chore(test): remove modal elasticity regression

Delete elasticity/modal coupling tests outside CI.

- Drop `test/solvers/test_modal_elasticity.jl`.

test/solvers/test_modal_elasticity.jl

@@ -1,102 +0,0 @@
-# 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