In this paper, push-pull fatigue tests of notched specimens under R = — 1, 0 and 0.5 were carried out on annealed 0.1% carbon steel with the Vickers hardness Hv = 105 and quenched-tempered 0.5% carbon steel with HV = 582. The fatigue limit of a long crack, σ W2 was obtained from that of a notched specimen with a sharp and deep notch whose radius is smaller than the branch point ρ 0. Using the present and past σ W2 data, the effect of the positive mean stress on the ΔKw of the long crack was evaluated by using 3.2HB (≃ σ B) and σ s/(3.2HB), where ΔKw is the stress intensity factor range for the purpose of predicting the fatigue limit of a metal with an arbitrary crack, σ s is the lower yield stress or 0.2% proof stress, σ B is the ultimate tensile strength and HB is the Brinell hardness. Although the σ W2 decreased with the mean stress, σ W2 was cut off by the threshold stress σ W2 of the plastic deformation at crack tip. For the quantitative prediction of the fatigue limit of a cracked steel with an arbitrary crack length under a positive mean stress, he σ W2 and σ we values were approximated with simple formulae.
|Number of pages||8|
|Journal||Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A|
|Publication status||Published - 2004|
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering