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*University of Ulsan School of Naval Architecture and Ocean Engineering, Ulsan, Korea**Hyundai maritime Research Institute - Hyundai Heavy Industry Co. Ltd., Ulsan, KoreaKEY WORDS: Weld joints 용접연결부, Finite fatigue life 유한피로수명, Multiaxial fatigue 다축피로, Critical plane 임계평면, Critical distance method 임계거리법ABSTRACT: In this paper, the effects of irregular bead shapes on fatigue life were investigated. A modified S-N curve method was used to estimatethe fatigue life, which considered the inherent multiax iality caused by the geometrical feature produced by the weldin g process. The point method of the critical distance method was used to determine the fatigue effective stress. Three types of fillet joint models were tested in the fatigue experiments. For each model, real bead shapes were collected us ing a 3D laser scanner, and finite element analyses were perfor med. The results of the analyses with actual bead shapes were compared with those u sing an idealized bead shape model. The results of the present analytical methods showed good agreement with the experimental results.교신저자 양박달치: 울산광역시 남구 무거동 대학로 93, 052-259-2159, pdcyang@mail.ulsan.ac.kr본 연구는 2011년 대전에서 개최된 한국해양공학회 추계학술대회에 발표된 논문을 근간으로 하고 있음을 밝힙니다 .

*School of Naval Architecture and Ocean Engineering, Univ. of Ulsan, Ulsan, KoreaKEY WORDS: Local stress 국부응력, Fatigue effective notch stress 유효노치피로응력, Critical distance 임계거리, Finite fatigue life, 유한피로수명ABSTRACT: This paper analyzes the fatigue-life of welded joints using the notch stress approach. In the notch stress approach, the notch effects are usually approximated by introducing weld-bead parameters fo r the local detailed weld joints. The actual bead shape is comp lex and 3-dimensional. It may also greatly influence the fatigue strength. In this study, the welded shape was modeled using a 3D-scan ner. The critical distance method was adopted in the evaluation of the fatigue ef fective notch stress for the weldments. Fatigue life tests were performed to verify the present method of fatigue life estimation for two types of weld ed plates with longitudinal attachments. The estimated results of the present methods were applied to the results of the experiment. The results of t he analysis showed that the scatter of fatigue-life for the exp erimental data expressed in the nominal stress was significantly reduced by applying the effective fatigue stress of the present study.교신저자 양박달치: 울산광역시 남구 대학로 93, 052-259-2159, pdcyang@mail.ulsan.ac.kr

The notch effects on the fatigue strength of welded joints are both stress concentration and fatigue strength reduction. In the notch stress approach, t he notch effects are usually approximated by introducing weld-bead parameters for the local detailed weld joints. In this paper, well-known notch stress approaches - critical distance method, area method and fictitious rounding method are presented for the fatigue strength of cruciform joints. The estimated results of the present methods are applied to the experiments performed in this study and reported in the references. The results of the application show that the fatigue-life scatterness of the experimental data expressed in the nominal stress is significantly reduced by introducing the effective fatigue stress of the present study. ※Keywords: Notch stress analysis(노치응력해석), Fatigue effective notch stress(유효노치피로응 력), Fatigue strength of cruciform joints(십자형 용접 연결부 피로 강도)

This paper is concerned with the fatigue behaviour of welded joints by the notch stress approach. The actual welded shape is complex and 3-dimensional that may influence greatly the fatigue strength. The purpose of the paper is to pr esent a way of modelling the actual weld bead shape by using a 3-D Laser scanner for experim ental models of steel plates with longitudinal fillet welds, and applying its results to a proper notch stress method for the fatigue strength. The present approach to assess the fa tigue strength is quite promising with application to a variety of welded joints and effects of weld profiling to fatigue strength. ※Keywords: Notch fatigue analysis(노치피로강도), Bead shape modelling(비드형상모델링), Fatigue strength test for longitudinal-gusset plate(종거셋 판모델 피로 강도시험) 1. 서론 용접 연결부의 피로 강도평가는 현장과 관련된 설계 문제로 오랫동안 많은 관심을 받아왔다. 용접부는 응력집중 효과와 재질의 저하로 인해 강도상의 취약부가 된다. 피로강도평가의 높은 불확실성은 부재들의 용접과 열 영향을 통한 재질의 변화에 기인하는 것이지만 보다 근본적인 문제는 용 접수일: 2009년 5월 20일, 승인일: 2009년 7월 26일✝교신저자: pdcyang@mail.ulsan.ac.kr, ✝교신저자: 052-259-2159

Type A LPG Carrier is the ship using the low temperature independent cargo tank separate from the hull, which has various support structures fo r laying independent tanks on the hull. In this paper, the direct strength analysis for the support structures has been performed through the direct load analysis, load transfer, stre ss analysis and strength assessment. Also, a rational modeling method of support structu res has been proposed to obtain the dynamic load between the hull and the separate tank. ※Keywords: LPG carrier(LPG선), Support structure(지지구조), Direct strength analysis(직접강도해석), Fatigue strength analysis(피로강도해석), Dynamic response analysis(동적응답해석) 1. 서론 독립탱크 A형 LPG선은 저온의 액화석유가스를 운반하기 위해 선체와 분리된 저온식 독립화물탱크를 사용하는 선박으로서, 독립탱크를 선체에 탑재하기 위해 다양한 지지구조를 설치한다. 최근 접수일: 2008년 12월 18일, 승인일: 2009년 3월 17일✝교신저자: pdcyang@mail.ulsan.ac.kr, 052-259-2159 작용하는 하중이 크게 증가되어 이들 지지구조에LPG선의 대형화 추세에 따라, 탱크 지지구조에 대한 강도 평가가 중요해지고 있다. 특히, 선체와 화물탱크는 선체가 파랑에 의해 거동하는데 비해 화물탱크는 독립적이어서, 그 동적 거동이 다른 특성을 보이며 이를 지지하는 지지구조에 의해 이러한 동적 움직임이 전달되므로 지지구조에 대한 합리적인 해석 기법의 정립이 요망된다. 이 지지구조 중 상갑판과 화물탱크 사이에 설치되어 화물

We apply estimations of the intuitionistic fuzzy sets on the basis of which some amendments nay be undertaken. In particular, this paper describes the process of working out a university classes schedule.