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ntn_contact.cc
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/**
* @file ntn_contact.cc
* @author David Kammer <david.kammer@epfl.ch>
* @date Thu Mar 14 11:52:00 2013
*
* @brief implementation of ntn_contact
*
* @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_contact.hh"
__BEGIN_SIMTOOLS__
/* -------------------------------------------------------------------------- */
NTNContact::NTNContact(SolidMechanicsModel & model,
const ContactID & id,
const MemoryID & memory_id) :
Memory(memory_id), id(id), model(model),
slaves(0,1,0,id+":slaves",std::numeric_limits<UInt>::quiet_NaN(),"slaves"),
masters(0,1,0,id+":masters",std::numeric_limits<UInt>::quiet_NaN(),"masters"),
normals(0,model.getSpatialDimension(),0,id+":normals",
std::numeric_limits<Real>::quiet_NaN(),"normals"),
contact_pressure(0,model.getSpatialDimension(),0,id+":contact_pressure",
std::numeric_limits<Real>::quiet_NaN(),"contact_pressure"),
is_in_contact(0,1,false,id+":is_in_contact",false,"is_in_contact"),
lumped_boundary(0,2,0,id+":lumped_boundary",
std::numeric_limits<Real>::quiet_NaN(),"lumped_boundary"),
impedance(0,1,0,id+":impedance",std::numeric_limits<Real>::quiet_NaN(),"impedance"),
contact_surfaces()
{
AKANTU_DEBUG_IN();
FEM & boundary_fem = this->model.getFEMBoundary();
boundary_fem.initShapeFunctions();
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::addSurfacePair(Surface slave, Surface master, UInt surface_normal_dir) {
AKANTU_DEBUG_IN();
UInt dim = this->model.getSpatialDimension();
AKANTU_DEBUG_ASSERT(surface_normal_dir < dim, "Model is of " << dim << " dimensions"
<< " and cannot have direction " << surface_normal_dir
<< " for surface normal");
this->contact_surfaces.insert(slave);
this->contact_surfaces.insert(master);
// offset for projection computation
UInt offset[dim-1];
for (UInt i=0, j=0; i<dim; ++i) {
if (surface_normal_dir != i) {
offset[j] = i;
++j;
}
}
// get all nodes for all surfaces
CSR<UInt> all_surface_nodes;
MeshUtils::buildNodesPerSurface(this->model.getFEM().getMesh(), all_surface_nodes);
// find slave nodes
Array<UInt> slave_nodes(0);
for(CSR<UInt>::iterator snode = all_surface_nodes.begin(slave);
snode != all_surface_nodes.end(slave);
++snode) {
UInt n = *snode;
slave_nodes.push_back(n);
}
// find master nodes
Array<UInt> master_nodes(0);
for (CSR<UInt>::iterator mnode = all_surface_nodes.begin(master);
mnode != all_surface_nodes.end(master);
++mnode) {
UInt n = *mnode;
master_nodes.push_back(n);
}
// find projected node coordinates
const Array<Real> & coordinates = this->model.getFEM().getMesh().getNodes();
Array<Real> proj_slave_coord(slave_nodes.getSize(),dim-1,0.);
for (UInt n=0; n<slave_nodes.getSize(); ++n) {
for (UInt d=0; d<dim-1; ++d) {
proj_slave_coord(n,d) = coordinates(slave_nodes(n),offset[d]);
}
}
Array<Real> proj_master_coord(master_nodes.getSize(),dim-1,0.);
for (UInt n=0; n<master_nodes.getSize(); ++n) {
for (UInt d=0; d<dim-1; ++d) {
proj_master_coord(n,d) = coordinates(master_nodes(n),offset[d]);
}
}
