| Popis: |
A new model of ceramic creep in four point bending is proposed to determine the tensile creep rate which is difficult to test. Based on the assumption that ceramics creep only in tension and there is no creep in compression, the tensile creep rate of six ceramics is calculated in a simple way. The six ceramic compositions SiC, Al2O3/SiC, Mullite, Al2O3/Si3N4, Sialon and TZ-6Y, were subjected to a constant load which corresponded to initial maximum stress level of 135 MPa in four point bending. All test were performed at 1100°C for about 180 min. which is a time showing a steady short-time transient creep. Certain levels of creep, in terms of measured displacement, were observed in all the tested materials. The experiment shows that the lowest level of creep among the tested materials is in SiC, the highest is in TZ-6Y. The creep rate is expressed in terms of measured displacement and the calculated tensile creep rate at the apparent steady state is given for all tested materials. |
