Accession Number : ADA331243

Title :   Fracture Process Zone Studies of High Temperature Structural Ceramics

Descriptive Note : Final rept. 1 May 93-31 Aug 97

Corporate Author : HOUSTON UNIV TX DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : White, Kenneth W. ; Kobayashi, Albert S.

PDF Url : ADA331243

Report Date : SEP 1997

Pagination or Media Count : 13

Abstract : Our work on this AFOSR-funded project successfully completed the PFT database through 1280#161#C for alumina and through 600#161#C for the magnesium aluminate spinel, elucidating the importance of crystal structure and fracture topography on the toughening characteristics. We now have a firm understanding of the relationship between the PFT method and the crack growth resistance curve, and are now developing further insights into the role of the microstructural constituents in the crack growth resistance behavior. A first-generation finite element model of the fracture specimen uses both the moire and PFT data to faithfully predict the bulk behavior. Our examination of the electronic speckle pattern interferometry (ESPI) system for elevated temperature measurements of the crack profile have been discontinued, due to inadequate resolution of the available control software. Therefore, the moire experiments are now being modified for elevated temperature studies. We are initiating a second-generation model of the pullout micromechanism to predict the stress-displacement relationship based on the crystal structure properties, grain size distribution, and elastic properties. In response to the detailed studies by the PFT technique, modified micromechanisms are now being incorporated into the model, including high compliance bridging ligaments, such as asperity loading, grain rotation and ligament bending.

Descriptors :   *MICROSTRUCTURE, *FRACTURE(MECHANICS), *SPECKLE INTERFEROMETRY, FINITE ELEMENT ANALYSIS, ELASTIC PROPERTIES, TOUGHNESS, GRAIN SIZE, TOPOGRAPHY, CRACK PROPAGATION, MAGNESIUM COMPOUNDS, ALUMINATES, SPINEL.

Subject Categories : Ceramics, Refractories and Glass
      Optics
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE