• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.10a
• /
• pp.190-195
• /
• 2012

Small-scaled Rotor Test facility(GSRTS, General Small-scaled Rotor Test Facility) in KARI could not use the test because facility aging and parts discontinued. Also in order to perform a joint international research, GSRTS modifications should be needed. So requirements of GSRTS modifications were established and according to the requirements, GSRTS modifications were conducted. Facility operation test, 6-component fixed balance calibration, Small-scaled OLS rotor performance test were performed to verify the results of GSRTS modifications. Reasonable results were obtained in comparison to calculation results. Then GSRTS ready was completed to conduct international collaborative research and wind tunnel test.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.852-855
• /
• 2005

Structural Dynamic Modification(SDM) is a technique to improve structure's dynamic characteristics by adding and removing substructures or changing material properties and shape of structures. This paper describes SDM techniques applied to a large structure with too many DOFs. The goal of this SDM technique is to modify a targe structure efficiently for its natural frequencies to avoid excitation frequencies. In this case, models reduced by Component Mode Synthesis(CMS) method that is a coupling technique are used to analyze a large structure efficiently. This paper considers a helicopter deck model with 55,000 DOFs as an application.

• International Journal of Aeronautical and Space Sciences
• /
• v.12 no.2
• /
• pp.93-114
• /
• 2011

The current status of Canadian research on rotor-based actively controlled technologies for helicopters is reviewed in this paper. First, worldwide research in this field is overviewed to put Canadian research into context. Then, the unique hybrid control concept of Carleton University is described, along with its key element, the "stiffness control" concept. Next, the smart hybrid active rotor control system (SHARCS) projected's history and organization is presented, which aims to demonstrate the hybrid control concept in a wind tunnel test campaign. To support the activities of SHARCS, unique computational tools, novel experimental facilities and new know-how had to be developed in Canada, among them the state-of-the-art Carleton Whirl Tower facility or the ability to design and manufacture aeroelastically scaled helicopter rotors for wind tunnel testing. In the second half of the paper, details are provided on the current status of development on the three subsystems of SHARCS, i.e. that of the actively controlled tip, the actively controlled flap and the unique stiffness-control device, the active pitch link.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.5
• /
• pp.1983-1989
• /
• 2012

This paper presents the stability analysis of UH-60 helicopter with external store such like chaff/flare dispenser. An external store can affect the natural frequency of the aircraft and induce the resonance, which cause the failure of structures. In this paper, therefore, Rayleigh method is used to investigate the resonance with aircraft and external store, and transmission formula is used to determine the vibration load. Structural analysis with local modeling method are performed to present the robust design of aircraft with external store. The ground and flight test are also done to verify the stability of the aircraft.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.11a
• /
• pp.713-716
• /
• 2010

Slosh and vibration effects of fuel inside of fuel tank can be occurred due to the acceleration and flight speed during the rotorcraft flight. It can lead to the failure of internal fuel component and fuel tank skin can be damaged. This is directly related to human survival. Military specification (MIL-DTL-27422D) specifies that stability of aircraft fuel tank and internal component against slosh &vibration load shall be verified through the qualification test procedures. This report shows the establishment of slosh and vibration test facility and KUH fuel tank qualification test result.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.85-92
• /
• 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.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.3 s.258
• /
• pp.331-337
• /
• 2007

Rotating cantilever beams can be found in several practical engineering applications such as turbine blades and helicopter rotor blades. For reliable and economic design, it is necessary to estimate the dynamic characteristics of those structures accurately and efficiently since significant variation of dynamic characteristics resulted from rotational motion of the structures. Recently, Differential Transformation Method(DTM) was proposed by Zhou. This method has been applied to fluid dynamics and vibration problems, and has shown accuracy, efficiency and convenience in solving differential equations. The purpose of this study, the free vibration analysis of a rotating cantilever beam, is to seek for the reliable property of DTM and confidence in the results obtained by this method by comparing the results with that of finite element method applied to linear partial differential equations. In particular, this study is worked by supposing optional T-function values because the equations governing chordwise motion are based on two differential equations coupled with each other. This study also shows mode shapes of rotating cantilever beams for various rotating speeds.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.24 no.4
• /
• pp.357-367
• /
• 2021

This paper studies the simulations of active airframe vibration controls for the Sikorsky X2 helicopter with a lift-offset coaxial rotor. The 4P hub vibratory loads of the X2TD rotor are obtained from the previous work using a rotorcraft comprehensive analysis code, CAMRAD II. The finite element analysis software, MSC.NASTRAN, is used to model the structural dynamics of the X2TD airframe and to analyze the 4P vibration responses of the airframe. A simulation study using Active Vibration Control System(AVCS) with Fx-LMS algorithm to reduce the airframe vibrations is conducted. The present AVCS is modeled using MATLAB Simulink. When AVCS is applied to the X2TD airframe at 250 knots, the 4P longitudinal and vertical vibration responses at the specified airframe positions, such as the pilot seat, co-pilot seat, engine deck, and prop gearbox, are reduced by 30.65 ~ 94.12 %.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.04a
• /
• pp.361-369
• /
• 1996

The accurate prediction of modal parameters of a rotating blade is an important requirement in the assessment of the dynamics of a helicopter rotor. Indeed, predictions of flight loads and stability are normally dependent on initially predicting the undamped mode shapes. A measuring technique, known as Strain Pattern Analysis (SPA), appears to be the most successful technique for measuring the mode shapes of rotating blades. This method was developed to be used on actual aircraft so no attempt was made to measure rotating mode shapes directly in order to validate the SPA method. This report summarizes results from experimental investigations which were carried out to validate the SPA method for the prediction of aerodynamically damped modes of a rotating blade. A series of modal tests were carried out on two rotor models in which the non-rotating, undamped and aerodynamically damped rotating modes were measured directly (strain and displacement patterns). It is shown that the SPA method to be very successful in itself but there are a number of limitations in validating this technique. To provide data which could be used to confidently validate theoretical prediction codes, existing limitations should be addressed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2008.04a
• /
• pp.140-143
• /
• 2008

Experiments are performed to consider the ground effects on unsteady loading and acoustic generation. Partially inclined plate is used to maximize the unsteadiness of the rotor. Indirect method to recognize the unsteady effect is used by measuring the noise in the normal direction from the rotor plane. The experiment is conducted with a square plate of about $9m^2$ and one half of the plate is placed parallel with the rotor plane and the other half is inclined. The height of the plate and the angle of the inclined plate can be changed. Helicopter noise is also measured at the 4 different positions to study the directivity of the rotor noise. The distance between microphone and rotor hub is 1.3m. Tonal noise and broad band noise are measured and analyzed. Thickness noise, steady loading noise and unsteady loading noise are investigated from the rotor noise measurement.