On the dimensional analysis for the creep rate prediction of ceramic fibers

Abstract

A novel semi-empirical equation for the steady-state creep rate description of ceramic fibers is here proposed. Dimensional analysis was applied to identify the relationship between the variables related to the creep rate. Besides the variables known from the Arrhenius creep equation, a temperature factor that accounts for changes with the temperature was also taken into consideration. The resultant equation shows that the creep rate is proportional to the temperature, applied stress and two material constants, as well as inversely proportional to the fiber grain size. The two material constants k and C described in the equation can be easily determined by creep tests at different temperatures under the same applied stress. Therefore, this equation can be more efficiently applied to predict the creep rate of ceramic fibers under different applied stresses and initial grain sizes. To confirm this, the proposed equation was used to fit the creep rate data set of two ceramic fibers, Nextel 720 and CeraFib 75. In summary, the equation provides a good fit (adjusted R-squared up to 0.97) and prediction for the experimental data of tests with different temperatures, applied stresses and initial grain sizes.