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threed-beam-fea/tests/beam_element_tests.cpp

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// Copyright 2015. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//
// Author: ryan.latture@gmail.com (Ryan Latture)
#include "threed_beam_fea.h"
#include <gtest/gtest.h>
using namespace fea;
class beamFEATest : public testing::Test {
protected:
beamFEATest() : JOB_L_BRACKET(), BCS_L_BRACKET(0), FORCES_L_BRACKET(0),
JOB_CANTILEVER(), BCS_CANTILEVER(0), FORCES_CANTILEVER(0),
assembleK3D() { };
virtual void SetUp() {
using namespace fea;
// L-bracket setup
std::vector<double> normal_vec = {0.0, 1.0, 0.0};
Props PROPS1(10.0, 10.0, 10.0, 10.0, normal_vec);
Props PROPS2(10.0, 1.0, 1.0, 10.0, normal_vec);
std::vector<Node> NODES = {Node(0.0, 0.0, 0.0), Node(1.0, 0.0, 0.0), Node(2.0, 0.0, 0.0), Node(2.0, 0.0, 1.0)};
std::vector<Elem> ELEMS = {Elem(0, 1, PROPS1), Elem(1, 2, PROPS1), Elem(2, 3, PROPS2)};
JOB_L_BRACKET = Job(NODES, ELEMS);
BC bc1(0, 0, 0.0);
BC bc2(0, 1, 0.0);
BC bc3(0, 2, 0.0);
BC bc4(0, 3, 0.0);
BC bc5(0, 4, 0.0);
BC bc6(0, 5, 0.0);
BC bc7(3, 1, 0.5);
BCS_L_BRACKET = {bc1, bc2, bc3, bc4, bc5, bc6, bc7};
// cantilever setup
std::vector<double> normal_cantilever = {0.0, 0.0, 1.0};
Props props_cantilever(1.0, 1.0, 1.0, 1.0, normal_cantilever);
std::vector<Node> nodes_cantilever = {Node(0.0, 0.0, 0.0),
Node(1.0, 0.0, 0.0)};
std::vector<Elem> elems_cantilever = {Elem(0, 1, props_cantilever)};
BCS_CANTILEVER = {BC(0, 0, 0.0),
BC(0, 1, 0.0),
BC(0, 2, 0.0),
BC(0, 3, 0.0),
BC(0, 4, 0.0),
BC(0, 5, 0.0)};
FORCES_CANTILEVER = {Force(1, 1, 0.1)};
JOB_CANTILEVER = Job(nodes_cantilever, elems_cantilever);
}
Job JOB_L_BRACKET;
std::vector<BC> BCS_L_BRACKET;
std::vector<Force> FORCES_L_BRACKET;
Job JOB_CANTILEVER;
std::vector<BC> BCS_CANTILEVER;
std::vector<Force> FORCES_CANTILEVER;
GlobalStiffAssembler assembleK3D;
public:
EIGEN_MAKE_ALIGNED_OPERATOR_NEW;
};
TEST_F(beamFEATest, TransformsLocalToGlobalCoords) {
// test that identity matrix is recovered if local axes == global axes
Eigen::Vector3d nx(1.0, 0.0, 0.0);
Eigen::Vector3d nz(0.0, 0.0, 1.0);
assembleK3D.calcAelem(nx, nz);
LocalMatrix Aelem = assembleK3D.getAelem();
LocalMatrix expected;
expected.setIdentity();
for (size_t i = 0; i < Aelem.rows(); ++i) {
EXPECT_DOUBLE_EQ(expected(i), Aelem(i));
}
}
TEST_F(beamFEATest, AssemblesElementalStiffness) {
assembleK3D.calcKelem(0, JOB_L_BRACKET);
LocalMatrix Kelem = assembleK3D.getKelem();
std::vector<std::vector<double>> expected =
{{10., 0., 0., 0., 0., 0., -10., 0., 0., 0., 0., 0.},
{0., 120., 0., 0., 0., 60., 0., -120., 0., 0., 0., 60.},
{0., 0., 120., 0., -60., 0., 0., 0., -120., 0., -60., 0.},
{0., 0., 0., 10., 0., 0., 0., 0., 0., -10., 0., 0.},
{0., 0., -60., 0., 40., 0., 0., 0., 60., 0., 20., 0.},
{0., 60., 0., 0., 0., 40., 0., -60., 0., 0., 0., 20.},
{-10., 0., 0., 0., 0., 0., 10., 0., 0., 0., 0., 0.},
{0., -120., 0., 0., 0., -60., 0., 120., 0., 0., 0., -60.},
{0., 0., -120., 0., 60., 0., 0., 0., 120., 0., 60., 0.},
{0., 0., 0., -10., 0., 0., 0., 0., 0., 10., 0., 0.},
{0., 0., -60., 0., 20., 0., 0., 0., 60., 0., 40., 0.},
{0., 60., 0., 0., 0., 20., 0., -60., 0., 0., 0., 40.}};
for (size_t i = 0; i < expected.size(); i++) {
for (size_t j = 0; j < expected[i].size(); j++) {
EXPECT_DOUBLE_EQ(expected[i][j], Kelem(i, j));
}
}
}
TEST_F(beamFEATest, AssemblesGlobalStiffness) {
