• Title, Summary, Keyword: Fatigue spectrum

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The Development of Fatigue Load Spectrum and Fatigue Analysis for the Tilt Rotor UAV (틸트 로터 무인항공기의 피로하중 스펙트럼 생성 및 피로해석)

  • Im, Jong-Bin;Park, Young-Chul;Park, Jung-Sun;Lee, Jeong-Jin
    • Proceedings of the KSME Conference
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    • pp.654-659
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    • 2007
  • In this paper, the fatigue load spectrum for tilt rotor UAV is developed and fatigue analysis is achieved for flaperon joint. Tilt rotor UAV has two modes which are helicopter mode when UAV is taking off and landing and fixed wing mode when UAV is cruising. To make fatigue load spectrum, FELIX for helicopter mode and TWIST for fixed wing mode are used. And Fatigue analysis of flaperon joint is achieved using fatigue load spectrum we obtained. When S-N test data are analyzed, we use the Kriging meta model to get probability S-N curve for whole range of material life. The result which is life of flaperon joint obtained by suggested fatigue analysis procedure in this paper is compared with that obtained by MSC/Fatigue.

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Fatigue Damage Model Comparison with Tri-modal Spectrum under Stationary Gaussian Random Processes (정상 정규분포 확률과정의 삼봉형 스펙트럼에 대한 피로손상 모델 비교)

  • Park, Jun-Bum;Jeong, Se-Min
    • Journal of Ocean Engineering and Technology
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    • v.28 no.3
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    • pp.185-192
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    • 2014
  • The riser systems for floating offshore structures are known to experience tri-modal dynamic responses. These are owing to the combined loadings from the low-frequency response due to riser tension behavior, middle-range frequency response coming from winds and waves, and high-frequency response due to vortex induced-vibration. In this study, fatigue damage models were applied to predict the fatigue damages in a well-separated tri-modal spectrum, and the resultant fatigue damages of each model were compared with the most reasonable fatigue damage calculated by the inverse Fourier transform of the spectrum, rain-flow counting method, and Palmgren-Miner rule as a reference. The results show that the fatigue damage models developed for a wide-band spectrum are applicable to the tri-modal spectrum, and both the Benasciutti-Tovo and JB models could most accurately predict the fatigue damages of the tri-modal spectrum responses.

A Study on Load Spectrum for Fatigue Analysis of Helicopter Rotor Blades (헬리콥터 로터 블레이드의 피로해석을 위한 하중 스펙트럼연구)

  • Oh, Man-Seok;Kim, Hyun-Duk;Kee, Young-Jung;Park, Jung-Sun
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.15 no.3
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    • pp.15-23
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    • 2007
  • In this paper, we deducted the missions with respect to Korea utility helicopter (KUH) and consist of the scenarios which describe proper purpose of KUH. And so developed fatigue load spectrum of KUH by applying Helix that is fatigue load spectrum for blade of articulated helicopter rotor system. The developed load spectrum is applied to fatigue analysis of blade by modeled finite element with stress-life method (S-N). And we compared the result of fatigue analysis to prior to Helix for the sake of verifying the load spectrum that we generated.

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Tracked Vehicle Vibration Environmental Comparison using Fatigue Damage Spectrum (Fatigue Damage Spectrum을 이용한 궤도차량의 진동환경 비교)

  • 김재하;최병민;우호길
    • Journal of the Korea Institute of Military Science and Technology
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    • v.3 no.1
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    • pp.191-197
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    • 2000
  • This paper provides the test results of tracked vehicle at each driving condition and life cycle. Fatigue Damage Spectrum(FDS) has evaluated with the Power Spectrum Density(PSD) and the life time of equipment. Finally, provisional vibration qualification test level is evaluated.

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A Study of Fatigue Load for Rotor Blades of the Utility Helicopter (다목적 헬리콥터 로터 블레이드 피로하중에 대한 연구)

  • Oh, Man-Seok;Kim, Hyun-Duk;Park, Jung-Sun;Gi, Yeong-Jung
    • Proceedings of the KSME Conference
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    • pp.648-653
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    • 2007
  • In this study, we have generated fatigue load spectrum that is using to prediction of life time for the helicopter rotor blades. We derive utility helicopter missions for the sake of generating load spectrum. Helix and Felix are standard loading sequences which relate to the main rotors of helicopters with articulated and semi-rigid rotors respectively. We got scale factors which is applied to specific case and it did be obtained through the finite element analysis tools. The fatigue life of the rotor blade is estimated by using MSC/Fatigue. We suggest that generated our fatigue load spectrum in conjunction with small utility helicopter should use to rotor blade fatigue test of the korea helicopter program.

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Fatigue Damage Analysis Using Rainflow Counting Method (Rainflow Counting방법을 이용한 피로 손상 해석)

  • Kim, Jung-Hun;Lee, Hak;Zi, Goang-Seup;Park, Byung-Hoon;Kong, Jung-Sik
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.387-392
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    • 2007
  • The loss of strength in an aircraft structure as a result of cyclic stress over a period of life time is an important phenomenon for aircraft analysis. Load/stress spectrum can be constructed from the occurrence frequency based on the load/stress histories during a service lifetime. In this paper, three types of fatigue spectrum was compared. The rainflow counting method was applied to concentrate the stress spectrum obtained from the flight loads recorder(FLDR). A fatigue analysis for different stress spectrum was performed by using LUSAS computer application.

