juliafem / modelreduction.jl Goto Github PK

ModelReduction is a repository of JuliaFEM to reduce the dimension of a model for multibody dynamics problems. The package includes e.g. the Guyan reduction and the Craig-Bampton method.

Home Page: https://juliafem.github.io/ModelReduction.jl/latest/

License: MIT License

Julia 100.00%

fem model reduction condensation static dynamic multibody dynamics

modelreduction.jl's Introduction

ModelReduction.jl

ModelReduction.jl is a Julia package to perform model reduction methods for i.e. multibody dynamics problems. The packcage includes model order reduction methods such as the Guyan reduction and the Craig-Bampton method.

Reducing the sizes of stiffness and mass matrices of the model will greatly decrease the computation resources needed when performing dynamic analyses.

ModelReduction.jl is a part of JuliaFEM. All codes are MIT licensed.

Installing and testing the package

Install the package the same way other Julia packages are installed.

julia> Pkg.add("ModelReduction")

Test the package with Pkg.test etc.

julia> Pkg.test("ModelReduction")

Usage example

This example demonstrates how to use the Craig-Bampton method function.

Problem setup:

julia> K = [2 -1  0  0;
           -1  2 -1  0;
            0 -1  2 -1;
            0  0 -1  1]

julia> M = [2 0 0 0;
            0 2 0 0;
            0 0 2 0;
            0 0 0 1]

julia> r = [4]
julia> l = [1, 2, 3]
julia> n = 1

K = original stiffness matrix, M = original mass matrix, r = retained DOF:s, l = internal DOF:s, n = the number of the internal modes to keep. Calculate the reduced mass and stiffness matrices Mred and Kred.

julia> using ModelReduction

julia> Mred, Kred = ModelReduction.craig_bampton(K, M, r, l, n)
([2.75 -1.20711; -1.20711 1.0], [0.25 0.0; 0.0 0.292893])

Citing

If you like using our package, please consider citing our article:

@article{rapo2018implementing,
 title={Implementing model reduction to the JuliaFEM platform},
 volume={51},
 url={https://rakenteidenmekaniikka.journal.fi/article/view/69026},
 doi={10.23998/rm.69026},
 number={1},
 journal={Rakenteiden Mekaniikka},
 author={Rapo, Marja and Aho, Jukka and Koivurova, Hannu and Frondelius, Tero},
 year={2018},
 pages={36-54}
}

Contributing

Have a new great idea and want to share it with the open source community? From here and here you can look for coding styles. Here it is explained how to contribute to open source project, in general.

modelreduction.jl's People

Contributors

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tkelman josephcslater juliatagbot zhaoweisonake mfkiwl asclepiusinformatica yhpark64

modelreduction.jl's Issues

Create test model, calculate static and dynamic response

Let's start this with the following test problem: we have u'' = 0 with boundary conditions u(0) = 0 and u'(1) = 1, i.e. a truss with left boundary fixed and force F=1 is affecting to the right end. Use five node discretization, nodal coordinates is therefore [0.00, 0.25, 0.50, 0.75, 1.00]. And we have four elements.

Calculate static response using some FEM program. Stiffness matrix K and force vector f can be exported from finite element program.
Calculate dynamic response using some FEM program. Mass matrix can be exported from finite element program.
Upload matrices to testdata.
Read matrices above from files using julia, calculate static and dynamic response using julia. Verify results by making unit test.

You have to complete #5 to get this done.

Build is failing

ERROR: Unsatisfiable requirements detected for package ModelReduction [d4b734c2]

(v1.0) pkg> update
  Updating registry at `C:\Users\tfr004\.julia\registries\General`
  Updating git-repo `https://github.com/JuliaRegistries/General.git`
  Updating git-repo `https://github.com/JuliaPackaging/BinaryBuilder.jl.git`
 Resolving package versions...
ERROR: Unsatisfiable requirements detected for package ModelReduction [d4b734c2]:
 ModelReduction [d4b734c2] log:
 ├─possible versions are: [0.0.1-0.0.2, 0.1.1] or uninstalled
 ├─restricted to versions * by an explicit requirement, leaving only versions [0.0.1-0.0.2, 0.1.1]
 └─restricted by julia compatibility requirements to versions: uninstalled — no versions left

