• Title/Summary/Keyword: Welded

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An Experimental Study on the Fatigue Strength of Repair Welded Joints of Old Steel Bridge (신판교체 보수 용접부의 피로강도에 관한 실험적 연구)

  • Park Hyeon-Chan;Lee Jin-Hyeong;Kim Jae-Hwan;Jang Gap-Cheol;Jang Gyeong-Ho
    • Proceedings of the KWS Conference
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    • 2006.05a
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    • pp.94-96
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    • 2006
  • Recently, steel structures have been increasing because of its brilliant features. In general, cracks and corrosion are produced due to the numerous environmental factors in steel structures. However, the validity of repair method for the damaged steel structures has not been fully verified because of its lack of safety and reliability after application. Moreover, repair method by welding inevitably involves cutting and welding processes and reliability for the safety during the processes has net been established yet. Therefore, this study carried out experiments on the fatigue strength of repair welded joints of old steel bridge to investigate the fatigue characteristics in the repair welded joints. Fatigue tests were conducted by 250kN capacity MIS with the frequency of 5Hz under amplitude loading. From the results, it is known that fatigue strength grade of the repair welded joints was satisfied with C grade which specification requires.

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Fatigue Life Evaluation Model for Welded feints Based on Nominal Stress and Residual Stress Relaxation (잔류응력 완화를 고려한 공칭응력 기반 용접재의 피로수명 평가 모델)

  • 구병춘;양승용;정흥채;최성규
    • Proceedings of the KWS Conference
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    • 2004.05a
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    • pp.249-251
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    • 2004
  • According to our fatigue tests carried out at 20 ㎐, R=0.1 on transversely butt-welded joints, fatigue strengths of as-welded specimens, that is, specimens having residual stress are higher than those of annealed specimens in short hie range, but vice verse in long life range. This behavior seems to be concerned mainly with residual stress relaxation by applied loading. After analyzing the welding process, we conducted finite element analysis to quantify the degree of residual stress relaxation. By taking into account residual stress relaxation, modified Goodman diagram, and nominal stress, we evaluated the fatigue life of the welded joint from the S-N curve for the parent material. The estimated results are in a good agreement with the experimental results.

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Fatigue Test and Simulation on the Steel Welded L-Shaped Frame (L 형상 용접 프레임의 피로 실험 및 시뮬레이션)

  • Lee, Jung-Hee;Kim, Jae-Hoon;Kong, Jeong-Pyo;Han, Kyu-Hyun;Lee, Young-Shin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.1
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    • pp.63-69
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    • 2008
  • A fatigue test on the steel welded L-shaped frame was conducted. The frame was consisted with carbon steel tube and reinforced bracket. The four type reinforced brackets were fabricated. They were two rectangular plate reinforced bracket, two sided pentagon plate reinforced bracket, triangular plate reinforced bracket and fully reinforced bracket. The fatigue test of frame was conducted with axial tension loading. The fatigue simulation of the steel welded L-shaped frame was also performed by the finite element method with code FEMFAT. The frame of fully reinforced bracket had the highest fatigue life and reinforced quality factor.

A Study on the Fatigue Life Evaluation of Spot Welded Joints under Tensile-Shear Loading (인장-전단 하중을 받는 점용접부의 피로 수명 평가에 관한 연구)

  • Chung, K.;Kim, H.
    • Journal of Power System Engineering
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    • v.5 no.1
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    • pp.80-88
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    • 2001
  • The spot welding method has been used in the joining of structures, automotive body, railway carriage, aircraft, household electric appliances, precision parts etc., because of brief working, easy automation, available mass production, and convenience. In this paper, the effects of welding conditions on the fatigue life and the prediction of fatigue life based on fracture mechanics theory of spot welded joint were investigated. Fatigue tests were conducted with the tensile-shear specimens welded in the various current using cold rolled steel sheets. Fatigue life of spot welded joint was predicted and compared with experimental results. Using FEM(finite element method), we analysed the distribution of stress and the condition of deformation on the environments of nugget.

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The relationship between residual stresses and transverse weld cracks in the plate (후판용접부의 잔류응력과 횡균열의 상관관계)

  • 이해우;강성원;박종진
    • Proceedings of the KWS Conference
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    • 2003.05a
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    • pp.263-265
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    • 2003
  • The transverse crack, a type of cold crack, occurs perpendicular to the axis of the weld interface, longitudinal residual stresses ($\sigma$k direction) are more important in transverse crack occurrence from my own experience. Specimens were fabricated and welded under actual construction conditions, and then residual stresses of longitudinal stresses were measured for different welding conditions with SAW and FCAW process. The residual stress values for the specimen welded Interpass temperature below 30$^{\circ}C$ was higher than the specimen welded interpass temperature of 100~120$^{\circ}C$. And also the residual stress values for a specimen measured at weld surface, as welded condition, was higher than that of longitudinal residual stresses that was measured from a small test piece, due to the residual stress was relieved in the process of the cutting and machining. Transverse weld cracks were detected in the area of the maximum residual stresses both SAW and FCAW process.

