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  • Title/Summary/Keyword: Axial Mode

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Effect of Shielding Gases on the Weldability of High Efficient GMAW Process (고능률 GMAW의 용접성에 미치는 보호가스의 영향)

  • 한기형;한종만;이민우;이은배;한용섭
    • Journal of Welding and Joining
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    • v.13 no.1
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    • pp.127-137
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    • 1995
  • The possibility of new GMAW process using economic shielding gases including CO2 gas was investigated on the effect of shielding gas on weldabilty. In the optimum welding condition using 600A power source, FCAW process showed low depositions rate, 114 g/min at 300A, but new GMAW using other mixed shielding gases exhibited high deposition rate, 208-224 g/min at 450A. TIME gas, Ar+CO2 gas and Ar+CO2+O2 gas as a shielding gas were able to be used to the very high welding current(450A), moreover TIME gas and Ar+CO2 gas showed the highest arc stability among shielding gases studied in this experiments. The weld penetration was performed by axial spray transfer mode of weld droplet. On the basis of workability, weldability and economic point of view, Ar mixture (80%Ar+20%CO2) gas was recommended as a shielding gas for the development and application of new GMAW process. This shielding gas showed the low spatter, good weld quality, stable arc and low cost at the region of high welding current.

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Dynamic Behavior of Laminated Orthotropic Cylindrical Shells (複合材 圓筒쉘의 動的 擧動 硏究)

  • 김천욱;김치균
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.10
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    • pp.1807-1815
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    • 1992
  • The vibration characteristic of thin laminated orthotropic cylindrical shell is investigated based on the Donnell theory. The Rayleigh-Ritz variational procedure is employed. For the variety of shell end conditions, the beam characteristic function is used for the axial mode function. The result of the present analysis is in good agreement with some available analytical results and NASTRAN and BOSOR4 calculations. In the present study, the relation between natural frequencies and orthotropic parameter k is investigated. Introducing the frequency parameter, this study shows that the frequency parameter increases as the orthotropic parameter k approaches to one.

A Study on Development of Arc Sensor for Arc Welding Robot Using Consumable Electrode (소모성 전극을 사용하는 아크용접 로봇을 위한 아크센서 개발에 관한 연구)

  • 이승영;문형순;나석주;장영주;안병규
    • Journal of Welding and Joining
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    • v.11 no.3
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    • pp.22-33
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    • 1993
  • Arc sensor is indispensable to arc welding robot systems for compensating the joint misalignment such as mismatch of the workpiece, ill-conditioned positioner and thermal deformation during welding. Furthermore, the amount of these mismatches cannot be preivously expected, and changes from time to time. There are many kinds of seam trackers for correcting the welding path of the robot, where non-contact type sensors arc prevalently used in arc welding robot systems. In this study, an arc sensor was developed for GMA and FCA welding robot system. Since the arc sensor uses the arc characteristics during welding, the operating principle of the arc sensor must be adjusted according to the welding condition. Especially in GMA welding with the CO2 shielding gas, the welding arc is not stable because of the short circuit and non-axial globular transfer mode of the molten droplet. In this study, the 2nd order least square curve fitting algorithm was adopted and the applicability of this algorithm was investigated for robot welding systems. For easy usage of the arc sensor, the operating parameters for arc sensor were limited to eight which can be easily determined by the operator.

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Failure Assessment and Strength of Steam Generator Tubes with Wall Thinning (증기발생기 전열관 감육부의 강도 및 손상평가)

  • Seong, Ki-Yong;Ahn, Seok-Hwan;Yoon, Ja-Moon;Nam, Ki-Woo
    • Journal of Ocean Engineering and Technology
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    • v.21 no.2 s.75
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    • pp.50-59
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    • 2007
  • Steam generator tubes are degraded from wear, stress corrosion cracking, rupture and fatigue and so on. Therefore, the failure assessment of steam generator tube is very important for the integrity of energy plants. In the steam generator tubes, sometimes, the local wall thinning may result from severe degradations such as erosion-corrosion damage and wear due to vibration. In this paper, the elasto-plastic analysis was performed by FE code ANSYS on steam generator tubes with wall thinning. Also, the four-point bending tests were performed on the wall thinned specimens, and then it was compared with the analysis results. We evaluated the failure mode, fracture strength and fracture behavior from the experiment and FE analysis. Also, it was possible to predict the crack initiation point by estimating true fracture ductility under multi-axial stress conditions at the center of the thinned area from FE analysis.

Dynamic Optimal Shapes of Simple Beam-Columns with Constant Volume (일정체적 단순지지 보-기둥의 동적 최적단면)

  • Lee, Byoung Koo;Park, Kwang Kyou;Mo, Jeong Man;Lee, Sang Jin
    • Journal of Korean Society of Steel Construction
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    • v.9 no.2 s.31
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    • pp.221-228
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    • 1997
  • The main purpose of this paper is to determine the dynamic optimal shapes of simple beam-columns with the constant volume. The parabolic function is chosen as the variable equation for the depth of regular polygon cross-section. The ordinary differential equation including the effect of axial load is applied to calculate the natural frequencies. The Runge-Kutta and Regula-Falsi methods are used to integrate the differential equation and compute the frequencies, respectively. Then the dynamic optimal shape whose lowest natural frequency is highest is determined by reading the critical value of the frequency versus section ratio curve plotted by the frequency data. In the numerical examples, the simple beam-columns are analysed and the numerical results of this study are shown in tables and figures.

