Reissner shells (demo_FEA_shells.cpp)

Tutorial that teaches how to use the FEA module to perform FEA dynamics for shells of Reissner type.

// =============================================================================
// PROJECT CHRONO - http://projectchrono.org
//
// Copyright (c) 2014 projectchrono.org
// All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be found
// in the LICENSE file at the top level of the distribution and at
// http://projectchrono.org/license-chrono.txt.
//
// =============================================================================
// Authors: Alessandro Tasora
// =============================================================================
//
// FEA for shells of Reissner 6-field type
//
// =============================================================================
#include <vector>
#include "chrono/physics/ChBodyEasy.h"
#include "chrono/physics/ChLinkMate.h"
#include "chrono/physics/ChSystemSMC.h"
#include "chrono/timestepper/ChTimestepper.h"
#include "chrono/fea/ChElementShellReissner4.h"
#include "chrono/fea/ChLinkDirFrame.h"
#include "chrono/fea/ChLinkPointFrame.h"
#include "chrono/fea/ChMesh.h"
#include "chrono/fea/ChVisualizationFEAmesh.h"
#include "chrono_irrlicht/ChIrrApp.h"
#include "chrono_pardisomkl/ChSolverPardisoMKL.h"
#include "chrono_postprocess/ChGnuPlot.h"
#include "chrono_thirdparty/filesystem/path.h"
// Remember to use the namespace 'chrono' because all classes
// of Chrono::Engine belong to this namespace and its children...
using namespace chrono;
using namespace chrono::fea;
using namespace chrono::irrlicht;
using namespace chrono::postprocess;
using namespace irr;
// Output directory
const std::string out_dir = GetChronoOutputPath() + "FEA_SHELLS";
int main(int argc, char* argv[]) {
GetLog() << "Copyright (c) 2017 projectchrono.org\nChrono version: " << CHRONO_VERSION << "\n\n";
// Create (if needed) output directory
if (!filesystem::create_directory(filesystem::path(out_dir))) {
std::cout << "Error creating directory " << out_dir << std::endl;
return 1;
}
// Create a Chrono::Engine physical system
ChSystemSMC my_system;
// Create the Irrlicht visualization (open the Irrlicht device,
// bind a simple user interface, etc. etc.)
ChIrrApp application(&my_system, L"Shells FEA", core::dimension2d<u32>(800, 600));
// Easy shortcuts to add camera, lights, logo and sky in Irrlicht scene:
application.AddTypicalLogo();
application.AddTypicalSky();
application.AddTypicalLights();
application.AddTypicalCamera(core::vector3df(0.f, 6.0f, -10.f));
// Create a mesh, that is a container for groups
// of elements and their referenced nodes.
auto my_mesh = chrono_types::make_shared<ChMesh>();
// Remember to add the mesh to the system!
my_system.Add(my_mesh);
// my_system.Set_G_acc(VNULL); or
my_mesh->SetAutomaticGravity(false);
std::shared_ptr<ChNodeFEAxyzrot> nodePlotA;
std::shared_ptr<ChNodeFEAxyzrot> nodePlotB;
std::vector<std::shared_ptr<ChNodeFEAxyzrot>> nodesLoad;
ChVector<> load_torque;
ChVector<> load_force;
//
// BENCHMARK n.1
//
// Add an EANS SHELL cantilever:
//
if (false) // set as 'true' to execute this
{
double rect_thickness = 0.10;
double rect_L = 10.0;
double rect_W = 1;
// Create a material
double rho = 0.0;
double E = 1.2e6;
double nu = 0.0;
auto melasticity = chrono_types::make_shared<ChElasticityReissnerIsothropic>(E, nu, 1.0, 0.01);
auto mat = chrono_types::make_shared<ChMaterialShellReissner>(melasticity);
// In case you need also damping it would add...
