On this page, I intend to periodically post my ideas for the improvement of the strength of glasses. While these may occasionally (or perhaps always), seem off-the-wall, they are primarily meant to stimulate thinking on such issues. They may be 'off-the-cuff' in some cases and I will welcome any and all comments.
1. Effects and Importance of (high) mechanicalstress/strain on the flow and fracture in glass(posted 5 19 2009).
Here I want to suggest that since the failure of glass will always occur when the stress at the failure site equals the theoretical strength appropriate to the 'experimental' conditions' (~ 3 to 14 GPa), it is necessary to understand and KNOW all of the glass parameters at this stress. Because of the known non-linearities in some properties with stress or strain, it is suggested that certain properties of importance to the strength may be critically affected by such high stresses, e.g., increases in stress relaxation rate and or magnitude at these higher stresses at crack tips may result in higher strength. These properties should therefore be studied at high stresses as a function of composition.
2. Ratio of shear to volume flow during indentation and scratching.
(posted 5 19 2009).
Recent works by Roxel and Yoshida and others (Koike.... ) have shown that changes in glass composition can lead to changes in the relative amounts of shear and volume flow (compaction) that occur during indentation and scratching. Studies on the compaction of glasses (Bridgman, Mackenzie, Cohen, etc.) during the 1960's had showed that the amount of shear stress present during compaction had a very great effect on the amount of compaction that occurred. Studies of the compostion and indenter shape dependence of such behavior is therefore important.