• Title/Summary/Keyword: T 형상 용접

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A Study on Fatigue Life Prediction of Welded Joints Through Fatigue Test and Crack Propagation Analysis (피로실험 및 균열진전 해석을 통한 용접부의 피로수명 예측에 관한 연구)

  • Y.C. Jeon;Y.I. Kim;J.K. Kang;J.M. Han
    • Journal of the Society of Naval Architects of Korea
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    • v.38 no.3
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    • pp.93-106
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    • 2001
  • T-joint and hopper knuckle joint models are typical welded joints in ship structure, which are very susceptible to fatigue damage under service condition. Fatigue test and fracture mechanical analysis were performed on these joints to find out characteristics of fatigue behavior. Unified S-N curve was developed from the test results of these two types of joint using hot spot stress concept, and also propagation life was also estimated using Paris' crack propagation law. Residual stress effect on propagation life was considered in calculating propagation life, as was done with thermo-elasto-plastic FE analysis and residual stress intensity factor calculation. Fatigue life of similar kinds of welded joint could be predicted with this unified S-N curve and fracture mechanical analysis technique.

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Seismic Evaluation of Welded-formed square Column-Beam Connection for External Diaphragm Stress path (외다이아프램 응력경로에 따른 용접조립 각형기둥-보 접합부의 내진성능 평가)

  • Kim, Sun Hee;Yom, Kyong Soo;Choi, Sung Mo
    • Journal of Korean Society of Steel Construction
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    • v.26 no.4
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    • pp.311-322
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    • 2014
  • Concrete filled tubular structure should be installed diaphragms for moment connection. However internal and through diaphragm should be special welded when connected to column tube. The other hand, that has become increase of stress concentration and extend of construction error. Therefore, In this study the seismic performance of beam to column connections with External Diaphragms and implement cycle loading experiment. we had evaluated seismic performance with mentioned experiment which is concrete filled or not, variable shapes, to be welded or not of diaphragm. Also, formula of strength of external diaphragm was analyzed and looked into adequacy with regard to formula of tension strength.

A Study on the Effect that Pin Shape on Mechanical Strength in Dissimilar Friction Stir Welding A6061-T6 and A5052-H32 (A6061-T6과 A5052-H32재의 이종 마찰교반용접시 핀 형상이 기계적 강도에 미치는 영향에 관한 연구)

  • Park, Hee-Sang;Choi, Won-Doo;Ko, Jun-Bin;Lee, Young-Ho;Shin, Ki-Seok;Kim, In-Chul;Choi, Man-Yong
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.18 no.3
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    • pp.270-278
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    • 2009
  • Friction stir welding is a relatively new solid state joining process. A6061-T6 and A5052-H32 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength to weight ratio and good corrosion resistance. This friction stir process uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, etc., and tool pin profile play a major role in deciding FSP zone formation in A6061-T6 and A5052-H32 aluminium alloy. Three different tool pin profiles have been used to fabricate the dissimilar butt joints. The formation of friction stir processed zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the friction stir processed zone formation.

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Mechanical Characteristic Evaluation by Spin Tool of Different Pin Shapes in Friction Stir Welding Al6061-T6 (Al6061-T6의 마찰교반용접 시 회전 Tool Pin 형상에 따른 기계적 특성 평가)

  • Lim, ByungChul;Kim, DaeHwan;Park, SangHeup
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.23 no.4
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    • pp.345-349
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    • 2014
  • In this study, an age-hardened 6061-T6 alloy sheet was used, which is commonly utilized for auto parts. The junction strength characteristics in relation to the stirring speed and welding speed were studied in accordance with the friction stir welding rotation of the tool pin. Micro hardness measurements of A type and B type pins, for a welding speed of 400 mm/min and a tool rotational speed 3000 rpm, were obtained as Hv104 and Hv111, respectively. For a welding speed of 200 mm/min and a tool rotational speed of 2000 rpm, we obtained Hv48 and Hv50 for A and B type pins, respectively. Microstructure observation showed that the stirring portion was fine and uniform, which occurred because of its plastic deformation. In the thermomechanically affected zone, partial recrystallization was present because of the plastic deformation. The crystal grains in the heat affected zone were coarsened due to the heat generated by friction stir welding.

A Study on the Effect that Pin Shape and Welding Speed have an Influence on Mechanical Strength in Friction Stir Welding A16061-T6 (A16061-T6 마찰교반용접시 핀 형상과 이송속도가 기계적 강도에 미치는 영향에 관한 연구)

  • Park, Hee-Sang;Lee, Young-Ho;Choi, Won-Doo;Ko, Jun-Bin
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.17 no.4
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    • pp.22-28
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    • 2008
  • Friction stir welding(FSW) is an relatively new solid state joining process. A1606l-T6 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength to weight ratio and good corrosion resistance. This friction stir process(FSP) uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, etc., and tool pin profile playa major role in deciding FSP zone formation in A16061-T6 aluminium alloy. Tow different tool pin profiles have been used to fabricate the joints. The formation of friction stir processed zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the friction stir processed zone formation.

