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Material for Solid

In one sentence: Assign elastic, thermal, and density properties to a solid body so the solver knows how the material responds to loads.

Overview

Workbench: FEM
Menu: FEM → Model → Materials → Material for Solid

Creates a Fem::Material object for a solid structural or thermal body. This is the most commonly used material tool in FEM — every structural or thermal analysis requires at least one.

Intuition

The solver works with numbers, not names. A material object gives the solver the numerical values it needs:

Property Symbol Description
Young's Modulus E Stiffness — how hard is it to stretch?
Poisson's Ratio ν Lateral contraction ratio
Density ρ Mass per volume (needed for self-weight and frequency)
Thermal Conductivity λ Heat flow rate through material
Specific Heat Capacity c Energy stored per degree
Thermal Expansion Coefficient α Expansion per °C

Typical values (steel)

Property Symbol Typical value
Young's Modulus E 210 000 MPa
Poisson's Ratio ν 0.30
Density ρ 7 900 kg/m³
Thermal Conductivity λ 50 W/(m·K)
Specific Heat Capacity c 500 J/(kg·K)
Thermal Expansion Coefficient α 12×10⁻⁶ /K

Step-by-step

  1. Activate the Analysis container.
  2. Optionally select the body to assign the material to.
  3. Choose FEM → Model → Materials → Material for Solid.
  4. In the task panel, select a material from the library or enter values.
  5. Click OK.

Common mistakes and pitfalls

Units must be included in property strings

All property values must include their unit string in FreeCAD quantity format (e.g. "210000 MPa", not "210000"). The task panel handles this automatically; the issue arises only in Python scripts.

Density required for inertial loads

Self-weight and centrifugal loads are proportional to mass. If density is zero or not set, these loads produce zero force.

Python API

import ObjectsFem
doc = App.ActiveDocument
analysis = doc.getObject("Analysis")

mat = ObjectsFem.makeMaterial(doc, "MaterialSteel")
mat.Category = "Solid"
mat.Material = {
    "Name": "Steel",
    "YoungsModulus": "210000 MPa",
    "PoissonRatio": "0.30",
    "Density": "7900 kg/m^3",
}
analysis.addObject(mat)
doc.recompute()

See also