void
ReturnMappingModel::computeStress(const Elem & /*current_elem*/, unsigned qp,
const SymmElasticityTensor & elasticityTensor,
const SymmTensor & stress_old,
SymmTensor & strain_increment,
SymmTensor & stress_new,
SymmTensor & inelastic_strain_increment)
{
// compute deviatoric trial stress
SymmTensor dev_trial_stress(stress_new);
dev_trial_stress.addDiag(-dev_trial_stress.trace()/3.0);
// compute effective trial stress
Real dts_squared = dev_trial_stress.doubleContraction(dev_trial_stress);
Real effective_trial_stress = std::sqrt(1.5 * dts_squared);
// compute effective strain increment
SymmTensor dev_strain_increment(strain_increment);
dev_strain_increment.addDiag(-strain_increment.trace()/3.0);
_effective_strain_increment = dev_strain_increment.doubleContraction(dev_strain_increment);
_effective_strain_increment = std::sqrt(2.0/3.0 * _effective_strain_increment);
computeStressInitialize(qp, effective_trial_stress, elasticityTensor);
// Use Newton sub-iteration to determine inelastic strain increment
Real scalar = 0;
unsigned int it = 0;
Real residual = 10;
Real norm_residual = 10;
Real first_norm_residual = 10;
std::string iter_output;
while (it < _max_its &&
norm_residual > _absolute_tolerance &&
(norm_residual/first_norm_residual) > _relative_tolerance)
{
iterationInitialize(qp, scalar);
residual = computeResidual(qp, effective_trial_stress, scalar);
norm_residual = std::abs(residual);
if (it == 0)
{
first_norm_residual = norm_residual;
if (first_norm_residual == 0)
{
first_norm_residual = 1;
}
}
scalar -= residual / computeDerivative(qp, effective_trial_stress, scalar);
if (_output_iteration_info == true ||
_output_iteration_info_on_error == true)
{
iter_output = "In the element " + Moose::stringify(_current_elem->id()) +
+ " and the qp point " + Moose::stringify(qp) + ": \n" +
+ " iteration = " + Moose::stringify(it ) + "\n" +
+ " effective trial stress = " + Moose::stringify(effective_trial_stress) + "\n" +
+ " scalar effective inelastic strain = " + Moose::stringify(scalar) +"\n" +
+ " relative residual = " + Moose::stringify(norm_residual/first_norm_residual) + "\n" +
+ " relative tolerance = " + Moose::stringify(_relative_tolerance) + "\n" +
+ " absolute residual = " + Moose::stringify(norm_residual) + "\n" +
+ " absolute tolerance = " + Moose::stringify(_absolute_tolerance) + "\n";
}
iterationFinalize(qp, scalar);
++it;
}
if (_output_iteration_info)
_console << iter_output;
if (it == _max_its &&
norm_residual > _absolute_tolerance &&
(norm_residual/first_norm_residual) > _relative_tolerance)
{
if (_output_iteration_info_on_error)
{
Moose::err << iter_output;
}
mooseError("Exceeded maximum iterations in ReturnMappingModel solve for material: " << _name << ". Rerun with 'output_iteration_info_on_error = true' for more information.");
}
// compute inelastic and elastic strain increments (avoid potential divide by zero - how should this be done)?
if (effective_trial_stress < 0.01)
{
effective_trial_stress = 0.01;
}
inelastic_strain_increment = dev_trial_stress;
inelastic_strain_increment *= (1.5*scalar/effective_trial_stress);
strain_increment -= inelastic_strain_increment;
// compute stress increment
stress_new = elasticityTensor * strain_increment;
// update stress
stress_new += stress_old;
computeStressFinalize(qp, inelastic_strain_increment);
}
void
RecomputeRadialReturn::computeStress(RankTwoTensor & strain_increment,
RankTwoTensor & inelastic_strain_increment,
RankTwoTensor & stress_new)
{
// Given the stretching, update the inelastic strain
// Compute the stress in the intermediate configuration while retaining the stress history
// compute the deviatoric trial stress and trial strain from the current intermediate configuration
RankTwoTensor deviatoric_trial_stress = stress_new.deviatoric();
// compute the effective trial stress
Real dev_trial_stress_squared = deviatoric_trial_stress.doubleContraction(deviatoric_trial_stress);
Real effective_trial_stress = std::sqrt(3.0 / 2.0 * dev_trial_stress_squared);
//If the effective trial stress is zero, so should the inelastic strain increment be zero
//In that case skip the entire iteration if the effective trial stress is zero
if (effective_trial_stress != 0.0)
{
computeStressInitialize(effective_trial_stress);
// Use Newton sub-iteration to determine the scalar effective inelastic strain increment
Real scalar_effective_inelastic_strain = 0;
unsigned int iteration = 0;
Real residual = 10; // use a large number here to guarantee at least one loop through while
Real norm_residual = 10;
Real first_norm_residual = 10;
// create an output string with iteration information when errors occur
std::string iteration_output;
while (iteration < _max_its &&
norm_residual > _absolute_tolerance &&
(norm_residual/first_norm_residual) > _relative_tolerance)
{
iterationInitialize(scalar_effective_inelastic_strain);
residual = computeResidual(effective_trial_stress, scalar_effective_inelastic_strain);
