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material_evaluator.hh
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/**
* @file material_evaluator.hh
*
* @author Till Junge <till.junge@altermail.ch>
*
* @date 12 Dec 2018
*
* @brief Helper to evaluate material laws
*
* Copyright © 2018 Till Junge
*
* µSpectre is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 3, or (at
* your option) any later version.
*
* µSpectre is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with µSpectre; see the file COPYING. If not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*
* Additional permission under GNU GPL version 3 section 7
*
* If you modify this Program, or any covered work, by linking or combining it
* with proprietary FFT implementations or numerical libraries, containing parts
* covered by the terms of those libraries' licenses, the licensors of this
* Program grant you additional permission to convey the resulting work.
*/
#ifndef SRC_MATERIALS_MATERIAL_EVALUATOR_HH_
#define SRC_MATERIALS_MATERIAL_EVALUATOR_HH_
#include "common/muSpectre_common.hh"
#include "materials/materials_toolbox.hh"
#include <libmugrid/T4_map_proxy.hh>
#include <libmugrid/ccoord_operations.hh>
#include <libmugrid/field.hh>
#include <exception>
#include <memory>
#include <sstream>
namespace muSpectre {
/**
* forward declaration to avoid incluning material_base.hh
*/
template <Dim_t DimS, Dim_t DimM>
class MaterialBase;
template <Dim_t DimM>
class MaterialEvaluator {
public:
using T2_t = Eigen::Matrix<Real, DimM, DimM>;
using T4_t = muGrid::T4Mat<Real, DimM>;
using T2_map = Eigen::Map<T2_t>;
using T4_map = muGrid::T4MatMap<Real, DimM>;
using T2_const_map = Eigen::Map<const T2_t>;
using T4_const_map = muGrid::T4MatMap<Real, DimM, true>;
using FieldColl_t = muGrid::GlobalFieldCollection<DimM>;
using T2Field_t = muGrid::TensorField<FieldColl_t, Real, secondOrder, DimM>;
using T4Field_t = muGrid::TensorField<FieldColl_t, Real, fourthOrder, DimM>;
//! Default constructor
MaterialEvaluator() = delete;
/**
* constructor with a shared pointer to a Material
*/
explicit MaterialEvaluator(
std::shared_ptr<MaterialBase<DimM, DimM>> material)
: material{material}, collection{std::make_unique<FieldColl_t>()},
strain{muGrid::make_field<T2Field_t>("gradient", *this->collection)},
stress{muGrid::make_field<T2Field_t>("stress", *this->collection)},
tangent{muGrid::make_field<T4Field_t>("tangent", *this->collection)} {
this->collection->initialise(muGrid::CcoordOps::get_cube<DimM>(1), {0});
}
//! Copy constructor
MaterialEvaluator(const MaterialEvaluator & other) = delete;
//! Move constructor
MaterialEvaluator(MaterialEvaluator && other) = default;
//! Destructor
virtual ~MaterialEvaluator() = default;
//! Copy assignment operator
MaterialEvaluator & operator=(const MaterialEvaluator & other) = delete;
//! Move assignment operator
MaterialEvaluator & operator=(MaterialEvaluator && other) = default;
/**
* for materials with state variables. See `muSpectre::MaterialBase` for
* details
*/
void save_history_variables() { this->material->save_history_variables(); }
/**
* Evaluates the underlying materials constitutive law and returns the
* stress P or σ as a function of the placement gradient F or small strain
* tensor ε depending on the formulation
* (`muSpectre::Formulation::small_strain` for σ(ε),
* `muSpectre::Formulation::finite_strain` for P(F))
*/
inline T2_const_map evaluate_stress(const Eigen::Ref<const T2_t> & grad,
const Formulation & form);
/**
* Evaluates the underlying materials constitutive law and returns the the
* stress P or σ and the tangent moduli K as a function of the placement
* gradient F or small strain tensor ε depending on the formulation
* (`muSpectre::Formulation::small_strain` for σ(ε),
* `muSpectre::Formulation::finite_strain` for P(F))
*/
inline std::tuple<T2_const_map, T4_const_map>
evaluate_stress_tangent(const Eigen::Ref<const T2_t> & grad,
const Formulation & form);
/**
* estimate the tangent using finite difference
*/
inline T4_t
estimate_tangent(const Eigen::Ref<const T2_t> & grad,
const Formulation & form, const Real step,
const FiniteDiff diff_type = FiniteDiff::centred);
protected:
/**
* throws a runtime error if the material's per-pixel data has not been set.
*/
void check_init() const;
std::shared_ptr<MaterialBase<DimM, DimM>> material;
std::unique_ptr<FieldColl_t> collection;
T2Field_t & strain;
T2Field_t & stress;
T4Field_t & tangent;
};
/* ---------------------------------------------------------------------- */
template <Dim_t DimM>
auto
MaterialEvaluator<DimM>::evaluate_stress(const Eigen::Ref<const T2_t> & grad,
const Formulation & form)
-> T2_const_map {
this->check_init();
this->strain.get_map()[0] = grad;
this->material->compute_stresses(this->strain, this->stress, form);
return T2_const_map(this->stress.get_map()[0].data());
}
/* ---------------------------------------------------------------------- */
template <Dim_t DimM>
auto MaterialEvaluator<DimM>::evaluate_stress_tangent(
const Eigen::Ref<const T2_t> & grad, const Formulation & form)
-> std::tuple<T2_const_map, T4_const_map> {
this->check_init();
this->strain.get_map()[0] = grad;
this->material->compute_stresses_tangent(this->strain, this->stress,
this->tangent, form);
return std::make_tuple(T2_const_map(this->stress.get_map()[0].data()),
T4_const_map(this->tangent.get_map()[0].data()));
}
template <Dim_t DimM>
void MaterialEvaluator<DimM>::check_init() const {
const auto & size{this->material->size()};
if (size < 1) {
throw std::runtime_error(
"Not initialised! You have to call `add_pixel(...)` on your material "
"exactly one time before you can evaluate it.");
} else if (size > 1) {
std::stringstream error{};
error << "The material to be evaluated should have exactly one pixel "
"added. You've added "
<< size << " pixels.";
throw std::runtime_error(error.str());
}
}
/* ---------------------------------------------------------------------- */
template <Dim_t DimM>
auto MaterialEvaluator<DimM>::estimate_tangent(
const Eigen::Ref<const T2_t> & grad, const Formulation & form,
const Real delta, const FiniteDiff diff_type) -> T4_t {
using T2_vec = Eigen::Map<Eigen::Matrix<Real, DimM * DimM, 1>>;
T4_t tangent{T4_t::Zero()};
const T2_t stress{this->evaluate_stress(grad, form)};
auto fun{[&form, this](const auto & grad_) {
return this->evaluate_stress(grad_, form);
}};
auto symmetrise{
[](auto & eps) { eps = .5 * (eps + eps.transpose().eval()); }};
static_assert(Int(decltype(tangent.col(0))::SizeAtCompileTime) ==
Int(T2_t::SizeAtCompileTime),
"wrong column size");
for (Dim_t i{}; i < DimM * DimM; ++i) {
T2_t strain2{grad};
T2_vec strain2_vec{strain2.data()};
switch (diff_type) {
case FiniteDiff::forward: {
strain2_vec(i) += delta;
if (form == Formulation::small_strain) {
symmetrise(strain2);
}
T2_t del_f_del{(fun(strain2) - stress) / delta};
tangent.col(i) = T2_vec(del_f_del.data());
break;
}
case FiniteDiff::backward: {
strain2_vec(i) -= delta;
if (form == Formulation::small_strain) {
symmetrise(strain2);
}
T2_t del_f_del{(stress - fun(strain2)) / delta};
tangent.col(i) = T2_vec(del_f_del.data());
break;
}
case FiniteDiff::centred: {
T2_t strain1{grad};
T2_vec strain1_vec{strain1.data()};
strain1_vec(i) += delta;
strain2_vec(i) -= delta;
if (form == Formulation::small_strain) {
symmetrise(strain1);
symmetrise(strain2);
}
T2_t del_f_del{(fun(strain1).eval() - fun(strain2).eval()) /
(2 * delta)};
tangent.col(i) = T2_vec(del_f_del.data());
break;
}
default: {
throw std::runtime_error("Unknown FiniteDiff value");
break;
}
}
static_assert(Int(decltype(tangent.col(i))::SizeAtCompileTime) ==
Int(T2_t::SizeAtCompileTime),
"wrong column size");
}
return tangent;
}
} // namespace muSpectre
#endif // SRC_MATERIALS_MATERIAL_EVALUATOR_HH_

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