• Title/Summary/Keyword: Misalignment

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Study on Rub Vibration of Rotary Machine for Turbine Blade Diagnosis (터빈 블레이드 진단을 위한 회전기계 마찰 진동에 관한 연구)

  • Yu, Hyeon Tak;Ahn, Byung Hyun;Lee, Jong Myeong;Ha, Jeong Min;Choi, Byeong Keun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.26 no.6_spc
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    • pp.714-720
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    • 2016
  • Rubbing and misalignment are the most usual faults that occurs in rotating machinery and with them severe effect on power plant availability. Especially blade rubbing is hard to detect on FFT spectrum using the vibration signal. In this paper, the possibility of feature analysis of vibration signal is confirmed under blade rubbing and misalignment condition. And the lab-scale rotor test device provides the blade rubbing and shaft misalignment modes. Feature selection based on GA (genetic algorithm) is processed by the extracted feature of the time domain. Then, classification of the features is analyzed by using SVM (support vector machine) which is one of the machine learning algorithm. The results of features selection based on GA compared with those based on PCA (principal component analysis). According to the results, the possibility of feature analysis is confirmed. Therefore, blade rubbing and shaft misalignment can be diagnosed by feature of vibration signal.

Natural Frequencies of a Spinning Disk Misaligned with the Axis of Rotation (회전축 정렬불량을 가지는 유연 회전디스크의 고유치 해석)

  • 허진욱;정진태;김원석
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.11b
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    • pp.817-825
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    • 2001
  • The natural frequencies of a flexible spinning disk misaligned with the axis of rotation are studied in an analytic manner. The effects of misalignment on the natural frequency need to be investigated, because the misalignment between the axis of symmetry and the axis of rotation cannot be avoided in the removable disks such as CD-R, CD-RW or DVD disks. Assuming that the in-plane displacements are in steady state and the out-of-plane displacement is in dynamic state, the equations of motion are derived for the misaligned spinning disk. After the exact solutions are obtained for the steady-state in-plane displacements, they are plugged into the equation for the dynamic-state out-of-plane motion. The resultant equation is a linear equation for the out-of-plane displacement, which is discretized by the Galerkin method. Based on the discretized equations, the effects of the misalignment are analyzed on the vibration characteristics of the spinning disk, i.e., the natural frequencies and the critical speed

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Development of Shaft Analysis Model for Power Transmission System Optimization (동력전달 시스템의 최적화를 위한 축 해석 모델 개발)

  • Lee, Ju-Yeon;Kim, Su-Chul
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.20 no.5
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    • pp.8-16
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    • 2021
  • This study develops a shaft analysis model for the optimization of the power transmission system. The finite element method was used for the shaft analysis model. The shaft and gear were assumed Timoshenko beams. Strength was evaluated according to DIN 743, and gear misalignment was calculated through ISO 6336 and the coordinate system rotation. The analysis software for a power transmission system was developed using Visual Studio 2019. The analysis results of the developed program were compared with those of commercial software (MASTA, KISSsoft, and Romax). We confirmed that the force, deformation, and safety factors at each node were the same as those of the commercial software. The absolute value of the gear misalignment of the developed program and commercial software was different. However, the gear misalignment tended to increase with increasing the displacement in the tooth width direction.

Evaluation of shear-key misalignment in grouted connections for offshore wind tower under axial loading

  • Seungyeon Lee;Seunghoon Seo;Seungjun Kim;Chulsang Yoo;Goangseup Zi
    • Computers and Concrete
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    • v.33 no.5
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    • pp.509-518
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    • 2024
  • In this study, we investigated the effect of shear-key placement on the performance of grouted connections in offshore wind-turbine structures. Considering the challenges of height control during installation, we designed and analyzed three grouted connection configurations. We compared the crack patterns and strain distribution in the shear keys under axial loading. The results indicate that the misalignment of shear keys significantly influences the ultimate load capacity of grouted connections. Notably, when the shear keys were positioned facing each other, the ultimate load decreased by approximately 15%, accompanied by the propagation of irregular cracks in the upper shear keys. Furthermore, the model with 50% misalignment in the shear-key placement exhibited the highest ultimate strength, indicating a more efficient load resistance than the reference model. This indicates that tensile-load-induced cracking and the formation of compressive struts in opposite directions significantly affect the structural integrity of grouted connections. These results demonstrate the importance of considering buckling effects in the design of grouted connections, particularly given the thin and slender nature of the inner sleeves. This study provides valuable insights into the design and analysis of offshore wind-turbine structures, highlighting the need for refined design formulas that account for shifts in shear-key placement and their structural implications.

EFFECT OF MISALIGNMENT ON THE STATIC CHARACTERISTICS OF 3-LOBE proceeding BEARING

  • Strzelecki, S.;Radulski, W.
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.95-96
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    • 2002
  • The operation of proceeding bearing in the conditions of misaligned axis of proceeding and bush leads to the load concentration on the bearing edges causing further mixed lubrication conditions, unstable operation and intensive wear of mating parts. For the design process of proceeding bearing the knowledge of static characteristics determined from the oil film pressure and temperature distribution is very important. For the 3-lobe proceeding bearing, the pressure, temperature and viscosity fields, load capacity, minimum oil film thickness, power loss, oil flow and maximum oil film temperature have been determined by iterative solution of the Reynolds', energy and viscosity equations. The paper introduces the results of theoretical investigations of static characteristics of 3-lobe proceeding bearing operating at misaligned axis of proceeding and bush. An effect of misalignment ratio, length to diameter ratio of the proceeding bearing, the lobe clearance ratio on the static characteristics was investigated. Laminar, adiabatic model of oil film for the solution of Reynolds, energy and viscosity equations was applied.

