feat(linear-static-mitc4-shell): step 4 - mitc4-stiffness-drilling

This commit is contained in:
KOKO\Mimi
2026-08-12 19:54:27 +09:00
parent 33d039bb73
commit 1a6a9bfc71
3 changed files with 620 additions and 6 deletions
+442
View File
@@ -2,12 +2,15 @@
#include <gtest/gtest.h>
#include <algorithm>
#include <array>
#include <cmath>
#include <cstddef>
#include <cstdint>
#include <limits>
#include <stdexcept>
#include <string>
#include <vector>
namespace {
@@ -124,6 +127,194 @@ bool hasPositiveCholeskyPivots(const fesa::Matrix& matrix) {
return true;
}
double frobeniusNorm(const fesa::Matrix& matrix) {
double squaredNorm = 0.0;
for (std::size_t row = 0U; row < matrix.rows(); ++row) {
for (std::size_t column = 0U; column < matrix.columns(); ++column) {
squaredNorm += matrix(row, column) * matrix(row, column);
}
}
return std::sqrt(squaredNorm);
}
double scaledSymmetryError(
const fesa::Matrix& matrix,
std::size_t dofsPerNode,
double elementLength) {
fesa::Matrix difference{matrix.rows(), matrix.columns()};
fesa::Matrix scaled{matrix.rows(), matrix.columns()};
for (std::size_t row = 0U; row < matrix.rows(); ++row) {
const double rowScale = row % dofsPerNode < 3U ? elementLength : 1.0;
for (std::size_t column = 0U; column < matrix.columns(); ++column) {
const double columnScale =
column % dofsPerNode < 3U ? elementLength : 1.0;
scaled(row, column) =
rowScale * matrix(row, column) * columnScale;
difference(row, column) = rowScale *
(matrix(row, column) - matrix(column, row)) * columnScale;
}
}
return frobeniusNorm(difference) / frobeniusNorm(scaled);
}
fesa::Matrix scaledStiffness(
const fesa::Matrix& matrix,
std::size_t dofsPerNode,
double elementLength) {
fesa::Matrix scaled{matrix.rows(), matrix.columns()};
for (std::size_t row = 0U; row < matrix.rows(); ++row) {
const double rowScale = row % dofsPerNode < 3U ? elementLength : 1.0;
for (std::size_t column = 0U; column < matrix.columns(); ++column) {
const double columnScale =
column % dofsPerNode < 3U ? elementLength : 1.0;
scaled(row, column) =
rowScale * matrix(row, column) * columnScale;
}
}
return scaled;
}
std::vector<double> symmetricEigenvalues(fesa::Matrix matrix) {
if (matrix.rows() != matrix.columns()) {
throw std::invalid_argument{"Symmetric eigensolve requires a square matrix."};
}
const std::size_t size = matrix.rows();
double matrixScale = 0.0;
for (std::size_t row = 0U; row < size; ++row) {
for (std::size_t column = 0U; column < size; ++column) {
matrixScale = (std::max)(matrixScale, std::abs(matrix(row, column)));
}
}
if (matrixScale != 0.0) {
const double convergenceTolerance = 1.0e-14 * matrixScale;
const std::size_t iterationLimit = 100U * size * size;
for (std::size_t iteration = 0U; iteration < iterationLimit; ++iteration) {
std::size_t pivotRow = 0U;
std::size_t pivotColumn = 0U;
double largestOffDiagonal = 0.0;
for (std::size_t row = 0U; row < size; ++row) {
for (std::size_t column = row + 1U; column < size; ++column) {
const double candidate = std::abs(matrix(row, column));
if (candidate > largestOffDiagonal) {
largestOffDiagonal = candidate;
pivotRow = row;
pivotColumn = column;
}
}
}
if (largestOffDiagonal <= convergenceTolerance) {
break;
}
const double pivot = matrix(pivotRow, pivotColumn);
const double tau =
(matrix(pivotColumn, pivotColumn) - matrix(pivotRow, pivotRow)) /
(2.0 * pivot);
const double tangent = tau >= 0.0
