Development of Dynamic Photoplasticity.
Final rept. 26 Jun 64-31 Jan 69,
CALIFORNIA UNIV BERKELEY
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An examination of the feasibility of the use of birefringent techniques to the domain of large deformations produced by dynamic loading has indicated that it is possible to generate plastic tensile and compressive waves in specimens of carefully selected or fabricated plastic materials. Of about ten candidate materials examined for this purpose, a mixture of 83 per cent Paraplex P-13, 16 per cent styrene cross-linked with 1 per cent benzoyl peroxide proved to be the most acceptable substance for this purpose. Under quasi-static conditions, this material exhibited a linearly visco-elastic perfectly-plastic behavior with a yield point dependent on strain rate and a linear relation between birefringence and strain independent of strain rate. Under impact conditions, the substance could be adequately characterized by a four-parameter model involving two springs, a dashpot, and a sliding element a logarithmically linear relation was found to exist between strain rate and fringe order per unit thickness. The analysis of uniaxial wave phenomena in this substance involving plastic components has been effected for large strains by means of a computer solution using a finite difference scheme. Author