Accession Number : ADA181266

Title :   Study of High Temperature Failure Mechanisms in Ceramics.

Descriptive Note : Annual rept. 1 Apr 86-31 Mar 87,

Corporate Author : SOUTHWEST RESEARCH INST SAN ANTONIO TEX DEPT OF MATERIALS SCIENCES

Personal Author(s) : Page,Richard A ; Lankford,James

PDF Url : ADA181266

Report Date : Apr 1987

Pagination or Media Count : 64

Abstract : This report summarizes the results of a fundamental study involving experimental characterization and analytical modeling of grain boundary cavitation and creep crack growth in ceramics exposed to pure tensile loading. The major experimental techniques employed in the program are the use of small-angle neutron scattering to characterize cavity nucleation and growth and stereoimaging analysis to characterize the stress and strain fields associated with growing creep cracks. The major accomplishments described in the report include the design, construction, and successful testing of a creep apparatus that permits creep testing of ceramics under pure tensile loading, the determination of surface preparation conditions that are adequate for the stereoimaging analysis, and the conduct of a series of creep tests designed to characterize the kinetics of damage accumulation under pure tensile loading. Appended to the report is a manuscript that was prepared during the second year of the program titled Stochastic Aspects of Creep Cavitation in Ceramics. It is anticipated that this manuscript will provide the cornerstone for understanding creep damage and creep crack growth. Of particular interest are the development of a stochastic model of grain boundary sliding and a micromechanical model that relates the cavity nucleation rate to the statistics of grain boundary sliding events.

Descriptors :   *CERAMIC MATERIALS, *FAILURE, *HIGH TEMPERATURE, ACCUMULATION, ANGLES, CAVITATION, CAVITIES, CRACK PROPAGATION, CRACKS, CREEP, CREEP TESTS, DAMAGE, GRAIN BOUNDARIES, KINETICS, MATHEMATICAL MODELS, NEUTRON SCATTERING, NUCLEATION, PREPARATION, PURITY, RATES, SLIDING, STOCHASTIC PROCESSES, SURFACE PROPERTIES, TENSILE PROPERTIES, TEST AND EVALUATION, SILICON NITRIDES, SILICON CARBIDES, CYCLIC TESTS, AEROSPACE CRAFT, FLIGHT LOADS, TENSILE STRESS

Subject Categories : Refractory Fibers
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE