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H : 소장처정보

T : 목차정보

Journal of mechanical science and technology 22건

  1. [국내논문]   Nonlinear dynamic analysis of a relatively short spherical gas journal bearing system   SCIE

    Wang, Cheng-Chi (Department of Mechanical Engineering, Far East University ) , Kuo, Chao-Lin (Institute of Maritime Information and Technology, National Kaohsiung Marine University)
    Journal of mechanical science and technology v.24 no.8 ,pp. 1565 - 1571 , 2010 , 1738-494x ,

    초록

    This paper studies the nonlinear dynamic behavior and bifurcation of a rigid rotor supported by two relatively short spherical gas journal bearings. The modified Reynolds equation is solved by a hybrid numerical method combining the differential transformation method (DTM) and the finite difference method (FDM). The analytical results reveal a complex dynamic behavior comprising periodic, sub-harmonic and quasi-periodic responses as the rotor mass and bearing number are increased. The results obtained using the hybrid DTM&FDM scheme are found to be in good agreement with those of a hybrid scheme comprising the successive over relaxation (SOR) method and the FDM scheme. Therefore, the DTM&FDM method provides an effective means of gaining insights into the nonlinear dynamics of relatively short spherical gas rotor-bearing systems.

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  2. [국내논문]   Influence of rub groove on rotordynamics associated with leakage air flow through a labyrinth seal   SCIE

    Wang, Wei-Zhe (Key Lab of Education Ministry for Power Machinery and Engineering, Shanghai Jiao Tong University ) , Liu, Ying-Zheng (Key Lab of Education Ministry for Power Machinery and Engineering, Shanghai Jiao Tong University ) , Meng, Guang (State Key Lab of Mechanical System and Vibration, Shanghai Jiao Tong University ) , Jiang, Pu-Ning (Department of R&D, Shanghai Turbine Company)
    Journal of mechanical science and technology v.24 no.8 ,pp. 1573 - 1581 , 2010 , 1738-494x ,

    초록

    An extensive investigation of influence of rub grooves on dynamics and stability of the rotor, which is subjected to aerodynamic forcing associated with the leakage flow through 44 straight-through seals, was performed by using numerical calculations based on the single control-volume method and the perturbation analysis. Three cases of different groove configurations were chosen for the comparative study, e.g., the seal without rub groove (case1), the seal with upstream shifting of the seal tooth in respect to the rub groove (case2) and the seal with location of the seal tooth in the middle station of the rub groove (case3). The orifice contract coefficient adopted in reduction of rotordynamic coefficients was provided by using Computational Fluid Dynamics (CFD). Influence of rub grooves on the leakage flow was obtained in terms of the close-up view of the flow pattern near the seal tooth, leakage flow rate, distributions of the mean pressure and circumferential velocity in cavities. In comparison to case 1, the leakage flow in case 3 is considerably intensified, while which in case 2 is slightly increased. Dynamics and instability of the rotor in all cases was discussed in terms of the rotordynamic coefficients and the logarithmic decrement, respectively. The results disclosed that the aerodynamic forcing in case 2 intensified the destabilization of the rotor system.

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  3. [국내논문]   Correlation study of a rotor in descending flight using DYMORE with a freewake model   SCIE

    Park, Jae-Sang (Department of Aerospace Information Engineering, Konkuk University ) , Jung, Sung-Nam (Department of Aerospace Information Engineering, Konkuk University ) , Park, Soo-Hyung (Department of Aerospace Information Engineering, Konkuk University ) , Yu, Yung-Hoon (Department of Aerospace Information Engineering, Konkuk University)
    Journal of mechanical science and technology v.24 no.8 ,pp. 1583 - 1594 , 2010 , 1738-494x ,

