• 제목/요약/키워드: Stir-zone

검색결과 89건 처리시간 0.02초

FRICTION STIR WELDING OF MAGNESIUM ALLOYS

  • Kazuhiro Nakata;Kim, Young-Gon;Masao Ushio
    • Proceedings of the KWS Conference
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    • 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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    • pp.511-515
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    • 2002
  • Extruded and cast plates of AZ type magnesium alloys were successfully joined by friction stir welding (FSW). Effect of FSW conditions on the formation of the defect was revealed in relation to tool rotation speed and specimen travel speed. Magnesium alloy with higher aluminum content became difficult to be joined and the optimum condition without defect was restricted into narrow condition range. The structure of the stirred zone was a fine-grained recrystallized structure even in the case of cast AZ91D. FSW joint had better mechanical properties than those of GTA welded joint. Especially the toughness of the stirred zone increased more than that of the base metal.

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FSW Process Optimization for Al 2519 Alloys and Its Joint Characteristics(II) (후육 고강도 Al 2519합금의 FSW 접합기술 및 접합부 특성(II))

  • Kim, Heung-Ju;Jang, Ung-Seong;Yang, Gwang-Ha;Bang, Han-Seo
    • Proceedings of the KWS Conference
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    • 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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    • pp.174-176
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    • 2005
  • On the basis of successful experiences and data from author's past experimental results of friction stir welding on thin aluminum plates, thick aluminum plate of high strength 2000 series has been carried out in this study. For various combination of rotating speed, welding speed and tool (RIWRC38-C) shape, the butt welded specimens has been prepared to check the metallurgical characteristics, hardness distributions and defects. From the results, feasible welding conditions have been obtained as 450 rpm rotating speed and 5 mm/min welding speed. Using these optimum welding parameters, 38.1mm-thickness A2519-T87 plates have been FSWelded in single pass. A good weld surface appearance and defects free weld zone has been observed in X-ray inspection. Softened region has been generated by dissolution of precipitates and coarsened microstructure in the stir zone after FSWeld.

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Springback prediction of friction stir welded DP590 steel sheets considering permanent softening behavior (영구 연화 거동을 고려한 마찰교반용접(FSW) 된 DP강 판재의 탄성 복원 예측)

  • Park, T.;Lee, W.;Chung, K.H.;Kim, J.H.;Kim, D.;Kim, Chong-Min;Okamoto, Kazutaka;Wagoner, R.H.;Chung, K.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 한국소성가공학회 2008년도 추계학술대회 논문집
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    • pp.304-307
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    • 2008
  • In order to evaluate the effect of permanent softening behavior on springback prediction, 2D-draw bending simulations were compared with experiments for friction stir welded DP590 steel sheets. To account fur the nonlinear hardening behavior, the combined isotropic-kinematic hardening law was utilized with and without considering the permanent softening behavior during reverse loading. Also, the non-quadratic orthotropic yield function, Yld2000-2d, was used to describe the anisotropic initial-yielding behavior of the base sheet while anisotropic properties of the weld zone were ignored for simplicity.

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Evaluation of Residual Stresses in 12%-Cr Steel Friction Stir Welds by the Eigenstrain Reconstruction Method

  • Jun, Tea-Sung;Korsunsky, Alexander M.
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • 제24권1호
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    • pp.15-22
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    • 2015
  • In the present paper we report the results of a study into Friction Stir Welds (FSWs) made in 13 mm-thick 12%-Cr steel plates. Based on residual strains obtained by diffraction techniques, eigenstrain analysis was performed using the Eigenstrain Reconstruction Method (ERM), which is a novel methodology for the reconstruction of full-field residual strain and stress distributions within engineering components. Significant eigenstrain distributions were found at around Thermo-Mechanically Affected Zone (TMAZ) where the most severe plastic deformation was occurred. Microstructure analysis was used to elucidate this phenomenon showing that the grain structure in TMAZ was bent and not successfully recrystallised, resulting in severe deformation behaviour. The reconstructed residual strain distributions by the ERM agree well with the experimental results. It was found that the approach based on theory of eigenstrain is a powerful basis for reconstructing the full-field residual strain/stress distributions in engineering components and structures.

Evaluation of Joint Properties of Friction Stir Welded AZ31B Mg Alloy (FSW를 이용한 AZ31B Mg합금의 접합성 평가)

  • 노중석;김흥주;장웅성;방국수
    • Journal of Welding and Joining
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    • 제22권3호
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    • pp.56-61
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    • 2004
  • Friction stir weldability of AZ31B Mg alloy was studied using microstructural observation and mechanical tests. Defect free joints was obtained under the condition of 2000rpm-100mm/min. In TMAZ, a lot of twin deformation were observed due to the mechanical effect of the FSW tool and thus relatively high hardness was obtained. In SZ, the twin deformation was disappeared by recovery and the hardness decreased because the. grain structure was coarsened by dynamic recrystallization and grain growth. The Al-Mn precipitates were observed throughout the joint regions. On the other hand, $$\beta$-Mg_{17}Al_{12}$ intermetallic compounds were not observed in either of the zone. The joint efficiency was about 80% and the impact value of the joint was almost equal to that of base metal.

