diff --git a/src/Mod/Fem/App/FemVTKTools.cpp b/src/Mod/Fem/App/FemVTKTools.cpp
index abde902d02..18707a93f1 100644
--- a/src/Mod/Fem/App/FemVTKTools.cpp
+++ b/src/Mod/Fem/App/FemVTKTools.cpp
@@ -700,7 +700,7 @@ std::map<std::string, std::string> _getFreeCADMechResultVectorProperties() {
 // some scalar list are not needed on VTK file export but they are needed for internal VTK pipeline
 // TODO some filter to only export the needed values to VTK file but have all in FreeCAD VTK pipline
 std::map<std::string, std::string> _getFreeCADMechResultScalarProperties() {
-    // see src/Mod/Fem/femobjects/_FemResultMechanical
+    // see src/Mod/Fem/femobjects/result_mechanical.py
     // App::PropertyFloatList will be a list of scalars in vtk
     std::map<std::string, std::string> resFCScalProp;
     resFCScalProp["DisplacementLengths"] = "Displacement Magnitude";  // can be plotted in Paraview as THE DISPLACEMENT MAGNITUDE
@@ -726,6 +726,9 @@ std::map<std::string, std::string> _getFreeCADMechResultScalarProperties() {
     // thus TODO they might not be exported to external file format (first I need to know how to generate them in paraview)
     // but there are needed anyway because the pipline in FreeCAD needs the principal stress values
     // https://forum.freecadweb.org/viewtopic.php?f=18&t=33106&p=416006#p412800
+    resFCScalProp["PrincipalMax"] = "Major Principal Stress";       // can be plotted in Paraview as THE MAJOR PRINCIPAL STRESS MAGNITUDE
+    resFCScalProp["PrincipalMed"] = "Intermediate Principal Stress";// can be plotted in Paraview as THE INTERMEDIATE PRINCIPAL STRESS MAGNITUDE
+    resFCScalProp["PrincipalMin"] = "Minor Principal Stress";       // can be plotted in Paraview as THE MINOR PRINCIPAL STRESS MAGNITUDE
     resFCScalProp["vonMises"] = "von Mises Stress";
     resFCScalProp["Temperature"] = "Temperature";
     resFCScalProp["MohrCoulomb"] = "MohrCoulomb";
@@ -918,7 +921,6 @@ void FemVTKTools::exportFreeCADResult(const App::DocumentObject* result, vtkSmar
             }
 
             if ((it->first.compare("MaxShear") == 0)
-                || (it->first.compare("MaxShear") == 0)
                 || (it->first.compare("NodeStressXX") == 0)
                 || (it->first.compare("NodeStressXY") == 0)
                 || (it->first.compare("NodeStressXZ") == 0)