• Title/Summary/Keyword: Axial Mode

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Fluid-structure coupling of concentric double FGM shells with different lengths

  • Moshkelgosha, Ehsan;Askari, Ehsan;Jeong, Kyeong-Hoon;Shafiee, Ali Akbar
    • Structural Engineering and Mechanics
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    • v.61 no.2
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    • pp.231-244
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    • 2017
  • The aim of this study is to develop a semi-analytical method to investigate fluid-structure coupling of concentric double shells with different lengths and elastic behaviours. Co-axial shells constitute a cylindrical circular container and a baffle submerged inside the stored fluid. The container shell is made of functionally graded materials with mechanical properties changing through its thickness continuously. The baffle made of steel is fixed along its top edge and submerged inside fluid such that its lower edge freely moves. The developed approach is verified using a commercial finite element computer code. Although the model is presented for a specific case in the present work, it can be generalized to investigate coupling of shell-plate structures via fluid. It is shown that the coupling between concentric shells occurs only when they vibrate in a same circumferential mode number, n. It is also revealed that the normalized vibration amplitude of the inner shell is about the same as that of the outer shell, for narrower radial gaps. Moreover, the natural frequencies of the fluid-coupled system gradually decrease and converge to the certain values as the gradient index increases.

Restoration of pre-damaged RC bridge columns using basalt FRP composites

  • Fahmy, Mohamed F.M.;Wu, Zhishen
    • Earthquakes and Structures
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    • v.14 no.5
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    • pp.379-388
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    • 2018
  • This study aims to identify the effect of both longitudinal reinforcement details and damage level on making a decision of repairing pre-damaged bridge columns using basalt fiber reinforced polymer (BFRP) jackets. Two RC bridge columns with improper details of the longitudinal and/or transverse reinforcement were tested under the effect of a constant axial load and increasing lateral cyclic loading. Test results showed that the lap-splice column exhibited an inferior performance where it showed rapid degradation of strength before achieving the theoretical strength and its deformation capacity was limited; however, quick restoration is possible through a suitable rehabilitation technique. On the other hand, expensive repair or even complete replacement could be the decision for the column with the confinement failure mode. After that, a rehabilitation technique using external BFRP jacket was adopted. Performance-based design details guaranteeing the enhancement in the inelastic performance of both damaged columns were addressed and defined. Test results of the repaired columns confirmed that both reparability and the required repairing time of damage structures are dependent on the reinforcement details at the plastic hinge zone. Furthermore, lap-splice of longitudinal reinforcement could be applied as a key design-tool controlling reparability and restorability of RC structures after massive actions.

Combustion Dynamics of a Gas Generator Assembled with a Turbine Manifold (터빈 결합 환경의 가스발생기 동적 연소 특성)

  • Seo, Seong-Hyeon;Lim, Byung-Jik;Ahn, Kyu-Bok;Lee, Kwang-Jin;Kim, Jong-Gyu;Han, Yeoung-Min;Choi, Hwan-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.05a
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    • pp.121-124
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    • 2008
  • This paper presents experimental results of dynamic characteristics of fuel-rich gas generators. Pressure fluctuation measurements in the chamber and manifolds have been analyzed. Gas-generator-alone tests revealed stable combustion regardless of a chamber pressure but low-frequency combustion instabilities occurred for cases of turbine-manifold tests at chamber pressure conditions below 50 bar. The instabilities are considered as an axial resonant mode and acoustic intensity increases along with a chamber pressure.

