The Saint Venant-Kirchhoff thermohyperelastic solid constitutive model.
**Parameters**
- The bulk modulus $`\kappa`$.
- The shear modulus $`\mu`$.
- The coefficient of thermal expansion $`\alpha`$.
- The reference temperature $`T_\mathrm{ref}`$.
**External variables**
- The deformation gradient $`\mathbf{F}`$.
- The temperature $`T`$.
**Internal variables**
- None.
**Notes**
- The Green-Saint Venant strain measure is given by $`\mathbf{E}=\tfrac{1}{2}(\mathbf{C}-\mathbf{1})`$.