• Title, Summary, Keyword: Composite blades

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Stochastic modelling fatigue crack evolution and optimum maintenance strategy for composite blades of wind turbines

  • Chen, Hua-Peng;Zhang, Chi;Huang, Tian-Li
    • Structural Engineering and Mechanics
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    • v.63 no.6
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    • pp.703-712
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    • 2017
  • The composite blades of offshore wind turbines accumulate structural damage such as fatigue cracking due to harsh operation environments during their service time, leading to premature structural failures. This paper investigates various fatigue crack models for reproducing crack development in composite blades and proposes a stochastic approach to predict fatigue crack evolution and to analyse failure probability for the composite blades. Three typical fatigue models for the propagation of fatigue cracks, i.e., Miner model, Paris model and Reifsnider model, are discussed to reproduce the fatigue crack evolution in composite blades subjected to cyclical loadings. The lifetime probability of fatigue failure of the composite blades is estimated by stochastic deterioration modelling such as gamma process. Based on time-dependent reliability analysis and lifecycle cost analysis, an optimised maintenance policy is determined to make the optimal decision for the composite blades during the service time. A numerical example is employed to investigate the effectiveness of predicting fatigue crack growth, estimating the probability of fatigue failure and evaluating an optimal maintenance policy. The results from the numerical study show that the stochastic gamma process together with the proper fatigue models can provide a useful tool for remaining useful life predictions and optimum maintenance strategies of the composite blades of offshore wind turbines.

Design and Manufactures of Cyclocopter Composite Wing Blades (사이클로콥터의 복합재료 Wing blade 설계 및 제작)

  • 김승조;윤철용;백병주
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.187-190
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    • 2000
  • Cyclocopter is air vehicle to vertically take-off and land like a helicopter. This is an efficient and quiet means of being able to direct thrust compared to a helicopter. The rotor consists of several blades rotating about a horizontal axis perpendicular to the direction of normal flight. The direction of blade span is parallel to rotating axis and both end roots are connected to the hub to resist centrifugal force and to transmit the power. The pitch of the individual blades to the tangent of the circle of the blade's path is varied cyclically to gain thrust. In the paper, the design and manufactures of cyclocopter rotor blades are presented. Stress at the roots of cyclocopter blades is great due to centrifugal and aerodynamic forces and aeroelastic instabilities appear. The blades consist of main spar, front spar, polyurethan foam, weight, and skin and spars and skin are made of glass/epoxy composite.

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Structural Design and Analysis of Composite Cyclocopter Rotor Blades (복합재료 사이클로콥터 로터 블레이드의 구조 설계 및 해석)

  • Hwang In Seong;Hwang Chang Sup;Yun Chul Yong;Kim Seung Jo
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.91-94
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    • 2004
  • A cyclocopter with the cycloidal blades system can be the type of UAV which can combine the high-speed characteristics of the conventional airplane with the low-speed characteristics of the helicopter. The cycloidal blades system, which can be described as a horizontal rotary wing, offers powerful thrust levels, and a unique ability to change the direction of the thrust almost instantly. Rotor blades are designed to withstand tremendous transverse centrifugal loadings, and responding to a number of aerodynamic harmonic vibratory forcing frequencies. To reduce the weight and increase the strength, the blades are made of composite materials. The blades consist of the skin, spar, and trailing stiffener. In this study, static and dynamic behaviors of cyclocopter rotor blades are analyzed by using MSC/NASTRAN.

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Structural Dynamic Analysis of Low Vibrating Composite Helicopter Rotor Blades (복합재료 헬리콥터 로터 블레이드의 저진동 설계에 관한 연구)

  • Kee, Young-Jung;Shim, Jeong-Wook;Lee, Myeong-Kyu
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.902-905
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    • 2004
  • Recently, the composite materials are widely used for manufacturing the helicopter rotor blades. furthermore, composites show great potential on the design of rotor blades due to the advantages of strength, durability and weight of the materials. To keep with this advantages, it is necessary to calculate natural frequencies of a rotating blades for avoiding resonance. In this paper, the structural design process of airfoil cross section is introduced, and natural frequencies of composite rotor blades with variable rpm we investigated.

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A Simple Beam Model for Thin-Walled Composite Blades with Closed, Two-Cell Sections (폐쇄형 이중세포로 된 박벽 복합재료 블레이드의 단순화 해석 모델)

  • Jung, Sung-Nam;Park, Il-Ju;Lee, Ju-Young;Lee, Jung-Jin
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.187-190
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    • 2005
  • A simple beam model based on a mixed method is proposed for the analysis of thin-walled composite blades with a two-cell airfoil section. A semi-complementary energy functional is used to obtain the beam force-displacement relations. The theory accounts for the effects of elastic couplings, shell wall thickness, warping, and warping restraint. All the kinematic relations as well as the cross-section stiffnesses are evaluated in a closed-form through the current beam formulation. The theory has been applied to two-cell composite blades with extension-torsion couplings and fairly good correlation has been observed in comparison with a detailed analysis and other literature.

