Accession Number:

AD0745000

Title:

Investigation of Acoustic Emission from Ceramic Materials.

Descriptive Note:

Final rept. 25 May 71-24 May 72,

Corporate Author:

NORTH AMERICAN ROCKWELL CORP THOUSAND OAKS CALIF SCIENCE CENTER

Personal Author(s):

• Graham,Lloyd J.
• Alers,George A.

Report Date:

1972-05-19

Pagination or Media Count:

53.0

Abstract:

The frequency content, amplitude distribution, and rate of occurrence of acoustic emissions generated in model ceramic materials were determined. Single crystal MgO and glass, used as models of a ductile and a brittle ceramic, were mechanically loaded by three different means to produce rapid crack growth, controlled slow crack growth, and plastic deformation in both four-point bending and by cyclic bending at 100 cycles per second. A method was developed for easily determining the frequency spectrum of a single acoustic emission over the frequency range of 1 kHz to 3 MHz. The main results of the tests with the model materials were that no acoustic emissions were detected before rapid crack growth commenced or during slow crack growth in glass. Rapid crack growth produced acoustic emissions which had characteristic features in their frequncy spectra which seemed to depend on the size of the crack produced. Acoustic emissions were generated and were easily detected during plastic deformation of single crystal MgO. Author

Descriptors:

• (*CRACK PROPAGATION
• ACOUSTIC PROPERTIES)
• (*CERAMIC MATERIALS
• CRACK PROPAGATION)
• (*GLASS
• CRACK PROPAGATION)
• TEST METHODS
• SINGLE CRYSTALS
• MAGNESIUM OXIDES
• FAILURE(MECHANICS)
• GLASS
• SPECTRUM SIGNATURES
• FREQUENCY ANALYZERS

Subject Categories:

• Ceramics, Refractories and Glass
• Test Facilities, Equipment and Methods

Distribution Statement:

APPROVED FOR PUBLIC RELEASE