• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1992.10a
• /
• pp.71-76
• /
• 1992

축정렬이 불량한 경우 축진동이 과도하게 발생하여 출력이 감소하고 소음이 발생하며, 심한 경우 회전체의 파손과 같은 손실을 입을 수 있다. 특히 축 정렬불량으로 인한 진동은 교정이 안되는 것이 특징이므로 근본적으로 진동 을 해결하기 위해서는 축 정렬을 다시 시행해야 한다. 그러나 터빈은 다른 기계 구조물과 달리 분해 점검에 많은 시간과 경비가 요구되므로 축 정렬시 정확한 작업이 요구된다. 본 연구에서는 터빈계통의 축정렬을 수행하는 절차 와 방법에 대해서 검토하였다. 이를 위해 축정렬이 입력데이터로 쓰일 수 있 는 상태측정방법중 커플링 원주와 커플링 면 측정방법이 설명되었으며, 측정 값으로부터 축정렬을 수행하기 위해, 베어링의 이동량 계산과정과 쉼 가감량 의 계산방법을 기술하였다. 축정렬의 원리와 방법의 적용과정을 실제로 알아 보기 위해 평택화력 1,2호기에 대한 축정렬이 수행되었다. 1,2호기는 고압터 빈, 2단계의 저압터빈 및 발전기로 구성되어 있는 다축 시스템으로서, 제작 사측에서 요구하는 정렬 기준값을 감안하여 축정렬에 필요한 베어링 조정량 을 계산하였다. 계산과정은 기준로터로 지정된 저압터빈에서부터 축정렬상태 도를 작성하여 가면서 단계적으로 설명되었으며, 최종적으로 쉼의 가감량까 지를 보여줌으로서 축정렬과정을 완료하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.291-297
• /
• 2003

Fluid film tilting pad journal bearings are widely used for large steam turbines. However, bearing problems by pad fluttering, such as fatigue damage in the upper unloaded pad, the break of locking pins and the wear of pinholes etc., are frequently taken place in the actual steam turbines. The purpose of the present work is to investigate on the mechanism of pad fluttering and the prevention of pad fluttering with the variation of preload(m) in a tilting pad journal bearing. It is estimated that upper pad is easy to flutter because the film shape of upper pad is diverged one from the analysis of moment direction acting on pivot point. Effective preload range in order to be statically loaded pad under all operating conditions is suggested as m＞0.5. Also, as a bearing that can be prevented pad fluttering, design modified bearing is suggested. For the adjustment in actual steam turbines, bearing and rotor dynamic analysis are performed to identify bearing characteristics and to verify the reliability of rotor-bearing system.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1636_1637
• /
• 2009

회전기기는 산업설비에서 가장 큰 비중을 차지하는 장치로써 고장발생 시 전체 시스템의 shut-down에 의한 많은 경제적인 손실을 가져오게 된다. 회전기기의 고장은 노화에 의해서도 발생될 수 있지만 베어링 파손이나 축 불일치, 고정 불량등과 같이 다른 원인에 의해서도 발생될 수 있기 때문에 안정적인 설비의 운영을 위해서는 고장진단을 통한 지속적인 관리가 요구된다. 본 연구에서는 회전기기의 지속적인 모니터링 및 고장분석에 사용될 수 있는 DPCM 기법(압축전송기법)을 이용한 CAN 기반의 회전설비 고장진단 시스템을 제안하며 제안된 시스템의 성능검토를 위해 실제 제작된 test-bed 환경에서의 실험을 진행하였다.

• Proceedings of the KAIS Fall Conference
• /
• 2012.05b
• /
• pp.516-519
• /
• 2012

산업 현장에 필수적으로 사용하는 유틸리티 시스템(Utility System)의 하나인 에어를 생산하는 공기압 축기의 운전방식은 조작 패널부에 사용자가 설정한 셋팅값에 의해 내부의 밸브를 제어하여 로딩 및 언로딩 운전을 한다. 이로 인해 대용량(100HP, 200HP)의 공기압축기를 여러대 사용하는 수용가에서는 연속 다발적인 운전으로 인한 전력 사용량의 변동으로 역률 저하 및 연속가동으로 인한 설비 과부하 및 내부 기계 베어링 피로도 증가 및 파손 등 고장이 발생되는 문제점이 있다. 따라서 본 논문에서는 인공 신경회로망(ANN:Artificial Neural Network)을 이용하여 최적의 에너지 운용 알고리즘을 제안하여 실계통의 문제점을 분석하여 개선하고자 한다.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1992.04a
• /
• pp.33-37
• /
• 1992

