# FEM Tutorium Python

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Thema Tutorium Finite Element Analyse Fortgeschrittene 30 Minuten Bernd 0.18.15985 oder höher None

## Einführung

Dieses Tutorium soll zeigen, wie eine einfache Finite Element Analyse (FEA) in FreeCAD FEM Arbeitsbereich mit Python erstellt wird. Das Modell aus dem FEM CalculiX Freiträger 3D Tutorium wird für dieses Beispiel verwendet.

### Requirements

• The compatible version of FreeCAD as designated in the tutorial overview.
• Impotant Note: Due to the continuous development of the FEM Workbench it is recommended to use the latest development snapshot of FreeCAD especially for python scripted FEM analyses.
• A working FEM workbench. Run the FEM CalculiX Cantilever 3D analysis to ascertain this.

## Let's start

### New document and the part to analyze

```# new document
doc = App.newDocument("Scripted_CalculiX_Cantilever3D")

# part
import Part
box_obj.Height = box_obj.Width = 1000
box_obj.Length = 8000

# see how our part looks like

#
```

### Analysis and analysis objects

```# let us create some objects

# import to create objects
import ObjectsFem

# analysis
analysis_object = ObjectsFem.makeAnalysis(doc, "Analysis")

# solver (we gone use the well tested CcxTools solver object)
solver_object = ObjectsFem.makeSolverCalculixCcxTools(doc, "CalculiX")
solver_object.GeometricalNonlinearity = 'linear'
solver_object.MatrixSolverType = 'default'
solver_object.IterationsControlParameterTimeUse = False

# material
material_object = ObjectsFem.makeMaterialSolid(doc, "SolidMaterial")
mat = material_object.Material
mat['Name'] = "Steel-Generic"
mat['YoungsModulus'] = "210000 MPa"
mat['PoissonRatio'] = "0.30"
mat['Density'] = "7900 kg/m^3"
material_object.Material = mat

# fixed_constraint
fixed_constraint = ObjectsFem.makeConstraintFixed(doc, "FemConstraintFixed")
fixed_constraint.References = [(doc.Box, "Face1")]

# force_constraint
force_constraint = ObjectsFem.makeConstraintForce(doc, "FemConstraintForce")
force_constraint.References = [(doc.Box, "Face2")]
force_constraint.Force = 9000000.0
force_constraint.Direction = (doc.Box, ["Edge5"])
force_constraint.Reversed = True
```

### FEM mesh (manual)

This section contains the FEM mesh code. Please expand it to view the contents.

