Cthonios

Cthonios - Continuum THermodynamic Optimization-based Numerical Implementations Of Solid mechanics

This is a collection of tools for solving solid mechanics problems via optimization methods. This is larrgely inspired by the python package OptimiSM.

The tools build on several other packages such as Exodus.jl, ReferenceFiniteElements.jl, FiniteElementContainers.jl, and ConstitutiveModels.jl to name a few of the direct dependencies developed by the Cthonios organization.

Table of Contents

1. Installation
2. Documentation
3. Usage as an application
4. Example Script Solving a Forward Problem
5. Example Input File Solving a Forward Problem
6. Contributing

Installation

From the julia package manager (which can be entered by typing the "]" key after starting up julia) one can do the following

pkg> add Cthonios

Or one can use the Pkg module inside julia as follows

using Pkg
Pkg.add("Cthonios")

Documentation

Documentation deployed from main branch can be found here

Usage as an application

Using cthonios as an application is still very much in development. The easiest route is to do the following

using Cthonios
push!(ARGS, "-i")
push!(ARGS, "my_input_file.yaml")
Cthonios.cthonios_main(ARGS)

To avoid the above, an executable can be built with either PackageCompiler.jl or JuliaC(requires julia 1.12)

Example Script Solving a Forward Problem

Below is an example julia script for solving a column buckling problem in 3D with a trust region solver

# Load up necessary packages
using ConstitutiveModels
using Cthonios

# File management
mesh_file = Base.source_dir() * "/mesh.g"
output_file = splitext(mesh_file)[1] * "-output.exo"

# Times
times = TimeStepper(0., 1., 40)

# Physics and properties
physics = (;
    block_1 = SolidMechanics(
        ThreeDimensional(), NeoHookean()
    )
)
props = (;
    block_1 = Dict{String, Any}(
      "bulk modulus"  => 10.0,
      "shear modulus" => 1.0
    )
)

# Functions for BCs
func_1(x, t) = 0.0
func_2(x, t) = -0.5 * t
func_3(x, t) = @SVector [0., -0.025 * t, 0.]

# Boundary conditions
dirichlet_bcs = [
  DirichletBC("displ_x", "sset_y_negative", func_1)
  DirichletBC("displ_y", "sset_y_negative", func_1)
  DirichletBC("displ_z", "sset_y_negative", func_1)
  DirichletBC("displ_x", "sset_y_positive", func_1)
  DirichletBC("displ_z", "sset_y_positive", func_1)
  DirichletBC("displ_y", "sset_y_positive", func_2)
]

# Simulation setup
sim = SingleDomainSimulation(
    mesh_file, output_file, 
    times, physics, props;
    dirichlet_bcs=dirichlet_bcs
)

# objective setup
objective = Cthonios.QuasiStaticObjective()
objective_cache = Cthonios.setup_cache(objective, sim)

# solver setup
solver = Cthonios.TrustRegionSolverGPU(objective_cache; use_warm_start=true)

Cthonios.run!(objective_cache, solver, sim)

Example Input File Solving a Forward Problem

Below is an example input file (currently only YAML is supported) for solving a forward problem of metamaterial structure in 2D.

simulation:
  type: SingleDomainSimulation
  forward problem objective: QuasiStaticObjective

  mesh:
    type: UnstructuredMesh
    file name: examples/hole_array/mesh/hole_array_tri6.exo

  time:
    start time: 0.0
    end time: 1.0
    number of steps: 80

  materials:
    mat_1:
      NeoHookean:
        density: 1.0
        Young's modulus: 1.
        Poisson's ratio: 0.495
      Gent:
        density: 1.0
        Young's modulus: 1.
        Poisson's ratio: 0.495
        Jm: 3.

  physics:
    type: SolidMechanics
    kinematics formulation: PlaneStrain
    material assignment:
      mat_1:
        blocks: [Block1]
        model: NeoHookean

  nonlinear solvers:
    trs:
      type: TrustRegionSolverGPU
      verbose: true
      use_warm_start: true

  initial conditions: []

  dirichlet boundary conditions:
    - fields: ["displ_x", "displ_y"]
      function: (x, t) -> 0.0
      sidesets: [yminus_sideset]
    - fields: ["displ_x"]
      function: (x, t) -> 0.0
      sidesets: [yplus_sideset]
    - fields: ["displ_y"]
      function: (x, t) -> -8. * t
      sidesets: [yplus_sideset]

  neumann boundary conditions: []

  contact pairs: []

  nonlinear solver: trs

Contributing

Please file issues, open PRs, open discussions, etc.