The dynamic strain amplitude of sapphire whisker reinforced and nonwhisker reinforced types I, II, and III piezoelectric ceramics was measured as a function of increasing electric field until fracture occurred. The 1-in.-diam by 0.2-in.-thick disk specimens were poled in their [33] direction and excited at their planar resonance. The direct measurement of radial displacement amplitude allows accurate assessment of the nonlinear behavior of piezoelectric and elastic constants from low to very high excitation fields. Test results show that previous determinations of peak dynamic tensile strengths, based on calculations which assume linear d constants, can result in large error. In addition, the investigations show the whisker-reinforced ceramics exhibit linearity and excellent performance to excitation levels unattainable by their nonwhisker-reinforced counterparts. [This work sponsored in part by ONR Code 468.]

Investigations directed toward a better understanding of the effect of intense sound on solid materials and their resultant reduction in strength has dictated a need for new methods of probing the microstructure of metallic materials. Magnetic Barkhausen noise has been investigated as one possible means of assessing the change in dislocation density introduced by the effect of vibratory energy. Measurements of Barkhausen activity, in nickel and iron wires, as a function of vibratory stress amplitude, magnetic fields, and frequency, were carried out. Data are presented which provide a link between magnetic domain wall motion, peak vibratory stress, and the rate at which vibratory stress is applied. [Acknowledgment is made to Dr. W. W. Lester for his contributions during the course of this work. This work sponsored in part by ONR Code 468.]