norm_residual = std::abs(residual);
if (iteration == 0)
{
first_norm_residual = norm_residual;
if (first_norm_residual == 0)
first_norm_residual = 1;
}
Real derivative = computeDerivative(effective_trial_stress, scalar_effective_inelastic_strain);
scalar_effective_inelastic_strain -= residual / derivative;
if (_output_iteration_info || _output_iteration_info_on_error)
{
iteration_output = "In the element " + Moose::stringify(_current_elem->id()) +
+ " and the qp point " + Moose::stringify(_qp) + ": \n" +
+ " iteration = " + Moose::stringify(iteration ) + "\n" +
+ " effective trial stress = " + Moose::stringify(effective_trial_stress) + "\n" +
+ " scalar effective inelastic strain = " + Moose::stringify(scalar_effective_inelastic_strain) +"\n" +
+ " relative residual = " + Moose::stringify(norm_residual/first_norm_residual) + "\n" +
+ " relative tolerance = " + Moose::stringify(_relative_tolerance) + "\n" +
+ " absolute residual = " + Moose::stringify(norm_residual) + "\n" +
+ " absolute tolerance = " + Moose::stringify(_absolute_tolerance) + "\n";
}
iterationFinalize(scalar_effective_inelastic_strain);
++iteration;
}
if (_output_iteration_info)
_console << iteration_output << std::endl;
if (iteration == _max_its &&
norm_residual > _absolute_tolerance &&
(norm_residual/first_norm_residual) > _relative_tolerance)
{
if (_output_iteration_info_on_error)
Moose::err << iteration_output;
mooseError("Exceeded maximum iterations in RecomputeRadialReturn solve for material: " << _name << ". Rerun with 'output_iteration_info_on_error = true' for more information.");
}
// compute inelastic strain increments while avoiding a potential divide by zero
inelastic_strain_increment = deviatoric_trial_stress;
inelastic_strain_increment *= (3.0 / 2.0 * scalar_effective_inelastic_strain / effective_trial_stress);
}
else
inelastic_strain_increment.zero();
strain_increment -= inelastic_strain_increment;
stress_new = _elasticity_tensor[_qp] * (strain_increment + _elastic_strain_old[_qp]);
computeStressFinalize(inelastic_strain_increment);
}
void
ReturnMappingModel::computeStress( const Elem & /*current_elem*/, unsigned qp,
const SymmElasticityTensor & elasticityTensor,
const SymmTensor & stress_old,
SymmTensor & strain_increment,
SymmTensor & stress_new,
SymmTensor & inelastic_strain_increment )
{
// compute deviatoric trial stress
SymmTensor dev_trial_stress(stress_new);
dev_trial_stress.addDiag( -dev_trial_stress.trace()/3.0 );
// compute effective trial stress
Real dts_squared = dev_trial_stress.doubleContraction(dev_trial_stress);
Real effective_trial_stress = std::sqrt(1.5 * dts_squared);
// compute effective strain increment
SymmTensor dev_strain_increment(strain_increment);
dev_strain_increment.addDiag( -strain_increment.trace()/3.0);
_effective_strain_increment = dev_strain_increment.doubleContraction(dev_strain_increment);
_effective_strain_increment = std::sqrt(2.0/3.0 * _effective_strain_increment);
computeStressInitialize(qp, effective_trial_stress, elasticityTensor);
// Use Newton sub-iteration to determine inelastic strain increment
Real scalar = 0;
unsigned int it = 0;
Real residual = 10;
Real norm_residual = 10;
Real first_norm_residual = 10;
std::stringstream iter_output;
while (it < _max_its &&
norm_residual > _absolute_tolerance &&
(norm_residual/first_norm_residual) > _relative_tolerance)
{
iterationInitialize( qp, scalar );
residual = computeResidual(qp, effective_trial_stress, scalar);
norm_residual = std::abs(residual);
if (it == 0)
{
first_norm_residual = norm_residual;
if (first_norm_residual == 0)
{
first_norm_residual = 1;
}
}
scalar -= residual / computeDerivative(qp, effective_trial_stress, scalar);
if (_output_iteration_info == true ||
_output_iteration_info_on_error == true)
{
iter_output
<< " it=" << it
<< " trl_strs=" << effective_trial_stress
<< " scalar=" << scalar
<< " rel_res=" << norm_residual/first_norm_residual
<< " rel_tol=" << _relative_tolerance
<< " abs_res=" << norm_residual
<< " abs_tol=" << _absolute_tolerance
<< std::endl;
}
iterationFinalize( qp, scalar );
++it;
}
if (_output_iteration_info)
_console << iter_output.str();
if (it == _max_its &&
norm_residual > _absolute_tolerance &&
(norm_residual/first_norm_residual) > _relative_tolerance)
{
if (_output_iteration_info_on_error)
{
Moose::err << iter_output.str();
}
mooseError("Max sub-newton iteration hit during nonlinear constitutive model solve! (" << _name << ")");
}
// compute inelastic and elastic strain increments (avoid potential divide by zero - how should this be done)?
if (effective_trial_stress < 0.01)
{
effective_trial_stress = 0.01;
}
inelastic_strain_increment = dev_trial_stress;
inelastic_strain_increment *= (1.5*scalar/effective_trial_stress);
strain_increment -= inelastic_strain_increment;
// compute stress increment
stress_new = elasticityTensor * strain_increment;
// update stress
stress_new += stress_old;
computeStressFinalize(qp, inelastic_strain_increment);
}