オーステンパ球状黒鉛鋳鉄の疲労における切欠感度

概要

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Tensile fatigue tests were performed on smooth and notched specimens of a ferritic (FDI) and an austempered ductile iron (ADI). Stress to number of cycles to failure curves were measured, and a notch factor, K_f, was determined from the static strength to fatigue limit region at 5×10^6 cycles. In FDI, K_f is much lower than the form factor, α_e, of the notches, but in ADI, it was close to α_e. The notch sensitivity factor η in AID is 0.6-0.9 while it is 0.2 in FDI, indicating very high notch sensitivity of ADI. The results were discussed in terms of the over sressed depth (δ) concept estimated from the stress distribution at the notch root and the fatigue strength of smooth specimens. The δ is 0.1-0.2 mm in ADI while it is 0.5-1 mm in FDI. Macroscopic and SEM fractography were also performed, and the high notch sensitivity was attributed to the brittle and defect-sensitive ausferrite matrix.
一般社団法人日本機械学会の論文
1994-07-25