• Title/Summary/Keyword: Disk Failure

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Wear behavior of SM55C steel by rolling contact (구름접촉에 의한 SM55C의 마멸 거동)

  • Park, Beom-Su;Chae, Young-Hun;Kim, Seock-Sam
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.05a
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    • pp.240-247
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    • 2002
  • The rolling wear behavior of SM55C is investigated under lubrication. This is a comparative tribological behavior of heat treatment effect for SM55C. Rolling wear test method is used for Ball-on-disk type. Specimens can be classified into two main groups: as-annealing and non-annealing. As result of wear behavior, flanking initial time of non-annealing specimen keep at retard but it have not under high normal load. One of the notable features of annealing specimen is steady flanking initial time for a normal load in this experiment. Failure mechanism of SM55C is due to the fatigue wear such like flanking, pitting etc.. Flanking leads to abruptly fracture of worn surface. Fracture mechanism has a connection with normal load and polishing direction of specimens.

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Failure Recovery in the Linux Cluster File System SANiqueTM (리눅스 클러스터 화일 시스템 SANiqueTM의 오류 회복 기법)

  • Lee, Gyu-Ung
    • The KIPS Transactions:PartA
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    • v.8A no.4
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    • pp.359-366
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    • 2001
  • This paper overviews the design of SANique$^{TM}$ -a shred file system for Linux cluster based on SAN environment. SANique$^{TM}$ has the capability of transferring user data from network-attached SAN disks to client applcations directly without the control of centralized file server system. The paper also presents the characteristics of each SANique$^{TM}$ subsystem: CFM(Cluster File Manager), CVM(Cluster Volume Manager), CLM(Cluster Lock Manager), CBM(Cluster Buffer Manager) and CRM(Cluster Recovery Manager). Under the SANique$^{TM}$ design layout, then, the syndrome of '||'&'||'quot;split-brain'||'&'||'quot; in shared file system environments is described and defined. The work first generalizes and illustrates possible situations in each of which a shared file system environment may split into two or more pieces of separate brain. Finally, the work describes the SANique$^{TM}$ approach to the given "split-brain"problem using SAN disk named "split-brain" and develops the overall recovery procedure of shared file systems.

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Identification of Failure Cause for 300MW LP turbine Blade through Vibration Analysis (진동 해석을 통한 300MW급 저압터빈 블레이드의 손상 원인 규명)

  • Kim, Hee-Soo;Bae, Yong-Chae;Lee, Hyun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.05a
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    • pp.794-799
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    • 2005
  • The failure of blades frequently happened in the 300MW LP turbine until now and they are maintaining the blades periodically during outage. So the blade-disk system is analysed by FEM in order to identify the main cause of failure of blade row. It is found that the stress of root's hole is highest in comparison with other parts from the result of the steady stress analysis. Also, the two dangerous frequencies which is related to the resonance condition are found in the interference diagram. one is 1,516 Hz which is related to the operating speed. The other is 2,981 Hz which is related to the 1 nozzle passing frequency. The dynamic stress analysis is per-formed to identify more accurate root cause for failure of blade row. It is confirmed that the dynamic stress of the latter is higher than one of the former. From these results, it is concluded that the former has deeply something to do with the failure of blades more than the latter. Based on versatile investigation and deliberation, the change of blade's grouping is determined to avoid the resonance condition with the operating speed. After the blade grouping is changed, the former frequency vanish completely but the latter is still in existence in the interference diagram. Fortunately, It is confirmed that the dynamic stress of the new blade grouping is lower than one of the old blade grouping. 2 years has passed since modification and the LP turbine is operated well without failure so far.

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Effect of thermal-induced microcracks on the failure mechanism of rock specimens

