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ntn_base_friction.cc
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Thu, Dec 12, 17:13

ntn_base_friction.cc
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/**
* @file ntn_base_friction.cc
* @author David Kammer <david.kammer@epfl.ch>
* @date Mon Aug 26 17:11:29 2013
*
* @brief implementation of ntn base friction
*
* @section LICENSE
*
* Copyright (©) 2010-2011 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/>.
*
*/
/* -------------------------------------------------------------------------- */
// simtools
#include "ntn_base_friction.hh"
#include "dumper_text.hh"
__BEGIN_SIMTOOLS__
/* -------------------------------------------------------------------------- */
NTNBaseFriction::NTNBaseFriction(NTNBaseContact * contact,
const FrictionID & id,
const MemoryID & memory_id) :
Memory(id,memory_id),
Parsable(_st_friction, id),
Dumpable(),
contact(contact),
is_sticking(0,1,true,id+":is_sticking",true,"is_sticking"),
frictional_strength(0,1,0.,id+":frictional_strength",0.,"frictional_strength"),
friction_traction(0,contact->getModel().getSpatialDimension(),
0.,id+":friction_traction",0.,"friction_traction"),
slip(0,1,0.,id+":slip",0.,"slip"),
cumulative_slip(0,1,0.,id+":cumulative_slip",0.,"cumulative_slip"),
slip_velocity(0,contact->getModel().getSpatialDimension(),
0.,id+":slip_velocity",0.,"slip_velocity") {
AKANTU_DEBUG_IN();
this->contact->registerSynchronizedArray(this->is_sticking);
this->contact->registerSynchronizedArray(this->frictional_strength);
this->contact->registerSynchronizedArray(this->friction_traction);
this->contact->registerSynchronizedArray(this->slip);
this->contact->registerSynchronizedArray(this->cumulative_slip);
this->contact->registerSynchronizedArray(this->slip_velocity);
contact->getModel().setIncrementFlagOn();
this->registerExternalDumper(contact->getDumper(),
contact->getDefaultDumperName(),
true);
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNBaseFriction::updateSlip() {
AKANTU_DEBUG_IN();
SolidMechanicsModel & model = this->contact->getModel();
UInt dim = model.getSpatialDimension();
// synchronize increment
this->contact->getSynchronizerRegistry()->synchronize(_gst_cf_incr);
Array<Real> rel_tan_incr(0,dim);
this->contact->computeRelativeTangentialField(model.getIncrement(),
rel_tan_incr);
Array<Real>::const_iterator< Vector<Real> > it = rel_tan_incr.begin(dim);
UInt nb_nodes = this->contact->getNbContactNodes();
for (UInt n=0; n<nb_nodes; ++n) {
if (this->is_sticking(n)) {
this->slip(n) = 0.;
}
else {
const Vector<Real> & rti = it[n];
this->slip(n) += rti.norm();
this->cumulative_slip(n) += rti.norm();
}
}
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNBaseFriction::computeFrictionTraction() {
AKANTU_DEBUG_IN();
this->computeStickTraction();
this->computeFrictionalStrength();
SolidMechanicsModel & model = this->contact->getModel();
UInt dim = model.getSpatialDimension();
// get contact arrays
const SynchronizedArray<bool> & is_in_contact = this->contact->getIsInContact();
Array<Real> & traction = const_cast< Array<Real> & >(this->friction_traction.getArray());
Array<Real>::iterator< Vector<Real> > it_fric_trac = traction.begin(dim);
this->is_sticking.clear(); // set to not sticking
UInt nb_contact_nodes = this->contact->getNbContactNodes();
for (UInt n=0; n<nb_contact_nodes; ++n) {
// node pair is in contact
if (is_in_contact(n)) {
Vector<Real> & fric_trac = it_fric_trac[n];
// check if it is larger than frictional strength
Real abs_fric = fric_trac.norm();
if (abs_fric != 0.) {
Real alpha = this->frictional_strength(n) / abs_fric;
// larger -> sliding
if (alpha < 1.) {