//auto mdamping = chrono_types::make_shared<ChDampingReissnerRayleigh>(melasticity,0.01);
//auto mat = chrono_types::make_shared<ChMaterialShellReissner>(melasticity, nullptr, mdamping);
mat->SetDensity(rho);
// Create the nodes
int nels_L = 12;
int nels_W = 1;
std::vector<std::shared_ptr<ChElementShellReissner4>> elarray(nels_L * nels_W);
std::vector<std::shared_ptr<ChNodeFEAxyzrot>> nodearray((nels_L + 1) * (nels_W + 1));
std::vector<std::shared_ptr<ChNodeFEAxyzrot>> nodes_start(nels_W + 1);
std::vector<std::shared_ptr<ChNodeFEAxyzrot>> nodes_end(nels_W + 1);
for (int il = 0; il <= nels_L; ++il) {
for (int iw = 0; iw <= nels_W; ++iw) {
// Make nodes
ChVector<> nodepos(rect_L * ((double)il / (double)nels_L), 0, rect_W * ((double)iw / (double)nels_W));
ChFrame<> nodeframe(nodepos, noderot);
auto mnode = chrono_types::make_shared<ChNodeFEAxyzrot>(nodeframe);
my_mesh->AddNode(mnode);
mnode->GetInertia().fillDiagonal(0); // approx
mnode->SetMass(0);
nodearray[il * (nels_W + 1) + iw] = mnode;
if (il == 0)
nodes_start[iw] = mnode;
if (il == nels_L)
nodes_end[iw] = mnode;
// Make elements
if (il > 0 && iw > 0) {
auto melement = chrono_types::make_shared<ChElementShellReissner4>();
my_mesh->AddElement(melement);
melement->SetNodes(nodearray[(il - 1) * (nels_W + 1) + (iw - 1)],
nodearray[(il) * (nels_W + 1) + (iw - 1)], nodearray[(il) * (nels_W + 1) + (iw)],
nodearray[(il - 1) * (nels_W + 1) + (iw)]);
melement->AddLayer(rect_thickness, 0 * CH_C_DEG_TO_RAD, mat);
elarray[(il - 1) * (nels_W) + (iw - 1)] = melement;
}
}
}
nodesLoad = nodes_end;
nodePlotA = nodes_end.front();
nodePlotB = nodes_end.back();
for (auto mstartnode : nodes_start) {
mstartnode->SetFixed(true);
}
// applied load
// load_force = ChVector<>(200000,0, 20000);
load_force = ChVector<>(0, 4, 0);
// load_torque = ChVector<>(0, 0, 50*CH_C_PI/3.0);
// reference solution for (0, 4, 0) shear to plot
ref_Y.AddPoint(0.10, 1.309);
ref_X.AddPoint(0.40, 0.103);
ref_Y.AddPoint(0.20, 2.493);
ref_X.AddPoint(0.80, 0.381);
ref_Y.AddPoint(0.30, 3.488);
ref_X.AddPoint(1.20, 0.763);
ref_Y.AddPoint(0.40, 4.292);
ref_X.AddPoint(1.60, 1.184);
ref_Y.AddPoint(0.50, 4.933);
ref_X.AddPoint(2.00, 1.604);
ref_Y.AddPoint(0.60, 5.444);
ref_X.AddPoint(2.40, 2.002);
ref_Y.AddPoint(0.70, 5.855);
ref_X.AddPoint(2.80, 2.370);
ref_Y.AddPoint(0.80, 6.190);
ref_X.AddPoint(3.20, 2.705);
ref_Y.AddPoint(0.90, 6.467);
ref_X.AddPoint(3.60, 3.010);
ref_Y.AddPoint(1.00, 6.698);
ref_X.AddPoint(4.00, 3.286);
}
//
// BENCHMARK n.2
//
// Add a SLIT ANNULAR PLATE:
//
if (true) // set as 'true' to execute this
{
double plate_thickness = 0.03;
double plate_Ri = 6;
double plate_Ro = 10;
// Create a material
double rho = 0.0;
double E = 21e6;
double nu = 0.0;
auto mat = chrono_types::make_shared<ChMaterialShellReissnerIsothropic>(rho, E, nu, 1.0, 0.01);
// Create the nodes
int nels_U = 60;
int nels_W = 10;
double arc = CH_C_2PI * 1;
std::vector<std::shared_ptr<ChElementShellReissner4>> elarray(nels_U * nels_W);
std::vector<std::shared_ptr<ChNodeFEAxyzrot>> nodearray((nels_U + 1) * (nels_W + 1));
