FEM: Add Thick Pipe Internal Pressure 2D example (#25191)

Co-authored-by: Kacper Donat <kadet1090@gmail.com>

src/Mod/Fem/CMakeLists.txt

@@ -73,6 +73,7 @@ SET(FemExamples_SRCS
     femexamples/ccx_cantilever_nodeload.py
     femexamples/ccx_cantilever_prescribeddisplacement.py
     femexamples/ccx_rigid_body.py
+    femexamples/ccx_pipe_pressure_2D.py
     femexamples/constraint_centrif.py
     femexamples/constraint_contact_shell_shell.py
     femexamples/constraint_contact_solid_solid.py

src/Mod/Fem/femexamples/ccx_pipe_pressure_2D.py

@@ -0,0 +1,155 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+# ***************************************************************************
+# *   Copyright (c) 2025 Jakub Michalski <jakub.j.michalski[at]gmail.com>         *
+# *                                                                         *
+# *   This file is part of FreeCAD.                                         *
+# *                                                                         *
+# *   FreeCAD is free software: you can redistribute it and/or modify it    *
+# *   under the terms of the GNU Lesser General Public License as           *
+# *   published by the Free Software Foundation, either version 2.1 of the  *
+# *   License, or (at your option) any later version.                       *
+# *                                                                         *
+# *   FreeCAD is distributed in the hope that it will be useful, but        *
+# *   WITHOUT ANY WARRANTY; without even the implied warranty of            *
+# *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU      *
+# *   Lesser General Public License for more details.                       *
+# *                                                                         *
+# *   You should have received a copy of the GNU Lesser General Public      *
+# *   License along with FreeCAD. If not, see                               *
+# *   <https://www.gnu.org/licenses/>.                                      *
+# *                                                                         *
+# ***************************************************************************
+
+import FreeCAD as App
+
+import Part
+import ObjectsFem
+
+from . import manager
+from .manager import get_meshname
+from .manager import init_doc
+
+
+def get_information():
+    return {
+        "name": "Thick Pipe Internal Pressure 2D",
+        "meshtype": "face",
+        "meshelement": "Tria6",
+        "constraints": ["displacement", "pressure"],
+        "solvers": ["ccxtools"],
+        "material": "solid",
+        "equations": ["mechanical"],
+    }
+
+
+def get_explanation(header=""):
+    return (
+        header
+        + """
+
+To run the example from Python console use:
+from femexamples.ccx_pipe_pressure_2D import setup
+setup()
+
+
+Analytical solution - max von mises stress (at the inner surface) = 2.764 MPa = 2.764e6 Pa
+
+"""
+    )
+
+
+def setup(doc=None, solvertype="ccxtools"):
+
+    # init FreeCAD document
+    if doc is None:
+        doc = init_doc()
+
+    # explanation object
+    # just keep the following line and change text string in get_explanation method
+    manager.add_explanation_obj(doc, get_explanation(manager.get_header(get_information())))
+
+    # geometric objects
+    arc1 = Part.makeCircle(30, App.Vector(0, 0, 0), App.Vector(0, 0, 1), 0, 90)
+    arc2 = Part.makeCircle(50, App.Vector(0, 0, 0), App.Vector(0, 0, 1), 0, 90)
+    line1 = Part.makeLine((30,0,0),(50,0,0))
+    line2 = Part.makeLine((0,30,0),(0,50,0))
+    wire = Part.Wire([arc1,line1,arc2,line2])
+    Part.show(wire)
+    face = Part.Face(wire)
+    faceo = Part.show(face)
+    faceobj = doc.addObject("Part::Reverse", "Reverse")
+    faceobj.Source = faceo
+    doc.recompute()
+    if App.GuiUp:
+        faceobj.ViewObject.Document.activeView().viewTop()
+        faceobj.ViewObject.Document.activeView().fitAll()
+
+    # analysis
+    analysis = ObjectsFem.makeAnalysis(doc, "Analysis")
+
+    # solver,
+    if solvertype == "ccxtools":
+        solver_obj = ObjectsFem.makeSolverCalculiXCcxTools(doc, "CalculiXCcxTools")
+        solver_obj.WorkingDir = ""
+        solver_obj.SplitInputWriter = False
+        solver_obj.AnalysisType = "static"
+        solver_obj.ModelSpace = "plane strain"
+        analysis.addObject(solver_obj)
+    else:
+        FreeCAD.Console.PrintWarning(
+            "Unknown or unsupported solver type: {}. "
+            "No solver object was created.\n".format(solvertype)
+        )
+
+    # 2D element thickness
+    thickness_obj = ObjectsFem.makeElementGeometry2D(doc, 50.0, "ShellThickness")
+    analysis.addObject(thickness_obj)
+
+    # material
+    material_obj = ObjectsFem.makeMaterialSolid(doc, "MechanicalMaterial")
+    mat = material_obj.Material
+    mat["Name"] = "CalculiX-Steel"
+    mat["YoungsModulus"] = "210000 MPa"
+    mat["PoissonRatio"] = "0.0"
+    material_obj.Material = mat
+    material_obj.References = [(faceobj, "Face1")]
+    analysis.addObject(material_obj)
+
+    # constraint displacement 1
+    con_disp1 = ObjectsFem.makeConstraintDisplacement(doc, "ConstraintDisplacement1")
+    con_disp1.References = [(faceobj, "Edge2")]
+    con_disp1.yFree = False
+    con_disp1.yDisplacement = "0.0 mm"
+    analysis.addObject(con_disp1)
+
+    # constraint displacement 2
+    con_disp2 = ObjectsFem.makeConstraintDisplacement(doc, "ConstraintDisplacement2")
+    con_disp2.References = [(faceobj, "Edge4")]
+    con_disp2.xFree = False
+    con_disp2.xDisplacement = "0.0 mm"
+    analysis.addObject(con_disp2)
+    
+    # constraint pressure
+    con_press = ObjectsFem.makeConstraintPressure(doc, "ConstraintPressure")
+    con_press.References = [(faceobj, "Edge1")]
+    con_press.Pressure = "1 MPa"
+    analysis.addObject(con_press)
+
+    # mesh
+    femmesh_obj = analysis.addObject(ObjectsFem.makeMeshGmsh(doc, get_meshname()))[0]
+    femmesh_obj.Shape = faceobj
+    femmesh_obj.ElementOrder = "2nd"
+    femmesh_obj.CharacteristicLengthMax = "1 mm"
+    femmesh_obj.ViewObject.Visibility = False
+
+    # generate the mesh
+    from femmesh import gmshtools
+
+    gmsh_mesh = gmshtools.GmshTools(femmesh_obj, analysis)
+    gmsh_mesh.create_mesh()
+
+    doc.recompute()
+    return doc
+
+