From 18acfabea60811dacbc527708432fcabd0c7f1c4 Mon Sep 17 00:00:00 2001
From: FEA-eng <59876896+FEA-eng@users.noreply.github.com>
Date: Mon, 14 Jul 2025 18:03:43 +0200
Subject: [PATCH] FEM: Add thermal contact with CalculiX (#22121)

---
 src/Mod/Fem/App/FemConstraintContact.cpp               | 10 ++++++++++
 src/Mod/Fem/App/FemConstraintContact.h                 |  2 ++
 .../Fem/femsolver/calculix/write_constraint_contact.py |  5 +++++
 3 files changed, 17 insertions(+)

diff --git a/src/Mod/Fem/App/FemConstraintContact.cpp b/src/Mod/Fem/App/FemConstraintContact.cpp
index 51c74389b6..126365f744 100644
--- a/src/Mod/Fem/App/FemConstraintContact.cpp
+++ b/src/Mod/Fem/App/FemConstraintContact.cpp
@@ -58,6 +58,16 @@ ConstraintContact::ConstraintContact()
                       "ConstraintContact",
                       App::PropertyType(App::Prop_None),
                       "Stick slope");
+    ADD_PROPERTY_TYPE(EnableThermalContact,
+                      (false),
+                      "ConstraintContact",
+                      App::PropertyType(App::Prop_None),
+                      "Enable thermal contact");
+    ADD_PROPERTY_TYPE(ThermalContactConductance,
+                      (std::vector<std::string> {}),
+                      "ConstraintContact",
+                      App::PropertyType(App::Prop_None),
+                      "Thermal contact conductance");
 }
 
 App::DocumentObjectExecReturn* ConstraintContact::execute()
diff --git a/src/Mod/Fem/App/FemConstraintContact.h b/src/Mod/Fem/App/FemConstraintContact.h
index c2cc575b30..4e7c26cab5 100644
--- a/src/Mod/Fem/App/FemConstraintContact.h
+++ b/src/Mod/Fem/App/FemConstraintContact.h
@@ -51,6 +51,8 @@ public:
     App::PropertyBool Friction;
     App::PropertyFloat FrictionCoefficient;
     App::PropertyStiffnessDensity StickSlope;
+    App::PropertyBool EnableThermalContact;
+    App::PropertyStringList ThermalContactConductance;
 
     // etc
     /* */
diff --git a/src/Mod/Fem/femsolver/calculix/write_constraint_contact.py b/src/Mod/Fem/femsolver/calculix/write_constraint_contact.py
index fca26b40a1..99135ada6e 100644
--- a/src/Mod/Fem/femsolver/calculix/write_constraint_contact.py
+++ b/src/Mod/Fem/femsolver/calculix/write_constraint_contact.py
@@ -89,3 +89,8 @@ def write_constraint(f, femobj, contact_obj, ccxwriter):
         friction = contact_obj.FrictionCoefficient
         stick = contact_obj.StickSlope.getValueAs("MPa/mm").Value
         f.write(f"{friction:.13G}, {stick:.13G}\n")
+    if contact_obj.EnableThermalContact:
+        f.write("*GAP CONDUCTANCE\n")
+        for value in contact_obj.ThermalContactConductance:
+            f.write(f"{value}\n")
+        f.write("\n")