オーステンパ球状黒鉛鋳鉄の高サイクル疲労に及ぼす表面硬さの影響

概要

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Rotating bending high-cycle fatigue tests were carried out on austempered ductile cast iron (ADI) specimens with different levels of surface hardness. Special attention is paid to the relationship among the surface hardness, shape of S-N curve and fracture mode transition. For the specimen with Vickers hardness H_v<400, the S-N curve is of two-step bending type, similar to that of high-strength steel. That is, a surface-initiated crack dominates the fatigue process for short fatigue life, while so-called fish-eye pattern fractures or internally initiated cracks control the fatigue process in the very long fatigue life region of N_f>10^7. In contrast, the specimen with H_v>400 shows a typical S-N curve of single bending type. This means that increasing H_v shortens the initiation life of the internal crack and results in the fish-eye pattern occurring even for shorter fatigue life.
一般社団法人日本機械学会の論文
1996-03-25