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https://github.com/JuliaFEM/JuliaFEM.jl.git
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Jukka Aho
c631eb6d1c
Add a focused regression that `compute_stress` lands on the von Mises surface when the trial state lies outside yield, using the returned backstress state. - SPDX header refresh for the file.
239 lines
8.7 KiB
Julia
239 lines
8.7 KiB
Julia
# SPDX-FileCopyrightText: 2015-2026 Jukka Aho
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# SPDX-License-Identifier: MIT
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using Test
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using JuliaFEM
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using Tensors
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@testset "PerfectPlasticity Integration" begin
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@testset "Material instantiation and traits" begin
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# Create material
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mat = PerfectPlasticity(E=210e9, ν=0.3, σ_y=250e6, H=1e9)
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@test mat isa PerfectPlasticity
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@test mat.E == 210e9
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@test mat.ν == 0.3
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@test mat.σ_y == 250e6
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@test mat.H == 1e9
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# Test material traits
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physics = supported_physics(mat)
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@test physics isa Tuple
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@test length(physics) == 1
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@test physics[1] isa Elasticity{3}
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# Test state variable requirements
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state_vars = required_state_variables(mat)
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@test state_vars == (PlasticStrain, Backstress, EquivalentPlasticStrain)
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# Material should be stateful
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@test is_stateful(mat)
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end
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@testset "Global material cache creation" begin
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mat = PerfectPlasticity(E=210e9, ν=0.3, σ_y=250e6, H=1e9)
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n_ips = 8
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n_elems = 10
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# Create cache automatically from material
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cache = create_global_material_cache(mat, n_ips=n_ips, n_elems=n_elems)
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@test cache isa GlobalMaterialCache
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@test size(cache.states) == (n_ips, n_elems)
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@test size(cache.states_old) == (n_ips, n_elems)
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# All states should be initialized to zero
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for elem_id in 1:n_elems
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for ip in 1:n_ips
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state = get_state(cache, ip, elem_id)
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@test haskey(state, :ε_p)
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@test haskey(state, :α)
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@test haskey(state, :κ)
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@test state.ε_p == zero(SymmetricTensor{2,3})
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@test state.α == zero(SymmetricTensor{2,3})
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@test state.κ == 0.0
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end
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end
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end
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@testset "Direct NamedTuple state manipulation" begin
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# Test compositional state creation and access
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state_nt = (
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ε_p=SymmetricTensor{2,3}((0.001, 0.0, 0.0, 0.0, 0.0, 0.0)),
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α=SymmetricTensor{2,3}((100e6, 0.0, 0.0, 0.0, 0.0, 0.0)),
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κ=0.01
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)
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# State is just a NamedTuple - no conversion needed!
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@test state_nt isa NamedTuple
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@test haskey(state_nt, :ε_p)
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@test haskey(state_nt, :α)
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@test haskey(state_nt, :κ)
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# Can use directly with compute_stress
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mat = PerfectPlasticity(E=210e9, ν=0.3, σ_y=250e6, H=1e9)
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ε = SymmetricTensor{2,3}((0.002, 0.0, 0.0, 0.0, 0.0, 0.0))
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σ, 𝔻, state_new = compute_stress(mat, ε, state_nt, 0.0)
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@test state_new isa NamedTuple
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@test haskey(state_new, :ε_p)
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@test haskey(state_new, :α)
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@test haskey(state_new, :κ)
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end
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@testset "Direct cache access and manipulation" begin
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mat = PerfectPlasticity(E=210e9, ν=0.3, σ_y=250e6, H=1e9)
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cache = create_global_material_cache(mat, n_ips=4, n_elems=2)
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# Set states directly - no conversion needed
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state1 = (
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ε_p=SymmetricTensor{2,3}((0.001, 0.0, 0.0, 0.0, 0.0, 0.0)),
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α=SymmetricTensor{2,3}((50e6, 0.0, 0.0, 0.0, 0.0, 0.0)),
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κ=0.005
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)
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set_state!(cache, 1, 1, state1)
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# Retrieve states directly
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retrieved_state = get_state(cache, 1, 1)
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@test retrieved_state.ε_p == state1.ε_p
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@test retrieved_state.α == state1.α
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@test retrieved_state.κ == state1.κ
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# Modify state directly
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state2 = (
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ε_p=SymmetricTensor{2,3}((0.002, 0.0, 0.0, 0.0, 0.0, 0.0)),
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α=SymmetricTensor{2,3}((100e6, 0.0, 0.0, 0.0, 0.0, 0.0)),
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κ=0.01
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)
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set_state!(cache, 2, 1, state2)
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# Verify stored correctly
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state2_retrieved = get_state(cache, 2, 1)
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@test state2_retrieved.ε_p ≈ SymmetricTensor{2,3}((0.002, 0.0, 0.0, 0.0, 0.0, 0.0))
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@test state2_retrieved.α ≈ SymmetricTensor{2,3}((100e6, 0.0, 0.0, 0.0, 0.0, 0.0))
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@test state2_retrieved.κ ≈ 0.01
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end
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@testset "Elastic response (below yield)" begin
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# Test that material behaves elastically below yield
