#[cfg(test)]
mod test;
use crate::{
constitutive::{
ConstitutiveError,
solid::{Solid, TWO_THIRDS, elastic::Elastic},
},
math::{IDENTITY, Rank2},
mechanics::{CauchyStress, CauchyTangentStiffness, Deformation, DeformationGradient, Scalar},
};
#[doc = include_str!("doc.md")]
#[derive(Clone, Debug)]
pub struct SaintVenantKirchhoff {
pub bulk_modulus: Scalar,
pub shear_modulus: Scalar,
}
impl Solid for SaintVenantKirchhoff {
fn bulk_modulus(&self) -> Scalar {
self.bulk_modulus
}
fn shear_modulus(&self) -> Scalar {
self.shear_modulus
}
}
impl Elastic for SaintVenantKirchhoff {
#[doc = include_str!("cauchy_stress.md")]
fn cauchy_stress(
&self,
deformation_gradient: &DeformationGradient,
) -> Result<CauchyStress, ConstitutiveError> {
let jacobian = self.jacobian(deformation_gradient)?;
let (deviatoric_strain, strain_trace) =
((deformation_gradient.left_cauchy_green() - IDENTITY) * 0.5).deviatoric_and_trace();
Ok(deviatoric_strain * (2.0 * self.shear_modulus() / jacobian)
+ IDENTITY * (self.bulk_modulus() * strain_trace / 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_deformation_gradient = deformation_gradient * (self.shear_modulus() / jacobian);
let (deviatoric_strain, strain_trace) =
((deformation_gradient.left_cauchy_green() - IDENTITY) * 0.5).deviatoric_and_trace();
Ok(
(CauchyTangentStiffness::dyad_il_jk(&scaled_deformation_gradient, &IDENTITY)
+ CauchyTangentStiffness::dyad_ik_jl(&IDENTITY, &scaled_deformation_gradient))
+ CauchyTangentStiffness::dyad_ij_kl(
&IDENTITY,
&(deformation_gradient
* ((self.bulk_modulus() - self.shear_modulus() * TWO_THIRDS) / jacobian)),
)
- CauchyTangentStiffness::dyad_ij_kl(
&(deviatoric_strain * (2.0 * self.shear_modulus() / jacobian)
+ IDENTITY * (self.bulk_modulus() * strain_trace / jacobian)),
&inverse_transpose_deformation_gradient,
),
)
}
}