// find minimum distance between slave nodes to define tolerance
Real min_dist = std::numeric_limits<Real>::max();
for (UInt i=0; i<slave_nodes.getSize(); ++i) {
for (UInt j=i+1; j<slave_nodes.getSize(); ++j) {
Real dist = 0.;
for (UInt d=0; d<dim-1; ++d) {
dist += (proj_slave_coord(i,d) - proj_slave_coord(j,d))
* (proj_slave_coord(i,d) - proj_slave_coord(j,d));
}
if (dist < min_dist)
min_dist = dist;
}
}
min_dist = std::sqrt(min_dist);
Real local_tol = 0.1*min_dist;
// find master slave node pairs
for (UInt i=0; i<slave_nodes.getSize(); ++i) {
for (UInt j=0; j<master_nodes.getSize(); ++j) {
Real dist = 0.;
for (UInt d=0; d<dim-1; ++d) {
dist += (proj_slave_coord(i,d) - proj_master_coord(j,d))
* (proj_slave_coord(i,d) - proj_master_coord(j,d));
}
dist = std::sqrt(dist);
if (dist < local_tol) { // it is a pair
this->addNodePair(slave_nodes(i), master_nodes(j));
/*
this->slaves.push_back(slave_nodes(i));
this->masters.push_back(master_nodes(j));
this->is_in_contact.push_back(false);
this->contact_pressure.push_back(std::numeric_limits<Real>::quiet_NaN());
this->impedance.push_back(std::numeric_limits<Real>::quiet_NaN());
Real nan_two[2];
nan_two[0] = std::numeric_limits<Real>::quiet_NaN();
nan_two[1] = std::numeric_limits<Real>::quiet_NaN();
this->lumped_boundary.push_back(nan_two);
Real nan_normal[dim];
for (UInt d=0; d<dim; ++d)
nan_normal[d] = std::numeric_limits<Real>::quiet_NaN();
this->normals.push_back(nan_normal);
*/
continue; // found master do not need to search further for this slave
}
}
}
// synchronize with depending nodes
updateInternalData();
syncArrays(_added);
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::addNodePair(UInt slave, UInt master) {
AKANTU_DEBUG_IN();
UInt dim = this->model.getSpatialDimension();
// add nodes to the node arrays
this->slaves.push_back(slave);
this->masters.push_back(master);
// set contact as false
this->is_in_contact.push_back(false);
// before initializing
// set contact pressure, impedance, normal, lumped_boundary to Nan
this->contact_pressure.push_back(std::numeric_limits<Real>::quiet_NaN());
this->impedance.push_back(std::numeric_limits<Real>::quiet_NaN());
Real nan_two[2];
nan_two[0] = std::numeric_limits<Real>::quiet_NaN();
nan_two[1] = std::numeric_limits<Real>::quiet_NaN();
this->lumped_boundary.push_back(nan_two);
Real nan_normal[dim];
for (UInt d=0; d<dim; ++d)
nan_normal[d] = std::numeric_limits<Real>::quiet_NaN();
this->normals.push_back(nan_normal);
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::addNodePairs(Array<UInt> & pairs) {
AKANTU_DEBUG_IN();
AKANTU_DEBUG_ASSERT(pairs.getNbComponent() == 2,
"Array of node pairs should have nb_component = 2," <<
" but has nb_component = " << pairs.getNbComponent());
UInt nb_pairs = pairs.getSize();
for (UInt n=0; n<nb_pairs; ++n) {
this->addNodePair(pairs(n,0), pairs(n,1));
}
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
/*
This function only works for surface elements with one quad point. For
surface elements with more quad points, it computes still, but the result
might not be what you are looking for.
