Accession Number : ADA299693

Title :   High Temperature Fatigue of Structural Ceramics.

Descriptive Note : Final technical rept.,

Corporate Author : MICHIGAN UNIV ANN ARBOR DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s) : Chen, I-Wei

PDF Url : ADA299693

Report Date : 09 MAR 1995

Pagination or Media Count : 7

Abstract : The objective of the research effort was to establish a fundamental understanding of high temperature fatigue in structural ceramics. Two additional closely related areas, environmental effect on fatigue and temperature dependence on strength and toughness, were also targeted where basic understanding needed to be acquired. We were successful in establishing a comprehensive framework as the basis for understanding fatigue and fracture over a broad range of temperatures, static/cyclic loading conditions, and environmental conditions. The premises of that framework were: (1) Fatigue at low temperature is a process of mechanical balance in which resistance to crack advance is due to increased shielding whereas the impetus for crack advance is due to wear-caused degradation of crack wake shielding. (2) Fatigue at high temperature is a process of slow (creep) crack growth. Cyclic loading lowers the friction of grain boundary. The difference in crack growth rate in static and cyclic loadings can be rationalized by the different evolutions of crack-tip stress intensity factor under different grain boundary frictions. (3) Toughness in monolithic ceramics is due to grain pullout. jg p.1

Descriptors :   *STRUCTURAL PROPERTIES, *HIGH TEMPERATURE, *CERAMIC MATERIALS, *FATIGUE, STRESSES, THERMAL PROPERTIES, TEMPERATURE, LOW TEMPERATURE, MECHANICAL PROPERTIES, ENVIRONMENTS, DEGRADATION, RESISTANCE, LOADS(FORCES), STATIC LOADS, CRACKS, RATES, TOUGHNESS, STRENGTH(MECHANICS), FRACTURE(MECHANICS), CYCLES, CRACK PROPAGATION, WEAR, BALANCE, CREEP, SHIELDING, MONOLITHIC STRUCTURES(ELECTRONICS), FRICTION, GRAIN BOUNDARIES.

Subject Categories : Ceramics, Refractories and Glass
      Physical Chemistry
      Mechanics
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE