破壊力学に基づく浸炭歯車の強度評価に関する研究 : 第4報, 疲労き裂の進展に注目した曲げ強度評価法の提案

抄録

The bending fatigue strength of gears is quite sensitive to the qualities of the tooth root surface, such as roughness, heat treatment procedure and the properties of the gear materials. Howaver, in the conventional evaluation method for bending fatigue strength of gears, the influence of these qualities is not considered clerly. In this research, a method to evaluate the strength of carburized spur gear teeth is presented based on fracture mechanics. Under the assumption that the procedure of tooth fatigue breaking is that of crack growth the initial crack length, the length before the tooth was loaded, is calculated from the results of tooth bending fatigue experiments. Although the initial crack length is longer under a lower load used in the experiments, there is a limit on the initial crack length depending on the qualities of the tooth root surface. The bending fatigue strength can be determined by comparing the limit of initial crack length with the threshold crack length, which can be treated as a function of hardness for the carburized gear.