(v1.0) pkg>

Create function reading ABAQUS .mtx file format

Format of the operator matrix

The assembled sparse matrix operator data are written to the text file as a series of comma-separated lists. Each row in the file represents a single matrix entry; a row is written as a comma-separated list with the following elements:

Row node label
Degree of freedom for row node
Column node label
Degree of freedom for column node
Matrix entry

We want to read this file format and create sparse matrices from that using I,J,V vectors.

Sample:

1,1, 1,1,  1.000000000000000e+00
2,1, 1,1, -1.000000000000000e+00
1,2, 1,2,  0.000000000000000e+00
2,1, 2,1,  2.000000000000000e+00
3,1, 2,1, -1.000000000000000e+00
2,2, 2,2,  0.000000000000000e+00
3,1, 3,1,  2.000000000000000e+00
4,1, 3,1, -1.000000000000000e+00
3,2, 3,2,  0.000000000000000e+00
4,1, 4,1,  2.000000000000000e+00
5,1, 4,1, -1.000000000000000e+00
4,2, 4,2,  0.000000000000000e+00
5,1, 5,1,  1.000000000000000e+00
5,2, 5,2,  0.000000000000000e+00

Add docstrings

Add docstrings to mass and stiffness matrix functions.

Generated examples are missing

We should use Literate.jl to generate examples from tests. This is a good example where the whole package is broken so the static examples are definitely not working. First, we need to solve issue #28.

Info about upcoming removal of packages in the General registry

As described in https://discourse.julialang.org/t/ann-plans-for-removing-packages-that-do-not-yet-support-1-0-from-the-general-registry/ we are planning on removing packages that do not support 1.0 from the General registry. This package has been detected to not support 1.0 and is thus slated to be removed. The removal of packages from the registry will happen approximately a month after this issue is open.

To transition to the new Pkg system using Project.toml, see https://github.com/JuliaRegistries/Registrator.jl#transitioning-from-require-to-projecttoml.
To then tag a new version of the package, see https://github.com/JuliaRegistries/Registrator.jl#via-the-github-app.

If you believe this package has erroneously been detected as not supporting 1.0 or have any other questions, don't hesitate to discuss it here or in the thread linked at the top of this post.

Static and dynamic condensation of test model with some software

Reduce model described in #1 using fem software. We keep boundary nodes (1, 5) and eliminate inner nodes (2, 3, 4). Now we should have again new matrices. Let's upload them also to repository for testing purposes.

Perform dynamic condensation

Just like in #3, now everything described there for dynamics also.

Perform static condensation

For docs/src, create file theory_static_condensation.md and describe there how static condensation is done in matrix level. We can use LaTeX markup syntax. See documentation of Documenter.jl.

For test problem, calculate statically condensated matrix K_red and force vector f_red. Verify results against the ones calculated in #2. You can create some function, given proper input arguments is doing this.

Keep on mind that K_ss is huge because it contains all dofs of model to be eliminated. For that reason calculating inverse of K_ss using inv(K_ss) is not practical and matrix computation must be done piece by piece.

In reference there is no force f_s, in real application there might be (e.g. gravity force acting body), thus it must be taken into account.

References

https://en.wikipedia.org/wiki/Guyan_reduction

Example doesn't work

julia> using ModelReduction

julia> guyan_reduction(K, m, s)
ERROR: UndefVarError: guyan_reduction not defined

julia> ModelReduction.guyan_reduction(K, m, s)
2×2 Array{Float64,2}:
  0.25  -0.25
 -0.25   0.25

julia>

Either fix example or export guyan_reduction method.

The second examples doesn't work either:

julia> Mred, Kred = ModelReduction.craig_bampton(K, M, r, l, n)
ERROR: UndefVarError: craig_bampton not defined

julia> ModelReduction.
eval             global_mass       global_stiffness  guyan_reduction