• Title/Summary/Keyword: 진동하중(vibratory load)

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A Study on the Effect of Lateral Vibration of Sheet Pile on Vibratory Driving Force (널말뚝의 횡방향진동이 진동타입력에 미치는 영향에 대한 연구)

  • Lee, Seung-Hyun;Kim, Byoung-Il
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.8 no.4
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    • pp.848-852
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    • 2007
  • Many numerical analysis tools for predicting penetration speed of sheet pile are thought to be unreliable because they overestimate penetration speed for shallow depth of penetration. In order to overcome the defects of numerical analysis, lateral vibration model of sheet pile was suggested and energy consumption due to lateral vibration of sheet pile was estimated. Also, load reduction factor which explains reduction of vibratory driving force due to lateral vibration was introduced.

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HDS를 통한 헬리콥터 로우터 블레이드 동적 특성 및 하중 분석기법 연구

  • Kim, Deok-Kwan;Joo, Gene
    • Aerospace Engineering and Technology
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    • v.1 no.1
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    • pp.1-7
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    • 2002
  • This paper describes the analysis method about the dynamic characteristics and vibratory load through HDS(Helicopter Design Study). To analyze the dynamic characteristics of helicopter rotor blade, the natural frequencies and modes are calculated according to rotor operational speed(Ω). Generally the proximity of rotor natural frequency and N times of rotor operational speed is a dominant component to determine the helicopter vibration. Also we can predict the airframe vibration by calculating the airload of rotating blade exactly. We expect to establish the design procedure of rotor dynamics by describing the two major analysis methods necessary to rotor design.

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Effect of Lift-offset Rotor Hub Vibratory Load Components on Airframe Vibration Responses of High-Speed Compound Unmanned Rotorcrafts (고속비행 복합형 무인 회전익기의 Lift-offset 로터 허브 진동 하중 성분과 기체 진동 응답의 상관 관계의 연구)

  • Kim, Ji-Su;Hong, Sung-Boo;Kwon, Young-Min;Park, Jae-Sang
    • Journal of the Korea Institute of Military Science and Technology
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    • v.24 no.3
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    • pp.255-263
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    • 2021
  • This paper investigates numerically the effect of rotor hub vibratory load components on the airframe vibration responses of high-speed compound unmanned rotorcraft (HCUR) using a lift-offset coaxial rotor, wings, and two propellers. The rotor hub vibratory loads are predicted using a rotorcraft comprehensive analysis code, CAMRAD II, and the airframe vibration responses are calculated by a finite element analysis software, MSC.NASTRAN. It is shown that the vibratory hub pitch moment of a lift-offset coaxial rotor is the most dominant component for both the longitudinal and vertical vibration responses at four specified locations of the airframe.

Influence of Bias Weight of Vibratory Pile Driver on Load Transfer Characteristics of Piles (진동타입기의 사하중이 말뚝의 하중전이 특성에 미치는 영향)

  • Lee, Seung-Hyun;Kim, Byung-Il
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.10
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    • pp.5268-5273
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    • 2013
  • Technique for analyzing pile installed by vibratory pile driver was developed and results of analysis obtained from variation of bias weight were studied. It can be seen from load transfer curve for dynamic skin friction that load transfer curve shift to downward as bias weight increases. Shape of load transfer curve for dynamic skin friction becomes closer to shape of coil as the bias weight decreases. Magnitudes of toe resistances were not affected by the bias weight. Shape of load transfer curve for dynamic toe resistance shows the similar tendency as the load transfer curve for skin friction exhibits. Vertical displacement increases as the bias weight increases and the shape of vertical displacement with time shows more distinct shape of wave.

Validation for Performance and Hub Vibratory Load Analyses of Lift-offset Coaxial Rotors in Wind-Tunnel Tests (풍동 시험용 Lift-offset 동축 반전 로터에 대한 성능 및 허브 진동 하중 해석의 검증 연구)

  • Lee, Yu-Been;Park, Jae-Sang
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.50 no.7
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    • pp.497-505
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    • 2022
  • Performance and hub vibratory load analyses for a lift-offset coaxial rotor are conducted using a rotorcraft comprehensive analysis code, CAMRAD II. The lift-offset coaxial rotor is trimmed to match the total rotor thrust(lift-offset coaxial rotor's thrust) or the individual rotor thrust(upper and lower rotor thrusts, respectively) in this study. The individual rotor's lift and torque, and effective rotor lift to drag ratio for the total rotor are investigated for various advance ratios and lift-offset values. The two result sets with different trim methods are similar to each other and they are correlated well with the wind-tunnel test results. Therefore, the present study using CAMRAD II validates successfully the aeromechanics modeling and analysis techniques for the lift-offset coaxial rotor.

