JuliaFEM.jl/test/validation/test_plasticity_simple.jl

# This file is a part of JuliaFEM.
# License is MIT: see https://github.com/JuliaFEM/JuliaFEM.jl/blob/master/LICENSE.md

"""
Simple Plasticity Test: Single Hex8 Element with PerfectPlasticity

Demonstrates end-to-end workflow with compositional material cache:
1. Create GlobalMaterialCache from material traits
2. Assemble with state tracking
3. Verify plastic strain accumulates correctly

This is a UNIT TEST, not a validation test. Goal is to verify the
material cache integration works correctly.
"""

using Test
using JuliaFEM
using LinearAlgebra
using SparseArrays
using Tensors

@testset "Simple Plasticity - GlobalMaterialCache Integration" begin
    println("\n" * "="^70)
    println("SIMPLE PLASTICITY TEST - GlobalMaterialCache Integration")
    println("="^70)

    # ========================================================================
    # 1. Create Single Element Mesh
    # ========================================================================

    println("\n[1] Creating single element mesh...")

    # Unit cube Hex8 element
    nodes = [
        Vec{3}((0.0, 0.0, 0.0)),  # 1
        Vec{3}((1.0, 0.0, 0.0)),  # 2
        Vec{3}((1.0, 1.0, 0.0)),  # 3
        Vec{3}((0.0, 1.0, 0.0)),  # 4
        Vec{3}((0.0, 0.0, 1.0)),  # 5
        Vec{3}((1.0, 0.0, 1.0)),  # 6
        Vec{3}((1.0, 1.0, 1.0)),  # 7
        Vec{3}((0.0, 1.0, 1.0)),  # 8
    ]

    connectivity = [NTuple{8,UInt32}((1, 2, 3, 4, 5, 6, 7, 8))]
    element_sets = Dict{Symbol,Set{UInt32}}(:all => Set(UInt32[1]))
    mesh = Mesh{8,Hexahedron{8}}(nodes, connectivity, element_sets)

    println("  Nodes: $(length(nodes))")
    println("  Elements: $(length(connectivity))")

    # ========================================================================
    # 2. Material and GlobalMaterialCache
    # ========================================================================

    println("\n[2] Creating material and global cache...")

    # Plasticity material
    E = 210e9  # Pa
    ν = 0.3
    σ_y = 250e6  # Pa (250 MPa yield stress)
    H = 1e9      # Pa (hardening modulus)

    material = PerfectPlasticity(E=E, ν=ν, σ_y=σ_y, H=H)

    println("  Material: PerfectPlasticity")
    println("  E = $(E/1e9) GPa")
    println("  σ_y = $(σ_y/1e6) MPa")
    println("  H = $(H/1e9) GPa")

    # Verify material traits
    state_vars = required_state_variables(material)
    @test state_vars == (PlasticStrain, Backstress, EquivalentPlasticStrain)
    println("  State variables: $state_vars")

    # Create global material cache
    nips = 8  # Hex8 has 8 integration points (2x2x2 Gauss)
    nelems = 1
    global_cache = create_global_material_cache(material, n_ips=nips, n_elems=nelems)

    @test global_cache isa GlobalMaterialCache
    @test size(global_cache.states) == (nips, nelems)
    println("  Created GlobalMaterialCache: $(size(global_cache.states))")

    # Verify initial state is zero
    for ip in 1:nips
        state = get_state(global_cache, ip, 1)
        @test state.ε_p == zero(SymmetricTensor{2,3})
        @test state.α == zero(SymmetricTensor{2,3})
        @test state.κ == 0.0
    end
    println("  ✓ All states initialized to zero")

    # ========================================================================
    # 3. Demonstrate Material Response
    # ========================================================================

    println("\n[3] Testing material response...")

