Introduction to FEA cables (demo_FEA_cables.cpp)

Tutorial that teaches how to use the FEA module to create basic FEA cables, that fall and swing under the effect of gravity. Some rigid bodies (boxes) are connected to the cables.

// =============================================================================
// 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, Radu Serban
// =============================================================================
//
// FEA for 3D beams of 'cable' type (ANCF gradient-deficient beams)
//
// =============================================================================
 
#include "chrono/physics/ChSystemSMC.h"
#include "chrono/solver/ChDirectSolverLS.h"
#include "chrono/solver/ChIterativeSolverLS.h"
#include "chrono/timestepper/ChTimestepper.h"
 
#include "FEAvisualization.h"
#include "FEAcables.h"
 
using namespace chrono;
using namespace chrono::fea;
 
ChVisualSystem::Type vis_type = ChVisualSystem::Type::VSG;
 
// Select solver type (SPARSE_QR, SPARSE_LU, or MINRES).
ChSolver::Type solver_type = ChSolver::Type::SPARSE_QR;
 
int main(int argc, char* argv[]) {
    std::cout << "Copyright (c) 2017 projectchrono.org\nChrono version: " << CHRONO_VERSION << std::endl;
 
    // Create a Chrono::Engine physical system
    ChSystemSMC sys;
 
    sys.SetNumThreads(std::min(4, ChOMP::GetNumProcs()), 0, 1);
 
    // Create a mesh, that is a container for groups of elements and
    // their referenced nodes.
    auto mesh = chrono_types::make_shared<ChMesh>();
 
    // Create one of the available models (defined in FEAcables.h)
    auto model = Model3(sys, mesh);
 
    // Remember to add the mesh to the system!
    sys.Add(mesh);
 
    // Visualization of the FEM mesh.
    // This will automatically update a triangle mesh (a ChVisualShapeTriangleMesh 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 ChVisualShapeTriangleMesh).
    auto vis_beam_A = chrono_types::make_shared<ChVisualShapeFEA>(mesh);
    vis_beam_A->SetFEMdataType(ChVisualShapeFEA::DataType::ELEM_BEAM_MZ);
    vis_beam_A->SetColorscaleMinMax(-0.4, 0.4);
    vis_beam_A->SetSmoothFaces(true);
    vis_beam_A->SetWireframe(false);
    mesh->AddVisualShapeFEA(vis_beam_A);
 
    auto vis_beam_B = chrono_types::make_shared<ChVisualShapeFEA>(mesh);
    vis_beam_B->SetFEMglyphType(ChVisualShapeFEA::GlyphType::NODE_DOT_POS);
    vis_beam_B->SetFEMdataType(ChVisualShapeFEA::DataType::NONE);
    vis_beam_B->SetSymbolsThickness(0.006);
    vis_beam_B->SetSymbolsScale(0.01);
    vis_beam_B->SetZbufferHide(false);
    mesh->AddVisualShapeFEA(vis_beam_B);
 
    // Set solver and solver settings
    switch (solver_type) {
        case ChSolver::Type::SPARSE_QR: {
            std::cout << "Using SparseQR solver" << std::endl;
            auto solver = chrono_types::make_shared<ChSolverSparseQR>();
            sys.SetSolver(solver);
            solver->UseSparsityPatternLearner(true);
            solver->LockSparsityPattern(true);
            solver->SetVerbose(false);
            break;
        }
        case ChSolver::Type::SPARSE_LU: {
            std::cout << "Using SparseLU solver" << std::endl;
            auto solver = chrono_types::make_shared<ChSolverSparseLU>();
            sys.SetSolver(solver);
            solver->UseSparsityPatternLearner(true);
            solver->LockSparsityPattern(true);
            solver->SetVerbose(false);
            break;
        }
        case ChSolver::Type::MINRES: {
            std::cout << "Using MINRES solver" << std::endl;
            auto solver = chrono_types::make_shared<ChSolverMINRES>();
            sys.SetSolver(solver);
            solver->SetMaxIterations(200);
            solver->SetTolerance(1e-14);
            solver->EnableDiagonalPreconditioner(true);
            solver->EnableWarmStart(true);  // IMPORTANT for convergence when using EULER_IMPLICIT_LINEARIZED
            solver->SetVerbose(false);
            break;
        }
        default: {
            std::cout << "Solver type not supported." << std::endl;
            break;
        }
    }
 
    // Create the run-time visualization system
    auto vis = CreateVisualizationSystem(vis_type, CameraVerticalDir::Y, sys, "Cables FEM", ChVector3d(0, 0.6, -1.0));
 
    // Set integrator
    sys.SetTimestepperType(ChTimestepper::Type::EULER_IMPLICIT_LINEARIZED);
 
    while (vis->Run()) {
        vis->BeginScene();
        vis->Render();
        vis->EndScene();
        sys.DoStepDynamics(0.01);
    }
 
    return 0;
}