• Geotechnical Engineering
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• v.11 no.3
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• pp.55-68
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• 1995

This paper is the analysis of the relationship between RQD and decay constant, blasting vi bration constant of cube root scaling and square root scaling, through experimental blast ins test in subway construction for excavation of shaft hole by bottom blasting. The magnitude of particle velocity is largely effected by the distance from blasting source, the maximum charge per delay and the properties of ground. In order to verify the effects of ground properties on blast-induced vibration, the relation-ship between magnitude of blasting vibration and Rock Quality Disignation which stands for joint property was studied. The results of test are verified that blasting vibration constant "K" and the absolute value("n") of decay constant relatively increse as RQD increased. According to the result, it can be predict the particle velocity by the blast -induced vibration in bottom blasting pattern.om blasting pattern.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.648-655
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• 2005

The resilient mounts of a diesel engine installed onboard a ship should be designed for both static and dynamic loads. If possible, the resonance frequencies of the six rigid body modes of the installation and the flexible modes of the engine support structure should not lie within the engine operation range. In this paper a design criterion is proposed to evaluate an isolation system which involves the summation of dynamic forces transmitted through the resilient mounts and elastic potential energy index stored in the mounts. A case study is also presented in which a diesel engine generator, which had an elastic foundation and was mounted in a 5500 TEU container vessel, was studied both theoretically and experimentally. The theoretical analysis of the test model was performed by using a single mass 6 degree of freedom system. Actual measurements of mechanical vibration of the Engine and its foundation onboard were carried out, which showed the importance of including the flexibility of the engine support structure in the mode

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.329-338
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• 2006

The resilient mounts of a diesel engine installed onboard a ship should be designed for both static and dynamic loads. If possible, the resonance frequencies of the six rigid body modes of the installation and the flexible modes of the engine support structure should not lie within the engine operation range. In this paper a design criterion is proposed to evaluate an isolation system which involves the summation of dynamic forces transmitted through the resilient mounts and elastic potential energy index stored in the mounts. A case study is also presented in which a diesel engine generator, which had an elastic foundation and was mounted in a 5500 TEU container vessel, was studied both theoretically and experimentally. The theoretical analysis of the test model was performed by using a single mass 6 degree of freedom system. Actual measurements of mechanical vibration of the engine and its foundation onboard were carried out, which showed the importance of including the flexibility of the engine support structure in the mode.

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.216-221
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• 2005

Many tanks such as a fresh water tank, an aft peak tank and oil tanks are arranged in the engine room and aft part areas of the ship. By added mass effect of the fluid inside the tanks, the natural frequency will be changed according to filling height of the tank. For this reason, there is possibility of occurrence of excessive vibration by resonance between natural frequencies of local structure and excitation frequencies of the propeller or main engine. Therefore, calculation of natural frequencies is required for structure for many types of tank which are contacting with water or oil to consider added mass effect for anti-resonance design at design stage. In this study, a case of structure damage on the fresh water tank for 2600 TEU container vessel is introduced. In addition, natural frequency analysis and vibration measurement have been performed to investigate vibration characteristics for excessive vibration control.

• Journal of Advanced Marine Engineering and Technology
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• v.4 no.1
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• pp.2-22
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• 1980

In the earlier days, when the diesel engine was used for ship propulsion, its shaft had often been broken by uncertain causes. Bauer suggested, for the first time in 1900, that it resulted from the torsional vibration of the shaft system. From 1901 to 1902, Gumbel and Frahm found out that shaft failures were caused by the resonance of the shaft system in critical speed. Since that time, valuable theories, empirical formulae and methods of vibration analysis were introduced by many investigators such as Geiger, Holzer, Lewis, Carter, Porter, Constant, Timoshenko, Dorey, Den Hartog, Tuplin, Ker Wilson, Bradbury etc. But, as the calculation of the damping energy involves very complicated and uncertain factors, the estimated amplitude of the torsional vibration is incorrect and uncertain. Besides, as high-powered engines have been installed on large vessels or special vessels and exciting force has been increased, new problems of the torsional vibration have continuously occurred. Although we can calculate the approximate natural frequencies or estimate their amplitude and additional stress in the design stage, through the above mentioned studies, the results of the calculations are unsatisfactory, and so much time is needed to carry out the calculation by hand. The authors have developed a computer program to calculate its natural frequencies, the amplitudes and additional stresses of the torsional vibration in the marine diesel engine shafting. In developing the computer program, the authors have paid the special attention to the calculation of the damping energy. To verify the reliability of the developed computer program, the torsional vibration of several propulsion shaftings which are driven by the diesel engine has been analyzed. The results calculted by the authors' computer program show good agreements with those of the actual measurements and are better than the results of engine maker's calculation.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.4
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• pp.503-508
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• 2010

