Ultrasonic Studies of the Nonlinear Behavior of Solids

The non‐Hookeian behavior of a solid is studied using the distortion of an initially sinusoidal ultrasonic wave. The nonlinear differential equation describing the propagation of a finite amplitude ultrasonic wave in a cubic crystal is shown to take the same form as that describing a fluid. The propagation distance required for discontinuity in the particle velocity is calculated for various directions in the crystal. It is shown that in a typical experiment the path length can be appreciably less than the discontinuity distance, so that the distortion can be represented as a linear increase of second harmonic content with path length. Experimental results are given for copper single crystals which have been annealed or neutron irradiated.