std::vector<std::shared_ptr<ChNodeFEAxyzrot>> nodes_start(nels_W + 1);
std::vector<std::shared_ptr<ChNodeFEAxyzrot>> nodes_end(nels_W + 1);
for (int iu = 0; iu <= nels_U; ++iu) {
for (int iw = 0; iw <= nels_W; ++iw) {
// Make nodes
double u = ((double)iu / (double)nels_U);
double w = ((double)iw / (double)nels_W);
ChVector<> nodepos((plate_Ri + (plate_Ro - plate_Ri) * w) * cos(u * arc), 0,
(plate_Ri + (plate_Ro - plate_Ri) * w) * sin(u * arc));
ChFrame<> nodeframe(nodepos, noderot);
auto mnode = chrono_types::make_shared<ChNodeFEAxyzrot>(nodeframe);
my_mesh->AddNode(mnode);
mnode->GetInertia().fillDiagonal(0.0);
mnode->SetMass(0);
nodearray[iu * (nels_W + 1) + iw] = mnode;
if (iu == 0)
nodes_start[iw] = mnode;
if (iu == nels_U)
nodes_end[iw] = mnode;
// Make elements
if (iu > 0 && iw > 0) {
auto melement = chrono_types::make_shared<ChElementShellReissner4>();
my_mesh->AddElement(melement);
melement->SetNodes(nodearray[(iu) * (nels_W + 1) + (iw)], nodearray[(iu - 1) * (nels_W + 1) + (iw)],
nodearray[(iu - 1) * (nels_W + 1) + (iw - 1)],
nodearray[(iu) * (nels_W + 1) + (iw - 1)]);
melement->AddLayer(plate_thickness, 0 * CH_C_DEG_TO_RAD, mat);
elarray[(iu - 1) * (nels_W) + (iw - 1)] = melement;
}
}
}
nodesLoad = nodes_end;
nodePlotA = nodes_end.front();
nodePlotB = nodes_end.back();
for (auto mstartnode : nodes_start) {
mstartnode->SetFixed(true);
}
load_force = ChVector<>(0, 0.8 * 4, 0);
load_torque = VNULL;
// reference solution to plot
ref_X.AddPoint(0.025, 1.305);
ref_Y.AddPoint(0.025, 1.789);
ref_X.AddPoint(0.10, 4.277);
ref_Y.AddPoint(0.10, 5.876);
ref_X.AddPoint(0.20, 6.725);
ref_Y.AddPoint(0.20, 9.160);
ref_X.AddPoint(0.30, 8.340);
ref_Y.AddPoint(0.30, 11.213);
ref_X.AddPoint(0.40, 9.529);
ref_Y.AddPoint(0.40, 12.661);
ref_X.AddPoint(0.50, 10.468);
ref_Y.AddPoint(0.50, 13.768);
ref_X.AddPoint(0.60, 11.257);
ref_Y.AddPoint(0.60, 14.674);
ref_X.AddPoint(0.70, 11.970);
ref_Y.AddPoint(0.70, 15.469);
ref_X.AddPoint(0.80, 12.642);
ref_Y.AddPoint(0.80, 16.202);
ref_X.AddPoint(0.9, 13.282);
ref_Y.AddPoint(0.90, 16.886);
ref_X.AddPoint(1.00, 13.891);
ref_Y.AddPoint(1.00, 17.528);
}
//
// BENCHMARK n.3
//
// Add a CLAMPED HALF CYLINDER :
//
if (false) {
double plate_thickness = 0.03;
double plate_R = 1.016;
double plate_L = 3.048;
// Create a material
double rho = 0.0;
double E = 2.0685e7;
double nu = 0.3;
auto mat = chrono_types::make_shared<ChMaterialShellReissnerIsothropic>(rho, E, nu, 1.0, 0.01);
// In case you want to test laminated shells, use this:
auto mat_ortho = chrono_types::make_shared<ChMaterialShellReissnerOrthotropic>(rho, 2.0685e7, 0.517e7, 0.3, 0.795e7,
0.795e7, 0.795e7, 1.0, 0.01);
// Create the nodes
int nels_U = 32;
int nels_W = 32;
double arc = CH_C_PI;
std::vector<std::shared_ptr<ChElementShellReissner4>> elarray(nels_U * nels_W);
std::vector<std::shared_ptr<ChNodeFEAxyzrot>> nodearray((nels_U + 1) * (nels_W + 1));
std::vector<std::shared_ptr<ChNodeFEAxyzrot>> nodes_start(nels_W + 1);