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Theoretical and experimental dynamic characteristics of a RC building model for construction stages

  • Turker, Temel;Bayraktar, Alemdar
    • Computers and Concrete
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    • v.17 no.4
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    • pp.455-475
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    • 2016
  • Dynamic characteristics, named as natural frequencies, damping ratios and mode shapes, affect the dynamic behavior of buildings and they vary depending on the construction stages. It is aimed to present the effects of construction stages on the dynamic characteristics of reinforced concrete (RC) buildings considering theoretical and experimental investigations. For this purpose, a three-storey RC building model with a 1/2 scale was constructed in the laboratory of Civil Engineering Department at Karadeniz Technical University. The modal testing measurements were performed by using Operational Modal Analysis (OMA) method for the bare frame, brick walled and coated cases of the building model. Randomly generated loads by impact hammer were used to vibrate the building model; the responses were measured by uni-axial seismic accelerometers as acceleration. The building's modal parameters at these construction stages were extracted from the processed signals using the Enhanced Frequency Domain Decomposition (EFDD) technique. Also, the finite element models of each case were developed and modal analyses were performed. It was observed from the experimental and theoretical investigations that the natural frequencies of the building model varied depending on the construction stages considerably.

Liquid-liquid extraction process for gas separation from water in polymeric membrane: Mathematical modeling and simulation

  • Salimi, Nahid;Moradi, Sadegh;Fakhar, Afsaneh;Razavi, Seyed Mohammad Reza
    • Membrane and Water Treatment
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    • v.7 no.5
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    • pp.463-476
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    • 2016
  • In this study, application of polypropylene hollow fiber membrane contactors for CO2 removal from water in liquid-liquid extraction (LLE) mode was simulated. For this purpose, a steady state 2D mathematical model was developed. In this model axial and radial diffusion was considered to CO2 permeation through the hollow fibers. CO2 laden water is fed at a constant flow rate into the lumen side, permeated through the pores of membrane and at the end of this process, CO2 solution in the lumen side was extracted by means of aqueous diethanolamine (DEA) and chemical reaction. The simulation results were validated with the experimental data and it was found a good agreement between them, which confirmed the reliability of the proposed model. Both simulation and experimental results confirmed the reduction in the percentage of CO2 removal by increment of feed flow rate.

Experimental investigation on CFRP-to-concrete bonded joints across crack

  • Anil, Ozgur;Belgin, Cagatay M.;Kara, M. Emin
    • Structural Engineering and Mechanics
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    • v.35 no.1
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    • pp.1-18
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    • 2010
  • Bonding of carbon fiber reinforced polymer (CFRP) composites has become a popular technique for strengthening concrete structures in recent years. The bond stress between concrete and CFRP is the main factor determining the strength, rigidity, failure mode and behavior of a reinforced concrete member strengthened with CFRP. The accurate evaluation of the strain is required for analytical calculations and design processes. In this study, the strain between concrete and bonded CFRP sheets across the notch is tested. In this paper, indirect axial tension is applied to CFRP bonded test specimen by a four point bending tests. The variables studied in this research are CFRP sheet width, bond length and the concrete compression strength. Furthermore, the effect of a crack- modeled as a notch- on the strain distribution is studied. It is observed that the strain in the CFRP to concrete interface reaches its maximum values near the crack tips. It is also observed that extending the CFRP sheet more than to a certain length does not affect the strength and the strain distribution of the bonding. The stress distribution obtained from experiments are compared to Chen and Teng's (2001) analytical model.

Non-linear vibration and stability analysis of an axially moving rotor in sub-critical transporting speed range

  • Ghayesh, Mergen H.;Ghazavi, Mohammad R.;Khadem, Siamak E.
    • Structural Engineering and Mechanics
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    • v.34 no.4
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    • pp.507-523
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    • 2010
  • Parametric and forced non-linear vibrations of an axially moving rotor both in non-resonance and near-resonance cases have been investigated analytically in this paper. The axial speed is assumed to involve a mean value along with small harmonic fluctuations. Hamilton's principle is employed for this gyroscopic system to derive three coupled non-linear equations of motion. Longitudinal inertia is neglected under the quasi-static stretch assumption and two integro-partial-differential equations are obtained. With introducing a complex variable, the equations of motion is presented in the form of a single, complex equation. The method of multiple scales is applied directly to the resulting equation and the approximate closed-form solution is obtained. Stability boundaries for the steady-state response are formulated and the frequency-response curves are drawn. A number of case studies are considered and the numerical simulations are presented to highlight the effects of system parameters on the linear and nonlinear natural frequencies, mode shapes, limit cycles and the frequency-response curves of the system.

Experimental studies on steel frame structures of traditional-style buildings

  • Xue, Jianyang;Qi, Liangjie
    • Steel and Composite Structures
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    • v.22 no.2
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    • pp.235-255
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    • 2016
  • This paper experimentally investigated the behavior of steel frame structures of traditional-style buildings subjected to combined constant axial load and reversed lateral cyclic loading conditions. The low cyclic reversed loading test was carried out on a 1/2 model of a traditional-style steel frame. The failure process and failure mode of the structure were observed. The mechanical behaviors of the steel frame, including hysteretic behaviors, order of plastic hinges, load-displacement curve, characteristic loads and corresponding displacements, ductility, energy dissipation capacity, and stiffness degradation were analyzed. Test results showed that the Dou-Gong component (a special construct in traditional-style buildings) in steel frame structures acted as the first seismic line under the action of horizontal loads, the plastic hinges at the beam end developed sufficiently and satisfied the Chinese Seismic Design Principle of "strong columns-weak beams, strong joints-weak members". The pinching phenomenon of hysteretic loops occurred and it changed into Z-shape, indicating shear-slip property. The stiffness degradation of the structure was significant at the early stage of the loading. When failure, the ultimate elastic-plastic interlayer displacement angle was 1/20, which indicated high collapse resistance capacity of the steel frame. Furthermore, the finite element analysis was conducted to simulate the behavior of traditional-style frame structure. Test results agreed well with the results of the finite element analysis.