linesearch_needed,
bool & ld_encountered,
bool & constraints_added,
RankFourTensor & consistent_tangent_operator)
{
/**
* the idea in the following is to potentially subdivide the
* strain increment into smaller fractions, of size "step_size".
* First step_size = 1 is tried, and if that fails then 0.5 is
* tried, then 0.25, etc. As soon as a step is successful, its
* results are put into the "good" variables, which are used
* if a subsequent step fails. If >= 2 consecutive steps are
* successful, the step_size is increased by 1.2
*
* The point of all this is that I hope that the
* time-step for the entire mesh need not be cut if there
* are only a few "bad" quadpoints where the return-map
* is difficult
*/
bool return_successful = false;
// total number of Newton-Raphson iterations used
unsigned int iter = 0;
Real step_size = 1.0;
Real time_simulated = 0.0;
// the "good" variables hold the latest admissible stress
// and internal parameters.
RankTwoTensor stress_good = stress_old;
RankTwoTensor plastic_strain_good = plastic_strain_old;
std::vector<Real> intnl_good(_num_models);
for (unsigned model = 0; model < _num_models; ++model)
intnl_good[model] = intnl_old[model];
std::vector<Real> yf_good(_num_surfaces);
// Following is necessary because I want strain_increment to be "const"
// but I also want to be able to subdivide an initial_stress
RankTwoTensor this_strain_increment = strain_increment;
RankTwoTensor dep = step_size * this_strain_increment;
_cumulative_pm.assign(_num_surfaces, 0);
unsigned int num_consecutive_successes = 0;
while (time_simulated < 1.0 && step_size >= _min_stepsize)
{
iter = 0;
return_successful = returnMap(stress_good,
stress,
intnl_good,
intnl,
plastic_strain_good,
plastic_strain,
E_ijkl,
dep,
yf,
iter,
step_size <= _max_stepsize_for_dumb,
linesearch_needed,
ld_encountered,
constraints_added,
time_simulated + step_size >= 1,
consistent_tangent_operator,
_cumulative_pm);
iterations += iter;
if (return_successful)
{
num_consecutive_successes += 1;
time_simulated += step_size;
if (time_simulated < 1.0) // this condition is just for optimization: if time_simulated=1 then
// the "good" quantities are no longer needed
{
stress_good = stress;
plastic_strain_good = plastic_strain;
for (unsigned model = 0; model < _num_models; ++model)
intnl_good[model] = intnl[model];
for (unsigned surface = 0; surface < _num_surfaces; ++surface)
yf_good[surface] = yf[surface];
if (num_consecutive_successes >= 2)
step_size *= 1.2;
}
step_size = std::min(step_size, 1.0 - time_simulated); // avoid overshoots
}
else
{
step_size *= 0.5;
num_consecutive_successes = 0;
stress = stress_good;
plastic_strain = plastic_strain_good;
for (unsigned model = 0; model < _num_models; ++model)
intnl[model] = intnl_good[model];
yf.resize(_num_surfaces); // might have excited with junk
for (unsigned surface = 0; surface < _num_surfaces; ++surface)
yf[surface] = yf_good[surface];
dep = step_size * this_strain_increment;
}
}
if (!return_successful)
{
if (_ignore_failures)
{
stress = stress_good;
plastic_strain = plastic_strain_good;
for (unsigned model = 0; model < _num_models; ++model)
intnl[model] = intnl_good[model];
for (unsigned surface = 0; surface < _num_surfaces; ++surface)
yf[surface] = yf_good[surface];
}
else
{
Moose::out << "After reducing the stepsize to " << step_size
<< " with original strain increment with L2norm " << this_strain_increment.L2norm()
<< " the returnMap algorithm failed\n";
_fspb_debug_stress = stress_good + E_ijkl * dep;
_fspb_debug_pm.assign(
_num_surfaces,
1); // this is chosen arbitrarily - please change if a more suitable value occurs to you!
