Premium
Dynamic Fatigue of Treated High‐Silica Glass: Explanation by Crack Tip Blunting
Author(s) -
HIRAO KAZUYUKI,
TOMOZAWA MINORU
Publication year - 1987
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1987.tb05654.x
Subject(s) - materials science , composite material , crack growth resistance curve , crack closure , growth rate , fracture (geology) , stress (linguistics) , indentation hardness , fracture mechanics , microstructure , linguistics , philosophy , geometry , mathematics
In previous papers, it was shown that when abraded high‐silica glass is soaked in hot water or annealed in air, its crack tip becomes blunt. The dynamic fatigue characteristics in various liquids of high‐silica glass with different treatments were examined. The stress rate dependence of fracture strength was determined for freshly abraded samples and for abraded and soaked (in hot water) or heat‐treated samples, in water, hydrazine, formamide, and acetonitrile. The stress rate susceptibility of the fracture strength was represented by the commonly used n value. Freshly abraded samples exhibited approximately the same low n values for all the liquids, which is consistent with the slope of the slow crack growth data. Treated samples, on the other hand, showed a slightly larger n value in water and extremely large n values in nonaqueous liquids. When the crack tip is sharp, only slow crack growth is involved in the fatigue. When the crack tip is blunt, crack initiation is involved in addition to the crack growth. The equation of dynamic fatigue based upon slow crack growth was modified to incorporate this effect of crack initiation and was applied to the present experimental results. The analysis showed that the crack initiation stress is stress rate dependent in water and is stress rate independent in nonaqueous liquids. This conclusion was supported by the crack initiation behavior observed using the microhardness indenter.