A number of optically important materials such as ZnS, SiO2, SiO2-TiO2, GaAs, and heavy metal fluoride (e.g., ZBLAN) glasses are subject to moisture- and/or liquid water-induced crack growth. A notable exception to this behavior appears to be Si. Such environmentally enhanced crack growth can lead to ultimate failure in service at stresses well below those expected from normal strength tests. The sensitivity of a material to water can be obtained by determining a crack growth parameter, N. This parameter can be combined with other easily obtainable fracture information which include measures of the strength and strength distribution to create a lifetime design diagram using fracture mechanics concepts. Methods for determining these fracture parameters including direct crack growth measurements and dynamic fatigue are reviewed, and the influence of environmental water on the materials is discussed. Crack growth mechanisms including physical (dielectric) and chemical reaction mechanisms are discussed, and lifetime design diagrams which can be used to determine stress levels in service are presented.
[1]
B. J. Pletka,et al.
A comparison of failure predictions by strength and fracture mechanics techniques
,
1982
.
[2]
T. Michalske,et al.
A Molecular Mechanism for Stress Corrosion in Vitreous Silica
,
1983
.
[3]
J. J. Mecholsky,et al.
Influence of Microstructure on Crack Propagation in ZnSe
,
1975
.
[4]
E. Fuller,et al.
Environmentally Enhanced Crack Growth in Soda-Lime Glass
,
1985
.
[5]
R. Cook,et al.
Effect of microstructure on reliability predictions for glass ceramics
,
1986
.
[6]
S. Freiman,et al.
Crack propagation in alkaline‐earth fluorides
,
1978
.
[7]
E. Fuller,et al.
Theory of Fatigue for Brittle Flaws Originating from Residual Stress Concentrations
,
1983
.
[8]
S. Freiman.
Brittle fracture behavior of ceramics
,
1988
.