    초록

    In this work, the Blade Vortex Interaction (BVI) airloads characteristic for a rotor in descending flight condition is investigated using a nonlinear flexible multibody dynamics analysis code DYMORE. A free vortex wake model is incorporated into the comprehensive analysis system and improvement of airloads prediction as well as collective and cyclic pitch control settings is obtained over the finite-state dynamic inflow model that is adopted in the conventional DYMORE analysis. The three test conditions in the HART (Higher harmonic control Aeroacoustic Rotor Test) II are considered to illustrate the present investigation. It is found that the BVI airloads characteristic is significantly influenced by the higher harmonic pitch control inputs. The influence of BVI oscillatory peaks along with the miss-distance between the blade and the vortices is studied in detail to identify the mechanism of reducing noise and vibration in the HART II experiment.

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  4. [국내논문]   Determination of the force of the actuators and constraint forces in the inverse dynamic analysis of mechanisms   SCIE

    Jordi-Nebot, Lluisa (ETSII de Barcelona. Dept. Ingenieria Mecanica. Universitat Politecnica de Catalunya ) , Puig-Ortiz, Joan (ETSII de Barcelona. Dept. Ingenieria Mecanica. Universitat Politecnica de Catalunya ) , Cardona-Foix, Salvador (ETSII de Barcelona. Dept. Ingenieria Mecanica. Universitat Politecnica de Catalunya)
    Journal of mechanical science and technology v.24 no.8 ,pp. 1595 - 1601 , 2010 , 1738-494x ,

    초록

    In the computer analysis of mechanisms it is usual to choose the actuators that drive them in terms of the ease with which they can be introduced into the definition of the system rather than in terms of describing the reality. Once the force of the replacement actuator used has been obtained, that of the real actuator must be determined and some of the calculated constraint forces differ from the real ones. This work studies the situation described in the inverse dynamic analysis of mechanisms of 1-DOF. It will show how to obtain the force of the real actuator from the force of the actuator used in the simulation process, and proposes the use of auxiliary mechanisms which aid in the description of the real actuators. It also provides criteria for determining which constraint forces obtained in the simulation process with the replacement actuator are different to the real ones.

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    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  5. [국내논문]   Single-point diamond turning of electroless nickel for flat X-ray mirror   SCIE

    Chon, Kwon-Su (Department of Radiological Science, Catholic University of Daegu ) , Namba, Yoshiharu (Department of Mechanical Egineering, Chubu University)
    Journal of mechanical science and technology v.24 no.8 ,pp. 1603 - 1609 , 2010 , 1738-494x ,

    초록

    X-ray mirrors require a super-smooth surface to prevent strong X-ray scattering. We examined the fabrication possibility of the X-ray mirror by single-point diamond turning (SPDT) for electroless nickel. The stable and unstable cutting modes for the electroless nickel were obtained by observing the relative position of a diamond tool for machining. A super-smooth surface of 0.95 nm rms was achieved within the stable cutting mode. The surface roughness of the electroless nickel mirror measured with an optical profiler was compared with the X-ray reflectivity measurement. The electroless nickel mirror could be successfully used as a soft X-ray reflector and a low-pass filter for the hard X-rays.

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  6. [국내논문]   Stress profiles at contact surface in ring compression test   SCIE 피인용횟수: 1

    Noh, Jeong-Hoon (Department of Mechanical Engineering, Inha University ) , Kim, Min-Tae (Department of Mechanical Engineering, Inha University ) , Hwang, Beong-Bok (Department of Mechanical Engineering, Inha University)
    Journal of mechanical science and technology v.24 no.8 ,pp. 1611 - 1616 , 2010 , 1738-494x ,