Vibratory Hub Loads of Helicopters due to Uncertainty of Composite Blade Properties (복합재료 블레이드의 불확실성을 고려한 헬리콥터 허브 진동하중 해석)

  • You, Young-Hyun;Jung, Sung-Nam
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.7
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    • pp.634-641
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    • 2009
  • In this work, the behavior of vibratory hub loads induced due to the uncertainties of composite material properties for each of the participating rotor blades is investigated. The random material properties of composites available from the existing experimental data are processed by using the Monte-Carlo simulation technique to obtain the stochastic distribution of sectional stiffnesses of composite blades. The coefficients of variation (standard deviation divided by the mean) obtained from the sectional stiffness constants are used as an input to the comprehensive aeroelastic analysis code that can evaluate the hub loads of a rotor system. It is found that the uncertainty effects of composite material properties inevitably bring a dissimilarity to the rotor system. The influence of hub vibration response with respect to the individual stiffness (flatwise bending, chordwise bending and torsion) changes is also identified.

Design optimization and vibratory loads analysis of active twist rotor blades incorporating single crystal piezoelectric fiber composites (단결정 압전섬유작동기를 사용한 능동 비틀림 로터 블레이드의 최적 설계 및 진동하중 해석)

  • Park, Jae-Sang;Shin, Sang-Joon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.85-92
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    • 2007
  • This paper presents a design optimization of a new Advanced Active Blade Twist (AATR-II) blade incorporating single crystal Macro Fiber Composites (MFC) and conducts vibratory loads reduction analysis using an obtained optimal blade configuration. Due to the high actuation performance of the single crystal MFC, the AATR blade may reduce the helicopter vibration more efficiently even with a lower input-voltage as compared with the previous ATR blades. The design optimization provides the optimal cross-sectional configuration to maximize the tip twist actuation when a certain input-voltage is given. In order to maintain the properties of the original ATR blade, various constraints and bounds are considered for the design variables selected. After the design optimization is completed successfully, vibratory load reduction analysis of the optimized AATR-II blade in forward flight condition is conducted. The numerical result shows that the hub vibratory loads are reduced significantly although 20% input-voltage of the original ATR blade is used.

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Parametric Study on Lateral Vibration Model of Steel Sheet Pile (강널말뚝의 횡방향 진동모델에 대한 매개변수 연구)

  • Lee, Seung-Hyun;Kim, Byung-Il;Kim, Zu-Cheol;Kim, Jeong-Hwan
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.3
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    • pp.1047-1052
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    • 2010
  • Influence of lateral spring constant on energy dissipation and load reduction factor with erespect to lateral vibration of steel sheet pile installed by vibratory pile driver. Energy dissipation and load reduction factor varying with free length of steel sheet pile are more affected by eccentricity than flexural rigidity of steel sheet pile regardless of the magnitudes of lateral spring constants. Load reduction factors were converged when lateral spring constant was equal or larger than 10000N/m.

Characteristics of Behavior of Steel Sheet Pile installed by Vibratory Pile Driver (진동타입기에 의해 시공되는 강널말뚝의 거동특성)

  • Lee, Seung Hyun;Kim, Byoung Il;Kim, Zu Cheol;Kim, Jeong Hwan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.1C
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    • pp.27-35
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    • 2010
  • Instrumented steel sheet piles being driven by vibratory pile driver were installed in granular soil deposit and behaviors of the sheet piles were investigated. One of the instrumented steel sheet pile was installed without clutch and the other was installed with clutch. Sheet pile with clutch means that of installed in connection with pre-installed sheet pile. Penetration rates of sheet piles measured from depth measuring drum has shown that interlock friction had great effect on penetration speed of sheet pile. Clutch friction shows irregular distribution along the depths of penetration and its magnitude was estimated as 19.1kN/m. According to the accelerations obtained from accelerometer, it was seen that steel sheet pile behaviored nearly as a rigid body. Efficiency factor of an isolated sheet pile was 0.42 and that of the connected sheet pile was 0.71. Shapes of dynamic load transfer curves obtained from analysis of measuring devices was similar to those suggested by Dierssen.

Design and Analysis of Flexbeam in SNUF Blade Equipped with Active Trailing-Edge Flap for Helicopter Vibratory Load Reduction (헬리콥터 진동 하중 저감을 위한 능동 뒷전 플랩이 장착된 SNUF 블레이드의 유연보의 설계 및 해석)

  • Im, Byeong-Uk;Eun, Won-Jong;Shin, SangJoon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.7
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    • pp.542-550
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    • 2018
  • This paper presents design of a bearingless main rotor of SNUF (Seoul National University Flap) blade equipped with active trailing-edge flap to reduce the hub vibratory loads during helicopter forward flight. For that purpose, sectional design of the flexbeam is carried out using the thin-walled composite material rotating beam vibration analysis program (CORBA77_MEMB) in EDISON. Using the multi-body dynamics analysis program, DYMORE, blade dynamic characteristics and those of the loads control are examined using the active trailing-edge flap in terms of the flexbeam sectional design.