? 1.0 / (tau + std::sqrt(1.0 + tau * tau))
: -1.0 / (-tau + std::sqrt(1.0 + tau * tau));
const double cosine = 1.0 / std::sqrt(1.0 + tangent * tangent);
const double sine = tangent * cosine;
const double rowDiagonal = matrix(pivotRow, pivotRow);
const double columnDiagonal = matrix(pivotColumn, pivotColumn);
matrix(pivotRow, pivotRow) = rowDiagonal - tangent * pivot;
matrix(pivotColumn, pivotColumn) = columnDiagonal + tangent * pivot;
matrix(pivotRow, pivotColumn) = 0.0;
matrix(pivotColumn, pivotRow) = 0.0;
for (std::size_t index = 0U; index < size; ++index) {
if (index == pivotRow || index == pivotColumn) {
continue;
}
const double rowValue = matrix(index, pivotRow);
const double columnValue = matrix(index, pivotColumn);
const double rotatedRow = cosine * rowValue - sine * columnValue;
const double rotatedColumn = sine * rowValue + cosine * columnValue;
matrix(index, pivotRow) = rotatedRow;
matrix(pivotRow, index) = rotatedRow;
matrix(index, pivotColumn) = rotatedColumn;
matrix(pivotColumn, index) = rotatedColumn;
}
}
}
std::vector<double> eigenvalues(size);
for (std::size_t index = 0U; index < size; ++index) {
eigenvalues[index] = matrix(index, index);
}
return eigenvalues;
}
std::size_t numericalRank(const fesa::Matrix& scaledMatrix) {
const auto eigenvalues = symmetricEigenvalues(scaledMatrix);
double spectralScale = 0.0;
for (double eigenvalue : eigenvalues) {
spectralScale = (std::max)(spectralScale, std::abs(eigenvalue));
}
return static_cast<std::size_t>(std::count_if(
eigenvalues.begin(), eigenvalues.end(), [spectralScale](double eigenvalue) {
return std::abs(eigenvalue) > 1.0e-9 * spectralScale;
}));
}
double symmetricOperatorNorm(const fesa::Matrix& matrix) {
const auto eigenvalues = symmetricEigenvalues(matrix);
double result = 0.0;
for (double eigenvalue : eigenvalues) {
result = (std::max)(result, std::abs(eigenvalue));
}
return result;
}
double quadraticEnergy(const fesa::Matrix& stiffness, const fesa::Vector& vector) {
return 0.5 * vector.dot(stiffness.multiply(vector));
}
fesa::Vector physicalField(const std::array<std::array<double, 5>, 4>& values) {
fesa::Vector result{20U};
for (std::size_t nodeIndex = 0U; nodeIndex < 4U; ++nodeIndex) {
for (std::size_t component = 0U; component < 5U; ++component) {
result[5U * nodeIndex + component] = values[nodeIndex][component];
}
}
return result;
}
void expectStrain(
const fesa::Mitc4Shell& shell,
const fesa::Vector& field,
double xi,
double eta,
double zeta,
const std::array<double, 5>& expected) {
const auto actual = shell.strainDisplacement20(xi, eta, zeta).multiply(field);
for (std::size_t component = 0U; component < expected.size(); ++component) {
EXPECT_NEAR(actual[component], expected[component], 1.0e-12)
<< "component " << component;
}
}
fesa::Vector physicalRigidMode(
const std::array<fesa::Node, 4>& nodes,
const Vector3& translation,
const Vector3& rotation) {
fesa::Vector mode{24U};
for (std::size_t nodeIndex = 0U; nodeIndex < nodes.size(); ++nodeIndex) {
const Vector3 rotationalTranslation = cross(
rotation, nodes[nodeIndex].coordinates);
const std::size_t offset = 6U * nodeIndex;
for (std::size_t component = 0U; component < 3U; ++component) {
mode[offset + component] =
translation[component] + rotationalTranslation[component];
}
// Remove the director-parallel component: it is numerical drilling,
// not part of the five-DOF physical rigid motion.
