ショットピーニング処理フェライト・パーライト球状黒鉛鋳鉄の長寿命域高サイクル疲労特性

概要

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Rotating bending fatigue tests were carried out on specimens of ferrite-pearlitic ductile cast iron (FPDI) with a shot peening (SP) treatment. In addition, influences of the SP treatment on the fracture mechanism have been investigated, and changes in initial residual stress were discussed. As sesults, the S-N diagram showed a two-step bending behavior in long life region over 10^7 cycles. The surface hardened layer and the compressive residual stresses were observed more than 300 μm from the surface. Furthermore, the sites of the fatigue crack initiations were transferred from the surface to subsurface over 10^7 cycles region. Form the observations of the fracture surface before 10^7 cycles it was clarified that the fatigue crack initiated at the surface. In this case, the compressive residual stress became smaller by cyclic loading. However, the crack initiation sites on long life regions were casting defects which exist over 300 μm from the surface. And the fatigue strength of a horizontal part at 10^e〜10^7 cycles was dependent on surface hardness.
一般社団法人日本機械学会の論文
1999-10-25