セラミック工具の強度信頼性に関する破壊力学的研究 : アルゴリズムの提案と初期欠損の解析例

概要

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The subject of this study is to determine the strength reliability of ceramic cutting tools on the basis of the fracture mechanics concept. An algorithm for the application of the linear fracture mechanics theory is proposed to analyze the brittle failure of the ceramic tools. According to the algorithm, the boundary curve between safe and dangerous zones is determined in terms of critical cutting force and the critical crack length above which the early fracture of the cutting tool is caused by unstable crack propagation for given cutting conditions and the mechanical properties of the tool material. It was found that the critical cutting force increases as the fracture toughness KIC of Al2O3 ceramic tool increases and as the angle of resultant cutting force increases. The cutting edge encounteres a more dangerous situation in the state of concentrated force at the tip of the cutting edge than that of distributed force along the rake face of the tool. The safe zone of Al2O3 tool was also found to be reduced to about one third of that of WC-Co tool.