PyCCX - Python Library for Calculix

Provides a library for creating and running 3D FEA simulations using the opensource Calculix FEA Package.

The aims of this project was to provide a simple framework for implemented 3D FEA Analysis using the opensource Calculix solver. The analysis is complimented by use of the recent introduction of the GMSH-SDK , an extension to GMSH to provide API bindings for different programming languages by the project authors to provide sophisticated 3D FEA mesh generation outside of the GUI implementation. This project aims to provide an integrated approach for generating full 3D FEA analysis for use in research, development and prototyping in a Python environment. Along with setting up and processing the analysis, convenience functions are included.

The inception of this project was a result of finding no native Python/Matlab package available to perfom full non-linear FEA analysis of 3D CAD models in order to prototype a concept related to 3D printing. The project aims to compliment the work of the PyCalculix project, which currently is limited to providing capabilities to generate 2D Meshes and FEA analysis for 2D planar structures. The potential in the future is to provide a more generic extensible framework compatible with different opensource and commercial FEA solvers (e.g. Abaqus, Marc, Z88, Elmer).

An interface that built upon GMSH was required to avoid the use of the GUI, and the domain specific .geo scripts. Learn more.

Structure

PyCCX framework consists of classes for specifying common components on the pre-processing phase, including the following common operations:

• Mesh generation
• Creating and applying boundary conditions
• Creating load cases
• Creating and assigning material models
• Performing the simulation

In addition, a meshing class provides an interface with GMSH for performing the meshing routines and for associating boundary conditions with the elements/faces generated from geometrical CAD entities. The Simulation class assembles the analysis and performs the execution to the Calculix Solver. Results obtained upon completion of the analysis can be processed. Currently the analysis is unit-less, therefore the user should ensure that all constant, material paramters, and geometric lengths are consistent - by default GMSH assumes 'mm' units.

Current Features

Meshing:

• Integration with GMSH for generation 3D FEA Meshes (Tet4, Tet10 currently supported)
• Merging CAD assemblies using GMSH
• Attaching boundary conditions to Geometrical CAD entities

FEA Capabilities:

• Boundary Conditions (Acceleration, Convection, Fixed Displacements, Forces, Fluxes, Pressure, Radiation)
• Loadcase Types (Structural Static, Thermal, Coupled Thermo-Mechanical)
• Materials (Non-linear Elasto-Plastic Material)

Results Processing:

• Element and Nodal Results can be obtained across timesteps

Installation

Installation is currently supported on Windows, all this further support will be added for Linux environments. PyCCX can be installed along with dependencies for GMSH automatically using.

pip install pyccx

Depending on your environment, you will need to install the latest version of Calculix. This can be done through the conda-forge calculix package in the Anaconda distribution,

conda install -c conda-forge calculix

or alternatively downloading the package directly. On Windows platforms the path of the executable needs to be initialised before use.

from pyccx.core import Simulation

# Set the path for Calculix in Windows
Simulation.setCalculixPath('Path')

Usage

The following code excerpt shows an example for creating and running a steady state thermal analysis of model using PyCCX of an existing mesh generated using the pyccx.mesh.mesher class.

from pyccx.core import DOF, ElementSet, NodeSet, SurfaceSet, Simulation
from pyccx.results import ElementResult, NodalResult, ResultProcessor
from pyccx.loadcase import  LoadCase, LoadCaseType
from pyccx.material import ElastoPlasticMaterial

# Set the path for Calculix in Windows
Simulation.setCalculixPath('Path')

# Create a thermal load case and set the timesettings
thermalLoadCase = LoadCase('Thermal Load Case')

# Set the loadcase type to thermal - eventually this will be individual analysis classes with defaults
thermalLoadCase.setLoadCaseType(LoadCaseType.THERMAL)

# Set the thermal analysis to be a steady state simulation
thermalLoadCase.isSteadyState = True

# Attach the nodal and element result options to each loadcase
# Set the nodal and element variables to record in the results (.frd) file
nodeThermalPostResult = NodalResult('VolumeNodeSet')
nodeThermalPostResult.useNodalTemperatures = True

elThermalPostResult = ElementResult('Volume1')
elThermalPostResult.useHeatFlux = True

# Add the result configurations to the loadcase
thermalLoadCase.resultSet = [nodeThermalPostResult, elThermalPostResult]

# Set thermal boundary conditions for the loadcase using specific NodeSets
thermalLoadCase.boundaryConditions.append(
    {'type': 'fixed', 'nodes': 'surface6Nodes', 'dof': [DOF.T], 'value': [60]})

thermalLoadCase.boundaryConditions.append(
    {'type': 'fixed', 'nodes': 'surface1Nodes', 'dof': [DOF.T], 'value': [20]})

# Material
# Add a elastic material and assign it to the volume.
# Note ensure that the units correctly correspond with the geometry length scales
steelMat = ElastoPlasticMaterial('Steel')
steelMat.density = 1.0    # Density
steelMat.cp =  1.0        # Specific Heat
steelMat.k = 1.0          # Thermal Conductivity

analysis.materials.append(steelMat)

# Assign the material the volume (use the part name set for geometry)
analysis.materialAssignments = [('PartA', 'Steel')]

# Set the loadcases used in sequential order
analysis.loadCases = [thermalLoadCase]

# Analysis Run #
# Run the analysis
analysis.run()

# Open the results  file ('input') is currently the file that is generated by PyCCX
results = analysis.results()
results.load()

The basic usage is split between the meshing facilities provided by GMSH and analysing a problem using the Calculix Solver. Documented examples are provided in examples .