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mat = PerfectPlasticity(E=210e9, ν=0.3, σ_y=250e6, H=1e9)
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# Small elastic strain
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ε = SymmetricTensor{2,3}((1e-4, 0.0, 0.0, 0.0, 0.0, 0.0)) # ~21 MPa << 250 MPa
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state_old = NamedTuple() # Empty state = initial
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# Compute stress
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σ, 𝔻, state_new = compute_stress(mat, ε, state_old, 0.0)
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# Should be purely elastic (no plastic strain)
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@test state_new.ε_p == zero(SymmetricTensor{2,3})
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@test state_new.α == zero(SymmetricTensor{2,3})
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@test state_new.κ == 0.0
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# Stress should be elastic prediction
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@test norm(σ) > 0.0
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@test norm(σ) < mat.σ_y # Below yield
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end
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@testset "J2 yield surface after radial return (‖dev(σ−α)‖_vm ≈ σᵧ)" begin
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mat = PerfectPlasticity(E = 210e9, ν = 0.3, σ_y = 250e6, H = 2.1e9)
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ε = SymmetricTensor{2,3}((0.02, -0.005, 0.0, 0.0, 0.0, 0.0))
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σ, _, st = compute_stress(mat, ε, NamedTuple(), 0.0)
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s = dev(σ - st.α)
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seq = sqrt(3 / 2 * (s ⊡ s))
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@test seq ≈ mat.σ_y rtol = 1e-5 atol = 1.0
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end
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@testset "Plastic response (above yield)" begin
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# Test that material yields when stress exceeds yield
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mat = PerfectPlasticity(E=210e9, ν=0.3, σ_y=250e6, H=1e9)
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# Large elastic strain that will cause yielding
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# σ_y = 250 MPa, E=210 GPa → ε ≈ 0.0012 should yield
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ε = SymmetricTensor{2,3}((0.005, 0.0, 0.0, 0.0, 0.0, 0.0)) # Large strain
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state_old = NamedTuple() # Empty state = initial
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# Compute stress
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σ, 𝔻, state_new = compute_stress(mat, ε, state_old, 0.0)
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# Should have plastic strain
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@test norm(state_new.ε_p) > 0.0
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@test state_new.κ > 0.0
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# Stress should be at/near yield surface
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@test norm(σ) > 0.0
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end
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@testset "Time stepping workflow" begin
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# Simulate a complete time-stepping workflow
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mat = PerfectPlasticity(E=210e9, ν=0.3, σ_y=250e6, H=1e9)
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cache = create_global_material_cache(mat, n_ips=4, n_elems=1)
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# Step 1: Apply small load (elastic)
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ε1 = SymmetricTensor{2,3}((1e-4, 0.0, 0.0, 0.0, 0.0, 0.0))
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state1_old = get_state(cache, 1, 1) # Get directly from cache
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σ1, 𝔻1, state1_new = compute_stress(mat, ε1, state1_old, 0.0)
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set_state!(cache, 1, 1, state1_new) # Store directly in cache
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# Verify elastic (no plastic strain)
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@test get_state(cache, 1, 1).κ == 0.0
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# Update cache for next step
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update_cache!(cache)
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# Step 2: Apply larger load (plastic)
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ε2 = SymmetricTensor{2,3}((0.005, 0.0, 0.0, 0.0, 0.0, 0.0))
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state2_old = get_state(cache, 1, 1) # Get directly from cache
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σ2, 𝔻2, state2_new = compute_stress(mat, ε2, state2_old, 0.0)
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set_state!(cache, 1, 1, state2_new) # Store directly in cache
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# Verify plastic strain accumulated
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@test get_state(cache, 1, 1).κ > 0.0
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# Old state should still be from step 1 (elastic)
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@test get_old_state(cache, 1, 1).κ == 0.0
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end
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@testset "State variable helpers" begin
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# Test get/set state variable helpers
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state = (
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ε_p=SymmetricTensor{2,3}((0.001, 0.0, 0.0, 0.0, 0.0, 0.0)),
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α=SymmetricTensor{2,3}((100e6, 0.0, 0.0, 0.0, 0.0, 0.0)),
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κ=0.01
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)
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# Get individual variables
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ε_p = get_state_variable(state, PlasticStrain)
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α = get_state_variable(state, Backstress)
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κ = get_state_variable(state, EquivalentPlasticStrain)
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@test ε_p == state.ε_p
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@test α == state.α
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@test κ == state.κ
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# Set individual variables (immutable update)
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new_κ = 0.02
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state_updated = set_state_variable(state, EquivalentPlasticStrain, new_κ)
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@test state_updated.κ == new_κ
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@test state_updated.ε_p == state.ε_p # Unchanged
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@test state_updated.α == state.α # Unchanged
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@test state.κ == 0.01 # Original unchanged
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end
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@testset "Type stability" begin
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# Verify type stability of key operations
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mat = PerfectPlasticity(E=210e9, ν=0.3, σ_y=250e6, H=1e9)
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cache = create_global_material_cache(mat, n_ips=4, n_elems=2)
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# Cache access should be type-stable
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@inferred get_state(cache, 1, 1)
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@inferred get_old_state(cache, 1, 1)
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# compute_stress should be type-stable
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state_nt = (ε_p=zero(SymmetricTensor{2,3}), α=zero(SymmetricTensor{2,3}), κ=0.0)
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ε = SymmetricTensor{2,3}((1e-4, 0.0, 0.0, 0.0, 0.0, 0.0))
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@inferred compute_stress(mat, ε, state_nt, 0.0)
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end
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end
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