On the Stress in Service Condition and Fatigue Strength of Propeller Blade on the High-Speed Twin-Screw Container Ship

Abstract

In recent years, considerable attention has been given to the fatigue strength of ship propeller to establish a reasonable design standard.
The authors carried out the strain measurement of high-speed twin-screw propeller in service condition, and conducted fatigue tests with the corroded fatigue specimens. The fatigue life of the propeller was discussed by using the stress-frequency curve and the fatigue results.
The following conclusions may be drawn from the results of this work;
(1) The blade stress conditions were as follows;
mean stress and stress amplitude were 3.3±2.6 kg/mm² in ordinary navigation, in transient state on turning, however, the stress amplitude became up to ±4.4 kg/mm².
(2) The stresses obtained in this measurement were good agreement with the stresses which were calculated under the load condition of blade estimated by using the torque and thrust taking account of axial wake distribution.
(3) The fatigue results on corroded specimen under varying stress amplitude showed that the fatigue damage was caused by the stress amplitude being lower than the fatigue limit, and the S-N curve was on a partly shorter side of the fatigue lives explained by the modified Miner's rule.
(4) The fatigue life of the blade was predicted by using the results of the fatigue test and the stress-frequency distribution from the measurements.
It was known that the fatigue life using the modified Miner's rule on semi-logarithmic plotting of S-N diagram was nearly equal to the failed blade life.