回転曲げ疲労下における鋼の寿命解析

概要

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The lives required for crack initiation and crack growth should be separately dealt with in fatigue life prediction. The crack growth life estimated on the basis of the da/dN-ΔKε relationship exhibits a steeper slope on the log Δε/2-log N_P diagram than that in the experiment, where da/dN and ΔKε are crack growth rate and strain intensity factor range, and N_P is life required for crack growth. The da/dN-ΔKσ and da/dN-ΔKε relationships show the stress dependency, unless crack closure is considered, where the strain intensity factor range is denoted as ΔKε. This, however, disappears in the da/dN-EΔKε_<eff> relationship where ΔKε_<eff> is the effective strain intensity factor range. Furthermore, the crack growth life curve determined from the da/dN-ΔKε_<eff> relationship agrees well with the test data. The crack-initiation-to-final-failure-life ratio shows the stress dependency, ranging from 0.4 to 0.6, in the high-cycle-fatigue region under rotation bending. Consequently, we can predict the EΔε/2-N_f curve by combining the stress dependency of the crack initiation life and the da/dN-EΔKε_<eff> relationship under rotation bending.
一般社団法人日本機械学会の論文
1991-06-25