A study on the type-b hot spot stress
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RESEARCH PAPER
A study on the type-b hot spot stress Norio Yamamoto 1 & Tomohiro Sugimoto 1 & Kinya Ishibashi 1 & Satoyuki Tanaka 2 Received: 8 December 2019 / Accepted: 15 July 2020 # International Institute of Welding 2020
Abstract Stress distributions in the vicinity of type-b hot spot in the in-plane gusset welded joints and in the free edge of the stiffened cruciform welded joints were evaluated according to the solid model, the fine mesh shell model, and the coarse mesh shell model. The hot spot stress (HSS) of each FE model was evaluated by extrapolating the stresses at the read out point (ROP) to the hot spot position according to the recommendations of IIW and were compared. Regarding the in-plane gusset welded joints, it is confirmed that the HSS by the solid model and the shell model are corresponding in the case of in-plane notch in which the thicknesses of the main plate and the gusset plate are same. It is observed that the shell model estimates lower HSS than that by the solid model when the main plate is thicker than the gusset plate. The reason of this difference is considered that the shell model does not evaluate the stress distribution in the thickness direction of the main plate in front of the in-plane gusset plate but evaluate the averaging stress. A simple correction factor to the HSS evaluated by the shell model based on the ratio of both plate thicknesses was examined. Regarding the free edge of the loaded attached plate in the stiffened cruciform welded joints, it is confirmed that the hot spot is on the corner edge of the attached plate. It is observed that the shell model estimates lower HSS than that by the solid model. Keywords Hot spot stress . Type-b . In-plane gusset welded joints . In-plane notch . Free edge . Solid model . Shell model
1 Introduction When assessing fatigue strength, a nominal stress, a HSS, or a notch stress is used according to the way of assessment. In the fatigue assessment of ship structures, an HSS approach is commonly used [1] because ship structures consist of plates stiffened by web and frame and the hot spots are usually at the welded joints in the complex structure. In general, the HSS is evaluated based on the shell element model with relatively coarse mesh closed to the relevant plate thickness. HSS is an engineering stress, which considers a stress concentration due to the structural discontinuity excluding a stress concentration due to the weld. The definition of HSS, the procedure of Recommended for publication by Commission XIII - Fatigue of Welded Components and Structures * Norio Yamamoto [email protected] 1
Hull Rule Development Department, Nippon Kaiji Kyokai, 3-3, Kioi-cho, Chiyoda-ku, Tokyo 102-0094, Japan
2
Graduate School of Engineering, Hiroshima University, 1-4-1, Kagamiyama, Higashi, Hiroshima 739-8527, Japan
evaluation of HSS, and the S-N curve used for the fatigue assessment should have a close relationship. The typical hot spots in the ship structures are the welded joints between plates, which is categorized as type-a hot
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