Photomechanics Methods for Inelastic Stress Analysis.
Final rept. 1 Feb 74-31 Jan 76,
IOWA STATE UNIV AMES ENGINEERING RESEARCH INST
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In this report, complete mechanical and optical properties are presented for a polyester material which is suitable for model studies in the inelastic range of material response. Data from a series of uniaxial tensile and compressive tests, together with data from a series of pressurized thin-walled cylinder tests, indicates that the fringe order at a point in the material is a function of the instantaneous principal strain difference at the point. Under load, the function is non-linear and multi-valued. Upon removal of the load, however, the retained fringe order is a single-valued linear function of the principal strain difference. Data from the uniaxial and cylinder tests also indicates that the material follows a modified von Mises yield criterion which accounts for differences in tensile and compressive yield strengths.