mode[offset + 3U] = rotation[0];
mode[offset + 4U] = rotation[1];
mode[offset + 5U] = 0.0;
}
return mode;
}
std::array<fesa::Node, 4> planarNodes() {
return {
node(1, {-1.0, -1.0, 0.0}),
@@ -381,3 +572,254 @@ TEST(Mitc4ShellKinematics, UsesOneFixedTwoByTwoByTwoQuadratureOrder) {
EXPECT_DOUBLE_EQ(points[point].weight, 1.0);
}
}
// MITC4-KERNEL-001
TEST(Mitc4ShellKernel, FormsFiniteScaledSymmetricPhysicalAndStabilizedStiffness) {
const auto nodes = planarNodes();
const auto shellCandidate = fesa::Mitc4Shell::create(
nodePointers(nodes), directors(), section(), material());
ASSERT_TRUE(shellCandidate.hasValue());
const auto stiffnessCandidate = shellCandidate.value().stiffness();
ASSERT_TRUE(stiffnessCandidate.hasValue());
const auto& stiffness = stiffnessCandidate.value();
EXPECT_EQ(stiffness.physicalLocal20.rows(), 20U);
EXPECT_EQ(stiffness.physicalLocal20.columns(), 20U);
EXPECT_EQ(stiffness.physicalGlobal24.rows(), 24U);
EXPECT_EQ(stiffness.drillingGlobal24.rows(), 24U);
EXPECT_EQ(stiffness.stabilizedGlobal24.rows(), 24U);
for (const fesa::Matrix* matrix : {
&stiffness.physicalLocal20,
&stiffness.physicalGlobal24,
&stiffness.drillingGlobal24,
&stiffness.stabilizedGlobal24}) {
for (std::size_t row = 0U; row < matrix->rows(); ++row) {
for (std::size_t column = 0U; column < matrix->columns(); ++column) {
EXPECT_TRUE(std::isfinite((*matrix)(row, column)));
}
}
}
EXPECT_LE(scaledSymmetryError(stiffness.physicalLocal20, 5U, 2.0), 1.0e-12);
EXPECT_LE(scaledSymmetryError(stiffness.physicalGlobal24, 6U, 2.0), 1.0e-12);
EXPECT_LE(scaledSymmetryError(stiffness.drillingGlobal24, 6U, 2.0), 1.0e-12);
EXPECT_LE(scaledSymmetryError(stiffness.stabilizedGlobal24, 6U, 2.0), 1.0e-12);
const auto repeatedCandidate = shellCandidate.value().stiffness();
ASSERT_TRUE(repeatedCandidate.hasValue());
const auto& repeated = repeatedCandidate.value();
expectMatrixNear(repeated.physicalLocal20, stiffness.physicalLocal20, 0.0);
expectMatrixNear(repeated.physicalGlobal24, stiffness.physicalGlobal24, 0.0);
expectMatrixNear(repeated.drillingGlobal24, stiffness.drillingGlobal24, 0.0);
expectMatrixNear(repeated.stabilizedGlobal24, stiffness.stabilizedGlobal24, 0.0);
EXPECT_DOUBLE_EQ(repeated.drillingStiffness, stiffness.drillingStiffness);
}
// MITC4-KERNEL-002
TEST(Mitc4ShellKernel, PreservesPhysicalEnergyUnderTwentyToTwentyFourCongruence) {
const auto nodes = planarNodes();
const auto shellCandidate = fesa::Mitc4Shell::create(
nodePointers(nodes), directors(), section(), material());
ASSERT_TRUE(shellCandidate.hasValue());
const auto stiffnessCandidate = shellCandidate.value().stiffness();
ASSERT_TRUE(stiffnessCandidate.hasValue());
const auto& stiffness = stiffnessCandidate.value();
fesa::Vector globalField{24U};
for (std::size_t index = 0U; index < globalField.size(); ++index) {
globalField[index] = 0.125 * static_cast<double>(
