pycalculix

pycalculix is a Python 3 library to automate and build finite element analysis (FEA) models in Calculix.

Website: http://justinablack.com/pycalculix/
Source Code: https://github.com/spacether/pycalculix
Documentation: https://pycalculix.readthedocs.io/en/latest/index.html

Usefull applications of Pycalculix

• Trade studies for plane stress, plane strain, or axisymmetric parts
• Quick Kt analysis of 2D geometry
• Learning finite element analyis (FEA) and Python

Installation

Mac OS X

1. Install python3, pycalculix and the fea programs that it uses

brew install python3
python3 -mpip install -U numpy
python3 -mpip install -U matplotlib
pip3 install pycalculix
pycalculix-add-feaprograms

2. You are done! See 'Usage'

Windows

1. Install python3 for 32bit machines or 64 bit machines
2. In a terminal run the below lines to install needed python libraries, pycalculix, and the fea programs that it uses

python -mpip install -U numpy
python -mpip install -U matplotlib
pip install pycalculix
pycalculix-add-feaprograms

3. You are done! See 'Usage'

Linux, assumes Ubuntu 16.04

1. Install python3-pip, numpy, matplotlib, pycalculix, and the fea programs that it uses

sudo apt-get install python3-pip python3-tk
pip3 install --upgrade pip
python3 -mpip install -U numpy
sudo python3 -mpip install -U matplotlib
pip3 install pycalculix
pycalculix-add-feaprograms

2. You are done! See 'Sample Program' and 'Usage'

Sample Program

# this is from examples/hole-in-plate-full.py
import pycalculix as pyc

# Vertical hole in plate model, make model
proj_name = 'hole-in-plate-full'
model = pyc.FeaModel(proj_name)
model.set_units('m') # this sets dist units to meters

# Define variables we'll use to draw part geometry
diam = 2.0 # hole diam
ratio = 0.45
width = diam/ratio   #plate width
print('D=%f, H=%f, D/H=%f' % (diam, width, diam/width))
length = 2*width  #plate length

# Draw part geometry, you must draw the part CLOCKWISE, x, y = radial, axial
part = pyc.Part(model)
part.goto(length*0.5, -width*0.5)
part.draw_line_ax(width)
part.draw_line_rad(-length)
part.draw_line_ax(-width)
part.draw_line_rad(length)
hole_lines = part.draw_hole(0, 0, diam*0.5, filled=False)
model.set_ediv(hole_lines, 10)
part.chunk()
model.plot_geometry(proj_name+'_geom') # view the geometry

# set loads and constraints
pressure = -1000
model.set_load('press', part.top, pressure)
model.set_load('press', part.bottom, pressure)
model.set_constr('fix', ['P6', 'P8'], 'y')
model.set_constr('fix', ['P4', 'P7'], 'x')

# set part material
mat = pyc.Material('steel')
mat.set_mech_props(7800, 210*(10**9), 0.3)
model.set_matl(mat, part)

# set the element type and mesh database
model.set_eshape('quad', 2)
model.set_etype('plstress', part, 0.1)
model.mesh(1.0, 'gmsh') # mesh 1.0 fineness, smaller is finer
model.plot_elements(proj_name+'_elem')   # plot part elements
model.plot_pressures(proj_name+'_press')
model.plot_constraints(proj_name+'_constr')

# make and solve the model
prob = pyc.Problem(model, 'struct')
prob.solve()

# view and query results
sx = prob.rfile.get_nmax('Sx')
print('Sx_max: %f' % sx)

# Plot results
fields = 'Sx,Sy,S1,S2,S3,Seqv,ux,uy,utot,ex'    # store the fields to plot
fields = fields.split(',')
for field in fields:
    fname = proj_name+'_'+field
    prob.rfile.nplot(field, fname, display=False)

