Fatigue Strength as a Function of Preloading in Dynamic Fatigue Testing of Glass and Ceramics

Abstract

The solution of fatigue strength as a function of preloading in dynamic fatigue (constant stress-rate) testing was obtained analytically and numerically. The effect of preloading on dynamic fatigue strength decreases with increasing fatigue parameter (n), and for n ≥ 20 the effect is negligible up to a preloading of 90 percent. The solution was verified by dynamic fatigue experiments conducted with soda-lime glass and alumina specimens in room-temperature distilled water. This result showed that one can apply a preloading corresponding up to 90 percent of fatigue strength for most glass and ceramic materials, resulting in a dramatic saving of testing time in dynamic fatigue testing. The key feature that makes this technique feasible is that most of the slow crack growth under dynamic fatigue loading occurs close to failure time where the dynamic fatigue strength is defined.