Static Fatigue of Ceramic Materials.

Abstract

Time-dependent failure in the temperature range ambient to 900C is being studied using variable strain rate and static load tests in four-point bending. The materials investigated are sapphire, alumina, hot pressed Si3N4 and reaction sintered Si3N4. The bulk of the work is being performed on the latter two materials. The test environment has been varied to determine the effects of moisture and pH on time-dependent failure. All of the materials exhibited strain rate and/or time-dependent failures in this temperature range in an environment of flowing air, saturated with water at room temperature. The strength decrease is moisture-dependent and the decrease is more marked in the presence of acids. A theory is proposed for the mechanism of static fatigue of the polycrystalline materials. The theory is based on ion exchange occurring in the glassy grain boundary phase. (Modified author abstract)

Document Details

Document Type
Technical Report
Publication Date
Jul 01, 1974
Accession Number
AD0786231

Entities

People

  • Arthur G. Metcalfe
  • Mary E. Gulden

Tags

DTIC Thesaurus Topics

  • Abstracts
  • Boundaries
  • Ceramic Materials
  • Chemical Compounds
  • Environment
  • Grain Boundaries
  • Inorganic Chemicals
  • Ion Exchange
  • Materials
  • Minerals
  • Moisture
  • Polycrystals
  • Sapphire
  • Static Loads
  • Strain Rate

Fields of Study

  • Materials science

Readers

  • Mechanical Engineering/Mechanics of Materials.
  • Powder metallurgy of Titanium alloys.
  • Structural Health Monitoring of Composite Structures.