PowerLawCreepStressUpdate.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 "PowerLawCreepStressUpdate.h"
 
registerMooseObject("TensorMechanicsApp", PowerLawCreepStressUpdate);
 
defineLegacyParams(PowerLawCreepStressUpdate);
 
InputParameters
PowerLawCreepStressUpdate::validParams()
{
  InputParameters params = RadialReturnCreepStressUpdateBase::validParams();
  params.addClassDescription(
      "This class uses the stress update material in a radial return isotropic power law creep "
      "model.  This class can be used in conjunction with other creep and plasticity materials for "
      "more complex simulations.");
 
  // Linear strain hardening parameters
  params.addCoupledVar("temperature", "Coupled temperature");
  params.addRequiredParam<Real>("coefficient", "Leading coefficient in power-law equation");
  params.addRequiredParam<Real>("n_exponent", "Exponent on effective stress in power-law equation");
  params.addParam<Real>("m_exponent", 0.0, "Exponent on time in power-law equation");
  params.addRequiredParam<Real>("activation_energy", "Activation energy");
  params.addParam<Real>("gas_constant", 8.3143, "Universal gas constant");
  params.addParam<Real>("start_time", 0.0, "Start time (if not zero)");
 
  return params;
}
 
PowerLawCreepStressUpdate::PowerLawCreepStressUpdate(const InputParameters & parameters)
  : RadialReturnCreepStressUpdateBase(parameters),
    _has_temp(isParamValid("temperature")),
    _temperature(_has_temp ? coupledValue("temperature") : _zero),
    _coefficient(getParam<Real>("coefficient")),
    _n_exponent(getParam<Real>("n_exponent")),
    _m_exponent(getParam<Real>("m_exponent")),
    _activation_energy(getParam<Real>("activation_energy")),
    _gas_constant(getParam<Real>("gas_constant")),
    _start_time(getParam<Real>("start_time"))
{
  if (_start_time < _app.getStartTime() && (std::trunc(_m_exponent) != _m_exponent))
    paramError("start_time",
               "Start time must be equal to or greater than the Executioner start_time if a "
               "non-integer m_exponent is used");
}
 
void
PowerLawCreepStressUpdate::computeStressInitialize(const Real /*effective_trial_stress*/,
                                                   const RankFourTensor & /*elasticity_tensor*/)
{
  if (_has_temp)
    _exponential = std::exp(-_activation_energy / (_gas_constant * _temperature[_qp]));
  else
    _exponential = 1.0;
 
  _exp_time = std::pow(_t - _start_time, _m_exponent);
}
 
Real
PowerLawCreepStressUpdate::computeResidual(const Real effective_trial_stress, const Real scalar)
{
  const Real stress_delta = effective_trial_stress - _three_shear_modulus * scalar;
  const Real creep_rate =
      _coefficient * std::pow(stress_delta, _n_exponent) * _exponential * _exp_time;
  return creep_rate * _dt - scalar;
}
 
Real
PowerLawCreepStressUpdate::computeDerivative(const Real effective_trial_stress, const Real scalar)
{
  const Real stress_delta = effective_trial_stress - _three_shear_modulus * scalar;
  const Real creep_rate_derivative = -1.0 * _coefficient * _three_shear_modulus * _n_exponent *
                                     std::pow(stress_delta, _n_exponent - 1.0) * _exponential *
                                     _exp_time;
  return creep_rate_derivative * _dt - 1.0;
}