Fatigue Life and Peneration Behaviour of Material under Combined Tension and Bending Stress

J. Ocean Eng. Technol. 1994;8(1):41-49.

인장 굽힘피로를 받는 부재의 피로수명과 균열관통

남기우

부산수산대학교 재료공학과

Keywords: Leak Before Break(LBB), Estimation Method of Stress Intensity Factor after Penetration, Eccentricity, Surface Crack, Combined Tension and Bending Stress

핵심용어: 파단전누실, 관통후 응력확대계수 평가법, 편심량, 표면균열, 조합된 인장과 굽힘응력

Abstract

The leak-before-break(LBB) design on the large structures such as ship's hull, tank structure, pressure vessels etc. is one of the most inportant subjects for the evaluation and the assurance of safety. In these structures, various loads are acting. In some structural members, therefore, out-of-plane stress due to bending often may become with in-plane stress due to stretching. In the present report, the characteristics of fatigue life and peneration behaviour from a surface cracked plate under combined tension and bending have been studied experimentally and analytically by using eccentricity. Estimation of fatigue crack growth was done with the Newman-Raju formula before penetration, and with the stress intensity factor after penetration proposed by the author. Calculated aspect ratio showed the good agreement with the experimental result. It was also found that particular crack growth behaviour and crack shape after penetration can be satisfactorily evaluated using the K solution proposed.