Filtern
Erscheinungsjahr
- 2019 (4) (entfernen)
Dokumenttyp
- Zeitschriftenartikel (2)
- Vortrag (1)
- Posterpräsentation (1)
Sprache
- Englisch (4) (entfernen)
Schlagworte
- Elastic constants (2)
- Glass (2)
- Microhardness (2)
- Soda-lime-silica glass (2)
- Water content (2)
- Crack growth (1)
- Soda-lime-silica (1)
- Stress intensity factor (1)
- Subcritical crack growth (1)
- Vickers (1)
Organisationseinheit der BAM
- 5 Werkstofftechnik (4) (entfernen)
Eingeladener Vortrag
- nein (1)
The effect of structural water on density, elastic constants and microhardness of water-bearing soda-lime-silica glasses of up to 21.5 mol% total water is studied. It is found that the Poisson ratio and the water content are positively correlated, while density and the elastic moduli decrease with increasing water content. Vickers hardness decreases by approximately 27% from the dry to the most hydrous glass. For water fractions <3 mol%, the dependencies are non-linear reflecting the non-linear change in the concentrations of OH and H2O molecules dissolved, whereas for water fractions >3 mol% linear dependencies are found. To distinguish the effect of structural water and environmental water, indentations were performed in toluene, nitrogen gas and air. Timedependent softening was evident for testing dry glasses in humid atmospheres as well as for tests of hydrous glasses in dry atmospheres. This indicates that the response times of dissolved water species are effectively equal in both scenarios.
Due to the stochastic nature of crack nucleation by Vickers indentation, a statistical analysis of propagation rates of 185 radial cracks was performed. Crack growth was observed directly using a video camera with high Image acquisition rate. It is found that propagation rates are controlled by the environmental reactions at the crack-tip shortly after their initiation (< 1 s). Calibration of the stress intensity KI showed that the residual stress factor χ and the exponent n of the equation KI==χPc−n (with P==load and c==crack length) are broadly distributed among the 185 analyzed cracks, ranging from 10−16 to 104 and from 0.1 to 5, respectively. For the most frequent crack, the equation KI==0.052Pc−1.47 holds. The results show that correlations of indentation-induced crack length to stress intensity necessitate the use of statistical significant data that are calibrated by the environmental reactions at the crack-tip.