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Vibration Characteristic Analysis using Acoustic Emission Signal (AE신호를 이용한 기어 정렬불량의 진동 특성 분석)

  • Gu, Dong-Sik;Kim, Byeong-Su;Lee, Jeong-Hwan;Yang, Bo-Suk;Choi, Byeong-Keun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.11a
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    • pp.43-48
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    • 2008
  • Gear system has been widely used in industrial applications and unexpected failures of gears are not only extremely damaging but also lead to economic losses. So, early detection of fault is important for diagnosis machine condition. And acoustic emission is an efficient non destructive testing technique for the diagnosis of machine health and is useful technique for early detection of fault because it can find low-amplitude and high-frequency signal on account of high sensibility. Therefore, in this paper, the AE signal was measured and preprocessed using envelop analysis for gearbox with misalignment between pinion and gear. And then the vibration characteristic of gear misalignment was analyzed.

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Analysis for the Effect of the Misalignment of the Power Line from the Displacement Caused by the Ship Motion of the Main Propulsion System (선체운동에 의한 주추진계의 변위가 동력축의 축 어긋남에 미치는 영향 분석)

  • Han, Hyung-Suk;Lee, Kyung-Hyun;Cho, Heung-Gi
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.1
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    • pp.46-52
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    • 2012
  • Since the engine and reduction gear in a naval vessel are usually supported by the mounting system separately, the misalignment between the input shaft of the reduction gear and the output shaft of the engine should occur caused by ship motion. In this study, this misalignment is estimated from the linear static analysis assuming that the phase of movements of the engine and reduction gear at low frequency range is same and the dynamic effect is not affect to them. Through comparing the relative displacement of the engine and reduction gear calculated from linear static analysis to that from dynamic analysis as well as experiment, the assumption in this study could be verified.

Bootstrap Simulation for Performance Evaluation of Optical Multifiber Connectors (붓스크랩 기법을 이용한 다심 광커넥터 손실특성 예측)

  • 전오곤;강기훈
    • Journal of Korean Society for Quality Management
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    • v.26 no.4
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    • pp.250-264
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    • 1998
  • The purpose of the thesis is to develop simulation program for forecasting of optical connector. So we can achieve the time and the money saving for making the optical connector. Optical performance (insertion loss) of optical connector mainly relies on 3 misalignment factors-ferrule factor due to mis-manufacture from design, auto-centering effect that is fiber behavior phenomena between hole and fiber, fiber misalignment factor. Simulation use experimental data with auto-centering effect and fiber factor and use pseudo data with ferrule through random number generation because it is developing stage. In this study we a, pp.y kernel density estimation method with experimental data in order to know whether it belong to or not specific parametric distribution family. And we simulate to forecast insertion loss of optical multifiber connector under specific design model using nonparametric bootstrap resampling data and parametric pseudo samples from uniform distribution. We obtain the tolerance specifications of misalignment factors satisfying not exceed in maximum 1.0dB and choose optimal hole diameter.

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Dosimetry for Resonance-Based Wireless Power Transfer Charging of Electric Vehicles

  • Park, Sang-Wook
    • Journal of electromagnetic engineering and science
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    • v.15 no.3
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    • pp.129-133
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    • 2015
  • This paper presents the dosimetry of a resonance-based wireless power transfer (RBWPT) system for electric vehicles applications. The compact RBWPT system is designed to transfer power at 150-mm distance. The electric and magnetic fields generated by the RBWPT system and the specific absorption rate in the human body model, which stands around the system, are calculated. These analyses are conducted in two cases: the alignment and the misalignment between the transmitter and the receiver. The matching loops are adjusted to maximize the power transfer efficiency of the RBWPT system for the misalignment condition. When the two cases were compared for the best power transfer efficiency, the specific absorption rates (SAR) in the misalignment case were larger than those in the alignment case. The dosimetric results are discussed in relation to the international safety guidelines.

Comparison of current, vibration and acoustic emission signal occurred by gear misalignment (기어 정렬불량에 의한 전류, 진동 및 음향방출 신호의 비교 분석)

  • Gu, Dong-Sik;Lee, Jeong-Hwan;Kim, Byeong-Su;Yang, Bo-Suk;Choi, Byeong-Keun
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.938-942
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    • 2008
  • To detect the failures in machine, the signals of current, vibration and acoustic emission are widely used in industry. And unexpected failures of gears are not only extremely damaging but also lead to economic losses. In this paper, to detect the misalignment occurred at between two gears in gearboxes, the signals of current, vibration and AE were measured at gearbox and motor power line. FFT(Fast Fourier Transform) was used for current and vibration signal analysis to find gear failure frequency. Especially, the envelop analysis and wavelet transform were applied for AE signal. Therefore, compared with the results of three kinds of signal, the possibility of earily detection by AE is identified or checked.

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