A sandwich technique which utilizes an embedded polariscope consisting of two sheets of polarizing material cemented within a plastic model was evaluated for application to three-dimensional photothermoelasticity. The evaluation included strength tests of cemented joints, photoelastic tests of simple bending models and a sphere, all under mechanical loading. The technique proved to be rather simple to apply particularly since the resulting fringe patterns are readily interpreted. The sandwich technique was then applied to thermal-stress problems associated with a thick-walled cylinder under steady-state conditions. The experimental results correlated well with theory. The results obtained indicate the general applicability of the sandwich technique to three-dimensional stress problems generated by mechanical or thermal loads. It is noted that since other experimental thermal-stress-analysis methods are not highly developed, photothermoelasticity would seem to be particularly useful.

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