A new method for fracture toughness determination of ceramic balls is presented. The starter crack is introduced into the surface of the ball by a Knoop indentation followed by grinding off the deformed zone. The loading through surface tensile stresses is realized by water quenching, i.e. dropping the heated ball into water. The temperature difference is stepwise increased to find the critical temperature difference for the initiation of crack growth. The geometric factor is calculated in a parametric finite element study, whereas the temperature distribution in the ball was previously determined by using the Biot concept. Combining experimentally measured critical temperature differences for different cracksizes and ball diameters with numerical results of the geometric factor, the fracture toughness of the silicon nitride balls is evaluated. For the evaluation, the knowledge of several material properties (e.g. the CTE) and other parameters is necessary, which have influence on the precision of the measurement. The overall measurement uncertainty is estimated to be about ± 10 %, what roughly corresponds to the value determined with standard measurement procedures. There is an excellent agreement with published fracture toughness results of these balls determined by the modified Surface Crack in Flexure procedure.

提出了一种确定陶瓷球断裂韧性的新方法。通过努氏压痕将起子裂纹引入球的表面，然后将变形区域磨掉。通过水淬，即将加热的球滴入水中，可以实现通过表面拉应力的加载。逐步增加温度差，以找到引发裂纹扩展的临界温度差。几何因子是在参数有限元研究中计算的，而球中的温度分布以前是使用Biot概念确定的。将针对不同裂纹尺寸和球直径的实验测得的临界温度差与几何因子的数值结果相结合，可以评估氮化硅球的断裂韧性。为了进行评估，需要了解几种材料特性（例如CTE）和其他参数，这些特性会影响测量的精度。总体测量不确定度估计约为±10％，大致与标准测量程序确定的值相对应。与这些球的已公布的断裂韧性结果完全一致，这些结果是由改进的“挠曲中的表面裂纹”程序确定的。