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FEM foundation B: heat transfer and thermal stress (solids, 2D, explicit), coupled temperature–displacement, solve.heat (#45)

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* Heat transfer and thermal stress: thermal materials, temperature BCs, heat loads, heat transfer and coupled temperature–displacement steps, solve.heat

Model: Material.thermal (conductivity, specific heat, expansion, isotropic or
per axis; reference temperature), BoundaryCondition::Temperature (dof 11),
loads SurfaceFlux, Convection, HeatSource and Temperature (a field in static
steps), procedures HeatTransfer { transient (θ-method) } and
CoupledTemperatureDisplacement; checks for missing conductivity/specific
heat/expansion. fem: heat conduction kernels (conductivity, capacity,
source, face flux/film, heat flux) on the DofLayout (one T per node), thermal
strain load and stress D(ε − ε_th) for every solid formulation incl.
incompatible modes. Solver: steady and transient heat transfer, thermal loads
in static steps, coupled steps (exact one-way coupling). Engine: solve.heat,
temperature/heat-flux result fields, probes. Decks refuse heat transfer by
name. Analytic verification: slab, source+convection/flux, thick cylinder,
erfc semi-infinite solid, free/constrained expansion, bimetal strip, coupled
step.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* thermal: strains in 2D elements and explicit dynamics

Plane::thermal_load and stresses_with for plane stress (εzz free), plane
strain (σzz = −D₃·ε_th) and axisymmetric elements, incompatible modes
included; the solver's 2D kernels take them. Explicit dynamics turns a
step's temperature loads into a per-element thermal strain rate (reached
linearly over the step) subtracted from each strain increment, so it feeds
J2 and Johnson–Cook updates. Verified: free expansion in every 2D theory
and element, a biaxially held plate, an explicit free bar (ΔL = αΔT L,
stress-free) and a clamped bar at −EαΔT, capped at the yield stress with
perfect plasticity.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* clippy

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* thermal: trusses take the axial thermal strain; keep the roadmap's M7 line

Truss::thermal_load and stresses_with project the thermal strain on the
member's tangent (Σ αₖ tₖ² ΔT); the static solver applies them to rod2/rod3
(#38). Explicit trusses take none yet and a warning says so.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