std::vector<std::shared_ptr<ChNodeFEAxyzrot>> nodes_end(nels_W + 1);
std::vector<std::shared_ptr<ChNodeFEAxyzrot>> nodes_left(nels_U + 1);
std::vector<std::shared_ptr<ChNodeFEAxyzrot>> nodes_right(nels_U + 1);
for (int iu = 0; iu <= nels_U; ++iu) {
for (int iw = 0; iw <= nels_W; ++iw) {
// Make nodes
double u = ((double)iu / (double)nels_U);
double w = ((double)iw / (double)nels_W);
ChVector<> nodepos((plate_R)*cos(w * arc), (plate_R)*sin(w * arc), u * plate_L);
ChFrame<> nodeframe(nodepos, noderot);
auto mnode = chrono_types::make_shared<ChNodeFEAxyzrot>(nodeframe);
my_mesh->AddNode(mnode);
mnode->GetInertia().fillDiagonal(0.0);
mnode->SetMass(0.0);
nodearray[iu * (nels_W + 1) + iw] = mnode;
if (iu == 0)
nodes_start[iw] = mnode;
if (iu == nels_U)
nodes_end[iw] = mnode;
if (iw == 0)
nodes_left[iu] = mnode;
if (iw == nels_W)
nodes_right[iu] = mnode;
// Make elements
if (iu > 0 && iw > 0) {
auto melement = chrono_types::make_shared<ChElementShellReissner4>();
my_mesh->AddElement(melement);
melement->SetNodes(nodearray[(iu) * (nels_W + 1) + (iw)], nodearray[(iu - 1) * (nels_W + 1) + (iw)],
nodearray[(iu - 1) * (nels_W + 1) + (iw - 1)],
nodearray[(iu) * (nels_W + 1) + (iw - 1)]);
melement->AddLayer(plate_thickness, 0 * CH_C_DEG_TO_RAD, mat);
// In case you want to test laminated shells, do instead:
// melement->AddLayer(plate_thickness/3, 0 * CH_C_DEG_TO_RAD, mat_ortho);
// melement->AddLayer(plate_thickness/3, 90 * CH_C_DEG_TO_RAD, mat_ortho);
// melement->AddLayer(plate_thickness/3, 0 * CH_C_DEG_TO_RAD, mat_ortho);
elarray[(iu - 1) * (nels_W) + (iw - 1)] = melement;
}
}
}
nodesLoad.push_back(nodes_end[nodes_end.size() / 2]);
nodePlotA = nodes_end[nodes_end.size() / 2];
nodePlotB = nodes_end[nodes_end.size() / 2];
for (auto mstartnode : nodes_start) {
mstartnode->SetFixed(true);
}
auto mtruss = chrono_types::make_shared<ChBody>();
mtruss->SetBodyFixed(true);
my_system.Add(mtruss);
for (auto mendnode : nodes_left) {
auto mlink = chrono_types::make_shared<ChLinkMateGeneric>(false, true, false, true, false, true);
mlink->Initialize(mendnode, mtruss, false, mendnode->Frame(), mendnode->Frame());
my_system.Add(mlink);
}
for (auto mendnode : nodes_right) {
auto mlink = chrono_types::make_shared<ChLinkMateGeneric>(false, true, false, true, false, true);
mlink->Initialize(mendnode, mtruss, false, mendnode->Frame(), mendnode->Frame());
my_system.Add(mlink);
}
load_force = ChVector<>(0, -2000, 0);
load_torque = VNULL;
// reference solution to plot
ref_X.AddPoint(0.10, 1 - 0.16);
ref_X.AddPoint(0.20, 1 - 0.37);
ref_X.AddPoint(0.30, 1 - 0.66);
ref_X.AddPoint(0.40, 1 - 1.13);
ref_X.AddPoint(0.50, 1 - 1.32);
ref_X.AddPoint(0.60, 1 - 1.44);
ref_X.AddPoint(0.70, 1 - 1.52);
ref_X.AddPoint(0.80, 1 - 1.60);
ref_X.AddPoint(0.90, 1 - 1.66);
ref_X.AddPoint(1.00, 1 - 1.71);
}
// ==Asset== attach a visualization of the FEM mesh.
// This will automatically update a triangle mesh (a ChTriangleMeshShape
// asset that is internally managed) by setting proper
// coordinates and vertex colors as in the FEM elements.