Common LED (Light Emitting Diode) lamp has many advantages to compare with fluorescent lamp, long life and no pollution matter like the mercury. The LED lamp is a good light source especially for shipboard lighting because of its compact structure which prevents explosion and shock. Also, low maintenance cost is expected due to its longer life time in comparison with conventional lamps. The LED lamp, however, need some estimates that change of voltage and frequency, vibration, moisture on board to definite accommodation of the LED lamp to shipboard. The purpose of this study is to compare physical properties of a fluorescent lamp with one of the common LED lamp so as to analyze accommodation of common LED lamp on board. This study was carried out in two stages. First, temperature, humidity of illumination, voltage, electric current, frequency and electric power were measured by using experimental equipments. Second, a comparative analysis of consumption electric power, annual oil charge, annual CO2 emission and lamp life time, etc of the fluorescent lamp and common LED one was made. As a result of the study, the consumption electric power of fluorescent lamp was 50% higher than one of the common LED lamp. As a result of measuring life time, it was found that life time of common LED lamp was more about 3.5 fold than one of the fluorescent lamp. Considering these results, it's thought that common LED lamp is verified that energy saving is possible and using is possible as substitute for fluorescent lamp on board.

• Journal of Navigation and Port Research
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• v.33 no.10
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• pp.671-678
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• 2009

Recently, there have been some researches in the equipment fault detection based on shock and vibration information. Most research of them is based on shock and vibration monitoring to determine the equipment fault or not. Different with engine fault detection based on shock and vibration information we focus on detection of engine for boat and system control. First, it use the duplicated-checking method for shock and vibration information to determine the engine fault or not. If there is a fault happened, we use the integral to determine the error engine shock wave width and detect the fault area. On the other hand, we use the engine trend analysis and standard of safety engine to implement the shock and vibration information database. Our simulation results show that the probability of engine fault determination is 98% and the probability of engine fault detection is 72%

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.3
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• pp.232-243
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• 2004

After studying the composition about the torsional shafting of main engine for fishing vessel with Power Take Off (PTO) System, the authors made a computer program using the transfer stiffness coefficient method (TSCM) for analyzing torsional vibration about the shafting with PTO system and nonlinear elastic coupling. The torsional shafting of main engine was separated by 3 types according to the connecting. The torsional shafting of main engine was separated by 3 types according to the connecting condition of main engine with propeller or the PTO system or both of them. In this paper, the change of natural frequencies and natural modes according to connecting condition of torsional shafting and nonlinear elastic coupling were analyzed. The accuracy of the TSCM was confirmed by comparing with the computational results of the Finite Element Method.

• Journal of Ocean Engineering and Technology
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• v.30 no.5
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• pp.400-404
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• 2016

This paper presents experimental results for the vibration characteristics of the small unmanned underwater vehicle (UUV) OPKO 300, which was designed and manufactured by Daewoo ship and Marine Engineering Ltd. The autonomy of UUVs has led to an increase in their use in scientific, military, and commercial areas because their autonomy makes it possible for UUVs to be utilized instead of humans in hazardous missions such as mine countermeasure missions (MCM). Since it is impossible to use devices based on electromagnetic waves to gather information in an underwater environment, only sonar systems, which use sound waves, can be used in underwater environments, and their performance can strongly affect the autonomy of a UUV. Since a thruster system, which combines a motor and propeller in a single structure, is widely used as the propulsion system of a UUV and is mounted on the outside of a UUV’s stern, it can generate vibration, which can be transferred throughout the shell of the UUV from its stern to its bow. The transferred vibration can affect the performance of various sonar systems such as side-scan sonar or forward-looking sonar. Therefore, it is necessary to estimate the effect of the transferred vibration of the UUV on the sonar systems. Even if various numerical methods were used to analyze the vibration problem of a UUV, it would be hard to predict the vibration phenomena of a UUV at the initial design stage. In this work, an experimental study using OKPO 300 and an impact hammer was carried out to analyze the vibration feature of a small real UUV in the air. The frequency response function of the vibration based on the experimental results is presented.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.3
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• pp.54-61
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• 1998

This paper presents a prediction method of natural frequencies of vertical hull girder vibration based on design sensitivity analysis in case of design modification and the variation of loading condition. The resented method premises the vibration analysis by the transfer matrix method. Governing sensitivity equation is derived from the direct differentiation of state vector and transfer matrix to parameters and its transfer over all the hull girder elements. Derivatives of natural frequencies and mode shapes are determined by two trial calculation of the governing equation. Using the derivatives, the changes of natural frequencies and mode shapes can be predicted when mass and stiffness parameter's are changed. As results, it is possible to optimize ship structure as well as to avoid troublesome calculation in hull girder vibration analysis rationally and efficiently. To verify the accuracy and efficiency of the resented method numerical results obtained by both the sensitivity analysis and the ordinary reanalysis far a real ore/bulk carrier in case of the change of mass and stiffness parameters are compared.