unsigned int dofs_per_elem = 6;
// calculate size of global stiffness matrix and force vector
size_t size = dofs_per_elem * JOB_L_BRACKET.nodes.size() + FORCES_L_BRACKET.size();
// construct global stiffness matrix and force vector
SparseMat Kg(size, size);
std::vector<Tie> ties;
assembleK3D(Kg, JOB_L_BRACKET, ties);
GlobalStiffMatrix KgDense(Kg);
std::vector<std::vector<double> > expected =
{{10., 0., 0., 0., 0., 0., -10., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.},
{0., 120., 0., 0., 0., 60., 0., -120., 0., 0., 0., 60., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.},
{0., 0., 120., 0., -60., 0., 0., 0., -120., 0., -60., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.},
{0., 0., 0., 10., 0., 0., 0., 0., 0., -10., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.},
{0., 0., -60., 0., 40., 0., 0., 0., 60., 0., 20., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.},
{0., 60., 0., 0., 0., 40., 0., -60., 0., 0., 0., 20., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.},
{-10., 0., 0., 0., 0., 0., 20., 0., 0., 0., 0., 0., -10., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.},
{0., -120., 0., 0., 0., -60., 0., 240., 0., 0., 0., 0., 0., -120., 0., 0., 0., 60., 0., 0., 0., 0., 0., 0.},
{0., 0., -120., 0., 60., 0., 0., 0., 240., 0., 0., 0., 0., 0., -120., 0., -60., 0., 0., 0., 0., 0., 0., 0.},
{0., 0., 0., -10., 0., 0., 0., 0., 0., 20., 0., 0., 0., 0., 0., -10., 0., 0., 0., 0., 0., 0., 0., 0.},
{0., 0., -60., 0., 20., 0., 0., 0., 0., 0., 80., 0., 0., 0., 60., 0., 20., 0., 0., 0., 0., 0., 0., 0.},
{0., 60., 0., 0., 0., 20., 0., 0., 0., 0., 0., 80., 0., -60., 0., 0., 0., 20., 0., 0., 0., 0., 0., 0.},
{0., 0., 0., 0., 0., 0., -10., 0., 0., 0., 0., 0., 22., 0., 0., 0., 6., 0., -12., 0., 0., 0., 6., 0.},
{0., 0., 0., 0., 0., 0., 0., -120., 0., 0., 0., -60., 0., 132., 0., -6., 0., -60., 0., -12., 0., -6., 0., 0.},
{0., 0., 0., 0., 0., 0., 0., 0., -120., 0., 60., 0., 0., 0., 130., 0., 60., 0., 0., 0., -10., 0., 0., 0.},
{0., 0., 0., 0., 0., 0., 0., 0., 0., -10., 0., 0., 0., -6., 0., 14., 0., 0., 0., 6., 0., 2., 0., 0.},
{0., 0., 0., 0., 0., 0., 0., 0., -60., 0., 20., 0., 6., 0., 60., 0., 44., 0., -6., 0., 0., 0., 2., 0.},
{0., 0., 0., 0., 0., 0., 0., 60., 0., 0., 0., 20., 0., -60., 0., 0., 0., 50., 0., 0., 0., 0., 0., -10.},
{0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., -12., 0., 0., 0., -6., 0., 12., 0., 0., 0., -6., 0.},
{0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., -12., 0., 6., 0., 0., 0., 12., 0., 6., 0., 0.},
{0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., -10., 0., 0., 0., 0., 0., 10., 0., 0., 0.},
{0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., -6., 0., 2., 0., 0., 0., 6., 0., 4., 0., 0.},
{0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 6., 0., 0., 0., 2., 0., -6., 0., 0., 0., 4., 0.},
{0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., -10., 0., 0., 0., 0., 0., 10.}};
for (size_t i = 0; i < expected.size(); i++) {
for (size_t j = 0; j < expected[i].size(); j++) {
EXPECT_DOUBLE_EQ(expected[i][j], KgDense(i, j));
}
}
}
TEST_F(beamFEATest, CorrectNodalDisplacementsNoTies) {
std::vector<Tie> ties;
Summary summary = solve(JOB_L_BRACKET, BCS_L_BRACKET, FORCES_L_BRACKET, ties, Options());
// the first 4 rows check nodal displacements
// the last row is associated with the reaction
// forces due to enforcing the BCs.
std::vector<std::vector<double> > expected = {{0., 0., 0., 0., 0., 0.},
{0., 0.0520833333333333, 0., -0.0625, 0., 0.09375},
{0., 0.16666666666666666, 0., -0.125, 0., 0.125},
{0., 0.5, 0., -0.4375, 0., 0.125},
{0., 0.625, 0., -0.625, 0., 1.25, -0.625}};
for (size_t i = 0; i < summary.nodal_displacements.size(); ++i) {
for (size_t j = 0; j < summary.nodal_displacements[i].size(); ++j) {
EXPECT_NEAR(expected[i][j], summary.nodal_displacements[i][j], 1.e-10);
}
}
}
// In this test I create the same mesh as above with 1 exception
// there are redundant nodes at (1,0,0) that I tie with extremely
// stiff linear and rotational springs. If the tie constraints are
// functioning properly, the ties should behave the same as having
// rigid nodal joints, at least to several decimal places.
TEST_F(beamFEATest, CorrectNodalDisplacementsWithStiffTies) {
std::vector<double> normal_vec = {0.0, 1.0, 0.0};
Props props1(10.0, 10.0, 10.0, 10.0, normal_vec);
Props props2(10.0, 1.0, 1.0, 10.0, normal_vec);
std::vector<Node> nodes = {Node(0.0, 0.0, 0.0),
Node(1.0, 0.0, 0.0),
Node(1.0, 0.0, 0.0),
Node(2.0, 0.0, 0.0),
Node(2.0, 0.0, 1.0)};
std::vector<Elem> elems = {Elem(0, 1, props1), Elem(2, 3, props1), Elem(3, 4, props2)};
Job job_tie(nodes, elems);
BC bc1(0, 0, 0.0);
BC bc2(0, 1, 0.0);
BC bc3(0, 2, 0.0);
BC bc4(0, 3, 0.0);
BC bc5(0, 4, 0.0);
BC bc6(0, 5, 0.0);
BC bc7(4, 1, 0.5);
std::vector<BC> bcs = {bc1, bc2, bc3, bc4, bc5, bc6, bc7};
std::vector<Tie> ties = {Tie(1, 2, 1.e8, 1.e8)};
std::vector<Force> forces;
Summary summary = solve(job_tie, bcs, forces, ties, Options());
// The verification program used to generate expected values outputs data as floats
std::vector<std::vector<double> > expected = {{0., 0., 0., 0., 0., 0.},
{0., 0.0520833333333333, 0., -0.0625, 0., 0.09375},
{0., 0.0520833333333333, 0., -0.0625, 0., 0.09375},
{0., 0.16666666666666666, 0., -0.125, 0., 0.125},
{0., 0.5, 0., -0.4375, 0., 0.125},
{0., 0.625, 0., -0.625, 0., 1.25, -0.625}};
for (size_t i = 0; i < summary.nodal_displacements.size(); ++i) {
for (size_t j = 0; j < summary.nodal_displacements[i].size(); ++j) {
EXPECT_NEAR(expected[i][j], summary.nodal_displacements[i][j], 1.e-7);
}
}
}
// This is simple cantilever beam with a point load at the
// free end. This checks the end displacements match the analytical results.
TEST_F(beamFEATest, CorrectTipDisplacementCantileverBeam) {
std::vector<Tie> ties;
Summary summary = solve(JOB_CANTILEVER, BCS_CANTILEVER, FORCES_CANTILEVER, ties, Options());
// the first row checks nodal displacements of fixed node are zero
// the second row checks the analytical result for tip displacement
// for the given load in the y-direction of 0.01 yields the correct
// displacement and rotation
std::vector<std::vector<double> > expected = {{0., 0., 0., 0., 0., 0.},
{0., 0.033333333333333333, 0., 0.0, 0.0, 0.05}};
for (size_t i = 0; i < summary.nodal_displacements.size(); ++i) {
for (size_t j = 0; j < summary.nodal_displacements[i].size(); ++j)
EXPECT_DOUBLE_EQ(expected[i][j], summary.nodal_displacements[i][j]);
}
}
// This test displaces a cantilever beam axially and
// transverse to the beam axis. Nodal forces are
// compared to the analytical result.