Usage

1. To run a pycalcuix file you have to have pycalulix installed, see 'Installation' above
2. The you can then write your own pycalculix programs or run one of the example files here: https://github.com/spacether/pycalculix/tree/master/examples
3. To run a file:

Windows

• Graphical user interface:
  • Double click the file
    If the .py extension is associated correctly you can double click it to run the .py program
• Console:
  • cd into the directory with your .py file in it, then in the terminal enter

  python the_program.py
  

  where the_program.py is the name of the file that you are running This assumes that python3 is your active python installation

Mac/Linux

• Console:
  • cd into the directory with your .py file in it, then in the terminal enter

  python3 the_program.py
  

  where the_program.py is the name of the file that you are running

Elements Supported:

Axisymmetric, plane stress, and plane strain elements are supported.

• First and second order triangles and quadrilaterals are supported.
  • First order elments only have corner nodes
  • Second order elements have corner and midside nodes

Second order elements produce more accurate results Setting element divisions on lines is supported

Geometry Building

• One can build separate parts made of points, lines, arcs, and areas.
• Straight lines and arcs are currently supported.
• One can draw a part made of straight lines, then smooth out corners by adding arcs with the part method: part.fillet_lines(L1, L2, arc_radius)
• The new arc will be tangent to both adjacent lines.

Loading

• Force loading
• Constant pressure
• Linearly varying pressure (water pressure)
• Gravity
• Rotational speed forces
• Displacement constraints
• Loads are stored on geometry primitives (points lines, areas) and can be applied before or after meshing.

Files Produced

Meshing and solving are done in the background using cgx or gmsh for meshing, and Calculix ccx for solving.

Files Used:

• .fbd (Calculix cgx gemetry file)
• .inp (Calculix solver input file, or mesh definition)
• .geo (Gmsh geometry file)
• .msh (Gmsh native mesh file)
• .frd (Calculix ccx nodal results file, values are at nodes and were created by interpolating element integration point results back to the nodes)
• .dat (Calculix ccx element results file, includes integration point results)

Uninstall

Windows

pycalculix-remove-feaprograms
pip uninstall pycalculix

Mac/Linux

pycalculix-remove-feaprograms
pip3 uninstall pycalculix

Devlopment

• Download this repo

git clone git@github.com:spacether/pycalculix.git

• Make python3 virtual env

python -m venv venv

• Activate it
  • Windows venv\scripts\activate
  • Mac/linux source venv/bin/activate
• Locally install pycalculix

pip install -e .
pycalculix-add-feaprograms

• Now any changes that you make to your local version of pycalculix will be live in your virtual environment

License

See LICENSE.txt (Apache 2.0)

Creator

Justin Black, justin.a.black[at-sign]gmail[dot]com Initial Release: December 2014

Change Log

1.1.2

• Sets part.left/right/top/bottom using geometry.ACC constant, tests added
• Fixes issue spacether#57 where part.left was not being set if a line was slightly skewed
• Fixes a mac install issue where gcc@7 was assuming a specific X.X.X version of gcc7

1.1.1

• Omits test_pinned_plate from Mac OS X with Python >= 3.6 because it does not converge in ccx

1.1.0

• Adds Microsoft Azure continuous integration tests to verify that the library is working. The following environments are tested:
  • Windows Server 2016 (x64 and x86 architecture)
  • Mac OS X (x64)
  • Ubuntu 16.04 (x64)
• Fixes a bug where cad files could not be loaded if they had a period in their path

1.0.0

• Fixes the issue where the windows FEA installer hangs: spacether#47
• Fixes the issue where the ccx version check in Windows fails spacether#48
• Fixes the issue on OS X High Sierra where ccx assumes that the host has gcc7 installed on it: spacether#50
  • Solution: install gcc@7 and symbolic link it to the expected location

0.9.6

• Fixes part.fillet_lines method, all tests now pass
  • Verified on Mac OS X
  • Closes github Issue 32: '2/15 of the tests fail'

0.9.5 (github + pypi)