  • Khodayar, Amin;Nejati, Hamid Reza
    • Computers and Concrete
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    • v.22 no.1
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    • pp.93-100
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    • 2018
  • It is seldom possible that geotechnical materials like rocks and concretes found without joints, cracks, or discontinuities. Thereby, the impact of micro-cracks on the mechanical properties of them is to be considered. In the present study, the effect of micro-crack on the failure mechanism of rock specimens under uniaxial compression was investigated experimentally. For this purpose, thermal stress was used to induce micro-cracks in the specimens. Several cylindrical and disk shape specimens were drilled from granite collected from Zanjan granite mine, Iran. Some of the prepared specimens were kept in room temperature and the others were heated by a laboratory furnace to different temperature levels (200, 400, 600, 800 and 1000 degree Celsius). During the experimental tests, Acoustic Emission (AE) sensors were used to monitor specimen failure at the different loading sequences. Also, Scanning Electron Microscope (SEM) was used to distinguish the induced micro-crack by heating in the specimens. The fractographic analysis revealed that the thin sections heated to $800^{\circ}C$ and $1000^{\circ}C$ contain some induced micro-fractures, but in the thin sections heated to $200^{\circ}C$, $400^{\circ}C$ and $600^{\circ}C$ have not been observed any micro-fracture. In the next, a comprehensive experimental investigation was made to evaluate mechanical properties of heated and unheated specimens. Results of experimental tests showed that induced micro-cracks significantly influence on the failure mode of specimens. The specimens kept at room temperature failed in the splitting mode, while the failure mode of specimens heated to $800^{\circ}C$ are shearing and the specimens heated to $1000^{\circ}C$ failed in the spalling mode. On the basis of AE monitoring, it is found that with increasing of the micro-crack density, the ratio of the number of shear cracks to the number of tensile cracks increases, under loading sequences.

Identification of Failure Cause for 300 MW LP Turbine Blade through Vibration Analysis (진동 해석을 통한 300 MW급 저압터빈 블레이드의 손상 원인 규명)

  • Bae, Yong-Chae;Lee, Hyun;Kim, Hee-Soo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.9 s.102
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    • pp.1100-1107
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    • 2005
  • The failure of blades frequently happened in the 300 MW LP(low pressure) turbine until now and they are maintaining the blades periodically during outage. So the blade-disk system is analysed by FEM in order to identify the main cause of failure of blade row. It is found that the stress of root's hole is highest in comparison with other parts from the result of the steady stress analysis. Also, the two dangerous frequencies which is related to the resonance condition are found in the interference diagram. One is 1,316 Hz. The other is 2,981 Hz which is related to the 1 nozzle passing frequency. The dynamic stress analysis is performed to identify more accurate root cause for failure of blade row It is confirmed that the dynamic stress of the former is higher than one of the latter From these results, it is concluded that the former has deeply something to do with the failure of blades more than the tatter. Based on versatile investigation and deliberation, the change of blade's grouping is determined to avoid the resonance condition with the operating speed. After the blade grouping is changed, the former frequency vanish completely but the latter is still in existence in the interference diagram. Fortunately, It is confirmed that the dynamic stress of the new blade grouping is lower than one of the old blade grouping. 2 years has passed since modification and the LP turbine is operated well without failure so far.

Wear Resistance of Crosslinked Ultra-high Molecular Weight Polyethylene (가교된 초고분자량 폴리에틸렌의 내마모성)

  • Im, Chae-Ik;Lee, Gwi-Jong;Jo, Jae-Yeong;Choe, Jae-Bong;Choe, Gwi-Won
    • Journal of Biomedical Engineering Research
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    • v.20 no.1
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    • pp.99-106
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    • 1999
  • Ultra-high molecular weight polyethylene (UHMWPE) was crosslinked in the melt state to enhance wear resistance, Dicumyl peroxide (DCP) and triallyl cyanurate (TAC) was used as a crosslinking agent and a promoter, respectively. With increasing amount of DCP and TAC used, gel content of crosslinked UHMWPE (XUMPE) increased, while the melting temperature, crystallizaiton temperature, crystallinity, and tensile properties decreased. The results of pin-on-disk wear test and ball-on-disk test with small applied load showed reduced wear volumes of XUMPE from that of the unmodified UHMWPE. As the wear mechanism effected in the experimental condition of this study was thought to be deformation rather than adhesion or fatigue, a new parameter, the ratio of maximum contact stress to yield stress, was proposed to correlate well with observed wear resistance. In ball-on-disk wear test with larger applied load, XUMPE showed higher wear volumes than that of the unmodified UHMWPE which were accompanied with increased friction coefficients and surface roughness of the wear tracks. When contact stress was well above yield stress, the failure of XUMPE, as well as deformation, was thought to be much accelerated.

