• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.840-846
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• 2007

This paper investigates the dynamic behavior of a HDD spindle system due to the imperfect roundness of a rotating shaft. The shaft of a spindle motor rotates with eccentricity by the unbalanced mass of the rotating part. The eccentricity generates the run-out of a spindle motor which results in the eccentric motion of a rotating part. Roundness of a shaft affects this motion which limits the memory capacity of a HDD. This research proposes a modified Reynolds equation for the coupled journal and thrust FDBs to include the variable film thickness due to the roundness. Finite element method is used to solve the Reynolds equation for the pressure distribution. Reaction forces and friction torque are obtained by integrating the pressure and shear stress, respectively. The dynamic behavior is determined by solving the equations of a motion of a HDD spindle system in six degrees of freedom with the Runge-Kutta method to characterize the motion of a rotating part. This research shows that the roundness of a rotating shaft causes the excitation frequency with integer multiple of a rotating frequency.

• Journal of Advanced Marine Engineering and Technology
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• 제22권5호
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• pp.626-634
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• 1998

Controllable pitch propeller(CPP) is usually adopted for easy and effective engine controls of a ship in a port. Unfortunately the torsional vibration may occur by a certain variation of engine torque and the major resonance peak may exist within the maximum continuous rating(MCR) In these cases an additional stress concentration on the oil passages such as longitudinal slots notches and circular holes of an oil distributor shaft(ODS) occurs by the torsional vibration of the CPP shaft. In this paper an analysis for the fatigue limit of an ODS system of the 5S70MC engine in a crude oil carrier is done by applying FEM and empirical formulas. Furthermore the additional stress on the ODS is investigated by analyzing the torsional vibration of the shaft system and a control method in which a tuning damper is adopted is introduced in the case of the additional stress exceeds the fatigue limit. The validity of analysis method is verified by comparing the results acquired by an actual measurement of the vibratory torque for the above ODS

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1986년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 17-18 Oct. 1986
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• pp.197-199
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• 1986

To meet tight tolerance requirements of mass produced shafts which are subcomponents of automobile parts, an automated measuring system has been developed. The system comprises of a non-contact shaft diameter measuring instrument using laser, a feed mechanism of a step motor and ball screw and a personal computer. The system can determine pass-fail of the piece under test and also analyze data for statistical process control.

• 한국자동차공학회논문집
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• 제6권3호
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• pp.115-122
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• 1998

For digital engine control timings, such as ignition, are based on the crank shaft angle. Therefore, it is very important that the angle of the crank shaft can be detected with accuracy for optimal ignition timing. Sequential multi-point injection(MPI) systems that have independent injection events for each cylinder, are used to inject an accurate quantity of fuel, and to cope with varying engine status promptly. In this study the distributorless ignition timing. A crankshaft position sensor has been installed such that it generates a number of pulses per crankshaft revolution to permit accurate detection of the crank shaft angle. An event detecting algorithm has been developed, which detects the crank shaft pulses generated by the position sensor, and the software outputs the required control signals at given crank angle values. We clarified that the hardware method is the best way to increase the performance of the control system, because the event detecting duration T(1+2)max becomes zero.

• 한국해양공학회지
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• 제32권6호
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• pp.518-526
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• 2018

As a new technical approach, this paper introduces a method for improving an electrically propelled outboard motor in consideration of the driving system applied to an electric-propulsion boat with solar cell energy. The most efficient model for a drive shaft, propeller shaft, and bevel gear was suggested and examined with respect to the results of test operation in prototype mode. Furthermore, this research included a performance evaluation of the manufactured prototype to acquire the purposed quantity value and the development items. After manufacturing the desired prototype of an electrically propelled outboard motor, the maximum sail time, thrust force, noise, and weight were evaluated in a performance test. An additional test in relation to the maximum sail speed (knots) of the completed prototype was conducted using a sea trial evaluation to acquire the optimum quantity.

• Geomechanics and Engineering
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• 제24권5호
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• pp.431-441
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• 2021

Rock-socketed drilled shafts are widely used to transfer the heavy loads from the superstructure especially in mountainous area. Extensive research has been done on the behavior of rock-socketed drilled shafts under compressive load. However, little attention has been paid to uplift behavior of drilled shaft in rock, which govern the overall behavior of the foundation system. In this paper, a series of centrifuge tests have been performed to investigate the uplift response of rock-socketed drilled shafts. The pull-out tests of drilled shafts installed in layered rocks having various strengths were conducted. The load-displacement response, axial load distributions in the shaft and the unit skin friction distribution under pull-out loads were investigated. The effects of the strength of rock socket on the initial stiffness, ultimate capacity and mobilization of friction of the foundation, were also examined. The results indicated that characteristics of rock-socket has a significant influence on the uplift behavior of drilled shaft. Most of the applied uplift load were carried by socketed rock when the drilled shaft was installed in the sand over rock layer, whereas substantial load was carried by both upper and lower rock layers when the drilled shaft was completely socketed into layered rock. The pattern of mobilized shaft friction and point where the maximum unit shaft friction occurred were also found to be affected by the socket condition surrounding the drilled shaft.

