# StructX > Resources > Stress and Strain > Thermal Expansion

## Assumptions and Limitations

Thermal expansion being the change in volume with change in temperature is something that effects all materials to some degree. StructX has provided formulas to help estimate such changes. Several assumptions have been made.

- Materials are considered to be homogeneous, isotropic and linear-elastic.
- Forces are evenly distributed over the cross-section and act through the centroid.
- Cross-sections are perpendicular to the longitudinal axis of the member.
- Plane sections before deformation remain plane after deformation.
- Stress and strain are linearly related and strains are small.
- Formulas are intended to be used with a linear expansion coefficient.