static_cast<int>(index % 7U) - 3);
}
const auto physicalField20 =
shellCandidate.value().physicalTransformation20().multiply(globalField);
const double localEnergy = quadraticEnergy(
stiffness.physicalLocal20, physicalField20);
const double globalEnergy = quadraticEnergy(
stiffness.physicalGlobal24, globalField);
ASSERT_NE(localEnergy, 0.0);
ASSERT_NE(globalEnergy, 0.0);
EXPECT_LE(
std::abs(globalEnergy - localEnergy) /
(std::abs(globalEnergy) + std::abs(localEnergy)),
1.0e-12);
}
// MITC4-KERNEL-003
TEST(Mitc4ShellKernel, RetainsSixRigidModesAndHasExpectedPhysicalAndStabilizedRank) {
const auto nodes = planarNodes();
const auto shellCandidate = fesa::Mitc4Shell::create(
nodePointers(nodes), directors(), section(), material());
ASSERT_TRUE(shellCandidate.hasValue());
const auto stiffnessCandidate = shellCandidate.value().stiffness();
ASSERT_TRUE(stiffnessCandidate.hasValue());
const auto& stiffness = stiffnessCandidate.value();
const auto scaledPhysical20 =
scaledStiffness(stiffness.physicalLocal20, 5U, 2.0);
const auto scaledPhysical24 =
scaledStiffness(stiffness.physicalGlobal24, 6U, 2.0);
const auto scaledStabilized24 =
scaledStiffness(stiffness.stabilizedGlobal24, 6U, 2.0);
EXPECT_EQ(numericalRank(scaledPhysical20), 14U);
EXPECT_EQ(numericalRank(scaledStabilized24), 18U);
const std::array<fesa::Vector, 6> rigidModes{
physicalRigidMode(nodes, {1.0, 0.0, 0.0}, {}),
physicalRigidMode(nodes, {0.0, 1.0, 0.0}, {}),
physicalRigidMode(nodes, {0.0, 0.0, 1.0}, {}),
physicalRigidMode(nodes, {}, {1.0, 0.0, 0.0}),
physicalRigidMode(nodes, {}, {0.0, 1.0, 0.0}),
physicalRigidMode(nodes, {}, {0.0, 0.0, 1.0})};
const double physicalNorm = symmetricOperatorNorm(scaledPhysical24);
const double stabilizedNorm = symmetricOperatorNorm(scaledStabilized24);
ASSERT_GT(physicalNorm, 0.0);
ASSERT_GT(stabilizedNorm, 0.0);
for (const auto& rigidMode : rigidModes) {
fesa::Vector scaledMode = rigidMode;
for (std::size_t nodeIndex = 0U; nodeIndex < 4U; ++nodeIndex) {
for (std::size_t component = 0U; component < 3U; ++component) {
scaledMode[6U * nodeIndex + component] /= 2.0;
}
}
const double modeNorm = scaledMode.norm();
ASSERT_GT(modeNorm, 0.0);
EXPECT_LE(
scaledPhysical24.multiply(scaledMode).norm() /
(physicalNorm * modeNorm),
1.0e-10);
EXPECT_LE(
scaledStabilized24.multiply(scaledMode).norm() /
(stabilizedNorm * modeNorm),
1.0e-10);
}
}
// MITC4-KERNEL-004
TEST(Mitc4ShellPatch, ReproducesIndependentMembraneBendingShearAndTwistFields) {
const auto nodes = planarNodes();
const auto shellCandidate = fesa::Mitc4Shell::create(
nodePointers(nodes), directors(), section(), material());
ASSERT_TRUE(shellCandidate.hasValue());
const auto& shell = shellCandidate.value();
const auto stiffnessCandidate = shell.stiffness();
ASSERT_TRUE(stiffnessCandidate.hasValue());
