船体構造部材の疲労強度

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Using the Miner's theory and the most probable largest load spectra in which the ship will experience during 10^8 wave encounters on the ocean sea, the fatigue criterion for ship structural members was proposed in order to secure against fatigue fracture. The following allowable tensile stress σAL may be given when mean results according to ordinary S-N_c curves for mild steel are used. σAL=σ_a+0.8/K_tσ_m=f_2 (1.5f+29/K_t) =f_2/K_t (8f+27) Kg/mm^2 where, K_t=stress concentration factor (K_t-values are not to be regarded as absolute values, but as relative values calibrated from experience for structural members) σ_a=stress amplitude (wave bending stress at a probability level of Q=10^-4) σ_m =mean stress (still water bending stress) f=usage factor defined as the cumulative fatigue damage ratio summed over a period of 20 years. f_2=σB/σBM (σBM; teusile strength of mild steel σB ; teusile strength) The above allowable stress for fatigue fracture was applited to the longitudinal and the transverse strength members.
社団法人日本船舶海洋工学会の論文
1977-06-30