• Title/Summary/Keyword: Fatigue strength of cruciform joints

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Fatigue Strength Assessment of the Cruciform Fillet Welded Joint Using Hot-spot Stress Approach (Hot-spot 응력을 이용한 십자형 필렛 용접재의 피로강도 평가)

  • Seok, Chang-Sung;Kim, Dae-Jin;Koo, Jae-Mean;Seo, Jung-Won;Goo, Byeong-Choon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.11 s.242
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    • pp.1488-1493
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    • 2005
  • In this study, fatigue tests to obtain S-N curves and FE analyses to obtain structural stress concentration factors were conducted for the two types of cruciform fillet welded joints, that is, load-carrying and non load-carrying types. Then we changed the obtained S-N curve of load carrying joint to that based on hot spot stress. As a result, the S-N curve of load carrying joint based on hot-spot stress was almost exactly coincided with that of non load-carrying joint based on nominal stress. So we have conducted that the fatigue strength of a welded joint with different geometry from the non stress distribution along the expected crack path.

A Study on Estimation of Infinite Fatigue Life in Cruciform Fillet Welded Joint (십자형 필릿 용접부에서의 무한 피로수명 평가에 관한 연구)

  • Lee, Yong-Bok
    • Journal of the Korean Institute of Gas
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    • v.17 no.1
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    • pp.19-25
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    • 2013
  • The joining methods of steel structures of gas facilities, bridges, ships etc. by welding are composed mostly of T-type or cruciform fillet welding and full penetration or partial penetration according to the uses and the shape of the structures. In this study, it was examined the characteristics of fatigue crack according to penetration depth in relation to material thickness in the cruciform fillet welded joints. From the results, it was investigated the safe design stresses within the range of infinite life. When the LOP length is long the range of infinite life is small with root failure and when the LOP length is short the range of infinite life is large with teo failure. For the specimen of material thickness, 20mm welded by 3 pass compared with 10mm, 15mm welded by 2 pass, the fatigue strength and the range of infinite life was more improved by increasing of notch toughness from formation of micro-ferrite acicular structure.

Fatigue Tests of Welded Joints and Comparison Study of Foreign Codes (용접부의 피로강도 시험평가 및 해외규격과의 비교연구)

  • Goo, Byeong-Choon;Kim, Jai-Hoon
    • Journal of Welding and Joining
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    • v.25 no.1
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    • pp.14-23
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    • 2007
  • A lot of fatigue tests on a material, JIS SM490A, with yielding strength of about 350 MPa and tensile strength of about 520 MPa were carried out. Various butt-welded specimens such as reinforcement removed, as-welded and weld toe ground, several types of fillet-welded specimens and full-size box type components were used. After having obtained S-N curves for the above- mentioned specimens, fatigue strengths were compared to those of foreign design codes, AWS, BS 7608 and ENV. It was found the fatigue strengths at low cycles are not in a good agreement with the foreign codes, but the fatigue limits are in a good agreement.

A Study on the Fatigue Strength Improvement of the Fillet Welded Connections with respect to Post-Weld Treatment (용접 후처리에 의한 필렛용접부의 피로강도 향상에 관한 연구)

  • Lee, Seung Yong;Kyung, Kab Soo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.5A
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    • pp.665-672
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    • 2008
  • In the study herein, the fatigue test was conducted on the fillet welds of the load carrying cruciform joint, which is frequently used in the steel structures such as bridges, ships, etc. In addition, the fatigue strength was analyzed with respect to the different post-weld treatment. The treatment methods used include Toe Grinding, TIG Dressing, and Weld Profiling. The fatigue test was under constant amplitude with repeated load for these test specimens. In the load carrying full penetration fillet welded joints, regardless the conduction of the post-weld treatment or not, they all secured the fatigue strength of category "F", which exceeds the fatigue design specifications of BS Code. In the comparison of the fatigue strength upon the post-weld treatment, the fatigue strength tends to increase according to the order: Toe Grinding, TIG Dressing, and Weld Profiling.

Fatigue Life Estimation of Welding Details by Using a Notch Strain Approach (노치변형률법을 적용한 용접구조상세의 피로수명평가)

  • Han, Jeong-Woo;Han, Seung-Ho;Shin, Byung-Chun;Kim, Jae-Hoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.7
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    • pp.977-985
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    • 2004
  • An evaluation of fatigue life of welded components is complicated due to various geometrically complex welding details and stress raisers in vicinity of weld beads, ego under cuts, overlaps and blow holes. These factors have a considerable influence on the fatigue strength of welded joints, as well as the welding residual stress which is relaxed depending on the distribution of local stress at the front of the stress raisers. To reasonably evaluate fatigue life, the effect of geometries and welding residual stress should be taken into account. The several methods based on the notch strain approach have been proposed in order to accomplish this. These methods, however, result in differences between analytical and experimental results due to discrepancies in estimated amount of relaxed welding residual stress present. In this paper, an approach that involves the use of a modified notch strain approach considering geometrical effects and a residual stress relaxation model based on experimental results was proposed. The fatigue life for five types of representative welding details, ego cruciform, cover plate, longitudinal stiffener, gusset and side attachment joint, are evaluated using this method.

A Study on Stress Concentration Factor at Fillet Welded Joint (필렛용접이음부의 응력집중계수에 관한 연구)

  • S.W. Kang;W.I. Ha;J.S. Shin;J.S. Jae
    • Journal of the Society of Naval Architects of Korea
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    • v.33 no.3
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    • pp.1-7
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    • 1996
  • The stress concentration factor gives the significant effect the fatigue strength of welded joints. The model used herein is the type of the load carrying fillet welded cruciform joint with full or partial penetration. In order to obtain the stress concentration factor at the weld toe of fillet joint, the reasonable element size of the toe part is investigated and the stress analysis for the series models by FEM under tensile load is performed. On the basis of the calculation results, the estimated formulae for the stress concentration factor(Kt) at weld toe part of the fillet welded joint, which the effect of toe radius, flank angle and other parameters are taken into account, is derived.

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