    초록

    A perfectly plastic material has been employed as a model material in simulation to analyze numerically the ring compression process, especially to examine the deformation patterns along the die/workpiece interface, which is strongly related to the frictional condition at the contact boundary. The main objective is to provide the deformation characteristics in detail in ring compression, especially at the tool/workpiece interface. The surface flow patterns at the contact boundary in ring compression are summarized and analyzed in terms of surface expansion, surface expansion velocity, pressure distributions exerted on the die surface, relative sliding velocity between die and workpiece, and sliding distance along the die surface. Movement of neutral positions and folding phenomenon are also investigated to see the effect on the deformation patterns at the interface, that is, geometrical change, which is important to measure the frictional condition at the interface using calibration curves. Finite element (FE) simulation using rigid-plastic finite element code has been performed for analysis. The results of this study reveal that surface expansion as well as other surface flow patterns, such as sliding velocity and so on, shows different and distinctive characteristics between low and high frictional conditions at the interface. This is directly related to the movement of neutral positions and folding, which affects the sensitivity of dimensional changes to tribological conditions at the interface.

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    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  7. [국내논문]   A new parameter and its effect on the formability in single point incremental forming: A fundamental investigation   SCIE

    Hussain, Ghulam (College of Mechanical & Electrical Engineering, Nanjing University of Aeronautics & Astronautics ) , Lin, Gao (College of Mechanical & Electrical Engineering, Nanjing University of Aeronautics & Astronautics ) , Hayat, Nasir (College of Mechanical & Electrical Engineering, Nanjing University of Aeronautics & Astronautics)
    Journal of mechanical science and technology v.24 no.8 ,pp. 1617 - 1621 , 2010 , 1738-494x ,

    초록

    A new parameter, blank stiffness, with a potential effect on the formability in single point incremental forming (SPIF) has been introduced and investigated. Various plates with a square hole at the center and half-side length of the square ranging from 12-56mm were used as backing plates for blanks. It is shown that with a decrease in the size of hole/work-piece, there is an increase in the blank stiffness. This increase in the stiffness in turn adversely affects the formability in SPIF process.

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    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  8. [국내논문]   Tooling device design for vibration-assisted high speed shaping of PMMA   SCIE 피인용횟수: 2

    Mostofa, Golam (Intelligent Control and Automation Division, Department of Mechanical Engineering, Pusan National University ) , Noh, J.H. (Intelligent Control and Automation Division, Department of Mechanical Engineering, Pusan National University ) , Kim, H.Y. (Research Institute of Mechanical Technology, Pusan National University ) , Ahn, J.H. (School of Mechanical Engineering, Pusan National University and ERC/NSDM ) , Kang, D.B. (School of Mechanical Engineering, Pusan National University and ERC/NSDM)
    Journal of mechanical science and technology v.24 no.8 ,pp. 1623 - 1629 , 2010 , 1738-494x ,

    초록

    PMMA optical components that are used as one of the most important parts of high precision equipments and machines are increasingly replacing the glass due to the various advantages of PMMA. Especially in Light Guide Panels, the PMMA sheet that is used in Liquid Crystal Displays plays an important role in scattering the incident light and requires very fine machining as the sheet is directly related to the optical characteristics of the panels. The High Speed End milling and High Speed Shaping processes that are widely adopted and applied to the precise machining of Light Incident Plane still have quality problems, such as cracks, breakages, poor waviness, and straightness. This paper presents the tooling device design for machining a Light Incident Plane through vibration-assisted High Speed Shaping for increasing the optical quality by minimizing the above-mentioned problems. The cutting tool and the tool post presented in this paper are designed by the authors to increase the magnitude of the cutting stroke by adopting the resonant frequency without weakening the stiffness and to reduce vibrations during even high speed feeding. The dynamic characteristics of the cutting tool and the tool post are evaluated through simulation and experiment as well. The results reveal very appropriate dynamic characteristics for vibration-assisted High Speed Shaping.