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Design of optimal fiber angles in the laminated composite fan blades (적층 복합재 팬-블레이드의 적층각도 최적화 설계)

  • Jeong, Jae-Yeon;Jo, Yeong-Su;Ha, Seong-Gyu
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.11
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    • pp.1765-1772
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    • 1997
  • The layered composites have a character to change of structure stiffness with respect to the layup angles. The deformations in the fan-blades to be initially designed by considering efficiency and noise, etc., which arise due to the pressure during the fan operation, can make the fan inefficient. Thus, so as to minimize the deformations of the blades, it is needed to increase the stiffness of the blades. An investigation has been performed to develop the three dimensional layered composite shell element with the drilling degree of freedom and the optimization module for finding optimal layup angles with sensitivity analysis. And then they have been verified. In this study, the analysis model is engine cooling fan of automobile. In order to analyzes the stiffness of the composite fan blades, finite element analysis is performed. In addition, it is linked with optimal design process, and then the optimal angles that can maximize the stiffness of the blades are found. In the optimal design process, the deformations of the blades are considered as multiobjective functions, and this results minimum bending and twisting simultaneously.

A Comparative Study on Structural Performance of Wind Turbine Composite Blades with Room-Temperature and Radiation Curing (상온 및 방사선 경화 복합재 풍력 블레이드의 구조성능 비교)

  • Jeon, Jae Heung;Kim, Sung Jun;Shin, Eui Sup
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.25 no.3
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    • pp.203-209
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    • 2012
  • In this paper, cross-sectional stiffnesses, static stresses, and dynamic natural frequencies are analyzed to examine the structural performance of wind turbine composite blades. The material properties of composite materials are based on room-temperature and radiation curing processes. The cross-sectional stiffnesses of composite blades are calculated by applying a beam theory with solid-profile cross sections. The wind turbine blades are modeled with a finite element program, and static analyses are carried out to check the maximum displacement and stress of the blades. In addition, dynamic analyses are performed to predict the rotating natural frequencies of the composite blades including the effects of centrifugal force. By comparing these analysis results, mainly owing to the material properties of composite materials, an improvement in the structural performance of the blades according to the curing process is investigated.

A Numerical Analysis on the Vibration Characteristics of Rotating Composite Blades (회전하는 복합재료 블레이드의 진동특성에 대한 수치해석)

  • Kee, Young-Jung;Song, Keun-Woong;Kim, Deog-Kwan;Shim, Jeong-Wook
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.300-303
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    • 2006
  • The rotor blade of a helicopter is the key structural units and provides three components such as vertical lifting force, horizontal propulsive force and control force. With advancements in aerospace technology, composite materials have been widely used in lightweight structures. In addition, composites show great potential on the design of rotor blades due to the advantages of strength, durability and weight of the materials. In the operational condition of a helicopter, it is required the vibration characteristics of the rotating blades for avoiding resonance and analysis of efficient performance prediction et al. In this study, the CAMRAD-II is used for analyzing the vibration characteristics of rotating composite blades. The effects of rotating speed and collective angles are investigated. Also, the numerical results are compared with experimental data.

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A Simple Mixed-Based Approach for Thin-Walled Composite Blades with Two-Cell Sections

  • Jung Sung Nam;Park Il-Ju
    • Journal of Mechanical Science and Technology
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    • v.19 no.11
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    • pp.2016-2024
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    • 2005
  • In this work, a mixed beam approach that combines both the stiffness and the flexibility methods has been performed to analyze the coupled composite blades with closed, two-cell cross-sections. The Reissner's semi-complementary energy functional is used to derive the beam force-displacement relations. Only the membrane part of the shell wall is taken into account to make the analysis simple and also to deliver a clear picture of the mixed method. All the cross section stiffness coefficients as well as the distribution of shear across the section are evaluated in a closed-form through the beam formulation. The theory is validated against experimental test data, detailed finite element analysis results, and other analytical results for coupled composite blades with a two-cell airfoil section. Despite the simple kinematic model adopted in the theory, an accuracy comparable to that of two-dimensional finite element analysis has been obtained for cases considered in this study.

A Study on Assessment of Composite Couplings for Helicopter Rotor Blades with Multi-cell Sections

  • Jung, Sung-Nam;Park, Il-Ju;Shi, Eui-Sup;Chopra, Inderjit
    • International Journal of Aeronautical and Space Sciences
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    • v.4 no.1
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    • pp.9-18
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    • 2003
  • In this work, a closed-form analysis is performed for the structural response of coupled composite blades with multi-cell sections. The analytical model includes the effects of shell wall thickness, transverse shear, torsion warping and constrained warping. The mixed beam approach based on Reissner's semi-complementary energy functional is used to derive the beam force-displacement relations. The theory is validated against experimental test data and other analytical results for coupled composite beams and blades with single-cell box-sections and two-cell airfoils. Correlation of the present method with experimental results and detailed finite element results is found to be very good.