Experimental Study on Double Skin Composite Walls Subjected to Cyclic Loading (주기하중을 받는 이중강판합성벽의 실험연구)

  • Eom, Tae Sung;Park, Hong Gun;Kim, Jin Ho;Chang, In Hwa
    • Journal of Korean Society of Steel Construction
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    • v.20 no.2
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    • pp.289-301
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    • 2008
  • Double skin composite (DSC) wall is a structural wall that is filed with concrete between two steel plate skins connected by tie bars. This type of wall was developed to enhance the structural performance of wall, to reduce wall thickness, and to enhance constructibility, eliminating the use of formwork and re-bars. In this study, cyclic tests were performed to investigate the inelastic behavior and earthquake resistance of isolated and coupled DSC walls with rectangular and T-shapedcross-sections. The DSC walls showed stable cyclic behaviors, exhibiting excellent energy dissipation capacity. The te st specimens failed by the tensile fracture of welded joints at the wall base and coupling beam and by the severe local buckling of the steel plate. The deformation capacity of the walls varied with the connection details at the wall base and their cross-sectional shapes. The specimens with well-detailed connections at the wall base showed relatively god deformation capacity ranging from 2.0% to 3.7% drift ratio. The load-carrying capacities of the isolated and coupled wall specimens were evaluated considering their inelastic behavior. The results were compared with the test results.

The Eeffect of Arc Length and Shield Gas on Penetration Aspect Ratio in A-TIG Welding (A-TIG 용접에서 용입 형상비에 미치는 아크길이와 실드가스의 영향)

  • Park, In-Ki;Ham, Hyo-Sik;Cho, Sang-Myung
    • Journal of Welding and Joining
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    • v.26 no.6
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    • pp.42-47
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    • 2008
  • TIG welding enables to produce high quality weldment. However it has some problems such as shallow penetration and large distortion due to low penetration aspect ratio after welding. In order to overcome those problems, there are many ongoing studies on A-TIG welding, which use active flux. In this study, the effect of arc length and shield gas on penetration aspect ratio with melt-run welding on STS 304 6t, on which active flux was spreaded, was investigated. Arc length was changed from 1mm to 3mm, and aspect ratio became higher as arc length was decreased in this range. 100% Ar gas, Ar-$H_2$ mixed gas, Ar-He mixed gas, and 100% He gas were used as shield gas in this study. When Ar-$H_2$ mixed gas, Ar-He mixed gas, and 100% He gas were applied, penetration and melting efficiency were both increased as compared with 100% Ar gas. Aspect ratio was the highest with Ar-2.5% $H_2$ mixed gas.

Seismic Performance of CFT column to H beam Connections Reinforced with T-stiffeners (T-스티프너로 보강된 CFT 기둥-H형강보 접합부의 내진성능)

  • Kim, YoungJu;Chae, Young Suk;Shin, Kyung Jae;Oh, Young Suk;Moon, Tae Sup
    • Journal of Korean Society of Steel Construction
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    • v.15 no.6 s.67
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    • pp.701-709
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    • 2003
  • The paper presented the seismic performance of T-stiffener moment connections for use in steel moment-resisting frames. The connections were strengthened by welding the vertical and horizontal clement of the T-stiffener to the beam flange and column f1ange. Finite clement analysis and experiments were conducted to determine the behavior of T-stiffener-reinforced connections. The results of the finite element analysis confirmed the effectiveness of the T-stiffener, whose horizontal element lengthened to mitigate local stress concentrations of the beam flange on the horizontal stiffener. Full-scale specimens were also tested cyclically to study hysteresis behavior. The main parameters used were the ratio of the T-stiffener to beam strength and the shape of the horizontal element. As the length of the horizontal element increased, the deformation capacity of the connections enhanced. Likewise, all specimens behaved according to the Ramberg-Osgood curve and showed stable hysteresis behavior.

Sensitivity Analysis of Nozzle Geometry Variables for Estimating Residual Stress in RPV CRDM Penetration Nozzle (원자로 상부헤드 관통노즐의 잔류응력 예측을 위한 노즐 형상 변수 민감도 연구)

  • Bae, Hong Yeol;Oh, Chang Young;Kim, Yun Jae;Kim, Kwon Hee;Chae, Soo Won;Kim, Ju Hee
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.3
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    • pp.387-395
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    • 2013
  • Recently, several circumferential cracks were found in the control rod drive mechanism (CRDM) nozzles of U.S. nuclear power plants. According to the accident analyses, coolant leaks were caused by primary water stress corrosion cracking (PWSCC). The tensile residual stresses caused by welding, corrosion sensitive materials, and boric acid solution cause PWSCC. Therefore, an exact estimation of the residual stress is important for reliable operation. In this study, finite element simulations were conducted to investigate the effects of the tube geometry (thickness and radius) on the residual stresses in a J-groove weld for different CRDM tube locations. Two different tube locations were considered (center-hole and steepest side hill tube), and the tube radius and thickness variables ($r_o/t$=2, 3, 4) included two different reference values ($r_o$=51.6, t=16.9mm).

용접부 쉐브론노치 형상에 대한 균열전파 특성

  • 김엽래
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 1996.10a
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    • pp.194-197
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    • 1996
  • The high-strength aluminum alloy 7075-T651 was used to observe the fatigue-crack-propagation behavior for the various stress ratios with constant amplitude loading and thus to predict the fatigue life. With a chevron notch in the specimen the fatigue-crack-propagation behavior of through crack was investigated. Crack propagation behavior of through crack in the depth direction and crack growth of weldments were experimentally studied. Base material heat affected zone and weld material were considered in the fracture of weldments. The change of crack-propagation length with respect to several parameters such as stress intensity factor range(ΔK) effective stress intensity factor range(ΔKeff)ration of effective stress intensity factor range(U) stress intensity factor of crack opening point(K op) maximum stress intensity factor(K max) and number of cycles(Nf)was determined. The crack length of through crack of weldments was 2.4mm and the remaining part was a base material. The experiment was accomplished by making the crack propagate near the base material.

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