Readme

conforce

ConForce is a Python package and Abaqus plug-in for the computation of configurational (material) forces. The computation is automatically generated and compiled from symbolic calculations into C code. A C binding allows access to the C functions from Python. This makes ConForce fast enough to compute an entire finite element model with several thousand elements within a few seconds.

ConForce features:

the computation of the following quantities for common 2D and 3D elements:
- static configurational forces
- static configurational stresses
- first Piola-Kirchhoff stresses
- deformation gradients
two formulations for the configurational stresses and forces:
- motion based formulation (Eshebly’s formulation)
- displacement based formulation
material models:
- non-linear elasticity in the large strain framework
- small-strain plasticity
material orientations: The stresses and displacements are automatically rotated to the global coordinate system.

Supported Operating Systems:

Windows (64-bit)
CentOS (64-bit)
other Linux distributions might work

ConForce is available as:

Python 3 package
Abaqus plug-in

Python 3 Package

The Python package requires Python 3 and contains:

methods to compute configurational forces, stresses, …
methods for the symbolic computation and code generation

Installation

PyPi

We recommend to install the latest stable version from PyPi.

pip install conforce

Remote Repository

The (unstable) development version of ConForce can be installed from our remote repository.

Download and unzip the ConForce repository.
Open a shell in the unzipped folder where the setup.py file is located.
Install ConForce by typing the following commands into the shell
```
pip install "."
```
In order to run examples or build the documentation, additional packages are required. The following options are available.
- Install requirements for the examples:
```
pip install ".[examples]"
```
- Install requirements to build the documentation
```
pip install ".[doc]"
```
- Install all requirements
```
pip install ".[examples, doc]"
```
To uninstall the package, type:
```
pip uninstall conforce
```

If git is available, the package can be installed directly from the remote repository by

pip install "conforce[examples, doc] @ git+https://github.com/mrettl/conforce"

The extras examples and doc are optional.

Usage

Configurational forces are computed using the cf_c module. The energy density e, the undeformed positions X, the displacement U, and the symmetric Cauchy stress tensor S are passed to the compute_CF function along with the element type and the computation method.

from conforce import cf_c

cf_c.compute_CF(
    e_at_int_points=[[10.]],
    X_at_nodes=[[
        [0., 0.],
        [1., 0.],
        [1., 1.],
        [0., 1.],
    ]],
    U_at_nodes=[[
        [0.0, 0.0],
        [0.1, 0.0],
        [0.1, 0.0],
        [0.0, 0.0],
    ]],
    S_at_int_points=[[[
        [100., 0.0],
        [0.0, 0.0]
    ]]],
    element_type="CPE4R",
    method="dbf"
)

This yields the configurational forces at the element nodes for a single CPE4R element and the displacement based formulation (”dbf”):

array([[[ 0., -5.],
        [ 0., -5.],
        [ 0.,  5.],
        [-0.,  5.]]])

Abaqus plug-in

The Abaqus plug-in contains:

methods to compute configurational forces, stresses, …
Abaqus specific code to read and write to *.odb files
a GUI for the Abaqus plug-in

Supported Abaqus versions:

>= Abaqus 2017

Installation

Open https://github.com/mrettl/conforce/releases and download the latest zip file called conforce_plugin_{version}.zip. The zip file has the following structure:

conforce_plugin_{version}.zip
- conforce
  - conforce_abq_plugin.py
  - …

There are several possibilities in which folder the plug-in files can be stored. Decide for one of the following valid plugin-folders:

plugin_central_dir: This folder is defined in the environment file abaqus_v6.env. For many installations this folder is located in C:\\SIMULIA\\CAE\\plugins\\{year}. Plug-ins stored in this folder are accessible for all users.
current_dir\abaqus_plugins: This is the folder in which Abaqus is started. Plug-ins are only accessible if Abaqus is stared again in the same folder.

Next, unzip the downloaded files and put them in the plugin-folder you selected: The folder tree should look like:

plugin-folder
- conforce
  - conforce_abq_plugin.py
  - …

Start Abaqus and navigate in the toolbar to Plug-ins -> Conf. Force. The GUI of the plug-in should open. If no toolbar entry called Conf. Force exists, check if the plug-in is stored in the right folder for the Abaqus version you are using.

Usage

Open an *.odb file in Abaqus. Navigate in the toolbar to Plug-ins -> Conf. Force. The plug-in gui opens:

plugin gui

Click Apply to compute the requested field outputs.

Report Bugs, Ask questions

Use the github issue tracker to report bugs and troubles or to ask questions. If you like our tool, please leave a star on our Github repository.