| Influence of density, Youngs modulus, temperature and other experimental
variables on strength and fracture toughness of reaction
bonded silicon nitride (RBSN) was studied. Fractographic study was
made to identify the nature of flaws. The density dependence of
strength could be expressed through proposed empirical equations.
Strength of RBSN was proportional to Youngs modulus. In the
range RT-1400°C some RBSN had constant strength, while others
had a peak in strength at 1200°C followed by degradation at 1400°C.
The density dependence of fracture toughness could be expressed
through some equations. Fracture toughness of RBSN had direct
dependence on strength and Youngs modulus. High temperature
fracture toughness and strength were directly dependent on each
other. Fracture toughness of RBSN at RT increased as notch tip
radius was increased in the range 79-225 fm, but it did not show any
systematic variation as the normalized notch length was varied. |
