Development of Experimental Stress Analysis Methods to Determine Stresses and Strains in Solid Propellant Grains. Photoelastic Analysis of Flexural Waves in a Bar

摘要

A complete, direct, full-field optical determination of dynamic stress distributions is illustrated. The method is applied to the study of flexural waves propagating in a photoelastic, urethane rubber bar. A displacement type of transverse, dynamic loading (which has approximately the form of a decaying sine wave) is applied at one end of the bar. The loading pulse can be repeated with good precision. Individual isochromatics and isoclinics are obtained using a still camera with a short duration (0.5 microsecond) flash. A series of isochromatics have also been obtained with a Fastax high speed motion picture camera. Photoelastic data is supplemented by isopachic patterns obtained by a modified method of holographic interferometry recently developed by the authors. As an example of complete determination of stress distributions a vectorial representation of the principal stresses at one instant is given. Comparisons are made with approximate theories of flexural waves. (Author)