Slow fracture model based on strained silicate structures

Journal Article · Thu Nov 15 04:00:00 EST 1984 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.333789· OSTI ID:6140870

Michalske, T A; Bunker, B C

Slow crack growth data, molecular-orbital calculations, and vibrational spectroscopy results are used to develop an atomistic model for environmentally controlled fracture of silica glass. The model is based on chemically active bond defects generated by the strain field of the crack tip. Molecular-orbital results suggest that bond angle deformations are most effective in increasing the chemical activity of the Si--O--Si bond. Vibrational spectra identify silica polymorphs containing highly strained bonding configurations. A comparison of strained bond reactivity with crack growth results shows that strained silica polymorphs can be used to model the crack tip chemical reactions controlling slow fracture. Based on model complexes, a two-dimensional fracture model involving kink site nucleation and motion is developed. The model shows that the stress intensity dependence of the crack growth rate is controlled by the energy required to form chemically active defects in the silica structure. The absolute rate of fracture depends on the combined rates of active bond formation and chemical attack at strain induced defects. Crack growth data suggest that for silica, strain activation occurs prior to the adsorption of environmental chemicals.

• Research Organization: Sandia National Laboratories, Albuquerque, New Mexico 87185
• OSTI ID: 6140870
• Journal Information: J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 56:10; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
ADSORPTION
CHALCOGENIDES
CHEMICAL BONDS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CORROSION
CRACK PROPAGATION
CRACKS
ENERGY LEVELS
EXCITED STATES
FAILURES
FRACTURE MECHANICS
FRACTURES
GLASS
KINETICS
MATHEMATICAL MODELS
MECHANICS
MINERALS
MOLECULAR ORBITAL METHOD
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
SILICA
SILICATES
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
STRAINS
STRESS CORROSION
SURFACES
VIBRATIONAL STATES