Effects of residual stress on crack growth of silicon nitride balls under cyclic pressure loads

Abstract

In order to examine the mechanism of splitting failures of silicon nitride balls under cyclic pressure loads, we carried out the fatigue tests of pre-cracked balls. In our previous works, we discovered that splitting failures of the balls were caused by pre-cracks which were initiated on their equators by Vickers indenter. In the present work, in order to further investigate this phenomenon, we carried out fatigue tests of two size balls (4.762mm and 9.525mm). We focus on the growth behavior of cracks whose initial length ranged from 0.260 to 0.290&mu;m and discuss about the effects of ball diameters on the fatigue strength. Based on the empirical features of the two balls, we found that the initial threshold limits of the equivalent stress intensity factor ranges &utri;<i>K_eq</i> for each ball were different. In order to look into this, we measured the residual stresses using the X-ray stress measuring method.