_fspb_debug_intnl.resize(_num_models);
for (unsigned model = 0; model < _num_models; ++model)
_fspb_debug_intnl[model] = intnl_good[model];
checkDerivatives();
checkJacobian(_my_elasticity_tensor.invSymm(), _intnl_old[_qp]);
checkSolution(_my_elasticity_tensor.invSymm());
mooseError("Exiting\n");
}
}
return return_successful;
}
bool
ComputeMultiPlasticityStress::returnMap(const RankTwoTensor & stress_old,
RankTwoTensor & stress,
const std::vector<Real> & intnl_old,
std::vector<Real> & intnl,
const RankTwoTensor & plastic_strain_old,
RankTwoTensor & plastic_strain,
const RankFourTensor & E_ijkl,
const RankTwoTensor & strain_increment,
std::vector<Real> & f,
unsigned int & iter,
bool can_revert_to_dumb,
bool & linesearch_needed,
bool & ld_encountered,
bool & constraints_added,
bool final_step,
RankFourTensor & consistent_tangent_operator,
std::vector<Real> & cumulative_pm)
{
// The "consistency parameters" (plastic multipliers)
// Change in plastic strain in this timestep = pm*flowPotential
// Each pm must be non-negative
std::vector<Real> pm;
pm.assign(_num_surfaces, 0.0);
bool successful_return = quickStep(stress_old,
stress,
intnl_old,
intnl,
pm,
cumulative_pm,
plastic_strain_old,
plastic_strain,
E_ijkl,
strain_increment,
f,
iter,
consistent_tangent_operator,
returnMap_function,
final_step);
if (successful_return)
return successful_return;
// Here we know that the trial stress and intnl_old
// is inadmissible, and we have to return from those values
// value to the yield surface. There are three
// types of constraints we have to satisfy, listed
// below, and calculated in calculateConstraints(...)
// f<=0, epp=0, ic=0 (up to tolerances), and these are
// guaranteed to hold if nr_res2<=0.5
//
// Kuhn-Tucker conditions must also be satisfied
// These are:
// pm>=0, which may not hold upon exit of the NR loops
// due to _deactivation_scheme!=optimized;
// pm*f=0 (up to tolerances), which may not hold upon exit
// of the NR loops if a constraint got deactivated
// due to linear dependence, and then f<0, and its pm>0
// Plastic strain constraint, L2 norm must be zero (up to a tolerance)
RankTwoTensor epp;
// Yield function constraint passed to this function as
// std::vector<Real> & f
// Each yield function must be <= 0 (up to tolerance)
// Note that only the constraints that are active will be
// contained in f until the final few lines of returnMap
// Internal constraint(s), must be zero (up to a tolerance)
// Note that only the constraints that are active will be
// contained in ic.
std::vector<Real> ic;
// Record the stress before Newton-Raphson in case of failure-and-restart
RankTwoTensor initial_stress = stress;
iter = 0;
// Initialize the set of active constraints
// At this stage, the active constraints are
// those that exceed their _f_tol
// active constraints.