const auto& stiffness = stiffnessCandidate.value().physicalLocal20;
constexpr double magnitude = 0.2;
const double gauss = 1.0 / std::sqrt(3.0);
std::array<std::array<double, 5>, 4> e11Values{};
std::array<std::array<double, 5>, 4> e22Values{};
std::array<std::array<double, 5>, 4> g12Values{};
std::array<std::array<double, 5>, 4> k11Values{};
std::array<std::array<double, 5>, 4> k22Values{};
std::array<std::array<double, 5>, 4> g13Values{};
std::array<std::array<double, 5>, 4> g23Values{};
std::array<std::array<double, 5>, 4> k12Values{};
for (std::size_t nodeIndex = 0U; nodeIndex < nodes.size(); ++nodeIndex) {
const double x = nodes[nodeIndex].coordinates[0];
const double y = nodes[nodeIndex].coordinates[1];
e11Values[nodeIndex][0] = magnitude * x;
e22Values[nodeIndex][1] = magnitude * y;
g12Values[nodeIndex][0] = 0.5 * magnitude * y;
g12Values[nodeIndex][1] = 0.5 * magnitude * x;
k11Values[nodeIndex][4] = magnitude * x;
k22Values[nodeIndex][3] = -magnitude * y;
g13Values[nodeIndex][2] = magnitude * x;
g23Values[nodeIndex][2] = magnitude * y;
k12Values[nodeIndex][2] = -0.5 * magnitude * x * y;
k12Values[nodeIndex][3] = -0.5 * magnitude * x;
k12Values[nodeIndex][4] = 0.5 * magnitude * y;
}
const std::array<fesa::Vector, 8> fields{
physicalField(e11Values), physicalField(e22Values),
physicalField(g12Values), physicalField(k11Values),
physicalField(k22Values), physicalField(g13Values),
physicalField(g23Values), physicalField(k12Values)};
expectStrain(shell, fields[0], gauss, -gauss, gauss, {magnitude, 0.0, 0.0, 0.0, 0.0});
expectStrain(shell, fields[1], gauss, -gauss, gauss, {0.0, magnitude, 0.0, 0.0, 0.0});
expectStrain(shell, fields[2], gauss, -gauss, gauss, {0.0, 0.0, magnitude, 0.0, 0.0});
expectStrain(shell, fields[3], gauss, -gauss, gauss, {gauss * magnitude, 0.0, 0.0, 0.0, 0.0});
expectStrain(shell, fields[4], gauss, -gauss, gauss, {0.0, gauss * magnitude, 0.0, 0.0, 0.0});
expectStrain(shell, fields[5], gauss, -gauss, gauss, {0.0, 0.0, 0.0, magnitude, 0.0});
expectStrain(shell, fields[6], gauss, -gauss, gauss, {0.0, 0.0, 0.0, 0.0, magnitude});
expectStrain(shell, fields[7], gauss, -gauss, gauss, {0.0, 0.0, gauss * magnitude, 0.0, 0.0});
for (const auto& field : fields) {
EXPECT_GT(quadraticEnergy(stiffness, field), 0.0);
}
}
// MITC4-KERNEL-005
TEST(Mitc4ShellDrilling, UsesOnlyEightPositivePhysicalRotationDiagonalsAndFixedFactor) {
const std::array<fesa::Node, 4> nodes{
node(1, {-50.0, -50.0, 0.0}), node(2, {50.0, -50.0, 0.0}),
node(3, {50.0, 50.0, 0.0}), node(4, {-50.0, 50.0, 0.0})};
const auto shellCandidate = fesa::Mitc4Shell::create(
nodePointers(nodes), directors(), section(0.1), material());
ASSERT_TRUE(shellCandidate.hasValue());
const auto stiffnessCandidate = shellCandidate.value().stiffness();
ASSERT_TRUE(stiffnessCandidate.hasValue());
const auto& stiffness = stiffnessCandidate.value();