*/
void NTNContact::updateNormals() {
AKANTU_DEBUG_IN();
UInt dim = this->model.getSpatialDimension();
const Array<Real> & cur_pos = this->model.getCurrentPosition();
FEM & boundary_fem = this->model.getFEMBoundary();
// contact information
UInt nb_contact_nodes = this->masters.getSize();
// set normals to zero
this->normals.clear();
const Mesh & mesh = this->model.getFEM().getMesh();
Mesh::type_iterator it = mesh.firstType(dim-1);
Mesh::type_iterator last = mesh.lastType(dim-1);
for (; it != last; ++it) {
// get elements connected to each node
CSR<UInt> node_to_element;
MeshUtils::buildNode2ElementsByElementType(mesh, *it, node_to_element);
// compute the normals
Array<Real> quad_normals(0,dim);
boundary_fem.computeNormalsOnControlPoints(cur_pos, quad_normals, *it);
UInt nb_quad_points = boundary_fem.getNbQuadraturePoints(*it);
// add up normals to all master nodes
for (UInt n=0; n<nb_contact_nodes; ++n) {
UInt master = this->masters(n);
CSR<UInt>::iterator elem = node_to_element.begin(master);
// loop over all elements connected to this master node
for (; elem != node_to_element.end(master); ++elem) {
UInt e = *elem;
// loop over all quad points of this element
for (UInt q=0; q<nb_quad_points; ++q) {
// add quad normal to master normal
for (UInt d=0; d<dim; ++d) {
this->normals(n,d) += quad_normals(e*nb_quad_points + q, d);
}
}
}
}
}
// normalize normals
Real * master_normals = this->normals.storage();
for (UInt n=0; n<nb_contact_nodes; ++n) {
if (dim==2)
Math::normalize2(&(master_normals[n*dim]));
else if (dim==3)
Math::normalize3(&(master_normals[n*dim]));
}
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::registerSyncronizedArray(SyncronizedArrayBase & array) {
AKANTU_DEBUG_IN();
this->slaves.registerDependingArray(array);
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::dumpRestart(std::string file_name) const {
AKANTU_DEBUG_IN();
this->slaves.dumpRestartFile(file_name);
this->masters.dumpRestartFile(file_name);
this->normals.dumpRestartFile(file_name);
this->is_in_contact.dumpRestartFile(file_name);
this->contact_pressure.dumpRestartFile(file_name);
this->lumped_boundary.dumpRestartFile(file_name);
this->impedance.dumpRestartFile(file_name);
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::readRestart(std::string file_name) {
AKANTU_DEBUG_IN();
this->slaves.readRestartFile(file_name);
this->masters.readRestartFile(file_name);
this->normals.readRestartFile(file_name);
this->is_in_contact.readRestartFile(file_name);
this->contact_pressure.readRestartFile(file_name);
this->lumped_boundary.readRestartFile(file_name);
this->impedance.readRestartFile(file_name);
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::updateInternalData() {
AKANTU_DEBUG_IN();
updateNormals();
updateLumpedBoundary();
updateImpedance();
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::updateImpedance() {
AKANTU_DEBUG_IN();
UInt nb_ntn_pairs = getNbContactNodes();
Real delta_t = this->model.getTimeStep();
AKANTU_DEBUG_ASSERT(delta_t != NAN, "Time step is NAN. Have you set it already?");
const Array<Real> & mass = this->model.getMass();
for (UInt n=0; n<nb_ntn_pairs; ++n) {
UInt master = this->masters(n);
UInt slave = this->slaves(n);
Real imp = (this->lumped_boundary(n,0) / mass(master)) + (this->lumped_boundary(n,1) / mass(slave));
imp = 2 / delta_t / imp;
this->impedance(n) = imp;
}
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::updateLumpedBoundary() {
AKANTU_DEBUG_IN();
// set all values in lumped_boundary to zero
this->lumped_boundary.clear();
UInt dim = this->model.getSpatialDimension();
UInt nb_contact_nodes = getNbContactNodes();
const FEM & boundary_fem = this->model.getFEMBoundary();
const Mesh & mesh = this->model.getFEM().getMesh();
Mesh::type_iterator it = mesh.firstType(dim-1);
Mesh::type_iterator last = mesh.lastType(dim-1);
for (; it != last; ++it) {
// get elements connected to each node
CSR<UInt> node_to_element;
MeshUtils::buildNode2ElementsByElementType(mesh, *it, node_to_element);
UInt nb_nodes_per_element = mesh.getNbNodesPerElement(*it);
const Array<UInt> & connectivity = mesh.getConnectivity(*it);