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Power upgrading of WWR-S research reactor using plate-type fuel elements part I: Steady-state thermal-hydraulic analysis (forced convection cooling mode)

  • Alyan, Adel;El-Koliel, Moustafa S.
    • Nuclear Engineering and Technology
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    • v.52 no.7
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    • pp.1417-1428
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    • 2020
  • The design of a nuclear reactor core requires basic thermal-hydraulic information concerning the heat transfer regime at which onset of nucleate boiling (ONB) will occur, the pressure drop and flow rate through the reactor core, the temperature and power distributions in the reactor core, the departure from nucleate boiling (DNB), the condition for onset of flow instability (OFI), in addition to, the critical velocity beyond which the fuel elements will collapse. These values depend on coolant velocity, fuel element geometry, inlet temperature, flow direction and water column above the top of the reactor core. Enough safety margins to ONB, DNB and OFI must-emphasized. A heat transfer package is used for calculating convection heat transfer coefficient in single phase turbulent, transition and laminar regimes. The main objective of this paper is to study the possibility of power upgrading of WWR-S research reactor from 2 to 10 MWth. This study presents a one-dimensional mathematical model (axial direction) for steady-state thermal-hydraulic design and analysis of the upgraded WWR-S reactor in which two types of plate fuel elements are employed. FOR-CONV computer program is developed for the needs of the power upgrading of WWR-S reactor up to 10 MWth.

Three-Dimensional Vibration Analysis of Solid Cylinders of N-Sided Polygonal Cross-Section Having V-notches or Sharp Cracks (V노치 및 예리한 균열을 갖는 N 다변형 단면 입체 실린더의 3차원 진동해석)

  • Kim, Joo Woo
    • Journal of Korean Society of Steel Construction
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    • v.21 no.4
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    • pp.433-442
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    • 2009
  • In this paper, new three-dimensional vibration data for the solid cylinders of the N-sided polygonal cross-section with V-notches or sharp cracks are presented, and a Ritz procedure is employed, which incorporates a mathematically complete set of algebraic-trigonometric polynomials in conjunction with an admissible set of edge functions that explicitly model the tri-axial stress singularities that exist along a terminus edge of the V-notch. Convergence studies demonstrate the necessity of adding the edge functions to achieve the accurate frequencies and mode shapes of N-sided polygonal cylindrical solids with stress singularities.

Nonlinear Finite Element Analysis on the Transmission of Column Loads through Slab-Column Connections

  • Lee, Joo-Ha;Yoon, Young-Soo;Sohn, Yu-Shin;Lee, Seung-Hoon
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.05a
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    • pp.466-469
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    • 2006
  • This paper presents the structural characteristics of slab-column connections by using nonlinear finite element analysis. FEA considering material non-linearity was performed to investigate average column strain, failure mode, principal stress distribution, and steel yielding conditions for various slab-column members. In addition, to investigate alternative methods for improving the strength of interior column-slab joints, some specimens were provided with different reinforcing types of high-strength concrete puddling, high-strength column longitudinal steels, dowel bars, and high-strength concrete core. To make certain of the reliability of the analytical program, analysis results for concrete material model developed and two specimens with and without puddling were compared with experimental results. It was found that providing the alternative reinforcing methods in the slab-column joint results in a significant improvement in performance. This includes an increase in the axial compressive strength, greater loading stiffness, and ductility.

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An Experimental Study of Nonlinear Viscoelastic Bushing Model for Axial Mode

  • Lee, Seong-Beom;Shin, Jung-Woog;Alan S. Wineman
    • Journal of Mechanical Science and Technology
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    • v.17 no.9
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    • pp.1324-1331
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    • 2003
  • A bushing is a device used in automotive suspension systems to cushion the force transmitted from the wheel to the frame of the vehicle. A bushing is essentially a hollow cylinder which is bonded to a solid metal shaft at its inner surface and a metal sleeve at its outer surface. The shaft is connected to the suspension and the sleeve is connected to the frame. The cylinder provides the cushion when it deforms due to relative motion between the shaft and sleeve. The relation between the force applied to the shaft or sleeve and its deformation is nonlinear and exhibits features of viscoelasticity. An explicit force-displacement relation has been introduced for multi-body dynamics simulations. The relation is expressed in terms of a force relaxation function and a method of determination by experiments on bushings has been developed. Solutions allow for comparison between the force-displacement behavior by experiments and that predicted by the proposed method. It is shown that the predictions by the proposed force-displacement relation are in very good agreement with the experimental results.

