The Application of Photoelasticity to the Study of Indeterminate Truss-Stresses 320068
THIS paper contains a brief description of the history, theory and application of photoelasticity, which is a new and useful optical method of stress analysis. A simple, cheap and compact photoelastic polariscope developed for the purpose is described.
The application of photoelasticity to indeterminate truss-stress analysis produces quantitative stress measurements within a maximum experimental error of 6 per cent. The tests yield with considerable speed and convenience information concerning stress concentrations at corners and fillets that cannot be obtained by other methods. The author describes a photoelastic test of an airplane-wing-rib model whereby the axial and bending stresses in the members are determined and severe stress concentrations at the spar corners are noted. The stress distribution in a truss bent, as shown by photoelasticity, is illustrated, and a design procedure that makes possible the application of the results of the tests to the design of a stamped-metal rib is developed.