PowerLawSlipRule.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/crystal_plasticity/PowerLawSlipRule.h"
#include "neml2/models/solid_mechanics/crystal_plasticity/SlipRule.h"
 
namespace neml2
{
register_NEML2_object(PowerLawSlipRule);
 
OptionSet
PowerLawSlipRule::expected_options()
{
  OptionSet options = SlipRule::expected_options();
  options.doc() =
      "Power law slip rule defined as \\f$ \\dot{\\gamma}_i = \\dot{\\gamma}_0 \\left| "
      "\\frac{\\tau_i}{\\hat{\\tau}_i} \\right|^{n-1} \\frac{\\tau_i}{\\hat{\\tau}_i} \\f$ with "
      "\\f$ \\dot{\\gamma}_i \\f$ the slip rate on system \\f$ i \\f$, \\f$ \\tau_i \\f$ the "
      "resolved shear, \\f$ \\hat{\\tau}_i \\f$ the slip system strength, \\f$ n \\f$ the rate "
      "senstivity, and \\f$ \\dot{\\gamma}_0 \\f$ a reference slip rate.";
 
  options.set<CrossRef<Scalar>>("gamma0");
  options.set("gamma0").doc() = "Reference slip rate";
 
  options.set<CrossRef<Scalar>>("n");
  options.set("n").doc() = "Rate sensitivity exponent";
 
  return options;
}
 
PowerLawSlipRule::PowerLawSlipRule(const OptionSet & options)
  : SlipRule(options),
    _gamma0(declare_parameter<Scalar>("gamma0", "gamma0")),
    _n(declare_parameter<Scalar>("n", "n"))
{
}
 
void
PowerLawSlipRule::set_value(bool out, bool dout_din, bool d2out_din2)
{
  neml_assert_dbg(!d2out_din2, "Second derivative not implemented.");
 
  // Grab the input
  const auto rss = Scalar(_rss, batch_dim() + 1);
  const auto tau = Scalar(_tau, batch_dim() + 1);
 
  if (out)
    _g = BatchTensor(_gamma0 * math::pow(abs(rss / tau), _n - 1.0) * rss / tau, batch_dim());
 
  if (dout_din)
  {
    _g.d(_rss) = BatchTensor(
        math::batch_diag_embed(_gamma0 * _n * math::pow(abs(rss / tau), _n - 1.0) / tau),
        batch_dim());
    _g.d(_tau) =
        BatchTensor(math::batch_diag_embed(-_n * _gamma0 * rss * math::pow(abs(rss), _n - 1.0) /
                                           math::pow(tau, _n + 1)),
                    batch_dim());
  }
}
} // namespace neml2