juliankarlbauer/mechkit

Continuum mechanics toolkit

mechkit

The Python package mechkit is a toolkit for researchers in the field of continuum mechanics and material modeling. mechkit contains methods and operators for elementary tasks concerning tensor algebra and tensor notation, focusing on second- and fourth-order tensors.

Please see license, acknowledgment and cite the latest Zenodo-DOI.

Documentation

Documentation is given in the docs.

Examples

Rendered example notebooks are in the docs. These notebooks and corresponding scripts can be found here.

Installation

Install with pip following instructions on Python Package Index, i.e.,

pip install mechkit

or install from local files

• Clone this repository to your machine
• Open a terminal and navigate to your local clone
• Install the package from the local clone into the current environment in develop mode:

   python setup.py develop

Note: Develop vs. install

Acknowledgment

The research documented in this repository has been funded by the German Research Foundation (DFG, Deutsche Forschungsgemeinschaft) - project number 255730231. The support by the German Research Foundation within the International Research Training Group “Integrated engineering of continuous-discontinuous long fiber reinforced polymer structures“ (GRK 2078) is gratefully acknowledged.

mechkit's Issues

Define additional notations in Docs

Extention of the doc string of "mechkit.notation.ExplicitConveter"
by representations of stiffnesses and compliances in

• Voigt
• UMAT
• VUMAT

notation would be a huge improvement.

Currently, some placeholder "todos" show where additional views may be placed.

Inspiration for the representations may be given by these views (actually the stiffness-representation for Voigt notation is included in the below screenshot)

In paper: Compare with other tensor packages

Addressing this review comment, a comparison with multi-purpose tensor packages should be contained within the mechki-JOSS-paper.

Notation: Rethink implementation

Current implementation focuses programmatically on extensibility and clarity
(e.g. dicts containing converter functions and scaling factors).
However, this extensibility is not truly existent.
Converter-commands like .to_mandel6, .to_tensor, .to_mandel9
identify the source format by analysis of the dimensions of the input quantity.

Possible structural changes:

• Switch from Converter to tensor-class
  • Keep underlying extensible structure of converter internally and
    supply information of the source notation explicitly.

In paper: Add overview tables

Add overview tables following suggestion by reviewer.

Improve contributing instructions

Addressing this comment, the contributing instructions should be improved and switch from "Github flow" to "Fork and Pull request".

Notation: Add new features

• Abaqus UMAT notation
  • stress
  • strain
  • stiffness
  • compliance
• Abaqus VUMAT notation (stress, strain, )
  • stress
  • strain
  • stiffness
  • compliance

Englarge visualization of engineering constants and fix arrow tips

Problems:
In rendered docs,
the svg-images show up

• a bit small
• without arrow tips.

It might be good to

• enlarge the images a bit
• fix arrow tips.

It might be better to switch to png-files with low resolution (keep data small).

pytest not installed following README instructions

When you run

python setup.py develop

Pytest is not installed and you can't run the test suite.

Add "completely symmetric" fourth-order tensors to notation.ExplicitConverter

Exchange of completely symmetric tensors, such as fiber orientation tensors of fourth order in a
minimal, i.e., nearly redundancy-free notation is a common task for engineers working with short fiber reinforced composites.

Support of

tensors = <bunch of  fourth order fiber orientation tensors>

con = mechkit.notation.ExplicitConverter()
con.convert(
inp=tensors, source="tensor", target="exchange", quantity="fiber_orientation"
)

with "exchange", e.g., being

[
N_1111, N_2222, N_3333,
N_2233, N_1133, N_1122,
N_1123, N_2223, N_3323, 
N_1113, N_2213, N_3313, 
N_1112, N_2212, N_3312, 
]

See also equations (38) to (40) in
Variety of fiber orientation tensors, Bauer and Böhlke 2021

It is clear, that, e.g., N_3333 could be omitted, as only 14 components are independent, but
not omitting it, will enable usage for, e.g., diffusion-weighted magnet resonance tomography tensors of fourth order,
which have no normalized trace.