Crack growth and splitting failure of silicon nitride ceramic balls under cyclic pressure loads

In order to examine the splitting failures of silicon nitride balls under cyclic pressure loads, fatigue tests of pre-cracked balls were carried out. The cracks of initial length ranging from 0.260 to 0.290 mm were observed under different stress ratio conditions and the effects of stress ratio and residual stress on the fatigue strength were investigated. Furthermore, the initial threshold limit of the equivalent stress intensity factor range (ΔKeqth) was measured.