• Title, Summary, Keyword: 피로 스펙트럼

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Prediction of Fatigue Life for Composite Rotor Blade of Multipurpose Helicopter Using Strength Degradation Model (강도저하모델을 이용한 다목적헬리콥터용 복합재로터깃 피로수명예측)

  • 권정호;서창원
    • Composites Research
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    • v.14 no.2
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    • pp.50-59
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    • 2001
  • The predictions of residual strength evolution and fatigue life of full scale composite rotor blade for multipurpose helicopter were studied using a strength degradation model. Flight-by-flight load spectrum was developed on the basis of FELIX standard spectrum data. The laminated structural analysis was also performed to obtain corresponding local stress and/or strain spectra for each ply of laminate skin and glass roving spar structures around the blade root where fatigue damage was severely anticipated.

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Damage Tolerance Assessment for Fatigue-Critical Locations of Wing Structure of Aged Aircraft (장기운영 항공기 주익 구조물 피로임계부위의 손상허용평가)

  • Chun, Young-Cheol;Kim, Won-Cheol;Jin, Ji-Won;Chung, Tae-Jin;Kang, Ki-Weon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.2
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    • pp.129-136
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    • 2017
  • This study aims to assess the damage tolerance of the wing structure of aged aircraft with long-term service through the fatigue crack growth analysis and tests. For the fatigue-critical locations (FCL) W2 and W4 in the wing structure, the fatigue stress spectrum was derived based on a previous study. Thereafter, a crack propagation analysis for the FCLs was conducted using the commercial software $NASGRO^{TM}$. The algorithm for the fatigue stress spectrum was verified. Fatigue crack growth tests were then performed for two types of specimens: Type #1 was extracted from the wing structure of aged aircraft, and Type #2 was made of the same material as the wing structure. By comparing the experimental results of these specimens, we assessed the damage tolerance of the wing structure of aged aircraft with service time.

EMG Power Spectrum Analysis of the Medial Gastrocnemius and the Soleus Under the Fatigued Condition (피로조건하에서의 내측 장딴지근과 가자미근의 근전도 스펙트럼 분석)

  • Cynn, Heonseock
    • Physical Therapy Korea
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    • v.5 no.4
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    • pp.9-19
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    • 1998
  • 연구목적 이 연구의 목적은 피로유발수축후 장딴지근과 가자미근의 근전도 power spectrum 중앙경항치를 비교 검사하는 것이다. 실험대상 열 여섯명의 자원자(남자 10, 여자 6)를 대상으로 하였다. 남자 대상자의 연령범위는 25세에서 33세(평균 $28.6{\pm}2.5$)였고 여자 대상자의 연령범위는 26세에서 31세($27.8{\pm}1.9$)였다. 실험방법 실험대상자는 피로유발수축전후 50% 최대등척성근수축을 수행하였다. 자료수집과 분석을 위해 LabVIEW 소프트웨어를 사용하였다. 결과 t-검정결과 내측 장딴지근에서는 피로유발수축후 주파수의 중위값과 평균이 통계적으로 유의하게 감소하였으나 가자미근에서는 통계적으로 유의한 차이가 없었다. t-검정결과 두 근육간 주파수 감소의 차이는 통계적으로 유의한 차이가 있었다. 토의 및 결론 이 결과들은 피로유발수축후 근전도 power spectrum 중앙경향치가 저주파대역으로 감소함을 나타내었다. 이 연구는 중앙주파수와 평균주파수가 피로지수로서의 신뢰도와 타당도가 뛰어나며 객관적 측정과 훈련효과 평가로 사용할수 있음을 보였다.

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Fatigue Test of Aircraft Landing Gear (항공기 착륙장치 피로시험)

  • Lee, Sang-Wook;Lee, Seung-Gyu;Shin, Jeong-Woo;Kim, Tae-Uk;Kim, Sung-Chan;Hwang, In-Hee;Lee, Je-Dong
    • Proceedings of the KAIS Fall Conference
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    • pp.503-506
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    • 2011
  • 항공기 착륙장치 피로 수명평가에는 안전 수명방법이 사용된다. 안전 수명방법은 항공기 전 수명기간을 모사하는 피로하중 스펙트럼 조건에서 균열 또는 유해한 변형과 같은 구조적 결함이 발생하지 않도록 설계/입증하는 것을 말한다. 설계 단계에서는 해석적 방법을 통해 착륙 및 지상운용하중을 구하고, 이를 착륙장치 피로해석에 적용하여 피로수명을 확인한다. 착륙장치는 수명 기간 중 일반적으로 High Cycle 피로를 겪게 되므로, 피로해석 시 응력 기반의 접근 방법이 적용된다. 시험평가 단계에서는 일반적으로 4배의 운용수명에 해당하는 피로하중 스펙트럼에 대해 시험을 수행하여, 착륙장치의 안전 수명을 최종 입증하게 된다. 이와 같이 항공기 착륙장치 피로 수명평가를 위해서는 착륙 및 지상운용 하중해석에서부터 피로해석, 피로시험에 이르기까지 전 과정이 유기적으로 결합되어 이루어져야 한다. 본 연구에서는 항공기 착륙장치 피로시험에 필요한 세부과정과 관련 기술을 실제 적용 사례와 함께 기술하였다.

