• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.04a
• /
• pp.544-549
• /
• 2011

Simplified formulae for axial and bending natural frequencies of bellows are developed using an equivalent thin-walled pipe model. The axial and bending stiffness of bellows is determined using lumped transfer matrix method. Accordingly, the Expansion Joint Manufacturers Association (EJMA) formula for axial and bending stiffness calculation is modified using two different equivalent radii. The results from the simplified formulae are verified by those from a experiment result and a finite element (FE) model and good agreement is shown between the each other.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.25 no.6
• /
• pp.399-405
• /
• 2015

In this work we use the mode decomposition technique employing chirplet transform, which is able to separate the individual modes from dispersive and multimodal waveform measured with the magnetostrictive sensor. The mode decomposition technique is also used to estimate the time-frequency centers and individual energies of the reflection, which would be used to locate and characterize axial defects. The arrival times of the separated modes are calculated and the axial defect lengths can be evaluated by using the estimated arrival time. Results from an experiment on a carbon steel pipe are presented and it is shown that the accurate and quantitative defect characterization could become enabled using the proposed technique.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.10 s.175
• /
• pp.150-157
• /
• 2005

The vibration system in this study is consisted of a rotating cantilever pipe conveying fluid and a tip mass. The equation of motion is derived by using the Lagrange's equation. The influences of the rotating angular velocity and the velocity of fluid flow on the natural frequencies of a cantilever pipe have been studied by the numerical method. The effects of a tip mass on the natural frequencies of a rotating cantilever pipe are also studied. The influences of a tip mass, the velocity of fluid, the angular velocity of a cantilever pipe and the coupling of these factors on the natural frequency of a cantilever pipe are analytically clarified. The natural frequencies of a cantilever pipe conveying fluid are proportional to the angular velocity of the pipe in both axial direction and lateral direction.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.12 no.12
• /
• pp.943-949
• /
• 2002

The propagation of the impulse wave discharged from the Inclined exit of a pipe is investigated through shock tube experiment and numerical computations. The pressure histories and directivities of the impulse wave propagating outside from the exit of pipe with several different configurations are analyzed for the range of the incident shock wave Mach number between 1.1 and 1.4. In the shock tube experiments, the impulse waves are visualized by a Schlieren optical system for the purpose of validation of computational work. