舶用プロペラ翼の疲労強度に関する研究-2-プロペラ翼の許容欠陥寸法と探傷範囲

概要

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An ultrasonic flaw detection technique has been successfully developed for the purpose of detecting internal flaw of marine propellers. When the technique is applied to an actual propeller, it must be decided what size of flaw is allowable and what area of blade should be detected. In this report, the following analysis and calculation have been developed for these purposes. (1) Whether fatigue crack will be more progressive from the flaw of propeller blade or not is analyzed by using linear-elastic fracture mechanics and the value of ΔKth of the propeller material. (2) The largest allowable dimensions of flaws are calculated at several conditions of stress, blade thickness and aspect ratio. (3) The stress distribution on the propeller blade in wake flaw is calculated by using unsteady lifting surface theory. The area should be detected flaws is decided from the distribution of critical flaw size for each propeller.