Stress Development and Fracture of Surface Nucleated Cristobalite on Silica Glass
Abstract
Stress development and fracture of isolated cristobalite spherulites in amorphous silica matrix were observed. High purity bulk silica was annealed to produce partial surface crystallization consisting of isolated and impinged spherulites in an amorphous matrix. The stress state of the amorphous silica surrounding cristobalite spherulites was qualitatively examined using crossed‐polars microscopy. Fracture was observed to occur with many spherulites encircled by cracks in the matrix and other spherulites observed to self‐fracture in a “mud‐cracking” pattern. The fracture was found to be size dependent with encircling matrix cracks occurring as a minority phenomena in spherulites 20–70 microns in diameter and “mud‐cracking” self‐fracture to occur in all spherulites over 70 microns in diameter. The stresses develop as a result of the strain associated with the 4.9% volume reduction in the cristobalite on transitioning from beta‐to‐alpha phase at ~250°C. Observed fracture behaviors were modeled. Matrix cracks encircling spherulites were found to be consistent with a Weibull failure model of the glass under a stress field derived from the Eshelby inclusion model. Self‐fractured spherulite failure was found to be consistent with a failure model based on thin films under biaxial stress.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Sep 05, 2014
- Source ID
- 10.1111/jace.13181
Entities
People
- John W. Halloran
- Ryan C. Breneman
Organizations
- University of Michigan