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material_cohesive_linear_fatigue.cc
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/**
* @file material_cohesive_linear_fatigue.cc
*
* @author Marco Vocialta <marco.vocialta@epfl.ch>
*
* @date creation: Fri Feb 20 2015
* @date last modification: Tue Jan 12 2016
*
* @brief See material_cohesive_linear_fatigue.hh for information
*
* @section LICENSE
*
* Copyright (©) 2015 EPFL (Ecole Polytechnique Fédérale de Lausanne) Laboratory
* (LSMS - Laboratoire de Simulation en Mécanique des Solides)
*
* Akantu 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 of the License, or (at your option) any
* later version.
*
* Akantu 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 Lesser General Public License for more
* details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with Akantu. If not, see <http://www.gnu.org/licenses/>.
*
*/
/* -------------------------------------------------------------------------- */
#include "material_cohesive_linear_fatigue.hh"
__BEGIN_AKANTU__
/* -------------------------------------------------------------------------- */
template <UInt spatial_dimension>
MaterialCohesiveLinearFatigue<spatial_dimension>
::MaterialCohesiveLinearFatigue(SolidMechanicsModel & model,
const ID & id) :
MaterialCohesiveLinear<spatial_dimension>(model, id),
delta_prec("delta_prec", *this),
K_plus("K_plus", *this),
K_minus("K_minus", *this),
T_1d("T_1d", *this),
switches("switches", *this),
delta_dot_prec("delta_dot_prec", *this),
normal_regime("normal_regime", *this) {
this->registerParam("delta_f", delta_f, Real(-1.) ,
_pat_parsable | _pat_readable,
"delta_f");
this->registerParam("progressive_delta_f", progressive_delta_f, false,
_pat_parsable | _pat_readable,
"Whether or not delta_f is equal to delta_max");
this->registerParam("count_switches", count_switches, false,
_pat_parsable | _pat_readable,
"Count the opening/closing switches per element");
this->registerParam("fatigue_ratio", fatigue_ratio, Real(1.),
_pat_parsable | _pat_readable,
"What portion of the cohesive law is subjected to fatigue");
}
/* -------------------------------------------------------------------------- */
template <UInt spatial_dimension>
void MaterialCohesiveLinearFatigue<spatial_dimension>::initMaterial() {
MaterialCohesiveLinear<spatial_dimension>::initMaterial();
// check that delta_f has a proper value or assign a defaul value
if (delta_f < 0) delta_f = this->delta_c_eff;
else if (delta_f < this->delta_c_eff)
AKANTU_DEBUG_ERROR("Delta_f must be greater or equal to delta_c");
delta_prec.initialize(1);
K_plus.initialize(1);
K_minus.initialize(1);
T_1d.initialize(1);
normal_regime.initialize(1);
if (count_switches) {
switches.initialize(1);
delta_dot_prec.initialize(1);
}
}
/* -------------------------------------------------------------------------- */
template<UInt spatial_dimension>
void MaterialCohesiveLinearFatigue<spatial_dimension>
::computeTraction(const Array<Real> & normal,
ElementType el_type,
GhostType ghost_type) {
AKANTU_DEBUG_IN();
/// define iterators
Array<Real>::vector_iterator traction_it =
this->tractions(el_type, ghost_type).begin(spatial_dimension);
Array<Real>::vector_iterator opening_it =
this->opening(el_type, ghost_type).begin(spatial_dimension);
Array<Real>::vector_iterator contact_traction_it =
this->contact_tractions(el_type, ghost_type).begin(spatial_dimension);
Array<Real>::vector_iterator contact_opening_it =
this->contact_opening(el_type, ghost_type).begin(spatial_dimension);
Array<Real>::const_vector_iterator normal_it = normal.begin(spatial_dimension);
Array<Real>::vector_iterator traction_end =
this->tractions(el_type, ghost_type).end(spatial_dimension);
const Array<Real> & sigma_c_array = this->sigma_c_eff(el_type, ghost_type);
Array<Real> & delta_max_array = this->delta_max(el_type, ghost_type);
const Array<Real> & delta_c_array = this->delta_c_eff(el_type, ghost_type);
Array<Real> & damage_array = this->damage(el_type, ghost_type);
Array<Real>::vector_iterator insertion_stress_it =
this->insertion_stress(el_type, ghost_type).begin(spatial_dimension);
Array<Real> & delta_prec_array = delta_prec(el_type, ghost_type);
Array<Real> & K_plus_array = K_plus(el_type, ghost_type);
Array<Real> & K_minus_array = K_minus(el_type, ghost_type);
Array<Real> & T_1d_array = T_1d(el_type, ghost_type);
Array<bool> & normal_regime_array = normal_regime(el_type, ghost_type);
Array<UInt> * switches_array = NULL;
Array<Real> * delta_dot_prec_array = NULL;
if (count_switches) {
switches_array = &switches(el_type, ghost_type);
delta_dot_prec_array = &delta_dot_prec(el_type, ghost_type);
}
Real * memory_space = new Real[2*spatial_dimension];
Vector<Real> normal_opening(memory_space, spatial_dimension);
Vector<Real> tangential_opening(memory_space + spatial_dimension,
spatial_dimension);
Real tolerance = Math::getTolerance();
/// loop on each quadrature point
for (UInt q = 0; traction_it != traction_end;
++traction_it, ++opening_it, ++normal_it,
++contact_traction_it, ++insertion_stress_it, ++contact_opening_it, ++q) {
/// compute normal and tangential opening vectors
Real normal_opening_norm = opening_it->dot(*normal_it);
normal_opening = (*normal_it);
normal_opening *= normal_opening_norm;
tangential_opening = *opening_it;
tangential_opening -= normal_opening;
Real tangential_opening_norm = tangential_opening.norm();
/**
* compute effective opening displacement
* @f$ \delta = \sqrt{
* \frac{\beta^2}{\kappa^2} \Delta_t^2 + \Delta_n^2 } @f$
*/
Real delta = tangential_opening_norm * tangential_opening_norm * this->beta2_kappa2;
bool penetration = normal_opening_norm < -tolerance;
if (this->contact_after_breaking == false && Math::are_float_equal(damage_array(q), 1.))
