Bending energy
= Bending energy
{title2=$\mathcal E_b=\frac12\int B(u-\hat u)^2\,dS$}
The part of an <elastic rod>'s <elastic energy> that penalizes departure of its <bending strain of a rod> $u$ from the intrinsic value $\hat u$. Here $B$ is the <bending stiffness> and $S$ is reference <arc length>. For an <inextensible rod>, the same formula can be written using spatial <curvature> and current <arc length>.