Torsion of tubes of arbitrary shape

The method of eigenfunction expansion and matching can be applied to arbitrary shaped, hollow tubes which are described by curved and straight pieces. The method is highly efficient and superior to finite differences. The oval tube and the rounded polygonal tube are studied in detail. Approximate formula for torsional rigidity from membrane analogy is valid only for thin tubes with thickness less than 0.2. Maximum shear stress occurs either at re-entrant inner comers or at the outer boundary on the minor axis. © 1997 Elsevier Science Ltd