The well-known photoelastic method for models in plane stress is extended to plates bent transversely by cementing together two similar plates with a thin layer of reflecting material between them. The light thus transverses twice one half of the full plate thickness, in which the stress is, in the simplest case, all of one sign, so that a net optical effect is obtained. Measurements on a strip of celluloid in pure bending, and with circular holes, yield results in conformity with theory; but a Bakelite model with circular holes showed discrepancies indicating that the cement bond between the Bakelite and the reflecting layer (aluminum foil) was not adequate. Results of measurements on semicircular notches in a strip under pure bending are also given. The difficulties and potentialities of the method are discussed.

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