TEST_F(beamFEATest, CorrectTipForcesCantileverBeam) {
std::vector<Tie> ties;
std::vector<Force> forces;
std::vector<BC> bcs = BCS_CANTILEVER;
bcs.push_back(BC(1, 0, 0.1));
bcs.push_back(BC(1, 1, 0.1));
Options opts;
opts.save_report = true;
opts.save_nodal_forces = true;
opts.save_nodal_displacements = true;
Summary summary = solve(JOB_CANTILEVER, bcs, forces, ties, opts);
std::vector<std::vector<double> > expected = {{-0.1, -0.3, 0., 0., 0., -0.3},
{0.1, 0.3, 0., 0.0, 0.0, 0.0}};
for (size_t i = 0; i < summary.nodal_forces.size(); ++i) {
for (size_t j = 0; j < summary.nodal_forces[i].size(); ++j)
EXPECT_DOUBLE_EQ(expected[i][j], summary.nodal_forces[i][j]);
}
}
// This tests the tie constraints correctly deform.
// I have extremely stiff elements and apply a
// displacement to the end node. It is expected
// that the tie will accommodate all the deformation.
TEST_F(beamFEATest, CorrectDisplacementWeakTies) {
std::vector<double> normal_vec = {0.0, 1.0, 0.0};
Props props(1.e9, 1.e9, 1.e9, 1.e9, normal_vec);
std::vector<Node> nodes = {Node(0.0, 0.0, 0.0),
Node(1.0, 0.0, 0.0),
Node(1.0, 0.0, 0.0),
Node(2.0, 0.0, 0.0)};
std::vector<Elem> elems = {Elem(0, 1, props), Elem(2, 3, props)};
Job job_tie(nodes, elems);
BC bc1(0, 0, 0.0);
BC bc2(0, 1, 0.0);
BC bc3(0, 2, 0.0);
BC bc4(0, 3, 0.0);
BC bc5(0, 4, 0.0);
BC bc6(0, 5, 0.0);
BC bc7(3, 0, 0.5);
std::vector<BC> bcs = {bc1, bc2, bc3, bc4, bc5, bc6, bc7};
std::vector<Tie> ties = {Tie(1, 2, 0.01, 0.01)};
std::vector<Force> forces;
Options opts;
opts.epsilon = 1e-10;
Summary summary = solve(job_tie, bcs, forces, ties, opts);
std::vector<std::vector<double> > expected = {{0.0, 0.0, 0.0, 0.0, 0.0, 0.0},
{0.0, 0.0, 0.0, 0.0, 0.0, 0.0},
{0.5, 0.0, 0.0, 0.0, 0.0, 0.0},
{0.5, 0.0, 0.0, 0.0, 0.0, 0.0}};
for (size_t i = 0; i < summary.nodal_displacements.size(); ++i) {
for (size_t j = 0; j < summary.nodal_displacements[i].size(); ++j) {
EXPECT_NEAR(expected[i][j], summary.nodal_displacements[i][j], 1e-10);
}
}
}
TEST_F(beamFEATest, CorrectForcesWeakTies) {
std::vector<double> normal_vec = {0.0, 1.0, 0.0};
Props props(1.e9, 1.e9, 1.e9, 1.e9, normal_vec);
std::vector<Node> nodes = {Node(0.0, 0.0, 0.0),
Node(1.0, 0.0, 0.0),
Node(1.0, 0.0, 0.0),
Node(2.0, 0.0, 0.0)};
std::vector<Elem> elems = {Elem(0, 1, props), Elem(2, 3, props)};
Job job_tie(nodes, elems);
BC bc1(0, 0, 0.0);
BC bc2(0, 1, 0.0);
BC bc3(0, 2, 0.0);
BC bc4(0, 3, 0.0);
BC bc5(0, 4, 0.0);
BC bc6(0, 5, 0.0);
BC bc7(3, 0, 0.5);
BC bc8(2, 3, 0.5);
std::vector<BC> bcs = {bc1, bc2, bc3, bc4, bc5, bc6, bc7, bc8};
std::vector<Tie> ties = {Tie(1, 2, 0.01, 0.01)};
std::vector<Force> forces;
Options opts;
opts.epsilon = 1e-10;
Summary summary = solve(job_tie, bcs, forces, ties, opts);
std::vector<std::vector<double> > expected = {{0.005, 0.0, 0.0, 0.005, 0.0, 0.0}};
for (size_t i = 0; i < summary.tie_forces.size(); ++i) {
for (size_t j = 0; j < summary.tie_forces[i].size(); ++j) {
EXPECT_NEAR(expected[i][j], summary.tie_forces[i][j], 1e-13);
}
}
}
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