Accession Number : AD0012803


Title :   A STUDY OF PHOTOPLASTICITY. THE PHOTOELASTIC EFFECT IN THE REGION OF LARGE DEFORMATION IN POLYETHYLENE


Corporate Author : WASHINGTON STATE INST OF TECH PULLMAN


Personal Author(s) : Fried, B ; Shoup, N H


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/012803.pdf


Report Date : May 1953


Pagination or Media Count : 17


Abstract : Polyethylene (I) was chosen for study because of its high optic al sensitivity and the similarity of its stress-strain relationships to those of engineering materials. Photoelastic uniformity and clarity of the sheets of I were improved by heating between strips of chromeplated brass to the softening range (100 deg to 170 deg C) and quenching in Hsub2O at room temperature. Calibration tests were made with instruments which autographically recorded stress, strain, and optical retardation as a function of time. The strain rate did not appear to influence the linear dependence of optical retardation on strain. Results of calibration tests under biaxial loading established the dependence of optical retardation on the principal strain difference. Creep tests were run at 70 deg F and difference stress levels; simultaneous measurements were made of optical retardation and strain as a function of time of loading. Nondimensional stress-strain curves were drawn for I and a prototype material, 3S Al sheet. Results of tests showed good agreement between strain gage data from the Al prototype and photoplasticity data from the I model on the basis of either of 2 postulated criteria of equivalence between the model and prototype. The technique appeared promising as an experimental method for studies of the inelastic behavior of stressed members.


Descriptors :   *OPTICAL PROPERTIES , *PHOTOPLASTIC MATERIALS , *STRESS STRAIN RELATIONS , *POLARIZATION , RATES , TEST METHODS , PROTOTYPES , OPTICAL MATERIALS , STRAIN RATE , STRAIN GAGES , CALIBRATION , SYNCHRONISM , RANGE(EXTREMES) , BIAXIAL STRESSES , CREEP TESTS , POLYETHYLENE , SOFTENING POINTS , ELASTIC PROPERTIES , MODELS , MEASUREMENT , TEST AND EVALUATION , STRESSES


Subject Categories : Mechanics
      Optical Detection and Detectors


Distribution Statement : APPROVED FOR PUBLIC RELEASE