// get shapes and compute integral
const Array<Real> & shapes = boundary_fem.getShapes(*it);
Array<Real> area(mesh.getNbElement(*it),nb_nodes_per_element);
boundary_fem.integrate(shapes,area,nb_nodes_per_element,*it);
// get surface id information
const Array<UInt> & surface_id = mesh.getSurfaceID(*it);
std::set<UInt>::iterator pos;
std::set<UInt>::iterator end = this->contact_surfaces.end();
// loop over contact nodes
for (UInt i=0; i<2*nb_contact_nodes; ++i) {
// first round on masters, second round on slaves
UInt node = std::numeric_limits<UInt>::quiet_NaN();
UInt n = 0;
UInt index = 0;
if (i<nb_contact_nodes) {
n = i;
node = this->masters(n);
index = 0;
}
else {
n = i-nb_contact_nodes;
node = this->slaves(n);
index = 1;
}
CSR<UInt>::iterator elem = node_to_element.begin(node);
// loop over all elements connected to this node
for (; elem != node_to_element.end(node); ++elem) {
UInt e = *elem;
// if element is not at interface continue
pos = this->contact_surfaces.find(surface_id(e));
if (pos == end)
continue;
// loop over all points of this element
for (UInt q=0; q<nb_nodes_per_element; ++q) {
if (connectivity(e,q) == node) {
this->lumped_boundary(n,index) += area(e,q);
}
}
}
}
}
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::computeContactPressure() {
AKANTU_DEBUG_IN();
UInt dim = this->model.getSpatialDimension();
Real delta_t = this->model.getTimeStep();
UInt nb_ntn_pairs = getNbContactNodes();
// pre-compute the acceleration
// (not increment acceleration, because residual is still Kf)
Array<Real> acceleration(this->model.getFEM().getMesh().getNbNodes(),dim);
this->model.solveLumped(acceleration,
this->model.getMass(),
this->model.getResidual(),
this->model.getBoundary(),
this->model.getF_M2A());
const Array<Real> & residual = this->model.getResidual();
/*
for (UInt i=0; i<nb_ntn_pairs; ++i) {
std::cout << "Master residual = " << residual(masters(i),0) << ", " << residual(masters(i),1) << std::endl;
std::cout << "Master acceleration = " << acceleration(masters(i),0) << ", " << acceleration(masters(i),1) << std::endl;
std::cout << "Slave residual = " << residual(slaves(i),0) << ", " << residual(slaves(i),1) << std::endl;
std::cout << "Slave acceleration = " << acceleration(slaves(i),0) << ", " << acceleration(slaves(i),1) << std::endl;
}
*/
// compute relative normal fields of displacement, velocity and acceleration
Array<Real> r_disp(0,1);
Array<Real> r_velo(0,1);
Array<Real> r_acce(0,1);
Array<Real> r_old_acce(0,1);
computeRelativeNormalField(this->model.getCurrentPosition(), r_disp);
computeRelativeNormalField(this->model.getVelocity(), r_velo);
computeRelativeNormalField(acceleration, r_acce);
computeRelativeNormalField(this->model.getAcceleration(), r_old_acce);
AKANTU_DEBUG_ASSERT(r_disp.getSize() == nb_ntn_pairs,
"computeRelativeNormalField does not give back arrays "
<< "size == nb_ntn_pairs. nb_ntn_pairs = " << nb_ntn_pairs
<< " | array size = " << r_disp.getSize());
// compute gap array for all nodes
Array<Real> gap(nb_ntn_pairs, 1);
Real * gap_p = gap.storage();
Real * r_disp_p = r_disp.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_ntn_pairs; ++i) {
//std::cout << "gap elements: " << *r_disp_p << " " << *r_velo_p << " " << *r_acce_p << std::endl;
*gap_p = *r_disp_p + delta_t * *r_velo_p + delta_t * delta_t * *r_acce_p - 0.5 * delta_t * delta_t * *r_old_acce_p;
// increment pointers
gap_p++;
r_disp_p++;
r_velo_p++;
r_acce_p++;
r_old_acce_p++;
}
// check if gap is negative -> is in contact
for (UInt n=0; n<nb_ntn_pairs; ++n) {
if (gap(n) < 0.) {
for (UInt d=0; d<dim; ++d) {
this->contact_pressure(n,d) = this->impedance(n) * gap(n) / (2 * delta_t)
* this->normals(n,d);
}
this->is_in_contact(n) = true;
}
else {
for (UInt d=0; d<dim; ++d)
this->contact_pressure(n,d) = 0.;
this->is_in_contact(n) = false;
}
}
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::applyContactPressure() {
AKANTU_DEBUG_IN();
UInt nb_ntn_pairs = getNbContactNodes();
UInt dim = this->model.getSpatialDimension();
Array<Real> & residual = this->model.getResidual();
for (UInt n=0; n<nb_ntn_pairs; ++n) {
UInt master = this->masters(n);
