diff --git a/test/solvers/test_modal_elasticity.jl b/test/solvers/test_modal_elasticity.jl new file mode 100644 index 0000000..6de4acc --- /dev/null +++ b/test/solvers/test_modal_elasticity.jl @@ -0,0 +1,102 @@ +# This file is a part of JuliaFEM. +# License is MIT: see https://github.com/JuliaFEM/JuliaFEM.jl/blob/master/LICENSE.md + +using JuliaFEM, Test, LinearAlgebra + +#= this has nothing to do here +@testset "calculate cross-sectional properties" begin + mesh_file = @__DIR__() * "/testdata/primitives.med" + mesh = aster_read_mesh(mesh_file, "CYLINDER_20_TET4") + # calculate cross-sectional properties A and Iₓ + fixed1 = Problem(Dirichlet, "left support", 3, "displacement") + fixed1.elements = create_elements(mesh, "FACE1") + A = calculate_area(fixed1) + @info("cross-section area: $A") + # real area is π + @test isapprox(A, pi; rtol=0.1) + Xc = calculate_center_of_mass(fixed1) + @info("center of mass: $Xc") + @test isapprox(Xc, [0.0, 0.0, 0.0]; atol=1.0e-12) + I = calculate_second_moment_of_mass(fixed1) + @info("moments:") + @info(I) + I_expected = zeros(3, 3) + I_expected[2,2] = I_expected[3,3] = pi/4 + rtol = norm(I[2,2]-I_expected[2,2]) / max(I[2,2],I_expected[2,2]) + @info("I rtol = $rtol") + @test isapprox(I, I_expected; rtol = 0.2) +end +=# + +#= +test subjects: +- calculate cross-sectional properties +- modal analysis with known solution + +Fixed-fixed solution is ωᵢ = λᵢ²√(EI/ρA) , where λᵢ = cosh(λᵢℓ)cos(λᵢℓ) + +1: 4.730040744862704 +2: 7.853204624095838 +3: 10.995607838001671 + +Youngs modulus is tuned such that lowest eigenfrequency matches 1.0 + +5 lowest eigenfrequencies using Code Aster and Tet4 elements: +numéro fréquence (HZ) norme d'erreur + 1 1.19789E+00 2.20137E-12 + 2 1.20179E+00 1.99034E-12 + 3 3.07391E+00 3.29226E-13 + 4 3.08812E+00 2.91550E-13 + 5 4.87370E+00 2.95986E-13 + +5 lowest eigenfrequencies using Code Aster and Tet10 elements: +numéro fréquence (HZ) norme d'erreur + 1 9.65942E-01 1.54950E-11 + 2 9.66160E-01 1.62712E-11 + 3 2.52127E+00 2.06544E-12 + 4 2.52187E+00 1.77970E-12 + 5 3.48584E+00 9.96170E-13 + + +[1] De Silva, Clarence W. Vibration: fundamentals and practice. CRC press, 2006, p.355 +=# + +# long rod natural frequencies +mesh_file = @__DIR__() * "/testdata/primitives.med" +mesh = aster_read_mesh(mesh_file, "CYLINDER_20_TET10") +body = Problem(Elasticity, "rod", 3) +body_elements = create_elements(mesh, "CYLINDER") +#E = 50475.44814745859 +E = 50475.5 +rho = 1.0 +update!(body_elements, "youngs modulus", E) +update!(body_elements, "poissons ratio", 0.3) +update!(body_elements, "density", rho) +add_elements!(body, body_elements) + +fixed1 = Problem(Dirichlet, "left support", 3, "displacement") +fixed1_elements = create_elements(mesh, "FACE1") +update!(fixed1_elements, "displacement 1", 0.0) +update!(fixed1_elements, "displacement 2", 0.0) +update!(fixed1_elements, "displacement 3", 0.0) +add_elements!(fixed1, fixed1_elements) + +fixed2 = Problem(Dirichlet, "right support", 3, "displacement") +fixed2_elements = create_elements(mesh, "FACE2") +update!(fixed2_elements, "displacement 1", 0.0) +update!(fixed2_elements, "displacement 2", 0.0) +update!(fixed2_elements, "displacement 3", 0.0) +add_elements!(fixed2, fixed2_elements) + +analysis = Analysis(Modal) +add_problems!(analysis, body, fixed1, fixed2) +analysis.properties.nev = 5 +run!(analysis) +freqs_jf = sqrt.(analysis.properties.eigvals)/(2.0*pi) + +# with Tet4 elements +#freqs_ca = [1.19789E+00, 1.20179E+00, 3.07391E+00, 3.08813E+00, 4.87370E+00] +# with Tet10 elements +freqs_ca = [9.65942E-01, 9.66160E-01, 2.52127E+00, 2.52187E+00, 3.48584E+00] +rtol = [norm(f1-f2) / max(f1,f2) for (f1, f2) in zip(freqs_jf, freqs_ca)] +@test maximum(rtol) < 3.0e-2