E. A. Hiedemann

Optical Methods for the Ultrasonic Determination of the Elastic Constants of Sapphire

Three optical methods, formerly only used for isotropic media, are applied to find the ultrasonic velocities in sapphire. From the results the elastic constants are calculated for this crystal. The elastic moduli are determined from measurements of ultrasonic velocities in different crystallographic directions, and Youngs modulus is plotted as function of these directions.

Corrected Values of the Elastic Moduli of Sapphire

Corrected values of the elastic moduli of sapphire are given based on earlier work of the authors but using more accurate crystal orientations.

Light Diffraction by Two Distorted Ultrasonic Waves

Light intensities in the orders of diffraction patterns produced by two distorted ultrasonic waves 180° out of phase are investigated. In the case where the two waves have the same intensity, the first diffraction orders vanish. The simultaneous increase in light intensity in the second orders is a measure of the second harmonic present in the waves, given for varying distances from the transducers. The change in light intensities in the zero and second orders is given for varying pressure ratios of the two waves.

Evaluation of two methods for the determination of the elastic constants of trigonal crystals

Two procedures for the computation of the elastic constants (trigonal system) from measured values of elastic wave velocities are discussed. The simplified procedure first used by Bhimasenachar is incorrect in principle although, in very rare cases, it may lead to only small numerical errors. A new procedure is mentioned which simplifies the use of the Christoffel equations in an exact way.

A simple method for the harmonic analysis of an ultrasonic wave

A study was made of the angular dependence of x-ray and bremsstrahlund spectra from thick anticathodes. An 0.184 mm thick square Pt anticathode was placed in the vacuum vessel of the 35-Mev beatron along with a 50 mu Al foil. The Al foil spreads out the electron beam before it reaches the anticathode. Energy distribution curves were obtained for 0 deg and 2.6 deg . The quotient of the activity ratios for the two angles was (Acu/Ac at 2.6 deg )/(Acu/Ac at 0 deg ) = 1.032 plus or minus 0.005. This result is apparently a confirmation of the angular dependence of the spectra and also shows the tonuclear processes. (T.R.H.)