pk2stress.hh

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// SPDX-FileCopyrightText: 2021-2025 The Ikarus Developers ikarus@ibb.uni-stuttgart.de
// SPDX-License-Identifier: LGPL-3.0-or-later
 
#pragma once
 
#include <dune/common/fvector.hh>
#include <dune/localfefunctions/eigenDuneTransformations.hh>
#include <dune/localfefunctions/expressions/greenLagrangeStrains.hh>
 
#include <Eigen/Core>
 
#include <ikarus/utils/tensorutils.hh>
 
namespace Ikarus::PS {
 
struct PK2Stress
{
  template <typename GEO, typename AST>
  static auto value(const GEO& geo, const Dune::FieldVector<double, GEO::mydimension>& gpPos, const AST& asFunction,
                    const auto& beta) {
    const auto P = asFunction(gpPos);
    return (P * beta).eval();
  }
 
  template <typename GEO, typename AST>
  static auto firstDerivative(const GEO& geo, const auto& uFunction, const auto& localBasis, const auto& gpIndex,
                              const Dune::FieldVector<double, GEO::mydimension>& gpPos, const AST& asFunction,
                              const auto& beta, const int node = sNaN) {
    return asFunction(gpPos);
  }
 
  template <typename GEO, typename ST, typename AST>
  static auto secondDerivative(const GEO& geo, const auto& uFunction, const auto& localBasis, const auto& gpIndex,
                               const Dune::FieldVector<double, GEO::mydimension>& gpPos,
                               const Eigen::Vector<ST, GEO::mydimension*(GEO::mydimension + 1) / 2>& S,
                               const AST& asFunction, const auto& beta, const int I = sNaN, const int J = sNaN) {
    constexpr int myDim             = GEO::mydimension;
    constexpr int assumedStressSize = AST::assumedStressSize;
 
    return Eigen::Matrix<ST, assumedStressSize, assumedStressSize>::Zero().eval();
  }
 
  static constexpr auto name() { return std::string("PK2 Stress"); }
 
private:
  static constexpr int sNaN = std::numeric_limits<int>::signaling_NaN();
};
 
} // namespace Ikarus::PS