• 한국지반공학회논문집
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• 제21권1호
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• pp.93-103
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• 2005

대구경 현장타설말뚝에 대하여 하중전이 측정을 수반한 정재하시험, 동재하시험 및 유한차분해석을 수행하여 주면 마찰력 거동특성에 대한 연구를 실시한다. 주면 마찰력은 말뚝과 지반의 상대변위와 직접적으로 관계되므로 임의의 심도에서 측정한 말뚝의 하중전이량과 유한차분해석에 의한 주면지반의 변위와 응력을 이용하여 거동특성을 분석한다. 하중전이측정결과에 의하면 현장타설말뚝 주면을 따라 발휘되는 극한단위주면 마찰력은 중간 깊이인 모래자갈층과 자갈층 상부에서 먼저 나타난다. 또한 동일한 현장타설말뚝에 대하여 동재하시험과 정재하시험을 실시한 결과 주면 마찰력과 선단지지력의 거동특성이 상이하게 평가되었으며, 그 차이점에 대하여 논의한다.

• Journal of Advanced Marine Engineering and Technology
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• 제38권2호
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• pp.123-132
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• 2014

The maritime sector is advancing with dedicated endeavor to reduce greenhouse gas in addressing issues with regards to global warming. Since 01 January 2013, the International Maritime Organization (IMO) regulation mandatory requirement for Energy Efficiency Design Index (EEDI) has been in place and should be satisfied by newly-built ships of more than 400 gross tonnage and the Ship Energy Efficiency Management Plan (SEEMP) for all ships type. Therefore, compliance to this necessitates planning during the design stage whereas verification can be carried-out through an acceptable method during sea trial. The MEPC-approved 2013 guidance, ISO 15016 and ISO 19019 on EEDI serves the purpose for calculation and verification of attained EEDI value. Individual ships EEDI value should be lower than the required value set by these regulations. The key factors for EEDI verification are power and speed assessment and their synchronization. The shaft power can be measured by telemeter system using strain gage during sea trial. However, calibration of shaft power onboard condition is complicated. Hence, it relies only on proficient technology that operates within the permitted ISO allowance. On the other hand, the ship speed can be measured and calibrated by differential ground positioning system (DGPS). An actual test on a newly-built vessel was carried out to assess the correlation of power and speed. The Energy-efficiency Design Index or Operational Indicator Monitoring System (EDiMS) software developed by the Dynamics Laboratory-Mokpo Maritime University (DL-MMU) and Green Marine Equipment RIS Center (GMERC) of Mokpo Maritime University was utilized for this investigation. In addition, the software can continuously monitor air emission and is a useful tool for inventory and ship energy management plan. This paper introduces the synchronization and identification method between shaft power and ship speed for EEDI verification in accordance with the ISO guidance.

• 대한조선학회논문집
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• 제42권3호
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• pp.259-267
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• 2005

The effects of hull flexibility on shaft alignment are growing as ship sizes are increased mainly for container carrier and LNG carrier. In order to consider hull flexibility on a propulsion shafting system, standardization of ship service conditions is necessary because hull deformation is continuously variable according to ship service conditions. How to summarize ship service conditions is suggested based on practically applicable four viewpoints : hull, engine, loading and sea status. Effects of the external forces acting on a ship propulsion shafting system are generally commented. Several design criteria regulated by classification societies are pointed at issue which seems to have Insufficient technical background. A qualitative verification is carried out to point out the invalidity of the assumption of effective supporting position. In this work, an elastic nonlinear multi-supporting bearing system is introduced as a key concept of the elastic shaft alignment. Hertz contact theory is proved to be more proper one than projected area method in calculation of the nonlinear elastic stiffness of the bearing, The squeezing and oil film pressure calculations in the long journal bearing like an after stern tube bearing are recognized as a necessary process for elastic shaft alignment design.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1998년도 추계학술대회 학술발표 논문집
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• pp.403-410
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• 1998

An immune system has powerful abilities such as memory recognition and learning how to respond to invading antigens, and has been applied to many engineering algorithms in recent year. In this paper, the combined optimization algorithm (Immune-Genetic Algorithm: IGA) is proposed for multi-optimization problems by introduction the capability of the immune system that controls the proliferation of clones to the genetic algorithm. The new combined algorithm is applied to minimize the total weight of the rotor shaft and the transmitted forces at the bearings in order to demonstrate the merit of the combined algorithm. The inner diameter of the shaft and the bearing stiffness are chosen as the design variables. the results show that the combined algorithm can reduce both the weight of the shaft and the transmitted forces at the bearing with dynamic constraints.