| [연구논문]비드형상 및 복수 표면균열의 확률적 특성을 고려한 필릿 용접부 피로수명 평가 |
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| Fatigue Life Estimation of Fillet Welded Joints Considering Statistical Characteristics of Weld Toe's Shape and Multiple Collinear Surface Cracks |
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Seung-Ho Han, Jeong-Woo Han |
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| Abstract |
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The fatigue life of welded joints is associated with crack initiation and propagation life. Theses cannot be easily separated, since the definition of crack initiation is vague due to the initiation of multiple cracks that are distributed randomly along the weld toes. In this paper a method involving a notch strain and fracture mechanical approach, which considers the characterisitics of welded joints, e.g. welding residual stress and statistical characteristics of multiple cracks, is proposed, in an attempt to reasonably estimate these fatigue lives. The fatigue crack initiation life was evaluated statistically, e.g. the probability of failure occurrence in 2.3, 50 and 97.7%, in which the cyclic response of the local stress/strain in the vicinity of the weld toes and notch factors derived by the irregular shape of the weld bead are taken into account. The fatigue crack propagation life was simulated by using monte-Carlo method in consideration of the Mk-factor and the mechanical behavior of mutual interaction/coalescence between two adjacent cracks. The estimated total fatigue life, (Nr)p50%, as a sum of crack initiation and propagation life under the probability of failure occurrence in 50% showed a good agreement with the experimental results. The developed technique for fatigue life estimation enables to provide a quantitative proportion of crack initiation and propagation life in the total fatigue life due to the nominal stress range, △S. |
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