Design of High Speed Spindle for 5-Axis Machining Equipment Equipped with Piezo-Electric Load Sensoring (압전형 부하 센서링이 장착된 5축 절삭가공기의 고속 주축시스템 설계)

  • Choi, Hyun-Jin;Park, Chul-Woo;Jang, Eun-Sil;Kim, Chung-Hyun;Choi, Seong-Dae
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.10 no.5
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    • pp.20-25
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    • 2011
  • In this paper, we reviewed the spindle system's motor and bearing and its mode safety for optimal design of a high speed spindle system that exceeds DmN value of 1,500,000. We could verify that it has a separation margin during critical speed by performing critical speed analysis. Also, we have selected an optimal sensoring installation location and actually manufactured & installed the sensor by identifying the stress concentration position in the axial load through finite element analysis to install the built-in piezo electric type load sensor to the spindle housing that can measure and monitor the machining load during high speed rotation of the spindle. Reproducibility is also verified by calibrating the error through the sensor's sensitivity adjustment after comparing the output between the plate dynamoneters and the load sensor to confirm the reproducibility of the load sensor.

Finite Element Analysis of Two-Dimensional Cold Forging By Using Modular Remeshing and Expert System (단위체 격자 재구성법과 전문가 시스템을 이용한 2차원 냉간 단조의 유한 요소 해석)

  • Yun, Hui-Do;Kim, Yeong-Tae;Lee, Nak-Gyu;Yang, Dong-Yeol;Lee, Byeong-Chae
    • Journal of the Korean Society for Precision Engineering
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    • v.9 no.3
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    • pp.83-101
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    • 1992
  • A systematic method of remeshing is required due to severe mesh distortion after some finite deformation in the finite element analysis of practical forging processes. In order to cope with the problem of mesh degeneracy during deformation, the proper design of meshes plays an improtant role in the analysis. In so-called "Modular Remeshing", the physical characteristics of metal flow and geometric characteristics are incorporated in "Module", which can be applied to the mesh design for a certain mode of deformation in so far as the topology of deforming region remains the same. For the purpose of more effective and systematic use of the modular remeshing scheme, an expert system has been developed in the framework of the proposed remeshing schemel. In oredr to show the effectiveness of the method, the rib-web type forging with axial relief or radial relief and spike forging are simulated. It has been thus shown that the proposed method of automatic remeshing by using modular remeshing and expert system can be futher extended and applied to various forging problems with complicated geometrical configurations.ical configurations.

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A Study on Vibration Characteristics of Flywheel Energy Storage System Using Superconducting Magnetic Bearings (초전도자기베어링을 이용한 플라이휠 에너지 저장장치의 진동특성에 관한 연구)

  • 김종수;이수훈
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.2
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    • pp.170-177
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    • 1998
  • The purpose of superconducting magnetic bearing flywheel energy storage system(SMB-FESS) is to store unused nighttime electricity as kinetic energy and convert it to electricity during daytime. The SMB-FESS is proposed as an efficient energy storage system because there is no mechanical problems, such as friction and wear The flywheel over SMB is rotated at a high speed, 50,000rpm. The major source of energy loss in the SMB-FESS is vibration of flywheel. Therefore, the vibration characteristics of SMB-FESS should be identified. In this study, the axial/radial stiffness and damping coefficient of SMB are measured by a vibration test. Natural frequencies and natural modes of flywheel and magnet are analyzed by a finite element method. The modal analysis of system is performed using the modal parameters of each component and the measured stiffness/damping coefficient. So, natural at frequencies and mode shapes of the joined system can be obtained. According to critical speed analysis, the system has two rigid conical modes in the low speed range. Nevertheless, the system has not been affected by the critical speed in the main operating range.

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