Study of high temperature failure mechanisms in ceramics. Annual report, 1 April 1985-31 March 1986

Technical Report · Tue Apr 01 04:00:00 EST 1986

OSTI ID:5144371

Page, R A; Lankford,

A fundamental study involving experimental characterization and analytical modeling of grain-boundary cavitation and creep crack growth in structural ceramics exposed to pure tensile loading is reported. The major experimental techniques employed in the program are the use of small-angle neutron scattering to characterize cavity nucleation and growth and stereo-imaging analysis to characterize the stress and strain fields associated with growing creep cracks. In the first section of the report, the experimental progress is summarized. The design of the pure tensile-creep apparatus, which is being used for the creation of bulk damage and for creep crack growth, is discussed. The progress made in the determination of surface-preparation conditions that are adequate for the stereo-imaging analysis is also discussed. The second section of the report describes the results of a critical review of recent experimental and theoretical studies of creep cavitation in ceramics. The results of this critical study identified a number of stochastic aspects of cavitation. The stochastic nature of cavitation arises primarily due to the dependence of both cavity nucleation and cavity growth on grain-boundary sliding. A degree of randomness is also imposed by the nonuniform distribution of nucleation sites. These results sugggest that the measurement of grain boundary sliding rates and the development of a statistical model of cavitation will be crucial to the understanding and modeling of tensile creep failure.

• Research Organization: Southwest Research Inst., San Antonio, TX (USA). Dept. of Materials Sciences
• OSTI ID: 5144371
• Report Number(s): AD-A-170001/2/XAB; SWRI-8578/2
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
CAVITATION
CERAMICS
CRACK PROPAGATION
CREEP
CRYSTAL STRUCTURE
FAILURES
GRAIN BOUNDARIES
HIGH TEMPERATURE
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NUCLEATION
STOCHASTIC PROCESSES