#[cfg(test)]
mod test;
use crate::{
constitutive::{
ConstitutiveError,
solid::{FIVE_THIRDS, Solid, TWO_THIRDS, elastic::Elastic, hyperelastic::Hyperelastic},
},
math::{IDENTITY, Rank2},
mechanics::{CauchyStress, CauchyTangentStiffness, Deformation, DeformationGradient, Scalar},
};
#[doc = include_str!("doc.md")]
#[derive(Clone, Debug)]
pub struct NeoHookean {
pub bulk_modulus: Scalar,
pub shear_modulus: Scalar,
}
impl Solid for NeoHookean {
fn bulk_modulus(&self) -> Scalar {
self.bulk_modulus
}
fn shear_modulus(&self) -> Scalar {
self.shear_modulus
}
}
impl Elastic for NeoHookean {
#[doc = include_str!("cauchy_stress.md")]
fn cauchy_stress(
&self,
deformation_gradient: &DeformationGradient,
) -> Result<CauchyStress, ConstitutiveError> {
let jacobian = self.jacobian(deformation_gradient)?;
Ok(
deformation_gradient.left_cauchy_green().deviatoric() / jacobian.powf(FIVE_THIRDS)
* self.shear_modulus()
+ IDENTITY * self.bulk_modulus() * 0.5 * (jacobian - 1.0 / jacobian),
)
}
#[doc = include_str!("cauchy_tangent_stiffness.md")]
fn cauchy_tangent_stiffness(
&self,
deformation_gradient: &DeformationGradient,
) -> Result<CauchyTangentStiffness, ConstitutiveError> {
let jacobian = self.jacobian(deformation_gradient)?;
let inverse_transpose_deformation_gradient = deformation_gradient.inverse_transpose();
let scaled_shear_modulus = self.shear_modulus() / jacobian.powf(FIVE_THIRDS);
Ok(
(CauchyTangentStiffness::dyad_ik_jl(&IDENTITY, deformation_gradient)
+ CauchyTangentStiffness::dyad_il_jk(deformation_gradient, &IDENTITY)
- CauchyTangentStiffness::dyad_ij_kl(&IDENTITY, deformation_gradient)
* (TWO_THIRDS))
* scaled_shear_modulus
+ CauchyTangentStiffness::dyad_ij_kl(
&(IDENTITY * (0.5 * self.bulk_modulus() * (jacobian + 1.0 / jacobian))
- deformation_gradient.left_cauchy_green().deviatoric()
* (scaled_shear_modulus * FIVE_THIRDS)),
&inverse_transpose_deformation_gradient,
),
)
}
}
impl Hyperelastic for NeoHookean {
#[doc = include_str!("helmholtz_free_energy_density.md")]
fn helmholtz_free_energy_density(
&self,
deformation_gradient: &DeformationGradient,
) -> Result<Scalar, ConstitutiveError> {
let jacobian = self.jacobian(deformation_gradient)?;
Ok(0.5
* (self.shear_modulus()
* (deformation_gradient.left_cauchy_green().trace() / jacobian.powf(TWO_THIRDS)
- 3.0)
+ self.bulk_modulus() * (0.5 * (jacobian.powi(2) - 1.0) - jacobian.ln())))
}
}