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Microstructure and mechanical properties of Nd:YAG Laser welded AZ31-H24 Magnesium alloy using AZ61 filler metal (AZ61 filler wire를 사용하여 Nd:YAG Laser 용접한 AZ31-H24합금의 미세조직과 기계적 특성)

  • Ryu, Chung-Seon;Lee, Mok-Yeong;Bang, Guk-Su;Jang, Ung-Seong
    • Proceedings of the KWS Conference
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    • 2007.11a
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    • pp.322-324
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    • 2007
  • Nd:YAG laser welding of AZ31B-H24 magnesium alloy was carried out using AZ61 filler wire(Mg-6wt%Al-1wt%Zn). Microstructure and mechanical properties of welded joint were examined by optical microscopy, scanning electronic microscopy(SEM), energy dispersive spectroscopy(EDS), electron probe micro analyzer(EPMA) and victors hardness, tensile test at the room and elevated temperature. Test results indicate that the specimens welded with AZ61 filler wire have better tensile strength, elongation and victors hardness at room temperature than those of welded without filler wire. However tensile strength are similar but elongation are quite different at elevated temperature.

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Stratigraphy and Petrology of the Volcanic mass in the Chilpo-Weolpo Area, the north of Pohang basin, Korea (포항분지(浦項盆地) 북부(北部)(칠포(七浦)-월포(月浦)일원)에 분포(分布)하는 화산암류(火山岩類)에 대한 암석학적(岩石學的)·층서적(層序的) 연구(硏究))

  • Yun, Sung Hyo
    • Economic and Environmental Geology
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    • v.21 no.2
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    • pp.117-129
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    • 1988
  • The purpose of this study is to determine the stratigraphy of the volcanic rocks in the Chilpo-Weolpo area, the north of Pohang basin, based on field survey and lithological properties of the rocks. The volcanic pile(Chilpo tuff) overlies the Cretaceous sedimentary formation and is unconformably overlain by the Miocene Yeonil Group. The Chilpo tuff comprises a thick sequence(>200m) of pyroclastic flow deposits. Five members are distinguished, each representing separate flow units, comprising none(or weakly) to densely welded rhyolite tuff. The Chilpo tuff consists of, in ascending order, greenish weakly welded tuff, volcanic conglomerate, alternation of tuff breccias and fine tuffs, greenish none to densely welded tuff and red-brownish densely to weakly welded vitric tuff. This study revealed that the volcanic rocks in this area were formed by 4 volcanic stages. On the basis of K-Ar age($44.7{\pm}1.1\;Ma$) and lithologic data, geological age of the Chilpo tuff may be Eocene.

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A Study on the Characteristics of Axial Force in Bridge with Continuous Welded Rail (장대레일화 된 교량의 축력거동특성 연구)

  • Kim, Doo-Hwan;Han, Kwang-Seob
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.7 no.1
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    • pp.251-258
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    • 2003
  • This study is to understand the characteristics of axial force behavior that operates to the part of continuous welded rail and to investigate the basic data for secure the structure's stability and retrofit of the track. To develop the FEM model that type of plate girder which is used in the domestic national railway among servicing railway type. It is to analyze the characteristics of axial force behavior according to equip of the expansion joint and support placing by using the axial force simulation in making the continuous welded rail. As the result of research on the parametric valuables through the analysis, it is investigated that 'FMFM type' is more efficient than the other support type. Also, it conclude that structures are having the expansion joint is the most safe condition.

Seismic design and assessment of steel-concrete frame structures with welded dissipative fuses

  • Calado, Luis;Proenca, Jorge M.;Sio, Joao
    • Steel and Composite Structures
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    • v.35 no.4
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    • pp.527-544
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    • 2020
  • This research presents the design and numerical assessment of composite steel-concrete frame structures with welded dissipative fuses. The assessment has been carried out based on linear response spectrum, nonlinear static pushover and time history procedures. The analytical expressions which define the envelope of the nonlinear response of the dissipative fuses are first presented and calibrated against experimental results available in literature. The assessment is then carried out according to a design methodology proposed herein. Outcomes of the numerical assessment indicate that the use of welded dissipative fuses successfully limited damage within the replaceable parts. Furthermore, although structures with dissipative fuses present lower strength and, generally, lower displacement capacity, their displacement ductility and global dissipative performance are generally higher than conventional structures, especially when the structure with dissipative fuses presents a dissipative configuration adjusted to the bending moment distribution diagram calculated for the applied seismic action.

Experimental Formability Investigation for FSW Sheets with Respect to Base Material's Directional Combination (모재의 방향성에 따른 마찰교반용접 판재의 성형성에 관한 실험적 연구)

  • Kim, Dae-Yong;Lee, Won-Oh;Kim, June-Hyung;Kim, Chong-Min;Chung, Kwan-Soo
    • Transactions of Materials Processing
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    • v.18 no.1
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    • pp.73-79
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    • 2009
  • In order to investigate the formability of friction stir welded(FSW) tailor welded blanks(TWB) with respect to the base material's directional combination, aluminum alloy AA6111-T4 sheets were welded with three different conjoining types: RD-RD, TD-RD and TD-TD. Here, RD and TD represent rolling and transverse directions, respectively. For experimental formability study, three tests with gradual complexity were performed: the simple tension test with various weld line directions for uni-axial elongation, the hemisphere dome stretching test for biaxial stretching and the cylindrical cup deep drawing test. As a result, all three forming tests showed that RD-RD type samples exhibited the best formability, while TD-TD type sheets showed the least formability performance.