オーステンパ球状黒鉛鋳鉄の疲労強度に及ぼす油環境の影響

概要

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In a fundamental study on austempered ductile iron, rotating bending fatigue tests were conducted with respect to environment durability. The S-N curve in this environment showed a tendency toward low fatigue limit. Fatigue fracture in high cycles was verified by changing the viscosity of grease. However, the typical fish-eye in the long-life region ( >10^7 cycles) was not observed on the fracture surface. When a low viscosity of grease penetrates into the cracks, crack propagation accelerates due to the wedge effect. The surface is brittle locally, because martensite in the matrix structure is formed by the work hardening process mentioned above. It is suggested that fatigue strength will be lower with the use of oils, because cracks initiate easily from martensite parts.
一般社団法人日本機械学会の論文
1995-10-25