fric_trac *= alpha;
}
else
this->is_sticking(n) = true;
}
else {
// frictional traction is already zero
this->is_sticking(n) = true;
}
}
}
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNBaseFriction::computeStickTraction() {
AKANTU_DEBUG_IN();
SolidMechanicsModel & model = this->contact->getModel();
UInt dim = model.getSpatialDimension();
Real delta_t = model.getTimeStep();
UInt nb_contact_nodes = this->contact->getNbContactNodes();
// get contact arrays
const SynchronizedArray<Real> & impedance = this->contact->getImpedance();
const SynchronizedArray<bool> & is_in_contact = this->contact->getIsInContact();
// pre-compute the acceleration
// (not increment acceleration, because residual is still Kf)
Array<Real> acceleration(model.getFEEngine().getMesh().getNbNodes(), dim, 0.);
model.solveLumped(acceleration,
model.getMass(),
model.getResidual(),
model.getBlockedDOFs(),
model.getF_M2A());
// compute relative normal fields of velocity and acceleration
Array<Real> r_velo(0,dim);
Array<Real> r_acce(0,dim);
Array<Real> r_old_acce(0,dim);
this->contact->computeRelativeTangentialField(model.getVelocity(), r_velo);
this->contact->computeRelativeTangentialField(acceleration, r_acce);
this->contact->computeRelativeTangentialField(model.getAcceleration(), r_old_acce);
AKANTU_DEBUG_ASSERT(r_velo.getSize() == nb_contact_nodes,
"computeRelativeNormalField does not give back arrays "
<< "size == nb_contact_nodes. nb_contact_nodes = " << nb_contact_nodes
<< " | array size = " << r_velo.getSize());
// compute tangential gap_dot array for all nodes
Array<Real> gap_dot(nb_contact_nodes, dim);
Real * gap_dot_p = gap_dot.storage();
Real * r_velo_p = r_velo.storage();
Real * r_acce_p = r_acce.storage();
Real * r_old_acce_p = r_old_acce.storage();
for (UInt i=0; i<nb_contact_nodes*dim; ++i) {
*gap_dot_p = *r_velo_p + delta_t * *r_acce_p - 0.5 * delta_t * *r_old_acce_p;
// increment pointers
gap_dot_p++;
r_velo_p++;
r_acce_p++;
r_old_acce_p++;
}
// compute friction traction to stop sliding
Array<Real> & traction = const_cast< Array<Real> & >(this->friction_traction.getArray());
Array<Real>::vector_iterator it_fric_trac = traction.begin(dim);
for (UInt n=0; n<nb_contact_nodes; ++n) {
Vector<Real> & fric_trac = it_fric_trac[n];
// node pair is NOT in contact
if (!is_in_contact(n)) {
fric_trac.clear(); // set to zero
}
// node pair is in contact
else {
// compute friction traction
for (UInt d=0; d<dim; ++d)
fric_trac(d) = impedance(n) * gap_dot(n,d) / 2.;
}
}
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNBaseFriction::applyFrictionTraction() {
AKANTU_DEBUG_IN();
SolidMechanicsModel & model = this->contact->getModel();
Array<Real> & residual = model.getResidual();
UInt dim = model.getSpatialDimension();
const SynchronizedArray<UInt> & slaves = this->contact->getSlaves();
const SynchronizedArray<Real> & lumped_boundary_slaves = this->contact->getLumpedBoundarySlaves();
UInt nb_contact_nodes = this->contact->getNbContactNodes();
for (UInt n=0; n<nb_contact_nodes; ++n) {
UInt slave = slaves(n);
for (UInt d=0; d<dim; ++d) {
residual(slave, d) -= lumped_boundary_slaves(n) * this->friction_traction(n,d);
}
}
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNBaseFriction::registerSynchronizedArray(SynchronizedArrayBase & array) {
AKANTU_DEBUG_IN();
this->frictional_strength.registerDependingArray(array);
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNBaseFriction::dumpRestart(const std::string & file_name) const {
AKANTU_DEBUG_IN();
this->is_sticking.dumpRestartFile(file_name);
this->frictional_strength.dumpRestartFile(file_name);
this->friction_traction.dumpRestartFile(file_name);
this->slip.dumpRestartFile(file_name);
this->cumulative_slip.dumpRestartFile(file_name);
this->slip_velocity.dumpRestartFile(file_name);
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNBaseFriction::readRestart(const std::string & file_name) {
AKANTU_DEBUG_IN();
this->is_sticking.readRestartFile(file_name);
this->frictional_strength.readRestartFile(file_name);
this->friction_traction.readRestartFile(file_name);
this->cumulative_slip.readRestartFile(file_name);
this->slip_velocity.readRestartFile(file_name);
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNBaseFriction::setParam(const std::string & name, UInt node, Real value) {
AKANTU_DEBUG_IN();
SynchronizedArray<Real> & array = this->get< SynchronizedArray<Real> >(name);
Int index = this->contact->getNodeIndex(node);
if (index < 0) {
AKANTU_DEBUG_WARNING("Node " << node << " is not a contact node. "
<< "Therefore, cannot set interface parameter!!");
}
else {
array(index) = value; // put value
}
AKANTU_DEBUG_OUT();
};
/* -------------------------------------------------------------------------- */
UInt NTNBaseFriction::getNbStickingNodes() const {
AKANTU_DEBUG_IN();
UInt nb_stick = 0;
UInt nb_nodes = this->contact->getNbContactNodes();
const SynchronizedArray<UInt> & nodes = this->contact->getSlaves();
const SynchronizedArray<bool> & is_in_contact = this->contact->getIsInContact();
const Mesh & mesh = this->contact->getModel().getMesh();
for (UInt n = 0; n < nb_nodes; ++n) {
bool is_local_node = mesh.isLocalOrMasterNode(nodes(n));
bool is_pbc_slave_node = this->contact->getModel().isPBCSlaveNode(nodes(n));
if (is_local_node
&& !is_pbc_slave_node
&& is_in_contact(n)
&& this->is_sticking(n)) {
nb_stick++;
}
}
StaticCommunicator::getStaticCommunicator().allReduce(&nb_stick, 1, _so_sum);
AKANTU_DEBUG_OUT();
return nb_stick;
}
/* -------------------------------------------------------------------------- */
void NTNBaseFriction::printself(std::ostream & stream, int indent) const {
AKANTU_DEBUG_IN();
std::string space;
for(Int i = 0; i < indent; i++, space += AKANTU_INDENT);
stream << space << "NTNBaseFriction [" << std::endl;
Parsable::printself(stream, indent);
stream << space << "]" << std::endl;
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNBaseFriction::addDumpFieldToDumper(const std::string & dumper_name,
const std::string & field_id) {
AKANTU_DEBUG_IN();
#ifdef AKANTU_USE_IOHELPER
// const SynchronizedArray<UInt> * nodal_filter = &(this->contact->getSlaves());
if(field_id == "is_sticking") {
this->internalAddDumpFieldToDumper(dumper_name,
field_id,
new DumperIOHelper::NodalField<bool>(this->is_sticking.getArray()));
}
else if(field_id == "frictional_strength") {
this->internalAddDumpFieldToDumper(dumper_name,
field_id,
new DumperIOHelper::NodalField<Real>(this->frictional_strength.getArray()));
}
else if(field_id == "friction_traction") {
this->internalAddDumpFieldToDumper(dumper_name,
field_id,
new DumperIOHelper::NodalField<Real>(this->friction_traction.getArray()));
}
else if(field_id == "slip") {
this->internalAddDumpFieldToDumper(dumper_name,
field_id,
new DumperIOHelper::NodalField<Real>(this->slip.getArray()));
}
else if(field_id == "cumulative_slip") {
this->internalAddDumpFieldToDumper(dumper_name,
field_id,
new DumperIOHelper::NodalField<Real>(this->cumulative_slip.getArray()));
}
else if(field_id == "slip_velocity") {
this->internalAddDumpFieldToDumper(dumper_name,
field_id,
new DumperIOHelper::NodalField<Real>(this->slip_velocity.getArray()));
}
else {
this->contact->addDumpFieldToDumper(dumper_name, field_id);
}
#endif
AKANTU_DEBUG_OUT();
}
__END_SIMTOOLS__

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