Low-Cycle to Ultrahigh-Cycle Fatigue Lifetime Measurement of Single-Crystal-Silicon Specimens Using a Microresonator Test Device

The authors used a ramping-amplitude fatigue-test method to perform low-cycle fatigue tests in micrometer-sized single-crystal-silicon specimens using a resonant-type fatigue-test device. Very short delayed fractures from 4 ms to 29 s were observed by controlling the amplitude ramping rates with two self-oscillation electric circuits and different parameters. These lifetimes were converted to corresponding constant-amplitude lifetimes from 101 to 105 cycles using the relationship derived from a crack-growth analysis. S-N plots of measured lifetimes exhibited the transition of fatigue lives at the high-cycle region with a crack-growth exponent of 18.0, to the static fracture strength of 6.50 GPa at the low-cycle region corresponding to the original crack length of 7.9 nm. The existence of a very rapid fatigue fracture within 1 s was confirmed. From the obtained crack-growth parameters, the evolution of crack length and the effects of humidity were discussed.