Accession Number : AD0638645

Title :   ULTRASONIC REVERBERATION IN SOLIDS FOR LOSS FACTORS EXCLUSIVE OF SCATTERING AND DIFFRACTION.

Descriptive Note : Technical memorandum.

Corporate Author : PENNSYLVANIA STATE UNIV UNIVERSITY PARK ORDNANCE RESEARCH LAB

Personal Author(s) : Droney,B. E.

Report Date : 19 AUG 1966

Pagination or Media Count : 106

Abstract : A reverberation method is investigated for ultrasonic loss measurements in solids at frequencies above 10 MHz. The diffuse sound field is generated by grain scattering and by reflection at the surface; in equilibrium this sound field consists of a mixture of shear and dilatation waves. The investigation of the energy balance between shear and dilatation for such a uniform diffuse field shows that once equilibrium is reached the energy is mainly contained in shear modes. Measurements of signal level and loss factor characterize the energy distribution throughout the sample as reverberant rather than pulse echo in character, after an initial conversion time required to establish the diffuse field. The decay slope is related to the acoustic loss in the solid and to the losses due to surface effects. Measurements of this reverberant decay slope as a function of frequency, temperature, time, and other parameters such as stress and geometry lead to increased knowledge of loss behavior of acoustic waves in solids. Loss factors in metals measured by the reverberation method from 10 to 100 MHz are frequently orders of magnitude lower than by pulse echo methods, since losses due to scattering are eliminated. (Author)

Descriptors :   (*ULTRASONIC RADIATION, *SOLID STATE PHYSICS), PROPAGATION, SOUND, VELOCITY, ATTENUATION, SOLIDS, ACOUSTICS

Subject Categories : Acoustics
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE