Accession Number : AD0479041

Title :   DEVELOPMENT OF NONDESTRUCTIVE TESTING METHODS FOR THE EVALUATION OF THIN AND ULTRATHIN SHEET MATERIALS.

Descriptive Note : Final rept. 30 May 64-1 Jun 65,

Corporate Author : GENERAL AMERICAN TRANSPORTATION CORP NILES IL GENERAL AMERICAN RESEARCH DIV

Personal Author(s) : Wieczorek, A. ; Schmitz, Gerald L.

Report Date : DEC 1965

Pagination or Media Count : 62

Abstract : High frequency (5 Mhz.) eddy current probes and signal processing circuitry were developed and extensively investigated resulting in a definition of detection sensitivity parameters. The lift-off effect was found to be acute and future work will be concerned with its compensation. Lamb waves were studied in aluminum using the FM system developed to interrogate the ultrasound spectrum. This system is described herein, as well as the results of experiments under the condition that phase velocity equal the longitudinal velocity of the material. Thickness measurements showed excellent correlation with values readily calculated from the Rayleigh-Lamb frequency equations, and it was observed that the signal strength varied in accordance with the third power of thickness for sheets less than about a wavelength in thickness. Measurements of the attenuation coefficient showed that in a sheet of a given thickness, this factor was essentially the same for all symmetric and high-order asymmetric modes, but increases sharply for lower order modes of the latter type. (Author)

Descriptors :   *NONDESTRUCTIVE TESTING, *SHEETS, *ULTRASONIC RADIATION, ELECTRIC CURRENT, SURFACES, HIGH FREQUENCY, TEST EQUIPMENT, TEST METHODS, EXPERIMENTAL DATA, THICKNESS, ATTENUATION, DEFECTS(MATERIALS), DETECTION, SENSITIVITY, PROBES, FREQUENCY MODULATION, INSTRUMENTATION, RESOLUTION, ALUMINUM.

Subject Categories : Fabrication Metallurgy

Distribution Statement : APPROVED FOR PUBLIC RELEASE