KocksMeckingActivationEnergy.cxx

// Copyright 2023, UChicago Argonne, LLC
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// Software Name: NEML2 -- the New Engineering material Model Library, version 2
// By: Argonne National Laboratory
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#include "neml2/models/solid_mechanics/KocksMeckingActivationEnergy.h"
 
namespace neml2
{
register_NEML2_object(KocksMeckingActivationEnergy);
 
OptionSet
KocksMeckingActivationEnergy::expected_options()
{
  OptionSet options = Model::expected_options();
  options.doc() =
      "Calculates the Kocks-Mecking normalized activation as \\f$g = \\frac{kT}{\\mu "
      "b^3} \\log \\frac{\\dot{\\varepsilon}_0}{\\dot{\\varepsilon}} \\f$ with \\f$ "
      "\\mu \\f$ the shear modulus, \\f$ k \\f$ the Boltzmann constant, \\f$ T \\f$ the absolute "
      "temperature, \\f$ b \\f$ the Burgers vector length, \\f$ \\dot{\\varepsilon}_0 \\f$ a "
      "reference strain rate, and \\f$ \\dot{\\varepsilon} \\f$ the current strain rate.";
 
  options.set<CrossRef<Scalar>>("shear_modulus");
  options.set("shear_modulus").doc() = "The shear modulus";
 
  options.set<Real>("eps0");
  options.set("eps0").doc() = "Reference strain rate";
 
  options.set<Real>("k");
  options.set("k").doc() = "The Boltzmann constant";
  options.set<Real>("b");
  options.set("b").doc() = "Magnitude of the Burgers vector";
 
  options.set<VariableName>("temperature") = VariableName("forces", "T");
  options.set("temperature").doc() = "Absolute temperature";
 
  options.set<VariableName>("strain_rate") = VariableName("forces", "effective_strain_rate");
  options.set("strain_rate").doc() = "Name of the effective strain rate";
 
  options.set<VariableName>("activation_energy") = VariableName("forces", "g");
  options.set("activation_energy").doc() = "Output name of the activation energy";
  return options;
}
 
KocksMeckingActivationEnergy::KocksMeckingActivationEnergy(const OptionSet & options)
  : Model(options),
    _mu(declare_parameter<Scalar>("shear_modulus", "shear_modulus")),
    _eps0(options.get<Real>("eps0")),
    _k(options.get<Real>("k")),
    _b3(options.get<Real>("b") * options.get<Real>("b") * options.get<Real>("b")),
    _T(declare_input_variable<Scalar>("temperature")),
    _eps_dot(declare_input_variable<Scalar>("strain_rate")),
    _g(declare_output_variable<Scalar>("activation_energy"))
{
}
 
void
KocksMeckingActivationEnergy::set_value(bool out, bool dout_din, bool d2out_din2)
{
  neml_assert(!d2out_din2, "Second derivatives not implemented");
 
  if (out)
    _g = _k * _T / (_mu * _b3) * math::log(_eps0 / _eps_dot);
 
  if (dout_din)
  {
    _g.d(_T) = _k / (_mu * _b3) * math::log(_eps0 / _eps_dot);
    _g.d(_eps_dot) = -_k * _T / (_mu * _b3 * _eps_dot);
    if (const auto mu = nl_param("shear_modulus"))
      _g.d(*mu) = -_k * _T / (_b3 * _mu * _mu) * math::log(_eps0 / _eps_dot);
  }
}
} // namespace neml2