• Title, Summary, Keyword: Fatigue Analysis

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ASSESSMENT OF THERMAL FATIGUE IN MIXING TEE BY FSI ANALYSIS

  • Jhung, Myung Jo
    • Nuclear Engineering and Technology
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    • v.45 no.1
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    • pp.99-106
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    • 2013
  • Thermal fatigue is a significant long-term degradation mechanism in nuclear power plants. In particular, as operating plants become older and life time extension activities are initiated, operators and regulators need screening criteria to exclude risks of thermal fatigue and methods to determine significant fatigue relevance. In general, the common thermal fatigue issues are well understood and controlled by plant instrumentation at fatigue susceptible locations. However, incidents indicate that certain piping system Tee connections are susceptible to turbulent temperature mixing effects that cannot be adequately monitored by common thermocouple instrumentations. Therefore, in this study thermal fatigue evaluation of piping system Tee-connections is performed using the fluid-structure interaction (FSI) analysis. From the thermal hydraulic analysis, the temperature distributions are determined and their results are applied to the structural model of the piping system to determine the thermal stress. Using the rain-flow method the fatigue analysis is performed to generate fatigue usage factors. The procedure for improved load thermal fatigue assessment using FSI analysis shown in this study will supply valuable information for establishing a methodology on thermal fatigue.

A parametric study based on spectral fatigue analysis for 170k LNGC

  • Park, Tae-Yoon;Jang, Chang-Doo;Suh, Yong-Suk;Kim, Bong-Jae
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.3 no.2
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    • pp.116-121
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    • 2011
  • The Spectral Fatigue Analysis is representative fatigue life assessment method for vessels. This Analysis is performed generally for the whole vessel and many assessment sites. The spectral fatigue analysis is performed through the process of hydrodynamic response analysis, global structural analysis, local structural analysis and calculation of fatigue damage. In these processes, fatigue damage is affected by many variables. The representative variables are S-N curve data, wave scatter data, wave spectrum, bandwidth effect and etc. In this paper, the effects of these variables to the fatigue damage are analyzed through the spectral fatigue analysis for 170k LNGC.

A Study on Optimal Spot-weld Layout Design of the Shock Tower Structure Considering Fatigue Life under Random Vibration Load (불규칙 진동하중을 받는 쇽 타워의 피로수명을 고려한 점용접 위치 최적설계)

  • Lee, Yong-Hoon;Lee, Seung-Yoon;Bae, Bok-Soo;Yim, Hong-Jae
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.538-543
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    • 2011
  • In this paper, optimal spot weld layout design of the shock tower structure is performed for increasing fatigue life of spot weld and fatigue life of shock tower simultaneously. To predict the fatigue life, linear static analysis is conducted then fatigue analysis is performed by applying random vibration load. To optimize the spot weld layout, design variables that have an effect on spot weld fatigue life are selected. Based on the DOE table, spot weld fatigue analysis is conducted. Finally, response surface model is made from fatigue analysis results and optimized spot weld layout model which increases fatigue life of sport weld and fatigue life of shock tower is determined.

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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 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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The fatigue analysis using cumulative damage rule (Miner's rule) for the welding areas of carbody structure (누적손상법(Miner's rule)을 이용한 철도차량 차체 용접부의 피로평가)

  • Kim, Kwang-Woo;Park, Geun-Soo;Park, Hyung-Soon
    • Proceedings of the KSR Conference
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    • pp.30-34
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    • 2007
  • Structural integrity of railway vehicles should last for a long period against various and continuous fatigue loadings, and the carbody structures of railway vehicle are manufactured by applying multiform welding types for each material. Since the most of cracks are occurred and proceeded at the vicinity of welding area during the lifetime of carbody structure, the fatigue strength evaluation for welding area of carbody structure should have been carried out. Rotem Company has evaluated lifetime and fatigue strength of carbody structure according to the fatigue analysis based on the international standard and/or inner-official regulation. This study introduces the fatigue analysis method that we have evaluated and calculated the damages for the welding areas of carbody structure under various fatigue loading conditions using cumulative fatigue damage rule(Miner's rule) to verify whether the cumulative damage does exceed unity. This study contains the fatigue test of specimens to derive stress-life relations(S-N curve), sub-modeling analysis and the calculation of cumulative damages under fatigue loading. The fatigue analysis verifies the welding area shall be capable of withstanding under fatigue loading, identifies how critical area shall be selected and presents the principles to be used for design verification.