---------

Co-authored-by: jyviko <2501648+jyviko@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
Irakli KourtisClaude Opus 5.5jyviko
 authored and GitHub committed 2026-10-13 22:15:03 -04:00
1 parent bf325bb234
commit e900f41ce3
37 files changed
+2576 -90
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crates/model/src/check.rs
+56 -4
View File
@@ -169,6 +169,8 @@ impl Model {
let mut d = Diagnostics::default();
let mut resolved = Resolved::default();
let units = self.units;
// Whether a step needs elasticity (every step but pure heat transfer).
let structural = self.steps.is_empty() || self.steps.iter().any(|s| s.procedure.is_structural());
// A model of fluid steps alone needs no mesh: its domains carry their own grid; one of
// point masses, springs and dashpots alone is its own mesh.
@@ -289,7 +291,7 @@ impl Model {
for (other, labels) in taken {
d.error(&subject, format!("elements {} are also in section `{other}`", first_labels(&labels)));
}
if self.materials.get(&sec.material).is_some_and(|m| m.elastic.is_none()) {
if structural && self.materials.get(&sec.material).is_some_and(|m| m.elastic.is_none()) {
d.error(&subject, format!("material `{}` has no elastic constants", sec.material));
}
}
@@ -307,7 +309,13 @@ impl Model {
let why = match s.procedure {
Procedure::Frequency { .. } => "extracts frequencies",
Procedure::ExplicitDynamic(_) => "is dynamic",
Procedure::Static {} | Procedure::Fluid { .. } => return None,
Procedure::HeatTransfer { transient: Some(_) } => "is transient heat transfer",
Procedure::Static {}
| Procedure::Fluid { .. }
| Procedure::HeatTransfer { transient: None }
| Procedure::CoupledTemperatureDisplacement {} => {
return None;
}
};
Some(format!("step `{}` {why}", s.name))
})
@@ -327,6 +335,33 @@ impl Model {
}
}
// Heat transfer needs conductivities (and heat capacities when transient); thermal strain
// needs expansion coefficients.
let used: BTreeSet<&str> = self.sections.values().map(|s| s.material.as_str()).collect();
let thermal = |m: &str| self.materials.get(m).and_then(|m| m.thermal);
for s in self.steps.iter().filter(|s| s.procedure.is_thermal()) {
for &m in &used {
let t = thermal(m);
if t.and_then(|t| t.conductivity).is_none() {
d.error(format!("material `{m}`"), format!("has no conductivity, and step `{}` conducts heat", s.name));
}
if matches!(s.procedure, Procedure::HeatTransfer { transient: Some(_) }) && t.and_then(|t| t.specific_heat).is_none() {
d.error(format!("material `{m}`"), format!("has no specific heat, and step `{}` is transient heat transfer", s.name));
}
}
}
let strains_thermally = self.steps.iter().any(|s| {
matches!(s.procedure, Procedure::CoupledTemperatureDisplacement {})
|| s.loads.iter().any(|l| matches!(self.loads.get(l), Some(Load::Temperature { .. })))
});
if strains_thermally {
for &m in &used {
if thermal(m).and_then(|t| t.expansion).is_none() {
d.warning(format!("material `{m}`"), "has no expansion coefficient, so temperatures do not strain it");
}
}
}
// Reference points and couplings.
resolved.reference_point_nodes = self.reference_point_nodes();
for (name, label) in &resolved.reference_point_nodes {
@@ -447,9 +482,24 @@ impl Model {
}
// The fluid domain holds its own conditions; nothing structural applies.
Procedure::Fluid { .. } => continue,
Procedure::HeatTransfer { .. } | Procedure::CoupledTemperatureDisplacement {} => {
let bcs = s.boundary_conditions.iter().filter_map(|b| self.boundary_conditions.get(b));
let loads: Vec<&Load> = s.loads.iter().filter_map(|l| self.loads.get(l)).collect();
let held = bcs.clone().any(BoundaryCondition::is_thermal) || loads.iter().any(|l| matches!(l, Load::Convection { .. }));
if !held && matches!(s.procedure, Procedure::HeatTransfer { transient: None } | Procedure::CoupledTemperatureDisplacement {}) {
d.warning(&subject, "no temperature boundary condition or convection is active, so the temperature level is undetermined");
}
}
}
// A free body is a natural case of transient dynamics (flight, impact).
if s.boundary_conditions.is_empty() && !s.procedure.is_dynamic() {
for l in s.loads.iter().filter(|l| self.loads.get(*l).is_some_and(|l| l.is_thermal() && !s.procedure.is_thermal())) {
d.warning(&subject, format!("heat load `{l}` has no effect in a {} step", s.procedure.name()));
}
// A free body is a natural case of transient dynamics (flight, impact); heat transfer
// has no rigid motion.
if s.procedure.is_structural()
&& s.boundary_conditions.iter().filter_map(|b| self.boundary_conditions.get(b)).all(BoundaryCondition::is_thermal)
&& !s.procedure.is_dynamic()
{
d.warning(&subject, "no boundary condition is active, so the model is free to move as a rigid body");
}
}
@@ -708,6 +758,8 @@ impl Model {
Load::Force { vector, .. } | Load::Traction { vector, .. } | Load::BodyForce { vector, .. } => vector[2] == 0.0,
Load::Gravity { acceleration, .. } => acceleration[2] == 0.0,
Load::Moment { .. } | Load::Pressure { .. } => true,
// Scalars.
Load::SurfaceFlux { .. } | Load::Convection { .. } | Load::HeatSource { .. } | Load::Temperature { .. } => true,
Load::Centrifugal { point, axis, .. } => {
let ok = if extent == Some(Extent::Revolved) {
axis[0] == 0.0 && axis[2] == 0.0 && point[0] == 0.0 && point[2] == 0.0