Fatigue crack growth has been studied in self-reinforced gas pressure sinte
red silicon nitride (GPS Si3N4) using four-point bending of indented sample
s (indentation flexure fatigue - IFF) at room temperature under static and
cyclic conditions. The method is simple, cost-effective, material and time
saving, and produces stable crack growth. However, the analysis requires an
estimation of the residual stress intensity factors produced by the indent
ations and assumptions about the shape of the indentation flaws to calculat
e the applied stress intensity factors. Crack growth parameters were calcul
ated assuming a Paris's power law dependence. It was found that crack growt
h resistance was significantly reduced under cyclic loading due to the wear
of the bridging ligaments in the crack wake. In the case of static fatigue
, the resulting Paris's exponent was compared with the value obtained from
the dynamic fatigue constant stress rate testing in 4-point bending using d
ifferent loading rates. The crack growth mechanisms were identified using s
canning electron microscope and have been correlated to the results of the
fatigue tests.