#[cfg(test)]
mod test;
use crate::{
constitutive::{
ConstitutiveError,
solid::{FIVE_THIRDS, Solid, TWO_THIRDS, elastic::Elastic, hyperelastic::Hyperelastic},
},
math::{IDENTITY, Quantity, Rank2, TensorRank4},
mechanics::{CauchyStress, CauchyTangentStiffness, Deformation, DeformationGradient, Scalar},
units::{EnergyDensity, Modulus, Stress},
};
const SEVEN_THIRDS: Scalar = 7.0 / 3.0;
#[doc = include_str!("doc.md")]
#[derive(Clone, Debug)]
pub struct Yeoh {
pub bulk_modulus: Quantity<Stress>,
pub shear_moduli: Vec<Quantity<Modulus>>,
}
impl Solid for Yeoh {
fn bulk_modulus(&self) -> Quantity<Stress> {
self.bulk_modulus
}
fn shear_modulus(&self) -> Quantity<Stress> {
self.shear_moduli.first().copied().unwrap_or_default()
}
}
impl Elastic for Yeoh {
#[doc = include_str!("cauchy_stress.md")]
fn cauchy_stress(
&self,
deformation_gradient: &DeformationGradient,
) -> Result<CauchyStress, ConstitutiveError> {
let jacobian = self.jacobian(deformation_gradient)?;
let (deviatoric_left_cauchy_green_deformation, left_cauchy_green_deformation_trace) =
deformation_gradient
.left_cauchy_green()
.deviatoric_and_trace();
let scalar_term = left_cauchy_green_deformation_trace / jacobian.powf(TWO_THIRDS) - 3.0;
Ok(deviatoric_left_cauchy_green_deformation
* self
.shear_moduli
.iter()
.enumerate()
.map(|(n, &modulus)| modulus * (((n as Scalar) + 1.0) * scalar_term.powi(n as i32)))
.sum::<Quantity<Modulus>>()
/ jacobian.powf(FIVE_THIRDS)
+ 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 left_cauchy_green_deformation = deformation_gradient.left_cauchy_green();
let scalar_term = left_cauchy_green_deformation.trace() / jacobian.powf(TWO_THIRDS) - 3.0;
let scaled_modulus = self
.shear_moduli
.iter()
.enumerate()
.map(|(n, &modulus)| modulus * (((n as Scalar) + 1.0) * scalar_term.powi(n as i32)))
.sum::<Quantity<Modulus>>()
/ jacobian.powf(FIVE_THIRDS);
let deviatoric_left_cauchy_green_deformation = left_cauchy_green_deformation.deviatoric();
let last_term = TensorRank4::dyad_ij_kl(
&deviatoric_left_cauchy_green_deformation,
&((left_cauchy_green_deformation.deviatoric()
* &inverse_transpose_deformation_gradient)
* (self
.shear_moduli
.iter()
.enumerate()
.skip(1)
.map(|(n, &modulus)| {
modulus
* (2.0
* ((n as Scalar) + 1.0)
* (n as Scalar)
* scalar_term.powi(n as i32 - 1))
})
.sum::<Quantity<Modulus>>()
/ jacobian.powf(SEVEN_THIRDS))),
);
Ok((TensorRank4::dyad_ik_jl(&IDENTITY, deformation_gradient)
+ TensorRank4::dyad_il_jk(deformation_gradient, &IDENTITY)
- TensorRank4::dyad_ij_kl(&IDENTITY, deformation_gradient) * (TWO_THIRDS))
* scaled_modulus
+ TensorRank4::dyad_ij_kl(
&(IDENTITY * (self.bulk_modulus() * 0.5 * (jacobian + 1.0 / jacobian))
- deviatoric_left_cauchy_green_deformation * (scaled_modulus * FIVE_THIRDS)),
&inverse_transpose_deformation_gradient,
)
+ last_term)
}
}
impl Hyperelastic for Yeoh {
#[doc = include_str!("helmholtz_free_energy_density.md")]
fn helmholtz_free_energy_density(
&self,
deformation_gradient: &DeformationGradient,
) -> Result<Quantity<EnergyDensity>, ConstitutiveError> {
let jacobian = self.jacobian(deformation_gradient)?;
let scalar_term =
deformation_gradient.left_cauchy_green().trace() / jacobian.powf(TWO_THIRDS) - 3.0;
Ok(0.5
* (self
.shear_moduli
.iter()
.enumerate()
.map(|(n, &modulus)| modulus * scalar_term.powi((n + 1) as i32))
.sum::<Quantity<Modulus>>()
+ self.bulk_modulus() * (0.5 * (jacobian.powi(2) - 1.0) - jacobian.ln())))
}
}