Note: Check out the Additional Information section below for how to script mesh generation with GMSH or Netgen mesh object.

```# mesh
import Fem
femmesh = Fem.FemMesh()

# nodes

# elements
femmesh.addVolume([40, 19, 10, 20, 168, 106, 196, 171, 66, 107], 149)
femmesh.addVolume([10, 31, 30, 40, 150, 79, 149, 196, 128, 129], 150)
femmesh.addVolume([38, 17, 18, 47, 163, 62, 166, 140, 197, 198], 151)
femmesh.addVolume([32, 41, 11, 12, 130, 199, 152, 165, 200, 56], 152)
femmesh.addVolume([12, 32, 41, 42, 165, 130, 200, 201, 143, 92], 153)
femmesh.addVolume([42, 21, 12, 22, 172, 110, 201, 185, 68, 123], 154)
femmesh.addVolume([10, 31, 40, 11, 150, 128, 196, 55, 151, 202], 155)
femmesh.addVolume([11, 12, 41, 21, 56, 200, 199, 109, 110, 173], 156)
femmesh.addVolume([20, 41, 11, 40, 170, 199, 108, 171, 91, 202], 157)
femmesh.addVolume([20, 41, 21, 11, 170, 173, 67, 108, 199, 109], 158)
femmesh.addVolume([32, 11, 41, 31, 152, 199, 130, 80, 151, 131], 159)
femmesh.addVolume([11, 10, 20, 40, 55, 107, 108, 202, 196, 171], 160)
femmesh.addVolume([38, 17, 47, 37, 163, 197, 140, 86, 162, 141], 161)
femmesh.addVolume([38, 18, 49, 48, 166, 204, 203, 145, 205, 206], 162)
femmesh.addVolume([46, 15, 45, 36, 207, 208, 96, 139, 159, 137], 163)
femmesh.addVolume([47, 16, 46, 37, 209, 210, 97, 141, 161, 138], 164)
femmesh.addVolume([18, 4, 2, 49, 122, 64, 63, 204, 189, 190], 165)
femmesh.addVolume([18, 17, 27, 47, 62, 120, 121, 198, 197, 183], 166)
femmesh.addVolume([38, 18, 48, 47, 166, 205, 145, 140, 198, 98], 167)
femmesh.addVolume([12, 23, 42, 22, 111, 175, 201, 123, 69, 185], 168)
femmesh.addVolume([26, 47, 27, 17, 180, 183, 73, 119, 197, 120], 169)
femmesh.addVolume([50, 29, 9, 6, 211, 147, 212, 195, 146, 53], 170)
femmesh.addVolume([27, 48, 18, 47, 182, 205, 121, 183, 98, 198], 171)
femmesh.addVolume([8, 7, 39, 50, 103, 89, 167, 192, 193, 213], 172)
femmesh.addVolume([40, 9, 39, 30, 214, 215, 90, 129, 148, 126], 173)
femmesh.addVolume([42, 21, 41, 12, 172, 173, 92, 201, 110, 200], 174)
femmesh.addVolume([50, 9, 29, 39, 212, 147, 211, 213, 215, 127], 175)
femmesh.addVolume([29, 7, 50, 39, 125, 193, 211, 127, 89, 213], 176)
femmesh.addVolume([31, 11, 41, 40, 151, 199, 131, 128, 202, 91], 177)
femmesh.addVolume([47, 16, 37, 17, 209, 161, 141, 197, 61, 162], 178)
femmesh.addVolume([40, 9, 30, 10, 214, 148, 129, 196, 54, 149], 179)
femmesh.addVolume([2, 38, 49, 1, 164, 203, 190, 100, 87, 191], 180)
femmesh.addVolume([2, 38, 18, 49, 164, 166, 63, 190, 203, 204], 181)
femmesh.addVolume([48, 49, 38, 3, 206, 203, 145, 99, 188, 142], 182)
femmesh.addVolume([38, 49, 1, 3, 203, 191, 87, 142, 188, 88], 183)
femmesh.addVolume([49, 4, 3, 48, 189, 102, 188, 206, 184, 99], 184)
femmesh.addVolume([28, 48, 4, 18, 187, 184, 75, 124, 205, 122], 185)
femmesh.addVolume([49, 18, 4, 48, 204, 122, 189, 206, 205, 184], 186)
femmesh.addVolume([7, 50, 5, 29, 193, 194, 76, 125, 211, 77], 187)
femmesh.addVolume([50, 6, 5, 29, 195, 101, 194, 211, 146, 77], 188)
femmesh.addVolume([50, 9, 19, 6, 212, 105, 216, 195, 53, 104], 189)
femmesh.addVolume([50, 19, 9, 39, 216, 105, 212, 213, 169, 215], 190)
femmesh.addVolume([50, 19, 8, 6, 216, 65, 192, 195, 104, 52], 191)
femmesh.addVolume([40, 9, 10, 19, 214, 54, 196, 168, 105, 106], 192)
femmesh.addVolume([51, 44, 34, 14, 217, 144, 218, 219, 220, 156], 193)
femmesh.addVolume([51, 24, 44, 14, 221, 186, 217, 219, 114, 220], 194)
femmesh.addVolume([25, 15, 24, 51, 116, 115, 71, 222, 223, 221], 195)
femmesh.addVolume([43, 12, 32, 13, 224, 165, 133, 225, 57, 153], 196)
femmesh.addVolume([43, 12, 23, 42, 224, 111, 174, 93, 201, 175], 197)
femmesh.addVolume([43, 12, 13, 23, 224, 57, 225, 174, 111, 112], 198)
femmesh.addVolume([43, 12, 42, 32, 224, 201, 93, 133, 165, 143], 199)
femmesh.addVolume([34, 13, 14, 44, 155, 58, 156, 144, 226, 220], 200)
femmesh.addVolume([14, 24, 15, 51, 114, 115, 59, 219, 221, 223], 201)
femmesh.addVolume([23, 24, 14, 44, 70, 114, 113, 176, 186, 220], 202)
femmesh.addVolume([33, 32, 13, 43, 81, 153, 154, 132, 133, 225], 203)
femmesh.addVolume([34, 33, 13, 43, 82, 154, 155, 134, 132, 225], 204)
femmesh.addVolume([35, 14, 15, 51, 157, 59, 158, 227, 219, 223], 205)
femmesh.addVolume([25, 45, 15, 51, 177, 208, 116, 222, 228, 223], 206)
femmesh.addVolume([44, 43, 13, 23, 94, 225, 226, 176, 174, 112], 207)
femmesh.addVolume([35, 34, 14, 51, 83, 156, 157, 227, 218, 219], 208)
femmesh.addVolume([46, 15, 36, 16, 207, 159, 139, 210, 60, 160], 209)
femmesh.addVolume([36, 35, 15, 45, 84, 158, 159, 137, 135, 208], 210)
femmesh.addVolume([37, 36, 16, 46, 85, 160, 161, 138, 139, 210], 211)
femmesh.addVolume([25, 26, 16, 46, 72, 118, 117, 179, 181, 210], 212)
femmesh.addVolume([47, 16, 17, 26, 209, 61, 197, 180, 118, 119], 213)
femmesh.addVolume([47, 16, 26, 46, 209, 118, 180, 97, 210, 181], 214)
femmesh.addVolume([27, 28, 18, 48, 74, 124, 121, 182, 187, 205], 215)
femmesh.addVolume([35, 34, 51, 45, 83, 218, 227, 135, 136, 228], 216)
femmesh.addVolume([13, 14, 44, 23, 58, 220, 226, 112, 113, 176], 217)
femmesh.addVolume([44, 25, 24, 51, 178, 71, 186, 217, 222, 221], 218)
femmesh.addVolume([44, 45, 25, 51, 95, 177, 178, 217, 228, 222], 219)
femmesh.addVolume([46, 15, 16, 25, 207, 60, 210, 179, 116, 117], 220)
femmesh.addVolume([46, 15, 25, 45, 207, 116, 179, 96, 208, 177], 221)
femmesh.addVolume([50, 8, 19, 39, 192, 65, 216, 213, 167, 169], 222)
femmesh.addVolume([35, 51, 15, 45, 227, 223, 158, 135, 228, 208], 223)
femmesh.addVolume([34, 44, 43, 13, 144, 94, 134, 155, 226, 225], 224)
femmesh.addVolume([51, 44, 45, 34, 217, 95, 228, 218, 144, 136], 225)
femmesh.addVolume([9, 29, 39, 30, 147, 127, 215, 148, 78, 126], 226)
femmesh.addVolume([40, 9, 19, 39, 214, 105, 168, 90, 215, 169], 227)

# add it to the analysis
femmesh_obj.FemMesh = femmesh
```

