Research of Microstructurally Developed Toughening Mechanisms in Ceramics. Part 1-4.
Abstract
An x-ray diffraction technique has been used to measure the residual surface stresses induced by surface grinding in A1203 and in transformation-toughened A1203/Zr02 composites. For the A1203, compressive stresses in the range 135 to 170 MPa were measured and were found to extend to a depth = 15 micron. It is believed that the compressive layer is produced by the elastic/plastic interaction of the abrasive grains with the cermaics. In the A1203/Zr02 composites, comprehesive surface stresses are a result of the Zr02 phase transformation, which is induced by the stresses during grinding. Residual compressive surfaces stresses up to approx. 1 GPa were measured. The role of the volume fraction of Zr02, grain size and stabilizer oxide content in controlling the phase transformation are discussed, and their influence on the residual surface stress were measured. It was found that the volume fraction of Zr02 primarily controlled the magnitude of the compressive surface stress, but that other factors such as grain size influenced the depth of the compressive zone. Finally, a fracture mechanics model is presented that allows the strengthening due to these residual stress to be predicted. The model, which allows for crack closure effects, showed that the strengthening depends on the ratio of the compressive zone depth to surface crack length, and on the strength of the material in the absence of residual stresses. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1982
- Accession Number
- ADA120867
Entities
People
- D. J. Green
- F. F. Lange
- Michael R. James