オーステンパ処理球状黒鉛鋳鉄円筒の高サイクル内圧疲労挙動におよぼす鋳造欠陥の影響

概要

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We carried out internal pressure tests on a large number of thin wall cylinders of austempered ductile iron (ADI), and investigated the influence of the casting defects on fatigue life distributions. As a result, it was observed that the fatigue life distributions at low-pressure levels were divided into two groups : a short-life group below 1×10^6 cycles and a long-life group fractured at near 1×10^7 cycles. After the SEM observation of the fracture surface around the casting defects, the short-life group showed significant roughness, and the long-life group tended to be flat ; it was supposed that the fracture mechanisms of the two were different. Specifically, in the short-life group, a proportional relationship was observed between the initial stress intensity factor of the casting defect and the fatigue life on the double log scale. It is apparent that crack propagation of the short-life group was caused under the Stage 2 process in which the Paris law was effective.
社団法人日本機械学会の論文
1992-11-25