구조물과 기계부품에 부하를 주는 하중은 여러가지 종류가 있고, 이에 따르는 파괴의 형식도 여러가지가 있다. 그중에서도 연강압연용 로울러, 베어링 레일등은 집중 압축하중을 받는데 이들 부재의 파괴사고가 빈번히 일어나고 잇다. 압축에 의한 파괴 중 frectting, 피팅등과 같은 마모 현상은 두 재료의 표면이 서로 미끌어질때 일어나며, 이것이 공구나 기계부품의 성능과 수명을 저하시키는 주원인이 되며, 이러한 궁구나 기계 부품을 수리 또는 교환을 하기위한 인적, 경제적 손실은 막대하다. 본 연구에서는 금형등 공구의 마모편이 발생되는 마지막 과정인 크렉의 성장을 고찰하기 위하여 Sub-surface크랙 모델을 설정하여 2차원 유한요소 법으로 경계층 근방에 크랙이 존재하는 반무한 평면에 집중하중이 작용할때의 응력확대계수를 해설하였는데, 일반화된 해석법으로 혼합모드에서의 응력확대계수를 결정하였다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2003.11a
• /
• pp.395-401
• /
• 2003

In this paper, the dent printing phenomena and critical dent size which lead to premature failure of deep grooved ball bearing for automobiles are presented. The results of newly assembled test bearings showed that the ball dent size strongly affect the bearing life and inner ring raceways were the major failed parts in spite of using the dented balls. The dent printing phenomena are a root cause of premature failure, which was not reported until now. And there exist the critical ball dent size for given rolling bearings and operating conditions. So, the initial condition of tribologically mating parts should be treated as important as the failed body itself.

• The Journal of the Acoustical Society of Korea
• /
• v.8 no.1
• /
• pp.5-12
• /
• 1989

This paper is concerned with the characteristics on the statistical parameters of vibration signal from bearing with changing its operating conditions as well as the spreading of faults. The rms, Kurtosis, crest factor, probability of exceedance and probability density function have been chose as the statistical parameters. To characterize of each, vibration signals have been recorded from four ball tester at different loads, operation speeds and time. The values of the statistical parameters for each frequency band have been calculated after A/D conversion and digital filtering of the recorded signals. It has been found that unlike rms values the statistical parameters such as Kurtosis etc. are almost unchanging with the change of the operating conditions such as load and speed. This suggests that the statistical parameters may be used for determining the development of faults independent of the operating conditions. In fact, the statistical parameters deviate considerably from their respective normal values when the faults developed under load conditions in the samples, conforming the suggestion.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.3
• /
• pp.429-436
• /
• 2013

This study considers how the fatigue behavior and probabilistic properties of SAE1055 steel are related to its hardness level. SAE1055 steel was heat-treated using induction hardening. Five types of specimens were prepared (A: base material, B: through hardened material with HV390, C: through hardened material with HV510, D: through hardened material with HV700, and E: surface hardened material with HV700). Fatigue tests were performed under a stress ratio of R = -1 using a 4-point rotary bending fatigue tester. The fatigue behaviors were greatly influenced by the hardness, but the fatigue limit did not increase over a hardness of HV510. In addition, the effect of the hardness level on the failure mechanism was evaluated using a scanning electron microscope. The probabilistic properties of the fatigue life were investigated using a probabilistic S-N approach, and the effect of the hardness level on these properties was evaluated using a residue analysis.

• Tribology and Lubricants
• /
• v.31 no.6
• /
• pp.281-286
• /
• 2015

Automotive transmission systems are assembled with a large number of gears and shafts, and rolling bearings are used to ensure their smooth operation. Gear oil in the gear box contains solid particles such as wear debris from contacting gears and metallic chips. This particle-enriched lubricating oil can cause premature failure of the rolling bearings. Research aimed at improving the service life of these rolling bearings has been confined mainly to design and lubrication of the inner/outer rings and the rolling elements. In this paper, we redesigned the shape of the cage pocket of a deep groove ball bearing to reduce the premature failure due to particle contamination. Test bearings are assembled with this new cage design containing a hole punched in the cage pocket. Endurance tests are carried out using the contaminated lubricating oil with miracle grid as hard particle. The duration and damaged bearing component shapes are compared for two different cages. The B₁₀ life of bearing with new cage is increased by about 66% compared to the conventional cage. This is because the hard particles can be easily discharged through the pocket hole without staying for a long time in the lubrication regions. This greatly decreases abrasive wear and dents on the highly stressed ball bearing surfaces. Therefore, the cage design of this study, containing a pocket hole, can significantly delay the premature failure of rolling bearings and improve the endurance life.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.2
• /
• pp.31-38
• /
• 2013

This research analyzed the acoustic emission signals collected from the pin loading tests and investigated the effect of hygrothermal exposure on the fracture behavior of the pin-jointed carbon fiber/epoxy composites. The composite specimens include: the Base specimen that has not been exposed to any environments, the RT specimen that has been immersed in room temperature water, and the HT specimen that has been immersed in high temperature water. According to the pin loading test, the RT and the HT specimens showed 2.2% and 13% decreases in the bearing strength compared to the Base specimen, respectively. The analysis of the acoustic emission signals showed different fracture acceleration points for three types of the specimens. Furthermore, for the RT and the HT specimens, the event from the matrix crack signals in the composites decreased. This shows the effect of the hygrothermal conditions on the acoustic emission signals. Additionally, upon investigating the fracture behaviors of the pin-jointed composites, the exposing specimens to hygrothermal environments decreases the interfacial characteristics of the composites.