double expectedReference = (std::numeric_limits<double>::max)();
double allDiagonalMinimum = (std::numeric_limits<double>::max)();
for (std::size_t nodeIndex = 0U; nodeIndex < 4U; ++nodeIndex) {
for (std::size_t rotation = 3U; rotation < 5U; ++rotation) {
const std::size_t index = 5U * nodeIndex + rotation;
const double diagonal = stiffness.physicalLocal20(index, index);
ASSERT_TRUE(std::isfinite(diagonal));
ASSERT_GT(diagonal, 0.0);
expectedReference = (std::min)(expectedReference, diagonal);
}
for (std::size_t component = 0U; component < 5U; ++component) {
const std::size_t index = 5U * nodeIndex + component;
const double diagonal = stiffness.physicalLocal20(index, index);
if (std::isfinite(diagonal) && diagonal > 0.0) {
allDiagonalMinimum = (std::min)(allDiagonalMinimum, diagonal);
}
}
}
EXPECT_DOUBLE_EQ(stiffness.drillingStiffness, 1.0e-3 * expectedReference);
EXPECT_LT(allDiagonalMinimum, expectedReference);
EXPECT_NE(stiffness.drillingStiffness, 1.0e-3 * allDiagonalMinimum);
}
// MITC4-KERNEL-006
TEST(Mitc4ShellDrilling, FailsNonfiniteReferenceAndStabilizesEachPureDrillCoordinate) {
const auto nodes = planarNodes();
const auto shellCandidate = fesa::Mitc4Shell::create(
nodePointers(nodes), directors(), section(), material());
ASSERT_TRUE(shellCandidate.hasValue());
const auto stiffnessCandidate = shellCandidate.value().stiffness();
ASSERT_TRUE(stiffnessCandidate.hasValue());
const auto& stiffness = stiffnessCandidate.value();
for (std::size_t nodeIndex = 0U; nodeIndex < 4U; ++nodeIndex) {
fesa::Vector pureDrill{24U};
pureDrill[6U * nodeIndex + 5U] = 1.0;
EXPECT_DOUBLE_EQ(
stiffness.physicalGlobal24.multiply(pureDrill).norm(), 0.0);
const auto drillAction = stiffness.drillingGlobal24.multiply(pureDrill);
EXPECT_DOUBLE_EQ(drillAction[6U * nodeIndex + 5U], stiffness.drillingStiffness);
EXPECT_GT(quadraticEnergy(stiffness.drillingGlobal24, pureDrill), 0.0);
}
const std::array<fesa::Node, 4> extremeNodes{
node(1, {-5.0e9, -5.0e9, 0.0}), node(2, {5.0e9, -5.0e9, 0.0}),
node(3, {5.0e9, 5.0e9, 0.0}), node(4, {-5.0e9, 5.0e9, 0.0})};
const auto extremeShell = fesa::Mitc4Shell::create(
nodePointers(extremeNodes), directors(), section(1.0), material(1.0e300));
ASSERT_TRUE(extremeShell.hasValue());
const auto failure = extremeShell.value().stiffness();
ASSERT_FALSE(failure.hasValue());
ASSERT_EQ(failure.status().diagnostics().size(), 1U);
EXPECT_EQ(failure.status().diagnostics()[0].code, "invalid-shell-stiffness");
const auto repeatedFailure = extremeShell.value().stiffness();
ASSERT_FALSE(repeatedFailure.hasValue());
ASSERT_EQ(repeatedFailure.status().diagnostics().size(), 1U);
EXPECT_EQ(
repeatedFailure.status().diagnostics()[0].code,
failure.status().diagnostics()[0].code);
EXPECT_EQ(
repeatedFailure.status().diagnostics()[0].message,
failure.status().diagnostics()[0].message);
}