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.

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")

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])

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}
}

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