= Solution
Write $B=A+H$ for the reference outer radius and $b=a+h$ for the current outer radius. The inner material normal is $-e_r$. A fluid <pressure> $P$ applies <traction> $-Pn=Pe_r$ there, so the radial <Cauchy stress tensor> component must be negative:
$$
\boxed{t_r(a)=-P,\qquad t_r(b)=0.}
$$
The second condition uses zero external gauge <pressure>. Both faces also have zero shear <traction>; the axisymmetric diagonal <stress> field satisfies those conditions automatically. The axial constraint is <plane strain>, so supports may supply an axial reaction; it does not imply zero axial <stress>.
Back to article page