    # Test 1: Elastic response (small strain)
    ε_elastic = SymmetricTensor{2,3}((1e-4, 0.0, 0.0, 0.0, 0.0, 0.0))
    state_old_1 = NamedTuple()  # Empty state = initial
    σ_1, 𝔻_1, state_new_1 = compute_stress(material, ε_elastic, state_old_1, 0.0)

    @test state_new_1.κ == 0.0  # No plastic strain
    println("  ✓ Elastic response: κ = $(state_new_1.κ)")

    # Test 2: Plastic response (large strain)
    ε_plastic = SymmetricTensor{2,3}((0.005, 0.0, 0.0, 0.0, 0.0, 0.0))
    state_old_2 = NamedTuple()  # Empty state = initial
    σ_2, 𝔻_2, state_new_2 = compute_stress(material, ε_plastic, state_old_2, 0.0)

    @test state_new_2.κ > 0.0  # Plastic strain accumulated
    println("  ✓ Plastic response: κ = $(state_new_2.κ)")

    # ========================================================================
    # 4. Direct NamedTuple Workflow (No Bridge!)
    # ========================================================================

    println("\n[4] Testing direct NamedTuple workflow...")

    # State is already a NamedTuple - use directly!
    @test state_new_2 isa NamedTuple
    @test haskey(state_new_2, :ε_p)
    @test haskey(state_new_2, :α)
    @test haskey(state_new_2, :κ)
    println("  ✓ State is native NamedTuple (no conversion needed)")

    # Store directly in global cache
    set_state!(global_cache, 1, 1, state_new_2)
    retrieved_state = get_state(global_cache, 1, 1)
    @test retrieved_state.κ == state_new_2.κ
    println("  ✓ State stored directly in GlobalMaterialCache")

    # Access directly from cache
    @test get_state(global_cache, 1, 1) isa NamedTuple
    println("  ✓ Direct access from cache (no extraction needed)")

    # ========================================================================
    # 5. Time-Stepping Workflow
    # ========================================================================

    println("\n[5] Testing time-stepping workflow...")

    # Reset cache
    reset_cache!(global_cache)

    # Step 1: Small load (elastic)
    println("  Step 1: Elastic loading...")
    state_step1_old = get_state(global_cache, 1, 1)  # Get directly
    σ_step1, 𝔻_step1, state_step1 = compute_stress(material, ε_elastic, state_step1_old, 0.0)
    set_state!(global_cache, 1, 1, state_step1)  # Set directly

    @test get_state(global_cache, 1, 1).κ == 0.0
    println("    κ = $(get_state(global_cache, 1, 1).κ) (elastic)")

    # Update cache for next step
    update_cache!(global_cache)

    # Step 2: Large load (plastic)
    println("  Step 2: Plastic loading...")
    state_step2_old = get_state(global_cache, 1, 1)  # Get directly
    σ_step2, 𝔻_step2, state_step2 = compute_stress(material, ε_plastic, state_step2_old, 0.0)
    set_state!(global_cache, 1, 1, state_step2)  # Set directly

    κ_current = get_state(global_cache, 1, 1).κ
    κ_old = get_old_state(global_cache, 1, 1).κ

    @test κ_current > 0.0  # Plastic strain accumulated
    @test κ_old == 0.0     # Old state still elastic
    println("    κ_current = $κ_current (plastic)")
    println("    κ_old = $κ_old (from previous step)")

    # ========================================================================
    # 6. Summary
    # ========================================================================

    println("\n" * "="^70)
    println("SUMMARY - Compositional Material Cache (No Bridge!)")
    println("="^70)
    println("  ✓ GlobalMaterialCache created from material traits")
    println("  ✓ NamedTuple states used directly (no conversion)")
    println("  ✓ compute_stress accepts/returns NamedTuple natively")
    println("  ✓ States stored and retrieved without any bridge")
    println("  ✓ Time-stepping workflow simplified")
    println("  ✓ Plastic strain accumulation tracked")
    println("  ✓ Pure compositional design - elegant and fast!")
    println("="^70)

    @test true  # If we got here, everything worked!
end