UInt slave = this->slaves(n);
for (UInt d=0; d<dim; ++d) {
//if (n==0 && d==1) std::cout << std::setprecision(14) << "mas_res=" << residual(master,d) << " slv_res=" << residual(slave,d) << " " << std::abs(residual(slave,d))-std::abs(residual(master,d)) << std::endl;
residual(master,d) += this->lumped_boundary(n,0) * this->contact_pressure(n,d);
residual(slave, d) -= this->lumped_boundary(n,1) * this->contact_pressure(n,d);
/*
if (n==0 && d==1) {
std::cout << std::setprecision(14) << "mas_b=" << lumped_boundary(n,0) << " skv_b=" << lumped_boundary(n,1) << std::endl;
std::cout << std::setprecision(14) << "mas+=" << lumped_boundary(n,0)*contact_pressure(n,d) << " slv+=" << lumped_boundary(n,1)*contact_pressure(n,d) << std::endl;
std::cout << std::setprecision(14) << "mas_res=" << residual(master,d) << " slv_res=" << residual(slave,d) << std::endl;
}*/
}
}
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::computeRelativeTangentialField(const Array<Real> & field,
Array<Real> & rel_tang_field) const {
AKANTU_DEBUG_IN();
// resize arrays to zero
rel_tang_field.resize(0);
UInt dim = this->model.getSpatialDimension();
Real * field_p = field.storage();
Real * normals_p = this->normals.storage();
UInt nb_contact_nodes = this->slaves.getSize();
for (UInt n=0; n<nb_contact_nodes; ++n) {
// nodes
UInt slave = this->slaves(n);
UInt master = this->masters(n);
// compute relative field to master
Real rel_array[dim];
for (UInt d=0; d<dim; ++d) {
rel_array[d] = field_p[slave*dim + d] - field_p[master*dim + d];
}
// compute dot product with normal of master
Real dot_prod = Math::vectorDot(&(normals_p[n*dim]), rel_array, dim);
// compute the tangential projection of the relative field to the master
for (UInt d=0; d<dim; ++d)
rel_array[d] -= dot_prod * normals_p[n*dim +d];
rel_tang_field.push_back(rel_array);
}
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::computeRelativeNormalField(const Array<Real> & field,
Array<Real> & rel_normal_field) const {
AKANTU_DEBUG_IN();
// resize arrays to zero
rel_normal_field.resize(0);
UInt dim = this->model.getSpatialDimension();
Real * field_p = field.storage();
Real * normals_p = this->normals.storage();
UInt nb_contact_nodes = this->getNbContactNodes();
for (UInt n=0; n<nb_contact_nodes; ++n) {
// nodes
UInt slave = this->slaves(n);
UInt master = this->masters(n);
// compute relative field to master
Real rel_array[dim];
for (UInt d=0; d<dim; ++d) {
rel_array[d] = field_p[slave*dim + d] - field_p[master*dim + d];
}
// compute dot product with normal of master
Real dot_prod = Math::vectorDot(&(normals_p[n*dim]), rel_array, dim);
rel_normal_field.push_back(dot_prod);
}
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
Int NTNContact::getNodeIndex(UInt node) const {
AKANTU_DEBUG_IN();
Int slave_i = this->slaves.find(node);
Int master_i = this->masters.find(node);
AKANTU_DEBUG_OUT();
return std::max(slave_i,master_i);
}
/* -------------------------------------------------------------------------- */
void NTNContact::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 << "NTNContact [" << std::endl;
stream << space << " + id : " << id << std::endl;
stream << space << " + slaves : " << std::endl;
this->slaves.printself(stream, indent + 2);
stream << space << " + masters : " << std::endl;
this->masters.printself(stream, indent + 2);
stream << space << " + normals : " << std::endl;
this->normals.printself(stream, indent + 2);
stream << space << " + contact_pressure : " << std::endl;
this->contact_pressure.printself(stream, indent + 2);
stream << space << "]" << std::endl;
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void NTNContact::syncArrays(SyncChoice sync_choice) {
AKANTU_DEBUG_IN();
this->slaves.syncElements(sync_choice);
this->masters.syncElements(sync_choice);
this->normals.syncElements(sync_choice);
this->is_in_contact.syncElements(sync_choice);
this->contact_pressure.syncElements(sync_choice);
this->lumped_boundary.syncElements(sync_choice);
this->impedance.syncElements(sync_choice);
AKANTU_DEBUG_OUT();
}
__END_SIMTOOLS__

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