• Journal of Advanced Marine Engineering and Technology
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• v.15 no.2
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• pp.44-52
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• 1991

The crankshaft system of engine is a complex vibratory object and its vibration modes are consisted of torsional, axial and their coupled vibration. Among them, the torsional vibration causes engine noise as well as serious fatigue faillures of crankshaft. If the troules of noises and crankshaft strength are forecasted by torsional vibration calculation in the design atage of crankshaft, the torsional damper is adopted as the final countermeasure. In this paper, some computer program to calculate crankshaft torsional vibration of engine are developed and with developed programs, an efficient rubber-viscous damper for automobile and with developed programs, an efficient rubber-viscous damper for automobile engine is designed and manufactured, and then it is fitted on the actual automobile engine to confirm its calculated efficiency. By comparing the measured result (with damper and without damper) with the calculated one, the reliability of developed computer programs and the performances of manufactured damper are confirmed.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.3
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• pp.482-492
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• 2004

Recently. the market trend for marine diesel engine has involved the lower running speeds. larger stroke/bore ratio and higher combustion pressure. Consequently, because of the flexible engine shafting system due to the larger mass. inertia and the more elasticity, the complicated coupled torsional-axial vibrations have occurred in the operating speed range. Also, the vibrations act as an excitation on the hull-structural vibration. To predict the vibration behavior with more accuracy and reliability. many studies have proposed the several kinds of method to calculate the stiffness matrix of crankshaft. However, most of these methods have a weak point to spend much time on three dimensional modeling and meshing work for crankshaft. Therefore. in this work. the stiffness matrix for the crankthrow is calculated using the energy method (Influence Coefficient Method, ICM) with the each mass having 6 degree of freedom. Its effectiveness is verified through the comparison with the stiffness matrix obtained by using the finite element method (FEM) and measured results for actual ships propulsion system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.9
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• pp.398-405
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• 2001

The maximum and mean indicated pressure of two stroke low speed diesel engine has been continuously increased with a view of increasing engine power and also reducing fuel consumption. As a result, axial excitation has been increased comparing to that of the previous one. So the axial vibration damper in standard one is applied to all two stroke low speed diesel engine at the free end of crankshaft. Though many studies were carried out for marine use, few has been made for diesel power plant because there was little demand for power plant. Nowadays, diesel engine is much to be used for many benefits. In this paper, the optimum design of axial vibration on the 65 kW diesel power plant with tow 9K80MC-S engines of 9 cylinders was carried out. And the axial-torsional coupled vibration of this shafting system is identified by theoretical analysis and vibration measurement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1816-1822
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• 2000

The maximum and mean indicated pressure of two stroke low speed diesel engine has been continuously increased with a view of increasing engine power and also reducing fuel consumption. As a result, axial excitation has been highed comparing to that of the previous and so in standard axial vibration damper is applied to all two stroke low speed diesel engine at the free end of crankshaft. Though many studies were carried out for marine use, few has been made for diesel power plant because there was little demand for power plant. Nowadays, diesel engine is much to be used for many benefits and so in this paper, the optimum design of axial vibration on the 65 MW diesel power plant with 9K80MC-S engine was carried out. And the axial-torsional coupled vibration of this shafting system is identified by theoretical analysis and vibration measurement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.376-381
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• 2009

The increasing needs for higher cargo capacity in the container vessels' fleet has led to ship builder's demand for higher power output rating engine to meet the propulsion requirement, thus, leading to the development of super large two stroke low speed diesel engines. This large sized bore engines with more than 12 cylinders are capable of delivering power output up to more than 100,000 bhp at maximum continuous rating. The thrust variation force due to axial vibration occurring in propulsion shafting of these ships are transmitted to ship structure via thrust bearing. This force may vibrate the super structure of ship in the fore-aft direction and the fatigue strength of crank shaft can be decreased by additional bending stress increase in crank shaft pin and journal. In this paper, the axial vibration of propulsion shafting system on the 14RT-flex96C super large diesel engine with 14 cylinders is identified by theoretical analysis and vibration measurement.

• Structural Engineering and Mechanics
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• v.62 no.6
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• pp.759-769
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• 2017

The effect of central axial load on natural frequencies of various thin-walled beams, are investigated by some researchers using different methods such as finite element, transfer matrix and dynamic stiffness matrix methods. However, there are situations that the load will be off centre. This type of loading is called eccentric load. The effect of the eccentricity of axial load on the natural frequencies of asymmetric thin-walled beams is a subject that has not been investigated so far. In this paper, the mentioned effect is studied using exact dynamic stiffness matrix method. Flexure and torsion of the aforesaid thin-walled beam is based on the Bernoulli-Euler and Vlasov theories, respectively. Therefore, the intended thin-walled beam has flexural rigidity, saint-venant torsional rigidity and warping rigidity. In this paper, the Hamilton‟s principle is used for deriving governing partial differential equations of motion and force boundary conditions. Throughout the process, the uniform distribution of mass in the member is accounted for exactly and thus necessitates the solution of a transcendental eigenvalue problem. This is accomplished using the Wittrick-Williams algorithm. Finally, in order to verify the accuracy of the presented theory, the numerical solutions are given and compared with the results that are available in the literature and finite element solutions using ABAQUS software.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.261-267
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• 2011

This study reveals the longitudinal vibration mechanism of tendon embedded in a prestressed concrete. The extensional and torsional displacements of the strand are coupled, and the applied prestress level of tendon affects not only axial rigidity but also torsional rigidity. Measuring the elastic wave velocity of tendon, the applied prestress level of tendon could be evaluated. This is because the elastic wave velocity is a function of extensional and torsional rigidity. Using the experimental results for the six prsteressed concrete beams with different prestress levels, the longitudinal vibration mechanism and the effect of prestress level have been examined. To estimate the system ridigities of tendon, a system identification algorithm has been newly developed. The estimated system rigidities have been compared with the available results of related previous study.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.2
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• pp.103-107
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• 1995

Longitudinal hull girder vibration has not been occurred severely since 1960's. However, recent low speed diesel driven ships equipped with overcritical shafting system, can be excited heavily in longitudinal direction by shaft axial farce coupled with torsional vibration. In this study the characteristics of longitudinal hull girder vibration of a 73,000 deadweight bulk carrier were investigated through onboard measurement, exciter test, and 3-D FEM analysis. Results showed that the longitudinal hullgirder vibration may occur in the ship which is not set up the barred speed range in engine operation. Moreover, this vibration occurs. only during the low speed voyage in harbour depending upon the ship loading condition.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.3
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• pp.1-12
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• 1989

The nonlinearity of a cable-stayed bridge results from the large displacement of main girder due to a long span, the catenary action of cables and the flexural stiffness reduced by large axial forces. The dynamic behaviour of a cable-stayed bridge plays an important role in determining its safety. Especially, when the eccentrically moving load is applied to a cable-stayed bridge, the torsional vibration and vertical vibration are coupled and moreover the variation of cable tensions shows important dynamic characteristics. This dissertation presents a theoretical study and a finite element procedure for analysis of a cable-stayed bridge under a eccentrically moving load. Attention is focused on the dynamic behaviours such as dynamic increments of cable tensions and nodal displacements, with the variety of velocities and eccentricities of moving load. It is found that a moving load with eccentricity can have significant effects upon the responses; the torsion of bridge deck and the increments of cable tensions, according to the present results in this study.