penetration = false;
if (penetration) {
/// use penalty coefficient in case of penetration
*contact_traction_it = normal_opening;
*contact_traction_it *= this->penalty;
*contact_opening_it = normal_opening;
/// don't consider penetration contribution for delta
*opening_it = tangential_opening;
normal_opening.clear();
}
else {
delta += normal_opening_norm * normal_opening_norm;
contact_traction_it->clear();
contact_opening_it->clear();
}
delta = std::sqrt(delta);
/**
* Compute traction @f$ \mathbf{T} = \left(
* \frac{\beta^2}{\kappa} \Delta_t \mathbf{t} + \Delta_n
* \mathbf{n} \right) \frac{\sigma_c}{\delta} \left( 1-
* \frac{\delta}{\delta_c} \right)@f$
*/
// update maximum displacement and damage
delta_max_array(q) = std::max(delta, delta_max_array(q));
damage_array(q) = std::min(delta_max_array(q) / delta_c_array(q), Real(1.));
Real delta_dot = delta - delta_prec_array(q);
// count switches if asked
if (count_switches) {
if ( (delta_dot > 0. && (*delta_dot_prec_array)(q) <= 0.) ||
(delta_dot < 0. && (*delta_dot_prec_array)(q) >= 0.) )
++((*switches_array)(q));
(*delta_dot_prec_array)(q) = delta_dot;
}
// set delta_f equal to delta_max if desired
if (progressive_delta_f) delta_f = delta_max_array(q);
// broken element case
if (Math::are_float_equal(damage_array(q), 1.))
traction_it->clear();
// just inserted element case
else if (Math::are_float_equal(damage_array(q), 0.)) {
if (penetration)
traction_it->clear();
else
*traction_it = *insertion_stress_it;
// initialize the 1d traction to sigma_c
T_1d_array(q) = sigma_c_array(q);
}
// normal case
else {
// if element is closed then there are zero tractions
if (delta <= tolerance)
traction_it->clear();
// otherwise compute new tractions if the new delta is different
// than the previous one
else if (std::abs(delta_dot) > tolerance) {
// loading case
if (delta_dot > 0.) {
if (!normal_regime_array(q)) {
// equation (4) of the article
K_plus_array(q) *= 1. - delta_dot / delta_f;
// equivalent to equation (2) of the article
T_1d_array(q) += K_plus_array(q) * delta_dot;
// in case of reloading, traction must not exceed that of the
// envelop of the cohesive law
Real max_traction = sigma_c_array(q) * (1 - delta / delta_c_array(q));
bool max_traction_exceeded = T_1d_array(q) > max_traction;
if (max_traction_exceeded) T_1d_array(q) = max_traction;
// switch to standard linear cohesive law
if (delta_max_array(q) > fatigue_ratio * delta_c_array(q)) {
// reset delta_max to avoid big jumps in the traction
delta_max_array(q) = sigma_c_array(q) / (T_1d_array(q) / delta + sigma_c_array(q) / delta_c_array(q));
damage_array(q) = std::min(delta_max_array(q) / delta_c_array(q), Real(1.));
K_minus_array(q) = sigma_c_array(q) / delta_max_array(q) * (1. - damage_array(q));
normal_regime_array(q) = true;
} else {
// equation (3) of the article
K_minus_array(q) = T_1d_array(q) / delta;
// if the traction is following the cohesive envelop, then
// K_plus has to be reset
if (max_traction_exceeded) K_plus_array(q) = K_minus_array(q);
}
} else {
// compute stiffness according to the standard law
K_minus_array(q) = sigma_c_array(q) / delta_max_array(q) * (1. - damage_array(q));
}
}
// unloading case
else if (!normal_regime_array(q)) {
// equation (4) of the article
K_plus_array(q) += (K_plus_array(q) - K_minus_array(q)) * delta_dot / delta_f;
// equivalent to equation (2) of the article
T_1d_array(q) = K_minus_array(q) * delta;
}
// applying the actual stiffness
*traction_it = tangential_opening;
*traction_it *= this->beta2_kappa;
*traction_it += normal_opening;
*traction_it *= K_minus_array(q);
}
}
// update precendent delta
delta_prec_array(q) = delta;
}
delete [] memory_space;
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
INSTANTIATE_MATERIAL(MaterialCohesiveLinearFatigue);
__END_AKANTU__

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