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A Recovery Scheme of Single Node Failure using Version Caching in Database Sharing Systems (데이타베이스 공유 시스템에서 버전 캐싱을 이용한 단일 노드 고장 회복 기법)

  • 조행래;정용석;이상호
    • Journal of KIISE:Databases
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    • v.31 no.4
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    • pp.409-421
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    • 2004
  • A database sharing system (DSS) couples a number of computing nodes for high performance transaction processing, and each node in DSS shares database at the disk level. In case of node failures in DSS, database recovery algorithms are required to recover the database in a consistent state. A database recovery process in DSS takes rather longer time compared with single database systems, since it should include merging of discrete log records in several nodes and perform REDO tasks using the merged lo9 records. In this paper, we propose a two version caching (2VC) algorithm that improves the cache fusion algorithm introduced in Oracle 9i Real Application Cluster (ORAC). The 2VC algorithm can achieve faster database recovery by eliminating the use of merged log records in case of single node failure. Furthermore, it can improve the performance of normal transaction processing by reducing the amount of unnecessary disk force overhead that occurs in ORAC.

Design of Main-Memory Database Prototype System using Fuzzy Checkpoint Technique in Real-Time Environment (실시간 시스템에서 퍼지 검사점을 이용한 주기억 데이터베이스 프로토타입 시스템의설계)

  • Park, Yong-Mun;Lee, Chan-Seop;Choe, Ui-In
    • The Transactions of the Korea Information Processing Society
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    • v.7 no.6
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    • pp.1753-1765
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    • 2000
  • As the areas of computer application are expanded, real-time application environments that must process as many transactions as possible within their deadlines, such as a stock transaction systems, ATM switching systems etc, have been increased recently. The reason why the conventional database systems can't process soft real-time applications is the lack of prediction and poor performance on processing transaction's deadline. If transactions want to access data stored at the secondary storage, they can not satisfy requirements of real-time applications because of the disk delay time. This paper designs a main-memory database prototype systems to be suitable to real-time applications and then this system can produce rapid results without disk i/o as all of the information are loaded in main memory database. In thesis proposed the improved techniques with respect to logging, checkpointing, and recovering in our environment. In order to improve the performance of the system, a) the frequency of log analysis and redo processing is reduced by the proposed redo technique at system failure, b) database consistency is maintained by improved fuzzy checkpointing. The performance model is proposed which consists of two parts. The first part evaluates log processing time for recovery and compares with other research activities. The second part examines checkpointing behavior.

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Ceramic-Ceramic Wear Zirconia/Alumina Composites For The Application Of Total Hip Joint Implant (인공 고관절 골두용 세라믹 복합재료에 대한 세라믹-세라믹 접촉 마멸 특성 분석)

  • Kim H.;Lee K.Y.;Kim D. J.;Lee M. H.;Seo W. S.
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2004.11a
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    • pp.355-361
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    • 2004
  • Ceramic femoral heads in the total hip replacement have been developed to reduce the polyethylene liner wear, Alumina and zirconia (3Y-TZP) having the excellent tribological properties are coupled against acetabular cups of polyethylene and are used in clinical application worldwide. However, alumina has a risk of catastrophic failure, and zirconia has the low temperature degradation in spite of enhanced fracture toughness. Recently, novel zirconia/alumina composite is very attractive due to the low temperature degradation (LTD)-free character and high fracture toughness. In the present study, we focus on the wear of ceramic on ceramic, which are able to be used as femoral heads and acetabular cups. Therefore, LTD-free zirconia/alumina composites with three compositions are made in a form of disk and cylinder, and the wear of the composites is performed on pin-on-disk type wear tester. The wear is conducted with or without lubricant. All the composites fabricated with the different composition show the good wear resistance.

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Effect of Particle Contamination of Objective Lens in a CD-ROM Drive on Laser Diode Power and Photo Diode RE Signal (CD-ROM 드라이브의 대물렌즈 입자오염이 레이저 다이오드 파워와 포토 다이오드 RF 신호에 미치는 영향)

  • Pae, Yang-Il;Lee, Jae-Ho;Hwang, Jung-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.1
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    • pp.66-71
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    • 2004
  • Airborne contaminant particles are intruded into optical disk drive(ODD) due to the flow caused by disk rotation and can be adhered to objective lens, which causes read/write errors. Such a phenomenon can be a serious problem for high-density storage devices. The purpose of this paper is to understand the effect of particle contamination of objective lens in a CD-ROM drive on laser diode power and photo diode RF signal. The measurements of laser power and readout RF signal were carried out by using a laser power meter and a time interval analyzer, respectively. The parameters for estimating a readout-signal' distortion were its jitter and amplitude. Alumina(Al$_2$O$_3$) particles were used as test dust particles. The results show that the failure for data access happened as the degree of lens contamination was greater than 20%.