std::vector<bool> act;
buildActiveConstraints(f, stress, intnl, E_ijkl, act);
// Inverse of E_ijkl (assuming symmetric)
RankFourTensor E_inv = E_ijkl.invSymm();
// convenience variable that holds the change in plastic strain incurred during the return
// delta_dp = plastic_strain - plastic_strain_old
// delta_dp = E^{-1}*(initial_stress - stress), where initial_stress = E*(strain -
// plastic_strain_old)
RankTwoTensor delta_dp = RankTwoTensor();
// whether single step was successful (whether line search was successful, and whether turning off
// constraints was successful)
bool single_step_success = true;
// deactivation scheme
DeactivationSchemeEnum deact_scheme = _deactivation_scheme;
// For complicated deactivation schemes we have to record the initial active set
std::vector<bool> initial_act;
initial_act.resize(_num_surfaces);
if (_deactivation_scheme == optimized_to_safe ||
_deactivation_scheme == optimized_to_safe_to_dumb ||
_deactivation_scheme == optimized_to_dumb)
{
// if "optimized" fails we can change the deactivation scheme to "safe", etc
deact_scheme = optimized;
for (unsigned surface = 0; surface < _num_surfaces; ++surface)
initial_act[surface] = act[surface];
}
if (_deactivation_scheme == safe_to_dumb)
deact_scheme = safe;
// For "dumb" deactivation, the active set takes all combinations until a solution is found
int dumb_iteration = 0;
std::vector<unsigned int> dumb_order;
if (_deactivation_scheme == dumb ||
(_deactivation_scheme == optimized_to_safe_to_dumb && can_revert_to_dumb) ||
(_deactivation_scheme == safe_to_dumb && can_revert_to_dumb) ||
(_deactivation_scheme == optimized_to_dumb && can_revert_to_dumb))
buildDumbOrder(stress, intnl, dumb_order);
if (_deactivation_scheme == dumb)
{
incrementDumb(dumb_iteration, dumb_order, act);
yieldFunction(stress, intnl, act, f);
}
// To avoid any re-trials of "act" combinations that
// we've already tried and rejected, i record the
// combinations in actives_tried
std::set<unsigned int> actives_tried;
actives_tried.insert(activeCombinationNumber(act));
// The residual-squared that the line-search will reduce
// Later it will get contributions from epp and ic, but
// at present these are zero
Real nr_res2 = 0;
for (unsigned surface = 0; surface < _num_surfaces; ++surface)
if (act[surface])
nr_res2 += 0.5 * Utility::pow<2>(f[surface] / _f[modelNumber(surface)]->_f_tol);
successful_return = false;
bool still_finding_solution = true;
while (still_finding_solution)
{
single_step_success = true;
unsigned int local_iter = 0;
// The Newton-Raphson loops
while (nr_res2 > 0.5 && local_iter++ < _max_iter && single_step_success)
single_step_success = singleStep(nr_res2,
stress,
intnl_old,
intnl,
pm,
delta_dp,
E_inv,
f,
epp,
ic,
act,
deact_scheme,
linesearch_needed,
ld_encountered);
bool nr_good = (nr_res2 <= 0.5 && local_iter <= _max_iter && single_step_success);
iter += local_iter;
// 'act' might have changed due to using deact_scheme = optimized, so
actives_tried.insert(activeCombinationNumber(act));
if (!nr_good)
{
// failure of NR routine.
// We might be able to change the deactivation_scheme and
// then re-try the NR starting from the initial values
// Or, if deact_scheme == "dumb", we just increarse the
// dumb_iteration number and re-try
bool change_scheme = false;
bool increment_dumb = false;
change_scheme = canChangeScheme(deact_scheme, can_revert_to_dumb);
if (!change_scheme && deact_scheme == dumb)
increment_dumb = canIncrementDumb(dumb_iteration);
still_finding_solution = (change_scheme || increment_dumb);
if (change_scheme)
changeScheme(initial_act,
can_revert_to_dumb,
initial_stress,
intnl_old,
deact_scheme,
act,
dumb_iteration,
dumb_order);
if (increment_dumb)
incrementDumb(dumb_iteration, dumb_order, act);
if (!still_finding_solution)
{
// we cannot change the scheme, or have run out of "dumb" options
successful_return = false;
break;
}
}
bool kt_good = false;
if (nr_good)
{
// check Kuhn-Tucker
kt_good = checkKuhnTucker(f, pm, act);
if (!kt_good)
{
if (deact_scheme != dumb)
{
applyKuhnTucker(f, pm, act);
// true if we haven't tried this active set before
still_finding_solution =
(actives_tried.find(activeCombinationNumber(act)) == actives_tried.end());
if (!still_finding_solution)
{
// must have tried turning off the constraints already.
