The Gent hyperelastic solid constitutive model.[^1]
**Parameters**
- The bulk modulus $`\kappa`$.
- The shear modulus $`\mu`$.
- The extensibility $`J_m`$.
**External variables**
- The deformation gradient $`\mathbf{F}`$.
**Internal variables**
- None.
**Notes**
- The Gent model reduces to the [Neo-Hookean model](super::NeoHookean) when $`J_m\to\infty`$.