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Fatigue Analysis of the Welded Bogie Frame for Rolling Stock Considering Dynamic Effects (동적효과를 고려한 철도차량 용접대차프레임의 피로해석)

  • Kim, Chul-Su
    • Journal of the Korean Society of Mechanical Technology
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    • v.19 no.1
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    • pp.100-106
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    • 2017
  • A fatigue analysis considering dynamic effects yields a more accurate fatigue life prediction than static fatigue analysis because it considers effects of inertia, flexibility and resonance that occur in the structure up to its natural frequency. However, the dynamic fatigue analysis of bogie frames of the rolling stock is not yet taken into account in the norm EN 13749. Therefore, in order to assure the safety of the rolling stocks, it is important to examine the fatigue analysis of that considering dynamic effects under applied load histories. Moreover, since the bogie frame consists of various welded joints, it is necessary to evaluate fatigue life of that considering welding properties as well as dynamic effects. In this study, under load histories converted from measured acceleration histories, static and dynamic fatigue analysis of the welded bogie frame are performed respectively.

A Study on the Fatigue Life Prediction and Evaluation of Rubber Components for Automobile Vehicle (자동차 방진고무부품의 피로수명 예측 및 평가)

  • Woo, Chang-Su;Kim, Wan-Doo;Kwon, Jae-Do
    • Transactions of the Korean Society of Automotive Engineers
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    • v.13 no.6
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    • pp.56-62
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    • 2005
  • The fatigue analysis and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. Fatigue lifetime prediction methodology of the rubber component was proposed by incorporating the finite element analysis and fatigue damage parameter from fatigue test. Finite element analysis of 3D dumbbell specimen and rubber component were performed based on a hyper-elastic material model determined from material test. The Green-Lagrange strain at the critical location determined from the FEM was used for evaluating the fatigue damaged parameter of the natural rubber. Fatigue life of the rubber component are predicted by using the fatigue damage parameter at the critical location. Predicted fatigue lifes of the rubber component agreed fairly well the experimental fatigue lives.

A Fatigue Analysis Study on the Fractured Fixing Bolts of Mobile Elevated Work Platforms (고소작업대의 파손된 고정볼트의 피로분석에 관한 연구)

  • Choi, Dong Hoon;Kim, Jae Hoon
    • Journal of the Korean Society of Safety
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    • v.34 no.5
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    • pp.1-6
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    • 2019
  • The mobile elevated work platforms(MEWPs) consist of work platform, extending structure, and car, and it is a facility to move persons to working positions. MEWPs are useful but composed complex pieces of equipments, and accidents are caused by equipment defects. Among them, accidents caused by fracture of the bolts fixing the extension structure and the turntable are increasing. In this study, fatigue failure and fatigue life of a turntable fixing bolt subjected to irregular fatigue load were analyzed by FEA. For this purpose, finite element modeling is proposed and structural analysis and fatigue analysis are performed simultaneously for fixing bolts. As a result of the structural analysis, it was confirmed that there is no risk of permanent deformation because the maximum stress acting on the fixing bolt is lower than the yield strength, and fatigue analysis was confirmed that the fatigue life is less than the design standard. The fatigue analysis results of this study can be effectively used for the design and the documentary assessment of the safety certification of the MEWPs by examining the fatigue life of the turntable fixing bolt.

Fatigue Analysis of Fiber-Reinforced Composites Using Damage Mechanics (손상역학을 이용한 섬유강화 복합재료의 피로해석)

  • Lim Dong-Min;Yoon Ihn-Soo;Kang Ki-Weon;Kim Jung-Kyun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.2
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    • pp.112-119
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    • 2006
  • Due to their intrinsic anisotropy, composite materials show quite complicated damage mechanism with their fiber orientation and stacking sequence and especially, their fatigue damage process is sequential occurrence of matrix cracking, delamination and fiber breakage. In the study, to propose new model capable of describing damage mechanism under fatigue loading, fatigue analysis of composite laminates based on damage mechanics, are performed. The average stress is disassembled with stress components of matrix, fiber and interlaminar interface through stress analysis. Each stress components are used to assess static damage analysis based on continuum damage mechanics (C.D.M.). Fatigue damage curves are obtained from hysteresis loop and assessed by the fatigue damage analysis. Then, static and fatigue damage analysis are combined. Expected results such as stress-cycle relation are verified by the experimental results of fatigue tests.