// Such triangle mesh can be rendered by Irrlicht or POVray or whatever
// postprocessor that can handle a colored ChTriangleMeshShape).
// Do not forget AddAsset() at the end!
auto mvisualizeshellA = chrono_types::make_shared<ChVisualizationFEAmesh>(*(my_mesh.get()));
mvisualizeshellA->SetSmoothFaces(true);
mvisualizeshellA->SetWireframe(true);
my_mesh->AddAsset(mvisualizeshellA);
/*
auto mvisualizeshellB = chrono_types::make_shared<ChVisualizationFEAmesh>(*(my_mesh.get()));
mvisualizeshellB->SetFEMdataType(ChVisualizationFEAmesh::E_PLOT_NONE);
mvisualizeshellB->SetFEMglyphType(ChVisualizationFEAmesh::E_GLYPH_NODE_DOT_POS);
mvisualizeshellB->SetSymbolsThickness(0.01);
my_mesh->AddAsset(mvisualizeshellB);
*/
auto mvisualizeshellC = chrono_types::make_shared<ChVisualizationFEAmesh>(*(my_mesh.get()));
mvisualizeshellC->SetFEMdataType(ChVisualizationFEAmesh::E_PLOT_NONE);
// mvisualizeshellC->SetFEMglyphType(ChVisualizationFEAmesh::E_GLYPH_NODE_CSYS);
mvisualizeshellC->SetSymbolsThickness(0.05);
mvisualizeshellC->SetZbufferHide(false);
my_mesh->AddAsset(mvisualizeshellC);
// ==IMPORTANT!== Use this function for adding a ChIrrNodeAsset to all items
// in the system. These ChIrrNodeAsset assets are 'proxies' to the Irrlicht meshes.
// If you need a finer control on which item really needs a visualization proxy in
// Irrlicht, just use application.AssetBind(myitem); on a per-item basis.
application.AssetBindAll();
// ==IMPORTANT!== Use this function for 'converting' into Irrlicht meshes the assets
// that you added to the bodies into 3D shapes, they can be visualized by Irrlicht!
application.AssetUpdateAll();
//
// THE SOFT-REAL-TIME CYCLE
//
// Change solver to PardisoMKL
auto mkl_solver = chrono_types::make_shared<ChSolverPardisoMKL>();
mkl_solver->LockSparsityPattern(true);
my_system.SetSolver(mkl_solver);
// Change type of integrator:
my_system.SetTimestepperType(ChTimestepper::Type::EULER_IMPLICIT);
//my_system.SetTimestepperType(ChTimestepper::Type::EULER_IMPLICIT_LINEARIZED);
//my_system.SetTimestepperType(ChTimestepper::Type::HHT);
if (auto mint = std::dynamic_pointer_cast<ChImplicitIterativeTimestepper>(my_system.GetTimestepper())) {
mint->SetMaxiters(5);
mint->SetAbsTolerances(1e-12, 1e-12);
}
double timestep = 0.1;
application.SetTimestep(timestep);
my_system.Setup();
my_system.Update();
double mtime = 0;
while (application.GetDevice()->run()) {
application.BeginScene();
application.DrawAll();
// .. draw also a grid
tools::drawGrid(application.GetVideoDriver(), 1, 1);
// ...update load at end nodes, as simple lumped nodal forces
double load_scale = mtime * 0.1;
for (auto mendnode : nodesLoad) {
mendnode->SetForce(load_force * load_scale * (1. / (double)nodesLoad.size()));
mendnode->SetTorque(load_torque * load_scale * (1. / (double)nodesLoad.size()));
}
// application.DoStep();
// mtime = my_system.GetChTime();
application.GetSystem()->DoStaticNonlinear(3);
// application.GetSystem()->DoStaticLinear();
mtime += timestep;
if (!application.GetPaused() && nodePlotA && nodePlotB) {
rec_Y.AddPoint(load_scale, nodePlotA->GetPos().y());
rec_X.AddPoint(load_scale, nodePlotB->GetPos().y());
}
application.EndScene();
if (load_scale > 1)
application.GetDevice()->closeDevice();
}
// Outputs results in a GNUPLOT plot:
std::string gplfilename = out_dir + "/shell_benchmark.gpl";
ChGnuPlot mplot(gplfilename.c_str());
mplot.SetGrid(false, 1, ChColor(0.8f, 0.8f, 0.8f));
mplot.SetLabelX("Torque T/T0");
mplot.SetLabelY("Tip displacement [m]");
mplot << "set key left top";
mplot.Plot(rec_Y, "W", " with lines lt -1 lc rgb'#00AAEE' ");
mplot.Plot(rec_X, "-U", " with lines lt -1 lc rgb'#AA00EE' ");
mplot.Plot(ref_Y, "W ref.", "pt 4 ps 1.4");
mplot.Plot(ref_X, "-U ref.", "pt 4 ps 1.4");
return 0;
}
void Add(std::shared_ptr< ChPhysicsItem > item)
Attach an arbitrary ChPhysicsItem (e.g.
