Some elementary principles of shell stress analysis with notes on the use of the shear center
A 1939 NACA technical note from the NASA Technical Reports Server, written for aircraft structures engineers to explain thin-walled shell stress analysis and the shear center. Its pictures are line diagrams of idealised box and wing-like sections under torsion and shear, with lettered cell walls, applied loads and dimensioned sketches. A designer could take from them the clean schematic method of showing stresses as arrows on a cross-section outline.
