Photoelastic Study of High-Frequency Stress Waves Propagating in Bars and Plates

Abstract

This paper deals with the photoelastic analysis of stress waves in bars and plates subjected to damped sinusoidal loading. The device used to apply the loading is a piezoelectric transducer which produces about 10 cycles of a decaying sine wave. The wavelength of the stress wave which propagates along the square bar is comparable to the thickness of the bar. A strobotac, or a microflash, is used as light source flashing with a continuously variable delay. The isochromatics and isoclinics can be seen directly by eye as static patterns. More than 100 repetitions of illumination can be used, permitting the use of fine grain film. The specimens are relatively thick, but by using embedded polarizers and analyzers, two-dimensional solutions can be obtained. Good correlations with theoretical computations are shown for phase and group velocities. Stress distributions are determined along the center line and the edge of the bar.