Accession Number : ADA130394

Title :   Research on Microstructurally Developed Toughening Mechanisms in Ceramics.

Descriptive Note : Final rept. 1 Jun 77-31 May 83,


Personal Author(s) : Green,D J

PDF Url : ADA130394

Report Date : Jun 1983

Pagination or Media Count : 50

Abstract : An approach is presented for predicting the strengthening of brittle materials by compressive surface stresses. The approach incorporates the effect of crack closure, which can significantly influence the stress intensity factor. The analysis is used for the example of tempering and it is found that the results give a better understanding of crack growth but also indicate approaches for optimization of the strengthening. Compressive surface stresses can be introduced into transformation-toughened Zr02 ceramics by grinding or impact. These techniques usually have associated damage effects. A new approach is introduced whereby surface compression is introduced by a heat treatment, which involves the removal of the oxide additives, that were originally introduced to retain the Zr02 in its tetragonal phase, from the surface region. The presence of the compressive surface stresses is confirmed and the ensuing improved resistance to indentation cracking is described. (Author)

Descriptors :   *Ceramic materials, *Microstructure, *Toughness, Composite materials, Cracking(Fracturing), Cracks, Stabilization, Strength(Mechanics), X ray diffraction, Impact, Optimization, Surface analysis, Heat treatment

Subject Categories : Ceramics, Refractories and Glass

Distribution Statement : APPROVED FOR PUBLIC RELEASE