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  9. [국내논문]   Comparison of tribological characteristics between aluminum alloys and polytetrafluoroethylene composites journal bearings under mineral oil lubrication   SCIE 피인용횟수: 1

    Ku, Bon-Cheol (School of Mechanical Engineering, Pusan National University ) , Park, Young-Do (School of Mechanical Engineering, Pusan National University ) , Sung, Chi-Un (School of Mechanical Engineering, Pusan National University ) , Han, Young-Chul (School of Mechanical Engineering, Pusan National University ) , Park, Jung-Hoon (School of Mechanical Engineering, Pusan National University ) , Hwang, Yu-Jin (School of Mechanical Engineering, Pusan National University ) , Lee, Jung-Eun (School of Mechanical Engineering, Pusan National University ) , Lee, Jae-Keun (School of Mechanical Engineering, Pusan National University ) , Kim, Hyeong-Seok (Digital Appliance Research Laboratory, LG Electronics Inc ) , Ahn, Sung-Young (Digital Appliance Research Laboratory, LG Electronics Inc ) , Kim, Soo-Hyung (Department of Nanosystem and Nanoprocess Engineering, Pusan National University)
    Journal of mechanical science and technology v.24 no.8 ,pp. 1631 - 1635 , 2010 , 1738-494x ,

    초록

    This study examined the tribological behavior of journal bearings made from polytetrafluoroethylene (PTFE) composites and aluminum (Al) alloys. The PTFE composite journal bearings consisted of a steel backing with a thickness of 1.6 mm, a middle layer of sintered porous bronze with a thickness of 0.24~0.27 mm, and a surface layer of PTFE filled with fluorinated ethylene propylene (FEP) powder and carbon fibers with a thickness 0.06~0.14 mm. The other was an aluminum alloy journal bearing consisted of a steel backing with a thickness of 1.5 mm and a surface layer of an Al-6Sn-6Si alloy with a thickness 0.35~0.75 mm. A series of lubrication tests were performed using a journal bearing tester under various normal loads. The tribological properties for each journal bearing were evaluated by measuring the lubricant oil temperature and friction coefficient as a function of the applied normal load. In addition, the chemical compositions and microstructures of the journal bearing materials used in this study was analyzed by inductively coupled plasma (ICP), optical microscopy (OM), and scanning electron microscopy (SEM), respectively. The experimental results showed that the Al alloy journal bearings reduce the friction coefficient by 28 % compared to the PTFE composites bearings. In addition, the Al alloy journal bearing worked properly at the maximum load of~8,000 N without adhesion. However, the PTFE composite journal bearings exhibited strong adhesion at the loads ranging from 6300 to 8000 N. This suggests that the Al alloy is a more promising material in journal bearings than PTFE composites.

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  10. [국내논문]   Determination of the minute range for RSM to select the optimum cutting conditions during turning on CNC lathe   SCIE 피인용횟수: 4

    Lee, Hyun-Wook (Department of Mechanical and Information Engineering, University of Seoul ) , Kwon, Won-Tae (Department of Mechanical and Information Engineering, University of Seoul)
    Journal of mechanical science and technology v.24 no.8 ,pp. 1637 - 1645 , 2010 , 1738-494x ,

    초록

    Taguchi method and RSM (response surface method) are two of the most well known DOE (design of experiment) techniques. The levels of parameters are recommended to be taken far apart in the Taguchi method in order to cover a wide region to increase the chance of capturing nonlinearity of the relationship between the control and control factors. On the contrary, as long as the optimum is located within the region, RSM needs it to be as small as possible to identify the exact optimum. In this study, the Taguchi method is used to determine the rough region first, followed by RSM technique to determine the exact optimum value during turning on a CNC lathe. A new region reducing algorithm is introduced to narrow down the region of the Taguchi method for RSM. To achieve the goal, the result from the Taguchi method is fed to train the artificial neural network (ANN), whose optimum value is used to drive the region reducing algorithm. The proposed algorithm is tested under different cutting condition with different insert and work material. Data located in the literature is also used to inspect the adequacy of the region reducing algorithm. Both results show that the introduced algorithm has a good region reducing capability. In a separated experiment, it is shown that the obtained cutting condition from RSM gives a better result than that from the Taguchi method.

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