// so try changing the scheme
if (canChangeScheme(deact_scheme, can_revert_to_dumb))
{
still_finding_solution = true;
changeScheme(initial_act,
can_revert_to_dumb,
initial_stress,
intnl_old,
deact_scheme,
act,
dumb_iteration,
dumb_order);
}
}
}
else
{
bool increment_dumb = false;
increment_dumb = canIncrementDumb(dumb_iteration);
still_finding_solution = increment_dumb;
if (increment_dumb)
incrementDumb(dumb_iteration, dumb_order, act);
}
if (!still_finding_solution)
{
// have tried turning off the constraints already,
// or have run out of "dumb" options
successful_return = false;
break;
}
}
}
bool admissible = false;
if (nr_good && kt_good)
{
// check admissible
std::vector<Real> all_f;
if (_num_surfaces == 1)
admissible = true; // for a single surface if NR has exited successfully then (stress,
// intnl) must be admissible
else
admissible = checkAdmissible(stress, intnl, all_f);
if (!admissible)
{
// Not admissible.
// We can try adding constraints back in
// We can try changing the deactivation scheme
// Or, if deact_scheme == dumb, just increase dumb_iteration
bool add_constraints = canAddConstraints(act, all_f);
if (add_constraints)
{
constraints_added = true;
std::vector<bool> act_plus(_num_surfaces,
false); // "act" with the positive constraints added in
for (unsigned surface = 0; surface < _num_surfaces; ++surface)
if (act[surface] ||
(!act[surface] && (all_f[surface] > _f[modelNumber(surface)]->_f_tol)))
act_plus[surface] = true;
if (actives_tried.find(activeCombinationNumber(act_plus)) == actives_tried.end())
{
// haven't tried this combination of actives yet
constraints_added = true;
for (unsigned surface = 0; surface < _num_surfaces; ++surface)
act[surface] = act_plus[surface];
}
else
add_constraints = false; // haven't managed to add a new combination
}
bool change_scheme = false;
bool increment_dumb = false;
if (!add_constraints)
change_scheme = canChangeScheme(deact_scheme, can_revert_to_dumb);
if (!add_constraints && !change_scheme && deact_scheme == dumb)
increment_dumb = canIncrementDumb(dumb_iteration);
still_finding_solution = (add_constraints || change_scheme || increment_dumb);
if (change_scheme)
changeScheme(initial_act,
can_revert_to_dumb,
initial_stress,
intnl_old,
deact_scheme,
act,
dumb_iteration,
dumb_order);
if (increment_dumb)
incrementDumb(dumb_iteration, dumb_order, act);
if (!still_finding_solution)
{
// we cannot change the scheme, or have run out of "dumb" options
successful_return = false;
break;
}
}
}
successful_return = (nr_good && admissible && kt_good);
if (successful_return)
break;
if (still_finding_solution)
{
stress = initial_stress;
delta_dp = RankTwoTensor(); // back to zero change in plastic strain
for (unsigned model = 0; model < _num_models; ++model)
intnl[model] = intnl_old[model]; // back to old internal params
pm.assign(_num_surfaces, 0.0); // back to zero plastic multipliers
unsigned num_active = numberActive(act);
if (num_active == 0)
{
successful_return = false;
break; // failure
}
actives_tried.insert(activeCombinationNumber(act));
// Since "act" set has changed, either by changing deact_scheme, or by KT failing, so need to
// re-calculate nr_res2
yieldFunction(stress, intnl, act, f);
nr_res2 = 0;
unsigned ind = 0;
for (unsigned surface = 0; surface < _num_surfaces; ++surface)
if (act[surface])
{
if (f[ind] > _f[modelNumber(surface)]->_f_tol)
nr_res2 += 0.5 * Utility::pow<2>(f[ind] / _f[modelNumber(surface)]->_f_tol);
ind++;
}
}
}
// returned, with either success or failure
if (successful_return)
{
plastic_strain += delta_dp;
for (unsigned surface = 0; surface < _num_surfaces; ++surface)
cumulative_pm[surface] += pm[surface];
if (final_step)
consistent_tangent_operator =
consistentTangentOperator(stress, intnl, E_ijkl, pm, cumulative_pm);