Cross-sectional area ($\mathcal{A}$)

The area of a planar section through a body. A homogeneous diagonal deformation with transverse stretch ratios ${\lambda }_1$ and ${\lambda }_2$ changes the area of a transverse section from ${\mathcal{A}}_0$ to $\mathcal{A}={\lambda }_1{\lambda }_2{\mathcal{A}}_0$. Cauchy stress tensor components use current cross-sectional area, whereas nominal tractions use reference cross-sectional area.