Preloading technique in dynamic fatigue testing of class and ceramics with an indentation flaw system

The solution of fatigue strength as a function of preloading in dynamic fatigue testing was obtained numerically for an indentation flaw system. The dynamic fatigue strength is dependent on preloading and fatigue parameter (n). The effect of preloading on dynamic fatigue strength decreases with increasing fatigue parameter: for n greater than or equal to 20 the effect is negligible up to a preloading of 90%. The solution was verified by dynamic fatigue experiments conducted with soda-lime glass and alumina specimens with as-indented flaws in room-temperature distilled water. The result indicates that one can apply a preloading corresponding up to 90% of fatigue strength for most glass and ceramic materials with no change in fatigue strength, resulting in a dramatic saving of testing time.