• Journal of Welding and Joining
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• v.23 no.6
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• pp.18-28
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• 2005

본 일반 지침은 용접 이음부나 구조물의 피로강도 평가에 사용되는 기준응력 계산에 관한 내용으로 핫스팟 응력(Hot Spot Stress, 이하 HSS)이라고 칭하는 응력 평가용 해석 기술 및 관련 내용을 다룬다. 국제용접협회 (IIW: International Institute of Welding)발간 지침서의 주요내용에 대한 간략한 소개와 함께 대한용접학회 용접강도연구위원회의 Round-Robin 시험결과를 바탕으로 유한요소 응력해석 기반 용접 이음부의 HSS 평가 방법에 관한 내용을 정리하였다.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.4 s.148
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• pp.476-483
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• 2006

Fatigue strength assessments with two types of load carrying fillet weldment under out-of-plane bending load have been carried out by using both hot spot stress and structural stress methods. In this study, a derivation for the structural stress method using shell element models is discussed in detail. Finite element analysis using shell element models have been performed for the assessment of fatigue strength. As a result of the fatigue strength evaluation for load carrying transverse fillet weldment, hot spot stress method is found to be consistent with structural stress method and measurement. Hot spot stress, however, estimated for the load carrying longitudinal fillet weldment exhibit large variation with respect to mesh size and element type while the calculated structural stress for the longitudinal fillet weldment is relatively independent of mesh size. On the other hand, drawbacks and doubts associated with applying the structural stress method such as the guidance of virtual node method have been discussed.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.2 s.140
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• pp.129-135
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• 2005

At present, fatigue design of welded structures is primarily based on a nominal stress or hot spot stress approach with a series of classified weld S-N curves. Although well accepted by major industries, the nominal stress based fatigue design approach is cumbersome in terms of securing a series of S-N curves corresponding to each class of joint types and loading modes. The hot spot stress based fatigue design has a difficulty of finding a proper stress through the global model, the midium size model, and the detail model of ship structure. Also, it is difficult to link proper displacements within three different mesh size models. Recently, the structural stress is proposed as a mesh-size insensitive structural stress definition that gives a stress state at weld toe with relatively large mesh size. However, this method requires an experimental validation in obtaining the fatigue strength of weldments. Therefore, in this study, a series of experiment is performed for various sizes of weldments.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.1
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• pp.20-26
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• 2007

In this study, fatigue strength of load-carrying cruciform fillet welded joints were evaluated using a new method proposed by Yamada, for geometric or structural stress in welded joint, that is, one-millimeter stress below the surface in the direction corresponding to the expected crack path. Validity of the method is verified by analyzing fatigue test results for load-carrying cruciform welded specimens has different size of weld toe radius, leg length and plate thickness reported in literature. Structural stress concentration factor for 1mm below the surface was calculated by finite element analysis for each specimen respectively. When compared to the basic fatigue resistance curve offered by BS7608, the one-millimeter stress method shows conservative evaluation for load-carrying cruciform fillet welded joints.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.267-269
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• 2004

현재 구조물의 피로설계에는 주로 공칭응력(Nominal Stress) 및 핫스팟 응력(Hot Spot Stress, HSS)이 사용되고 있다. 공칭응력을 바탕으로 구조물에 대한 피로설계를 할 경우에는 각 부재에 사용되는 각각의 용접부 형상에 대한 피로시험을 따로 수행하여 피로수명 곡선을 구해야 하는 번거로움이 있다. (중략)

• Journal of the Society of Naval Architects of Korea
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• v.45 no.3
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• pp.296-302
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• 2008

Recently, a mesh-size insensitive structural stress definition (structural stress method) is proposed that gives a stress state at weld toe with a relatively large mesh size. The structural stress definition is based on the elementary structural mechanics theory and provides an effective measure of a stress state in front of weld toe. In this study, a fatigue strength assessment for a side shell connection of a container vessel using both the hot spot stress and the Battelle structural stress method was carried out. A consistent approach to compute the extrapolated hot spot stress for design purpose is described and current fatigue guidance is evaluated. Fatigue strength predicted by the two methodologies, e.g. hot spot stress and structural stress approaches, at hot spot locations of a typical ship structure are compared and discussed.

• Journal of Ocean Engineering and Technology
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• v.29 no.1
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• pp.45-55
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• 2015

Because of the high stress concentration near the toe of a welded joint, the calculation of local stress using the finite element method which is relevant to the fatigue strength of the weld toe crack, is a challenging task. This is mainly caused by the sensitivity of finite element analysis, which usually occurs near the area of a dramatically changing stress field. This paper presents a novel numerical method through which a less mesh-sensitive local stress calculation can be achieved based on the 3D solid finite element, strictly sticking to the original definition of hot spot stress. In order to achieve the goal, a traction stress, defined at 0.5t and 1.5t away from the weld toe, was calculated using either a force-equivalent or work-equivalent approach, both of which are based on the internal nodal forces on the imaginary cut planes. In the force-equivalent approach, the traction stress on the imaginary cut plane was calculated using the simple force and moment equilibrium, whereas the equivalence of the work done by both the nodal forces and linearized traction stress was employed in the work-equivalent approach. In order to confirm the validity of the proposed method, five typical welded joints widely used in ships and offshore structures were analyzed using five different solid element types and four different mesh sizes. Finally, the performance of the proposed method was compared with that of the traditionally used surface stress extrapolation method. It turned out that the sensitivity of the hot spot stress for the analyzed typical welded joints obtained from the proposed method outperformed the traditional extrapolation method by far.

• Proceedings of the KAIS Fall Conference
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• 2011.05b
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• pp.832-835
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• 2011

최근까지 용접구조물의 피로설계는 용접품질 수준에 따라 공칭응력 또는 핫스팟 응력에 의한 S-N선 도로부터 수행하였다. 본 연구에서는 유한요소망의 크기에 덜 민감하면서 기존의 하중모드형식, 두께 효과 및 용접결합형식에 상관없는 등가구조응력(E2S2) 접근법을 이용한 Master S-N선도로부터 철도차량 대차프레임의 피로수명을 평가하고자 한다. 또한 합리적인 철도차량 용접대차프레임의 피로해석 연구일환으로서, 다축피로조건인 EN규격의 피로시험조건하에 이의 피로수명을 평가하고자 한다.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.4 s.142
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• pp.388-395
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• 2005

A numerical procedure is proposed as a mesh-size insensitive structural stress definition that gives a stress state at a weld toe with relatively large mesh size. The structural stress values obtained using different finite element types, i.e. shell element and solid element, are examined for typical weld structures. The calculation procedures are performed using the balanced nodal forces and moments obtained from finite element solutions. A consistent formulation based on work equivalent argument has been implemented to transform the balanced nodal forces and moments from shell to line force and line moments at each nodal position. The mesh-insensitivity, the effect of distance $\delta$(where the stress is calculated) and the potential limitations of the structural stress method are examined for various types of weldments. Based on the results from this study, it is expected to develop a more precise stress estimation technique for fatigue strength assessment of welded structures.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.1
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• pp.26-33
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• 2014

In this study, Non-load-carrying EH Grade steels in fillet welded joints were evaluated with both the hot spot stress method and the 1mm stress method. The thickness effect criterion for fatigue strength evaluation of welded of welded steel structures recommendations of the IIW was used to evaluate the fatigue strength of EH40 and EH36 and Both EH40 and EH36 have been compared with FAT 125 curve recommended in the IIW. Furthermore, fatigue strength of the welded tow and the ground conditions for Non-load-carrying EH36 based on the 1mm stress method has been discussed.