A Study on Welding Residual Stress by Numerical Simulation on friction Stir Welding

  • Bang, H.S.;Kim, H.J.;Go, M.S.;Chang, W.S.;Lee, C.W.
    • International Journal of Korean Welding Society
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    • 제2권1호
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    • pp.62-66
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    • 2002
  • The Friction Stir Welding (FSW) is a new joining method that was developed at The Welding Institute (TWI) in England in 1991. It applied heating by the rotational friction and material plastic flow. It was developed as a new joining method to solve the problems of epochally in the welding of Al alloys. In the study, 6000series of Alloy composed of Al-Mg-Si, one of the Al alloys that are utilized for shipbuilding and construction, is selected as a specimen and the numerical is executed against the welded zone of FSW. The material used in this study had the unique properties of strength and anti-corrosion, but since the welded joint of this material is easily softened by the welding heat, FSW is executed and the numerical analysis is carried out around the joint. To examine the mechanical behaviors and properties, F.E.M analysis is executed and the developed thermal-elastic-plastic finite analysis are used.

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Evaluation on Temperature of FSW Zone of Magnesium Alloy using Experiment and FE Analysis (시험 및 유한요소법을 이용한 마그네슘 합금 마찰교반용접부 온도 특성 평가)

  • Sun, Seung-Ju;Kim, Jung-Seok;Lee, Woo-Geun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • 제17권7호
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    • pp.434-441
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    • 2016
  • Friction Stir Welding (FSW) is a solid-state joining process involving the frictional heat between the materials and tools. The amount of heat conducted into the workpiece determines the quality of the welded zone. Excessive heat input is the cause of oxides and porosity defects, and insufficient heat input can cause problems, such as tunnel defects. Therefore, analyzing the temperature history and distribution at the center of the Friction Stir Welded zone is very important. In this study, the temperature distribution of the friction stir welding region of an AZ61 magnesium alloy was investigated. To achieve this goal, the temperature and metal flow was predicted using the finite element method. In FE analysis, the welding tool was simplified and the friction condition was optimized. Moreover, the temperature measuring test at the center of the welding region was performed to verify the FE results. In this study, the tool rotation speed was a more dominant factor than the welding speed. In addition, the predicted temperature at the center of the welding region showed good agreement with the measurement results within the error range of 5.4% - 7.7%.

Recent R&D status on friction stir welding of Ti and its alloys (티타늄과 그 합금의 마찰교반용접기술 현황)

  • Kang, Duck-Soo;Lee, Kwang-Jin
    • Journal of Welding and Joining
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    • 제33권2호
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    • pp.1-7
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    • 2015
  • This article describes the basic technical concepts for applying the friction stir welding (FSW) process to titanium and its alloys. Titanium and its alloys are demanding applications of FSW. During FSW, a protective atmosphere is needed at the welding region to prevent the joints from oxidation due to the absorption of interstitial elements (O, N, and H) at high temperature. The process parameters for FSW have great influence on the microstructure and properties of the joints. No phase transformation occurred in CP Ti because FSW was achieved below the ${\beta}$-transus temperature. Therefore, the mechanical properties of the joints with CP Ti were governed by recrystallization and grain refinement. Furthermore, the strong crystallographic texture indicating <0001>//ND formed in the stir zone. On the other hands, the phase transformation occurred in Ti-6Al-4V alloy because the process temperature reached above ${\beta}$-transus temperature. For this reason, the mechanical properties of the joints with Ti-6Al-4V alloy were altered by not only recry stallization and grain refinement but also phase transformation during FSW. Engineers who want to get sound FSW joints with Ti-6Al-4V alloy have to pay attention to the control about process conditions.

Defect Detection in Friction Stir Welding by Online Infrared Thermography

  • Kryukov, Igor;Hartmann, Michael;Bohm, Stefan;Mund, Malte;Dilger, Klaus;Fischer, Fabian
    • Journal of Welding and Joining
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    • 제32권5호
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    • pp.50-57
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    • 2014
  • Friction Stir Welding (FSW) is a complex process with several mutually interdependent parameters. A slight difference from known settings may lead to imperfections in the stirred zone. These inhomogeneities affect on the mechanical properties of the FSWed joints. In order to prevent the failure of the welded joint it is necessary to detect the most critical defects non-destructive. Especially critical defects are wormhole and lack of penetration (LOP), because of the difficulty of detection. Online thermography is used process-accompanying for defect detecting. A thermographic camera with a fixed position relating to the welding tool measures the heating-up and the cool down of the welding process. Lap joints with sound weld seam surfaces are manufactured and monitored. Different methods of evaluation of heat distribution and intensity profiles are introduced. It can be demonstrated, that it is possible to detect wormhole and lack of penetration as well as surface defects by analyzing the welding and the cooling process of friction stir welding by passive online thermography measurement. Effects of these defects on mechanical properties are shown by tensile testing.

Weld formation mechanism during friction stir spot welding of 6061 Al

  • Sato, Yutaka S.;Fujimoto, Mitsuo;Abe, Natsumi;Kokawa, Hiroyuki
    • Proceedings of the KWS Conference
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    • 대한용접접합학회 2009년 추계학술발표대회
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    • pp.239-242
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    • 2009
  • Friction stir spot welding (FSSW), developed based on principle of friction stir welding, has been paid attention as a new solid-state spot welding process. Since FSSW can produce high-quality weld in Al alloys more easily than resistance spot welding, this process has been already used for construction of Al components in the automotive industries. Despite the large industrial interests in FSSW, fundamental knowledge on welding phenomena of this process has not been fully understood. In this study, FSSW phenomena, such as the consolidation mechanism, the microstructural evolution and the material flow, were examined in Al alloy 6061. This study clarified that the elliptical zone found in the vicinity of the pin hole on the cross section was characterized by the initially lapped surface of two sheets. Moreover, the following material flow was proposed; capture of the upper material with the threads on the pin surface, spiral flow along the tool rotation, and then release at the tip of the pin.

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