鍛造コンロッドのクラッキング工法における機械加工割り溝の開発 : —凹み列単体と複合溝の破断特性の基礎的検討—

概要

論文の詳細を見る
For the separation of a connecting rod by application of fracture splitting, it is crucial that the split surface undergoes brittle fracture by impact, in view of reintegration and positioning accuracy. It is possible for a notch in a sintered steel rod to be mechanically grooved as a fracture initiation, but it is not applicable to a forged rod due to its brittleness. The purpose of this study is to establish a notch by mechanical processing to replace the presently employed laser scribing method. The feasibility of this technique was preliminarily investigated with respect to a proposed hybrid groove structure. The hybridized groove is an array of dents, formed using needle tools, located at the bottom of a V-notch, and is expected to make the splitting process easier. Fracture behaviors were evaluated and optimized through Charpy impact test and scanning electron microscopy using C70S6 steel samples. It was clarified that brittle fracture is much enhanced by the addition of an array of dents. The results were compared to the conventional laser scribing method. Finally, the compatibility of the proposed splitting technique is discussed with respect to the distortion of a split crank bore and the tool life used in a post-processing boring finish.