FRACTAL CHARACTERIZATION OF ULTRASONIC BACKSCATTERED SIGNALS FROM SINGLE-CRYSTAL AND POLYCRYSTALLINE MATERIALS

For the first time the concept of fractal geometry is introduced to characterize discrete ultrasonic time domain signals from a single crystal, a polycrystalline metal, and an alloy. These signals possess unique fractal dimensions and remain invariant with the change in sampling rate of signal capturing. The fractal dimension of these signals were evaluated by both the box counting method and the power spectrum method. The similarity and difference in the fractal dimension of these signals obtained fi om the above two methods have been discussed. (C) 1995 Acoustical Society of America.