fix: restore thickness factor in shell bending resultants

2026-09-26 23:56:00 +09:00
parent 97ffe46f63
commit 7b700ab491
2 changed files with 34 additions and 3 deletions
@@ -91,6 +91,37 @@ TEST(NonlinearMitc4Shell, UndeformedStateHasZeroPhysicalRecovery) {
  ExpectZeroRecovery(recovery.Value());
 }

+TEST(NonlinearMitc4Recovery, BendingResultantsMatchStressThicknessMoments) {
+  const auto nodes = Nodes();
+  auto trial = ZeroTrial();
+  trial.rotation_vector = {{{0.12, -0.05, 0.0},
+                            {-0.02, 0.13, 0.0},
+                            {-0.12, 0.05, 0.0},
+                            {0.02, -0.13, 0.0}}};
+  for (const double thickness : {0.2, 0.5, 2.0}) {
+    SCOPED_TRACE(thickness);
+    auto section = Section();
+    section.thickness = thickness;
+    const auto shell = fesa::NonlinearMitc4Shell::Create(
+        NodePointers(nodes), Frames(), section, Material());
+    ASSERT_TRUE(shell.HasValue());
+    const auto recovery = shell.Value().RecoverState(trial);
+    ASSERT_TRUE(recovery.HasValue());
+    for (const auto& point : recovery.Value().gauss_points) {
+      for (std::size_t component = 0U; component < 3U; ++component) {
+        // Flat reference geometry gives quadratic stress in z. Its odd
+        // thickness moment is exact from independently sampled face stresses.
+        const double moment = thickness * thickness / 12.0 *
+                              (point.stress[2U].components[component] -
+                               point.stress[0U].components[component]);
+        ASSERT_GT(std::abs(moment), 0.0);
+        EXPECT_NEAR(point.section_resultant[3U + component], moment,
+                    1.0e-12 * std::abs(moment));
+      }
+    }
+  }
+}
+
 // NSNR-ELEM-KIN-001A
 TEST(NonlinearMitc4Shell, RejectsInvalidNodeAndInitialFrameContracts) {
  const auto nodes = Nodes();