• Title/Summary/Keyword: Plastic Welding

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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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    • v.24 no.1
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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.

Fatugue Chacrateristics of Spot Welding between High Strength Steel and Galvanized Steel Sheet (II) (高張力 鋼板과 亞鉛鍍金 鋼板間의 疲勞特性 II)

  • 서창민;강성수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.2
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    • pp.229-235
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    • 1989
  • The influence of monogalvanized layer to fatigue strength of two different mating metal specimens (HS*GA, HS*GAB) of high strength steels(HS) and of monogalvanized steel sheets(GA, GAB) were investigated under tensile-shear repeated load, and hardness test. Some of the results are; (1) The main cause of crack initiation and growth at high load range is plastic bending hinge. (2) In low load range, the cracks initiated near the nugget front where the hardness variation is steep.

Inelastic behavior of standard and retrofitted rectangular hollow sectioned struts -II: Experimental study

  • Boutros, Medhat;McCulloch, James;Scott, Damian
    • Structural Engineering and Mechanics
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    • v.10 no.5
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    • pp.505-516
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    • 2000
  • This paper is a presentation of an experimental study about the elastic-partly plastic behavior of rectangular hollow steel pinned struts subjected to static cyclic axial loading and the evaluation of the compressive strength of retrofitted crooked struts. Retrofitting is achieved by welding stiffening plates along the webs of damaged struts. The material follows a quasi-kinematic hardening hysteresis path as observed from coupon tests. Test results are compared to those of an analytical model showing a good agreement for both standard and retrofitted struts. The comparison of different stiffener plate dimensions shows that more efficient strengthening is achieved by using long thin stiffeners rather than short thick ones.

Prediction of Cutting Stress by 2D and 3D-FEM Analysis and Its Accuracy (2D-3D FEM 해석에 의한 절단응력의 해석 및 정도)

  • 장경호;이상형;이진형
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2001.04a
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    • pp.95-101
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    • 2001
  • Steel bridges, which have been damaged by load and corrosion, need repair or strengthening. In general, before the repair welding procedure, cutting procedure carry out. Therefore, the investigating of the behavior of stress generated by cutting is so important for safety of structure. Residual stress produced by gas cutting was analyzed using 2D and 3D thermal elasto-plastic FEM. According to the results, the magnitude of temperature was analyzed by 2D-FEM is smaller than that was analyzed using the 3D-FEM program at the start and end edge of flange. And the magnitude and distribution of residual stress of perpendicular to the cutting line was analyzed by the 2D-FEM program was similar to that was analyzed by the 3B-FEM program. Therefore, it is possible to predict of cutting stress by 2D and 3D FEM.

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A Study on Cladding using the $CO_2$ Laser ($CO_2$레이저 클래딩)

  • 윤상원;강영주;김재도
    • Proceedings of the KWS Conference
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    • 1996.10a
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    • pp.186-190
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    • 1996
  • Laser cladding is a technique for modification on surface in materials. This study describes a laser cladding equipment design and the results of laser cladding nickel on rolled steel for general structure. The laser clsdding equipment designed to consider continuous supply, a fixed quantity. The material used MC plastic. Laser cladding condition is found out by processing parameters. The experiment advanced to suppy substrate with powder. The substrate is rolled steel for general structure(KS D 3503) and powder is using the nickel powder for the corrosion resitance, wear resistance and surface hardness of materials. When the substrate travel on X-Y table, laser beam irradiates to prevent from oxidize with shielding gas on it. The obtained specimens measure the victors hardness test. For the research laser cladding results make a comparative study the microstructure.

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Deformation by line heating for thin plate (박판 곡직을 위한 선 가열 시 변형 특성에 관한 연구)

  • Park, Jung-Gu;Jang, Gyeong-Bok;Jo, Si-Hun;Jang, Tae-Won
    • Proceedings of the KWS Conference
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    • 2005.06a
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    • pp.282-284
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    • 2005
  • The line heating methods is very widely employed to correct deformation of thin plate structures. In this study, evaluation was carried out on the temperature distribution of line heating methods using FEA and practical experiments. In FEA, heat input model was established using Tsuji's double Gaussian heat input mode. This model was verified by comparing with experimental data. Thermo elasto-plastic analysis was performed using commercial FE code, MSC/MARC. Transverse shrinkage and angular distortion were measured using 3D measuring apparatus. Based on these results, a simplified analysis method is applied by using equivalent loading method.

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Cyclic and static behaviors of CFT modular bridge pier with enhanced bracings

  • Kim, Dongwook;Jeon, Chiho;Shim, Changsu
    • Steel and Composite Structures
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    • v.20 no.6
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    • pp.1221-1236
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    • 2016
  • Modular structures consist of standardized modules and their connections. A modular bridge pier is proposed to accelerate bridge construction. Multiple concrete-filled steel tubes (CFTs) using commercial steel tubes were chosen as the main members. Buckling restrained bracings and enhanced connection details were designed to prevent premature low-cycle fatigue failure upon cyclic loading. The pier had a height of 7.95 m, widths of 2.5 m and 2.0 m along the strong and weak axis, respectively. Cyclic tests were performed on the modular pier to investigate structural performance. Test results showed that four CFT columns reached yielding without a premature failure of the bracing connections. The ultimate capacity of the modular pier was reasonably estimated based on the plastic-hinge-analysis concept. The modular CFT pier with enhanced bracing showed improved displacement ductility without premature failure at the welding joints.

The structural detailing effect on seismic behavior of steel moment resisting connections

  • Farrokhi, Hooman;Danesh, F. Ahmadi;Eshghi, Sassan
    • Structural Engineering and Mechanics
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    • v.35 no.5
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    • pp.617-630
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    • 2010
  • Different types of moment resisting connections are commonly used to transfer the induced seismic moments between frame elements in an earthquake resisting structure. The local connection behavior may drastically affect the global seismic response of the structure. In this study, the finite element and experimental seismic investigations are implemented on two frequently used connection type to evaluate the local behavior and to reveal the failure modes. An alternative connection type is then proposed to eliminate the unfavorable brittle fracture modes resulted from probable poor welding quality. This will develop a reliable predefined ductile plastic mechanism forming away from the critical locations. Employing this technique, the structural reliability of the moment resisting connections shall be improved by achieving a controllable energy dissipation source in form of yielding of the cover plates.

The Effect of residual stress on fracture behavior in the laser weldment (레이저용접부의 파괴에 미치는 잔류응력의 영향)

  • Cho, Sung-Kyu;Yang, Young-Soo;Noh, Young-Jin
    • Laser Solutions
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    • v.11 no.2
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    • pp.1-7
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    • 2008
  • The integrity of laser welded structures is decided in fracture strength and fatigue strength. This study made an effort to understand the fracture behavior considering residual stress. Experiments are conducted and analyses are performed to explore the influence of residual stress on fracture behavior of bead-on laser welded compact specimen. Fracture experiments are performed using ASTM 1820. The performed analyses included thermo-elasto-plastic analyses for residual stress and subsequent J-integral calculation. A modified J integral is calculated in the presence of residual stresses. The J-integral is path-independent for combination of residual stress field and stress due to mechanical loading. The results indicates that the tensile residual stress near crack front bring the low fracture load while the compressive residual stress bring the high fracture load compared to no residual stress specimen. These results quantitatively understand the influence of residual stress on fracture behavior.

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A Study on the Standard of Ship Hull Construction for Aluminium Alloys Fishing Boats (알루미늄 합금제 어선건조를 위한 선체구조기준 설정에 관한 연구)

  • Hong, Bong-Ki
    • Journal of Fisheries and Marine Sciences Education
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    • v.12 no.1
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    • pp.22-82
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    • 2000
  • The ship hull construction materials of fishing boat has changed in order that wooden, steel, and fiber glass reinforced plastic(FRP). The fishing boat made from FRP has increased every year because that materials has proved excellent of the characteries for fishing boats construction members. Recently, FRP tend towards evasion for the pollution of air enviroment. Therefore. the materials of fishing boat construction must be exchanged by another one. Aluminium alloys must be recommended for fishing boats construction mateials because that is light weight and corrosion resisting in the sea water. Regulation of the standard of ship hull construction for aluminium alloys fishing boats did not enact laws in the interior now. Therefore, this regulation was studied by the following items. that is Rudder, Bottom construction, Side hull plate construction, Deck plate construction, piller. Water tight bulkhead, Deep tank, Fish tank, Stern construction, Superstructure, Deck house construction, Hatch, Engine room opening, Hatch opening, Bulwark, Welding and Rivet etc. A study on the regulation will be contributed to enact laws for fishing boat construction of aluminium alloys.

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