### FEM mesh (gmsh)

```femmesh_obj = ObjectsFem.makeMeshGmsh(doc, box_obj.Name + "_Mesh")
femmesh_obj.Part = doc.Box

doc.recompute()

from femmesh.gmshtools import GmshTools as gt
gmsh_mesh = gt(femmesh_obj)
error = gmsh_mesh.create_mesh()
print(error)

```

### FEM mesh (netgen)

```mesh = doc.addObject('Fem::FemMeshShapeNetgenObject', 'FEMMeshNetgen')
mesh.Shape = doc.Box
mesh.MaxSize = 1000
mesh.Fineness = "Moderate"
mesh.Optimize = True
mesh.SecondOrder = True
doc.recompute()

```

### Recompute

```# recompute
doc.recompute()

###
```

## Run the analysis

To run the analysis using Python, an instance of the `ccxtools` module class `FemToolsCcx` needs to be created. Once this instance has been created, we have two choices when running the analysis:

1. Run all processes together at once (see "All in one" section below)
2. Run processes one after the other (see "Step by step" section below)

If there is only one analysis in the document and only one solver in the analysis, then no objects need to be passed on `fea init`. The `init` method of the `fea` class will activate the analysis if the GUI is up.

Activating an analysis using Python works a follows:

```# activating analysis
import FemGui
FemGui.setActiveAnalysis(doc.Analysis)

###
```

#### All in one

```# run the analysis all in one
from femtools import ccxtools
fea = ccxtools.FemToolsCcx()
fea.purge_results()
fea.run()

###
```

#### Step by step

```# run the analysis step by step
from femtools import ccxtools
fea = ccxtools.FemToolsCcx()
fea.update_objects()
fea.setup_working_dir()
fea.setup_ccx()
message = fea.check_prerequisites()
if not message:
fea.purge_results()
fea.write_inp_file()
# on error at inp file writing, the inp file path "" was returned (even if the file was written)
# if we would write the inp file anyway, we need to again set it manually
# fea.inp_file_name = '/tmp/FEMWB/FEMMeshGmsh.inp'
fea.ccx_run()
else:
FreeCAD.Console.PrintError("Houston, we have a problem! {}\n".format(message))  # in report view
print("Houston, we have a problem! {}\n".format(message))  # in python console

###
```

## Show the results

```# show some results
for m in analysis_object.Group:
if m.isDerivedFrom('Fem::FemResultObject'):
result_object = m
break

femmesh_obj.ViewObject.setNodeDisplacementByVectors(result_object.NodeNumbers, result_object.DisplacementVectors)
femmesh_obj.ViewObject.applyDisplacement(10)

###
```

#### Scripting FEM mesh objects

##### Netgen

Scripting the Netgen mesh object was attempted in the "Parametrized FEM study" (FreeCAD FEM subforum thread), but has some limitations.

##### GMSH

On the contrary, the GMSH mesh object fully supports python scripting. See the following forum posts:

See forum posts:

See forum posts:

#### Console mode

Writing the input file in FreeCAD console mode (no Gui) could be done in test mode. See this relevant forum post for more details and experimentation.

## Appendix

Have Fun! Also if you have feedback or any refinements, feel free to participate on the FreeCAD FEM subforum.