FEM: solver calculix, add buckling analysis

Implementation of buckling analysis between the solver Calculix and FreeCAD

src/Mod/Fem/Gui/Resources/ui/SolverCalculix.ui

@@ -61,7 +61,28 @@
       <property name="bottomMargin">
        <number>9</number>
       </property>
-      <item row="0" column="0">
+      <item row="2" column="0">
+       <widget class="Gui::PrefRadioButton" name="rb_thermomech_analysis">
+        <property name="text">
+         <string>Thermo mechanical</string>
+        </property>
+       </widget>
+      </item>
+      <item row="2" column="2">
+       <widget class="Gui::PrefRadioButton" name="rb_check_mesh">
+        <property name="text">
+         <string>Check Mesh</string>
+        </property>
+       </widget>
+      </item>
+      <item row="1" column="2">
+       <widget class="Gui::PrefRadioButton" name="rb_frequency_analysis">
+        <property name="text">
+         <string>Frequency</string>
+        </property>
+       </widget>
+      </item>
+      <item row="1" column="0">
        <widget class="Gui::PrefRadioButton" name="rb_static_analysis">
         <property name="text">
          <string>Static</string>
@@ -71,24 +92,10 @@
         </property>
        </widget>
       </item>
-      <item row="0" column="1">
-       <widget class="Gui::PrefRadioButton" name="rb_frequency_analysis">
+      <item row="3" column="0">
+       <widget class="Gui::PrefRadioButton" name="rb_buckling_analysis">
         <property name="text">
-         <string>Frequency</string>
-        </property>
-       </widget>
-      </item>
-      <item row="1" column="0">
-       <widget class="Gui::PrefRadioButton" name="rb_thermomech_analysis">
-        <property name="text">
-         <string>Thermo mechanical</string>
-        </property>
-       </widget>
-      </item>
-      <item row="1" column="1">
-       <widget class="Gui::PrefRadioButton" name="rb_check_mesh">
-        <property name="text">
-         <string>Check Mesh</string>
+         <string>Buckling</string>
         </property>
        </widget>
       </item>

src/Mod/Fem/femsolver/calculix/solver.py

@@ -41,7 +41,7 @@ from femtools import femutils
 if FreeCAD.GuiUp:
     import FemGui
 
-ANALYSIS_TYPES = ["static", "frequency", "thermomech", "check"]
+ANALYSIS_TYPES = ["static", "frequency", "thermomech", "check", "buckling"]
 
 
 def create(doc, name="SolverCalculiX"):
@@ -165,6 +165,15 @@ def add_attributes(obj, ccx_prefs):
     niter = ccx_prefs.GetInt("AnalysisMaxIterations", 200)
     obj.IterationsThermoMechMaximum = niter
 
+    obj.addProperty(
+        "App::PropertyIntegerConstraint",
+        "BucklingFactors",
+        "Fem",
+        "Calculates the lowest buckling modes to the corresponding buckling factors"
+    )
+    bckl = ccx_prefs.GetInt("BucklingFactors", 1)
+    obj.BucklingFactors = bckl
+
     obj.addProperty(
         "App::PropertyFloatConstraint",
         "TimeInitialStep",

src/Mod/Fem/femsolver/calculix/writer.py

@@ -880,7 +880,7 @@ class FemInputWriterCcx(writerbase.FemInputWriter):
     def write_constraints_selfweight(self, f):
         if not self.selfweight_objects:
             return
-        if not (self.analysis_type == "static" or self.analysis_type == "thermomech"):
+        if not (self.analysis_type == "static" or self.analysis_type == "thermomech" or self.analysis_type == "buckling"):
             return
 
         # write constraint to file
@@ -914,7 +914,7 @@ class FemInputWriterCcx(writerbase.FemInputWriter):
     def write_constraints_force(self, f, inpfile_split=None):
         if not self.force_objects:
             return
-        if not (self.analysis_type == "static" or self.analysis_type == "thermomech"):
+        if not (self.analysis_type == "static" or self.analysis_type == "thermomech" or self.analysis_type == "buckling"):
             return
 