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Fatigue Life and Stress Spectrum of Wing Structure of Aircraft (항공기 주익 구조물의 응력스펙트럼 및 피로수명 추정에 관한 연구)

  • Kang, Ki-Weon;Koh, Seung-Ki;Choi, Dong-Soo;Kim, Tae-Sung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.9
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    • pp.1185-1191
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    • 2010
  • Aged aircraft have several cracks as a results of long-term service, and these cracks affect the safety and decrease the rate of operation of the aircraft. To solve these problems, crack propagation analysis should be performed to determine the service life at fatigue critical location(FCL). It is, however, almost impossible to obtain the stress spectrum, which is crucial for crack propagation analysis of the FCLs of wing structure of aged aircraft. In this study, to analyze the fatigue crack propagation behavior at the FCL of an aged aircraft, first finite element analysis is performed for a 3D geometry model of the aircraft wing structure, which is obtained using CATIA based on the paper drawings. Then, the transfer function and stress-spectrum of the FCL are derived using the load factor data and the FEA results. Finally, the crack propagation rates of the FCL are evaluated using the commercial software, NASGRO 6.0.

An Efficient Algorithm in Spectral Fatigue Analysis of Ship Structures (선체의 스펙트럼 피로해석에 대한 효율적인 계산방법)

  • Jeung-Je Kim;Bum-Sang Yoon;Park-Dal-Chi Yang
    • Journal of the Society of Naval Architects of Korea
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    • v.30 no.4
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    • pp.93-101
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    • 1993
  • This paper deals tilth an efficient algorithm in spectral fatigue analysis of ship structures. The concept of stress influence coefficients is suggested in order to obtain stress transfer functions efficiently which are the structural responses for unit load components. Strip method is applied to obtain the motion response and pressure distributions exerted on the hull. Since a number of the structural analysis should be performed for the various wave frequencies and heading angles in the spectral analysis, the algorithm developed in this study improves the efficiency of the analysis. Finally, the calculation example with application to this concept is shown in this paper.

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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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A Study on the Spectral Fatigue Analysis for Offshore Structures (해양구조물의 스펙트럴 피로해석에 대한 사찰)

  • Jo, Gyu-Nam
    • Journal of Ocean Engineering and Technology
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    • v.4 no.2
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    • pp.59-72
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    • 1990
  • 본 논문은 해양 구조물에 대한 확률적 기법을 이용한 스펙트럴 피로해석 방법에 대하여 기술하고 있다. 환경조건 특히 파도 및 관련된 해상상태, 파도 스펙트럼에 대하여 조사하였다. 각종 공식을 이용한 응력 집중계수와 유한요소법을 이용한 응력 집중계수 산출 방법 및 피로수명에 대한 그 영향에 대하여 연구하고, S-N선도의 선택과 해상상태의 간략화 문제등에 관해서도 다루었다. 마지막으로 스펙트럴 피로해석 기법을 응용한 실제 피로해석 사례 연구를 통하여 본 방법의 유용성을 입증하였다.

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Vibration Fatigue Analysis for Multi-Point Spot-Welded SPCC Structure Considering Change of Dynamic Response (동적응답의 변화를 고려한 점용접부의 진동피로해석)

  • Kang, Ki-Weon;Chang, Il-Joo;Kim, Jung-Kyu
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.9
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    • pp.1193-1199
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    • 2010
  • Spot welding is the primary method of joining sheet metals in the automotive industry. As automobiles are subjected to fatigue loading, some spot welds may fracture before the whole system has failed. This local fracture of spot welds may lead to change in the dynamic response and consequently affect fatigue behavior of an automobile. Therefore, this change in dynamic response should be taken into consideration to assess the fatigue life of structures subjected to spectrum loading, such as automobiles. In this study, vibration fatigue analysis was performed by taking into consideration the change in the dynamic response due to accumulated damage at spot-welded parts. Fatigue tests were carried out on tensile-shear spot-welded specimens under constant amplitude loading condition. And the fatigue life of spot welds under spectrum loading was predicted using vibration fatigue analysis method based on finite element analysis.

Stress Spectrum Algorithm Development for Fatigue Crack Growth Analysis and Experiment for Aircraft Wing Structure (항공기 주익구조물의 피로균열 진전 해석 및 실험을 위한 응력 스펙트럼 알고리즘 개발)

  • Chun, Young Chal;Jang, Yun Jung;Chung, Tae Jin;Kang, Ki Weon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.12
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    • pp.1281-1286
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    • 2015
  • Fatigue cracks can be generated in aircraft as a result of the cumulative time spent during flight operations, which can extend for long periods of time and cover a variety of missions. If a crack occurs in an aircraft's main spar, it can generate many problems, including a lift time reduction. To solve this problem, it was necessary to perform an analysis of fatigue crack growth in the fatigue critical locations. Much time and expense is involved in generating the stress needed for a crack propagation analysis over a long period of time to obtain the amount of data required for an actual aircraft. In this paper, an algorithm is developed that can calculate the spectrum of stress over a long period of time for a mission by the Southwest Research Institute, which is based on the short-time load factor data produced using the peak-valley cycle counting method.