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refactor(domains): remove plates/api.jl stub ahead of plate kernel rework
Remove empty plate API entrypoint; DKT/basis material lives elsewhere now.
This commit is contained in:
Jukka Aho
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# Plate Elements API
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#
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# This file defines the interface for plate bending elements following
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# the modern JuliaFEM architecture with zero-allocation design.
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#
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# Reference: Batoz, J.-L., Bathe, K.-J., & Ho, L.-W. (1980).
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# "A study of three-node triangular plate bending elements."
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# International Journal for Numerical Methods in Engineering, 15(12), 1771-1812.
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# Dependencies
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using Tensors
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# This file is part of JuliaFEM, but can be tested standalone
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# When integrated: using ..JuliaFEM
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# When standalone: Define AbstractMaterial, AbstractPlateFormulation, etc. locally
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# ============================================================================
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# Abstract Types
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# ============================================================================
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"""
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AbstractPlateFormulation
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Abstract supertype for all plate bending formulations.
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Plate elements typically have 3 DOFs per node:
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- w: transverse displacement (out-of-plane)
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- θx: rotation about x-axis
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- θy: rotation about y-axis
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Implementations include:
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- DKT (Discrete Kirchhoff Triangle): Kirchhoff theory, C0 continuous
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- Mindlin plates: Mindlin-Reissner theory, includes shear deformation
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"""
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abstract type AbstractPlateFormulation <: AbstractFormulation end
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"""
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DKTFormulation <: AbstractPlateFormulation
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Discrete Kirchhoff Triangle plate bending element.
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Based on Kirchhoff plate theory (thin plates, neglects shear deformation).
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Uses a discrete approach to enforce Kirchhoff constraints at selected points.
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**Theory:**
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- 3-node triangular element (Tri3 topology)
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- 3 DOFs per node: w, θx, θy (9 total)
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- Kirchhoff hypothesis: γxz = γyz = 0 (no shear deformation)
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- C0 continuous (displacements), but enforces C1 behavior discretely
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- Accurate for thin plates (thickness/span < 1/20)
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**Material Properties Required:**
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- Young's modulus (E) - from AbstractMaterial
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- Poisson's ratio (ν) - from AbstractMaterial
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- Thickness (t) - stored in formulation
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**References:**
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- Batoz et al. (1980) - Original DKT formulation
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- Lucena Neto et al. (2017) - Geometric stiffness matrix
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"""
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struct DKTFormulation <: AbstractPlateFormulation
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thickness::Float64
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geometric_stiffness::Bool
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end
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"""
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DKTFormulation(; thickness, geometric_stiffness=true)
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Create DKT formulation with specified plate thickness.
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# Arguments
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- `thickness::Float64`: Plate thickness [m]
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- `geometric_stiffness::Bool`: Enable geometric stiffness for buckling analysis (default: true)
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# Example
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```julia
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dkt = DKTFormulation(thickness=0.01) # 10mm plate
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```
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"""
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DKTFormulation(; thickness::Real, geometric_stiffness::Bool=true) =
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DKTFormulation(Float64(thickness), geometric_stiffness)
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"""
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get_thickness(formulation::DKTFormulation) -> Float64
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Get plate thickness from DKT formulation.
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"""
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get_thickness(f::DKTFormulation) = f.thickness
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# ============================================================================
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# Material Properties for Plates
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# ============================================================================
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"""
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constitutive_matrix_plate(material::AbstractMaterial, thickness::Float64)
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Compute bending stiffness matrix D for Kirchhoff plate theory.
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Extracts Young's modulus E and Poisson's ratio ν from the material,
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then computes the 3×3 bending stiffness matrix.
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Returns 3×3 matrix relating curvatures to moments:
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```
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[Mx] [D11 D12 0 ] [κx ]
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[My] = [D21 D22 0 ] [κy ]
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[Mxy] [ 0 0 D33] [κxy]
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```
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where D₀ = (E*t³)/(12*(1-ν²))
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# Arguments
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- `material::AbstractMaterial`: Material with E and ν properties
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- `thickness::Float64`: Plate thickness [m]
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# Returns
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- `Tensor{2,3,Float64}`: 3×3 bending stiffness matrix [Pa·m³]
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# Example
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```julia
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steel = LinearElastic(E=210e9, ν=0.3)
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t = 0.01 # 10mm
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D = constitutive_matrix_plate(steel, t)
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```
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"""
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function constitutive_matrix_plate(material::AbstractMaterial, thickness::Float64)
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E = material.E
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ν = material.ν
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D0 = E * thickness^3 / (12 * (1 - ν^2))
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return Tensor{2,3}((
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D0, D0 * ν, 0.0,
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D0 * ν, D0, 0.0,
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0.0, 0.0, D0 * (1 - ν) / 2
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))
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end
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# ============================================================================
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# Displacement Field
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# ============================================================================
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"""
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PlateDisplacement <: AbstractField
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Displacement field for plate bending: w, θx, θy at each node.
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For a 3-node triangle:
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- 9 total DOFs: (w1, θx1, θy1, w2, θx2, θy2, w3, θx3, θy3)
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Convention:
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- w: positive upward (out-of-plane)
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- θx: rotation about x-axis (right-hand rule)
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- θy: rotation about y-axis (right-hand rule)
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"""
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struct PlateDisplacement <: AbstractField end
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# ============================================================================
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# API Functions (to be implemented by formulations)
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# ============================================================================
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"""
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assemble!(physics::Physics{F, PlateDisplacement, M, Mat}) where {F<:AbstractPlateFormulation, M<:AbstractMesh, Mat<:AbstractMaterial}
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Assemble plate element stiffness matrices into global system.
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This is the main assembly function following the Physics interface pattern.
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Each plate formulation must implement this method.
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The material (Mat) should provide:
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- `E::Float64`: Young's modulus (via `material.E`)
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- `ν::Float64`: Poisson's ratio (via `material.ν`)
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The formulation (F) provides:
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- `thickness::Float64`: Plate thickness
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# Example
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```julia
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steel = LinearElastic(E=210e9, ν=0.3)
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dkt = DKTFormulation(thickness=0.01)
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physics = Physics(dkt, PlateDisplacement(), mesh, steel)
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assemble!(physics)
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```
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"""
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# Note: assemble! function stub is defined in physics/api.jl
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# Plate formulations should implement specific methods for assemble!
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# Export types and functions
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export AbstractPlateFormulation, DKTFormulation
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export PlateDisplacement
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export constitutive_matrix_plate
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export get_thickness
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