• Adds tests: sample tests at tests/test_samples.py
• Adds tests: meshing tests at tests/test_meshing.py
• Adds solving and meshing timeout exception to capture when they hang
• Fixes dxf import feature, syntax updates to use dfxgrabber >= 0.8.0, Issue 32
• Adds requirement for dfxgrabber >= 0.8.0 to ensure that dxf import works
• Pegs Mac gmsh version to gmsh == 3.0.5 because version 3.0.6 throws segault errors when meshing
• Fixes a bug where solver input file does not write material before time steps, Issue 32
• Fixed ccx installer on Windows: zip file is now found and downloaded
• Throws an exception if ccx version is too old, v 2.7 and earlier is too old
• Pegs Win gmsh install version to 3.0.5
• Updates the calculation for element Seqv, S1, S2, and S3 avg max and min values. Now calculates Seqv and principal stresses at all integration points, then calculates the avg max and min of those values
• Win pegged ccx to version 2.12
• Mac brew brewsci/science/calculix-ccx is currently at ccx version 2.13
• Ubuntu apt-get calculix-ccx is currently is currently at version 2.11

0.9.4 (github only)

• removed gmsh and calculix
• moved dist and documentation building and example cleanup into make file
• changed the license to Apache 2.0
• added command line tool to install/uninstall gmsh and ccx for windows/mac os x/ubuntu
  • pycalculix-add-feaprograms
  • pycalculix-remove-feaprograms
• added requests library requirement for pycalculix-add-feaprograms
• fixed bug where frd files could no longer be read because Calculix results keywords changed since initial 2014 release

0.9.3

• ADDED: multiple parts with contacts
  • See example files: pipe-crush-elastic.py, pinned-plate.py
• ADDED: Import CAD geometry from dxf file
  • See pycalculix.CadImporter
  • Examples:
    • import-dxf.py
• ADDED: Element results plotting added
  • Element results plotting: pycalculix.Problem.rfile.eplot()
  • Nodal results plotting: pycalculix.Problem.rfile.nplot()
  • Number Formatting:
    • Strain results now use scientific formatting
    • Others use nearest 10**3 suffixes
  • Max and min values now listed above the colorbar
• ADDED: method to draw an arc by swept angle in degrees
  • part.draw_arc_angle(degrees_ccw, center_x, center_y)
• ADDED: min_val and max_val can now be passed to eplot and nplot
  • This lets the user set the results range that they want to see:
  • min_val <= colored results <= max_val
  • Values under and over are greyed out, darker under, lighter over
• ADDED: internal holes in parts
  • One can make circular holes, or draw complicated holes.
  • See examples:
    • hole-in-plate-full.py, multihole.py
• ADDED: Added set_ediv method to FeaModel class.
  • This method sets the number of elements on a line.
  • line.set_ediv still works.
• ADDED: Robust selection object: feamodel.view
  • This object is feamodel.view Most important methods are:
    • view.select_all, view.select, view.allsel_under
    • All plotting now uses the current selection set
  • SYNTAX: updated how parts, materials, problems are made
    • Make part:
      • pycalculix.FeaModel.make_part or pycalculix.Part
    • Make material:
      • pycalculix.FeaModel.make_matl or pycalculix.Material
    • Make problem (previously called model):
      • pycalculix.FeaModel.make_problem or pycalculix.Problem
    • Make Results File:
      • pycalculix.Problem.rfile or pycalculix.ResultsFile(problem)
• FIX: Plotting fix, closing triangles in the correct direction in matplotlib
• DOC: All code separated into modules for clarity.
• DOC: Docstrings added to all classes + methods + functions
• PLOTTING: Closed areas are now filled in yellow when plotting geometry.
• PLOTTING: Signed line names are shown and internal to the area.
• BACKEND: Implemented signed line and signed arc class.
  • Pressures can now be applied on these signed lines.
  • Many methods and variables made private to clean up name space.