         # check shape type of reference shape and get node loads
@@ -963,7 +963,7 @@ class FemInputWriterCcx(writerbase.FemInputWriter):
     def write_constraints_pressure(self, f, inpfile_split=None):
         if not self.pressure_objects:
             return
-        if not (self.analysis_type == "static" or self.analysis_type == "thermomech"):
+        if not (self.analysis_type == "static" or self.analysis_type == "thermomech" or self.analysis_type == "buckling"):
             return
 
         # get the faces and face numbers
@@ -1176,7 +1176,7 @@ class FemInputWriterCcx(writerbase.FemInputWriter):
         if self.solver_obj.IterationsThermoMechMaximum:
             if self.analysis_type == "thermomech":
                 step += ", INC=" + str(self.solver_obj.IterationsThermoMechMaximum)
-            elif self.analysis_type == "static" or self.analysis_type == "frequency":
+            elif self.analysis_type == "static" or self.analysis_type == "frequency" or self.analysis_type == "buckling":
                 # parameter is for thermomechanical analysis only, see ccx manual *STEP
                 pass
         # write step line
@@ -1197,6 +1197,8 @@ class FemInputWriterCcx(writerbase.FemInputWriter):
             analysis_type = "*COUPLED TEMPERATURE-DISPLACEMENT"
         elif self.analysis_type == "check":
             analysis_type = "*NO ANALYSIS"
+        elif self.analysis_type == "buckling":
+            analysis_type = "*BUCKLE"
         # analysis line --> solver type
         # https://forum.freecadweb.org/viewtopic.php?f=18&t=43178
         if self.solver_obj.MatrixSolverType == "default":
@@ -1228,7 +1230,7 @@ class FemInputWriterCcx(writerbase.FemInputWriter):
                 # Set time to 1 and ignore user inputs for steady state
                 self.solver_obj.TimeInitialStep = 1.0
                 self.solver_obj.TimeEnd = 1.0
-            elif self.analysis_type == "static" or self.analysis_type == "frequency":
+            elif self.analysis_type == "static" or self.analysis_type == "frequency" or self.analysis_type == "buckling":
                 pass  # not supported for static and frequency!
         # ANALYSIS parameter line
         analysis_parameter = ""
@@ -1255,6 +1257,9 @@ class FemInputWriterCcx(writerbase.FemInputWriter):
                 self.solver_obj.TimeInitialStep,
                 self.solver_obj.TimeEnd
             )
+        elif self.analysis_type == "buckling":
+            analysis_parameter = "{}\n".format(self.solver_obj.BucklingFactors)
+
         # write analysis type line, analysis parameter line
         f.write(analysis_type + "\n")
         f.write(analysis_parameter + "\n")
@@ -1818,6 +1823,7 @@ class FemInputWriterCcx(writerbase.FemInputWriter):
 
             # nonlinear material properties
             if self.solver_obj.MaterialNonlinearity == "nonlinear":
+
                 for nlfemobj in self.material_nonlinear_objects:
                     # femobj --> dict, FreeCAD document object is nlfemobj["Object"]
                     nl_mat_obj = nlfemobj["Object"]

src/Mod/Fem/femtaskpanels/task_solver_ccxtools.py

@@ -114,6 +114,11 @@ class _TaskPanel:
             QtCore.SIGNAL("clicked()"),
             self.select_check_mesh
         )
+        QtCore.QObject.connect(
+            self.form.rb_buckling_analysis,
+            QtCore.SIGNAL("clicked()"),
+            self.select_buckling_analysis
+        )
         QtCore.QObject.connect(
             self.Calculix,
             QtCore.SIGNAL("started()"),
@@ -161,6 +166,8 @@ class _TaskPanel:
             self.form.rb_thermomech_analysis.setChecked(True)
         elif self.fea.solver.AnalysisType == "check":
             self.form.rb_check_mesh.setChecked(True)
+        elif self.fea.solver.AnalysisType == "buckling":
+            self.form.rb_buckling_analysis.setChecked(True)
         return
 
     def femConsoleMessage(self, message="", color="#000000"):
@@ -386,3 +393,7 @@ class _TaskPanel:
 
     def select_check_mesh(self):
         self.select_analysis_type("check")
+
+    def select_buckling_analysis(self):
+        self.select_analysis_type("buckling")
+