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Damage Tolerant Design for the Tilt Rotor UAV (틸트 로터형 무인항공기의 손상허용 설계)

  • Park, Young Chul;Im, Jong Bin;Park, Jung Sun
    • Journal of Aerospace System Engineering
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    • v.1 no.2
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    • pp.27-36
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    • 2007
  • The Damage Tolerant Design is developed to help alleviate structural failure and cracking problems in aerospace structures. Recently, the Damage Tolerant Design is required and recommended for most of aircraft design. In this paper, the damage tolerant design is applied to tilt rotor UAV. First of all, the fatigue load spectrum for the tilt rotor UAV is developed and fatigue analysis is performed for the flaperon joint which has FCL (fatigue critical location). Tilt rotor UAV has two modes: helicopter mode when UAV is taking off and landing; fixed wing mode when the tilt rotor UAV is cruising. To make fatigue load spectrum, FELIX is used for helicopter mode. TWIST is used for fixed wing mode. Fatigue analysis of flaperon joint is performed using fatigue load spectrum. E-N curve approach is used for picking crack initiation point. The LEFM(Linear Elastic Fracture Method) is considered for analyzing crack growth or propagation. Finally, including the crack initiation and propagation, the fatigue life is evaluated. Therefore the Damage Tolerant Design can be done.

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Fatigue Life Estimation for Flaperon Joint of Tilt-Rotor UAV (틸트 로터 무인항공기의 플랩퍼론 연결부에 대한 피로수명 평가)

  • Kim, Myung Jun;Park, Young Chul;Lee, Jung Jin;Park, Jung Sun
    • Journal of Aerospace System Engineering
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    • v.3 no.2
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    • pp.12-19
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    • 2009
  • The research for the fatigue analysis is regarded greatly as important in aerospace field. Moreover, a study on the fatigue characteristic is very actively progressing. In this study, the fatigue life estimation was performed for Flaperon Joint which has FCL(fatigue critical location) of tilt-rotor UAV. The Flaperon Joint should be taken the various loads by several missions profiles of UAV. The fatigue load spectrum of Flaperon Joint is generated by the standard mission segment for the tilt-rotor UAV, and this spectrum is used for the fatigue test and analysis. The in-house fatigue analysis program is applied to calculate the fatigue life based on Stress-Life(S-N) method. The S-N curve is generated from the S-N data of Mil-Handbook by second order polynomial regression method. Moreover, the coefficient of determination is used to ensure how accuracy it has. In addition, the Goodman equation is used to consider the mean stress effect for evaluating more accurate fatigue life. Finally, the result of fatigue analysis is verified by comparing with the fatigue test result for the Flaperon Joint.

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Fatigue Damage Combination for Spread Mooring System under Stationary Random Process with Bimodal Spectrum Characteristics (바이모달 스펙트럼 특성을 가지는 정상확률과정에 대한 다점계류라인의 피로손상도 조합기법 연구)

  • Lim, Yu-Chang;Kim, Kyung-Su;Choung, Joon-Mo
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.6
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    • pp.813-820
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    • 2010
  • The spread mooring system for FPSO is developed to explore deep sea area, in which swell is dominant. It is known that the tension response of mooring lines in this sea area shows bimodal spectrum. Assuming normal distribution of tension profile and Rayleigh distribution of tension amplitude, the power spectral density function (PSD) of the mooring tension under the bimodal stationary random process is applied for the calculation of spectrum fatigue. Three popular methods, which are simple summation method, combined spectrum method and Jioa-Moan method, are used to combine fatigue damages from bimodal spectrum characteristics. Each damage value is compared with damage using Rainflow Cycle Counting (RCC) method which is believed to be close to exact solution. Vanmarcke' parameter and RMS(Root Mean Square) ratio are employed to assess relative damage variations between from RCC method and from three combination methods. Finally the most reliable fatigue damage combining method for spread mooring system is suggested.

Evaluation of typhoon induced fatigue damage using health monitoring data for the Tsing Ma Bridge

  • Chan, Tommy H.T.;Li, Z.X.;Ko, J.M.
    • Structural Engineering and Mechanics
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    • v.17 no.5
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    • pp.655-670
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    • 2004
  • This paper aims to evaluate the effect of typhoons on fatigue damage accumulation in steel decks of long-span suspension bridges. The strain-time histories at critical locations of deck sections of long-span bridges during different typhoons passing the bridge area are investigated by using on-line strain data acquired from the structural health monitoring system installed on the bridge. The fatigue damage models based on Miner's Law and Continuum Damage Mechanics (CDM) are applied to calculate the increment of fatigue damage due to the action of a typhoon. Accumulated fatigue damage during the typhoon is also calculated and compared between Miner's Law and the CDM method. It is found that for the Tsing Ma Bridge case, the stress spectrum generated by a typhoon is significantly different than that generated by normal traffic and its histogram shapes can be described approximately as a Rayleigh distribution. The influence of typhoon loading on accumulative fatigue damage is more significant than that due to normal traffic loading. The increment of fatigue damage generated by hourly stress spectrum for the maximum typhoon loading may be much greater than those for normal traffic loading. It is, therefore, concluded that it is necessary to evaluate typhoon induced fatigue damage for the purpose of accurately evaluating accumulative fatigue damage for long-span bridges located within typhoon prone regions.