Definition: ChSystem.cpp:146
std::shared_ptr< ChTimestepper > GetTimestepper() const
Get the timestepper currently used for time integration.
Definition: ChSystem.h:136
void AssetUpdateAll()
For all items in a ChSystem, this function sets up the Irrlicht nodes corresponding to the geometric ...
Definition: ChIrrApp.cpp:50
ChLog & GetLog()
Global function to get the current ChLog object.
Definition: ChLog.cpp:39
Class for lotting data with GNUplot.
Definition: ChGnuPlot.h:56
void SetTimestep(double val)
Set/Get the time step for time integration.
Definition: ChIrrAppInterface.cpp:552
Namespace with classes for the POSTPROCESS module.
Definition: ChApiPostProcess.h:54
ChFrame: a class for coordinate systems in 3D space.
Definition: ChFrame.h:42
Class to add some GUI to Irrlicht+ChronoEngine applications.
Definition: ChIrrApp.h:29
const ChApi ChQuaternion< double > QUNIT
Constant unit quaternion: {1, 0, 0, 0} , corresponds to no rotation (diagonal rotation matrix)
virtual void EndScene()
Call this to end the scene draw at the end of each animation frame.
Definition: ChIrrAppInterface.cpp:627
Class for setting a color (used by ChVisualization)
Definition: ChColor.h:25
Definition of general purpose 3d vector variables, such as points in 3D.
Definition: ChVector.h:35
const std::string & GetChronoOutputPath()
Obtain the path to the output directory for Chrono demos.
Definition: ChGlobal.cpp:110
bool DoStaticNonlinear(int nsteps=10, bool verbose=false)
Solve the position of static equilibrium (and the reactions).
Definition: ChSystem.cpp:1488
Class for a physical system in which contact is modeled using a smooth (penalty-based) method.
Definition: ChSystemSMC.h:31
Recorder function:
Definition: ChFunction_Recorder.h:54
virtual void SetSolver(std::shared_ptr< ChSolver > newsolver)
Attach a solver (derived from ChSolver) for use by this system.
Definition: ChSystem.cpp:270
Class defining quaternion objects, that is four-dimensional numbers, also known as Euler parameters.
Definition: ChQuaternion.h:45
void AssetBindAll()
Shortcut to add and bind a ChIrrNodeAsset to all items in a ChSystem.
Definition: ChIrrApp.cpp:42
virtual void BeginScene(bool backBuffer=true, bool zBuffer=true, irr::video::SColor color=irr::video::SColor(255, 0, 0, 0))
Call this to clean the canvas at the beginning of each animation frame.
Definition: ChIrrAppInterface.cpp:610
Main namespace for the Chrono package.
Definition: ChAsset.cpp:18
void SetGrid(bool dashed=true, double linewidth=1.0, ChColor mcolor=ChColor(0, 0, 0))
Shortcut to add the command that turns on the grid.
Definition: ChGnuPlot.h:279
void SetTimestepperType(ChTimestepper::Type type)
Set the method for time integration (time stepper type).
Definition: ChSystem.cpp:348
virtual void DrawAll()
Call this function inside a loop such as.
Definition: ChIrrAppInterface.cpp:750
Namespace for FEA classes.
Definition: ChChrono.h:52
void Update(double mytime, bool update_assets=true)
Updates all the auxiliary data and children of bodies, forces, links, given their current state.
Definition: ChSystem.cpp:639
virtual void Setup()
Counts the number of bodies and links.
Definition: ChSystem.cpp:558