• Structural Engineering and Mechanics
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• v.33 no.6
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• pp.747-763
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• 2009

In this work, the linear vibration characteristics of $90^{\circ}$ pipe bends and their cylindrical and toroidal shell components are studied. The finite element method, based on shear-deformation shell elements, is used to carry out a vibration analysis of metallic multiple $90^{\circ}$ mitred pipe bends. Single, double, and triple mitred bends are considered, as well as a smooth bend. Sample natural frequencies and mode shapes are given. To validate the procedure, comparison of the natural frequencies is made with existing results for cylindrical and toroidal shells. The influence of the multiplicity of the bend, the boundary conditions, and the various geometric parameters on the natural frequency is described. The differential quadrature method, based on classical shell theory, is used to study the vibration of components of these bends. Regression formulas are derived for cylindrical shells (straight pipes) with one or two oblique edges, and for sectorial toroidal shells (curved pipes, pipe elbows). Two types of support are considered for each case. The results given provide information about the vibration characteristics of pipe bends over a wide range of the geometric parameters.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.3
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• pp.315-321
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• 2021

In this study, the natural frequency analysis of the fuel pipe and vibration test jig was performed as a basic study to determine the vibration characteristics of the vehicle's fuel pipe and the stability analysis of fatigue failure of the pipe. The natural frequencies of the fuel pipe and the fuel pipe with the test jig were calculated and the results were compared. As a result of the analysis, it was found that the natural frequency of the fuel pipe and the natural frequency of the test jig differed about 7 times, so that the vibration of the test jig did not affect the vibration of the fuel pipe. In addition, as a result of the natural frequency analysis of the fuel pipe itself and the pipe with the test jig attached, the maximum error is less than about 1%. In the future, it was suggested that the analysis of the design changed fuel pipe may be performed without a test jig.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1957-1964
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• 1997

Torsional vibration is to vibrate strongly when the ignition pulses of the engine is excited with natural frequency of driveline. Torsional vibration like this can cause various noises as rattle and booming. For this study multi-degree of freedom analysis model of torsional vibration, which is combined with mass moment of inertia and torsional spring, was developed toward two wheel drive, four wheel drive and torsional vibration characteristics were compared and analyzed through the natural frequences, mode shapes and frequency response characteristics which was acquired by the simulation of it. The pertinence of that model was proved by the field test and the outcome of the simulations coincided with feeling test. Therefore, four wheel drive simulation model is considered to be useful thing for reducing torsional vibration of driveline and developing full-time four wheel drive vehicles.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.1
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• pp.26-32
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• 2003

The vibrational system of this study is consisted of a rotating cantilever pipe and the flow in the pipe. The equation of motion is derived by using Lagrange equation. The influences of the rotating angular velocity and the velocities of fluid flow in the pipe have been studied on the dynamic characteristics of a rotating cantilever pipe by numerical method. The tip-amplitude of axial vibration and maximum tip-deflection of axial direction of cantilever pipe are directly proportional to the velocity of fluid and rotating angular velocity of pipe In the steady state. respectively The bending tip-amplitude of cantilever pipe is inversely proportional to the velocity of fluid in the steady state. When the rotating angular velocity is 5 rad/s, the velocity of fluid increase with increasing the natural frequency of axial vibration at second mode and third mode, but the natural frequency axial direction of first mode is decreased. The natural frequency of lateral direction is decreased due to increase of the rotating angular velocity. It identifies that the Influence of velocity of fluid give much variation lower mode of vibration in lateral direction. And the Influence of velocity of fluid give much variation higher mode of vibration in axial direction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.155-160
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• 2001

This study is performed to evaluate and design the vibration characteristics of the onboard machinery with resilient mountings. To reduce the vibration level of onboard machinery with resilient mountings, it is important to evaluate and, if necessary, modify the vibration characteristics of the resilient mountings. In this study, we have developed a program to calculate natural frequencies of the machinery with resilient mountings, forced vibration levels due to internal excitation force of the machinery itself and external excitation forces. of the main engine and the propeller. and the force and motion transmissibility of the resilient mountings. The developed program is also able to be applied to optimal design of the resilient mountings for obtaining a target natural frequency and for achieving a minimum forced vibration level at the center of gravity of the machinery.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.10
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• pp.780-787
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• 2014

This paper experimentally deals with the vibration characteristics of flat ring transducers used for ultrasonic sensors and actuators. Radial vibration mode, which is the fundamental mode of a thin piezoelectric transducer, was measured by a laser in-plane vibrometer. An impedance analyzer was used to measure natural frequencies. The results measured by experiments verified theoretical predictions. The vibration characteristics of ring transducers were identified according to the outer diameter size. The shape of the fundamental mode is almost uniform but slightly decreases from the inner to the outer circumferential surfaces. The natural frequency of the fundamental mode decreases as the outer diameter increases. It appears that the ring type transducer is suitable to excite uniformly distributed vibration on a flat surface.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.99-104
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• 2008

The Carbon fiber epoxy composite material and aluminum have many advantages about higher specific stiffness and good fatigue characteristics. basically, the propeller shaft of automobile must satisfy high natural frequency more than 9,200 rpm to satisfy high number of rotation and high torsion torque more than 2,700Nm. In these reason, studied natural frequency and torsion torque characteristics of shaft according to parameter variations with the outdiameter and thickness. From the torsion tester and natural frequency experiments FE analyses was compared vibration and torque characteristics of hybrid shaft Designed hybrid shaft was experimented through FFT analyzer and torsion tester each and satisfied that hybrid shaft reverence 60mm and thickness 5mm by a these experiment is most suitable. Therefore, that can manufacture existent steel two piece type propeller shaft to one piece type hybrid shaft.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1280-1285
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• 2000

The paper deals with a theoretical study on the vibrational characteristics of piezoelectric torsional transducers. The differential equations of piezoelectric torsional motion have been derived in terms of the circumferential displacement and the electric potential. Applying mechanical and electrical boundary conditions has yielded the characteristic equations of natural vibration in several transducer types. Numerical results have clarified the effect of the piezoelectric phenomenon on the mechanical resonance and the effect of the elastic block of a Langevin-type transducer on the natural frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1202-1209
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• 2002

This paper presents the characteristics of the radial vibration of cylindrical piezoelectric transducers. The differential equations of piezoelectric radial motion have been derived in terms of the radial displacement and electric potential, which are functions of the radial and axial coordinates. Applying mechanical and electrical boundary conditions has yielded the characteristic equation of radial vibration. Numerical results of the natural frequencies have been compared with the experimental observations reported earlier for the transducers of several sizes, and have shown a good agreement for the fundamental mode. The paper discusses the dependence of the natural frequencies on the radius and thickness of the piezoelectric cylinders and the difference between Piezoelectric and elastic resonances

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.4
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• pp.57-62
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• 2003

A fundamental structural design consideration for a vehicle system is the overall vibration characteristics in bending and torsion. Vibration characteristics of such vehicle system are mainly influenced by the static and dynamic stiffness of the vehicle body structure and also by the material and physical properties of the components attached to the vehicle body structure. In this paper, modeling techniques for the vehicle components are presented and the flexibility and mass effects of the components for the vibration characteristics of the vehicle are investigated. The $1^{st}$ torsional frequency is increased by attaching windshields to the B.I.W. (body-in-white), but the $1^{st}$ bending frequency is decreased by the mass effect. And also, the natural frequencies of the vehicle are large decreased by attaching bumpers, seats, doors, trunk-lid etc. But, suspension system rarely affects the natural frequencies of the vehicle. The study shows thai the dynamic characteristics of the vehicle system can be effectively predicted in the initial design stage.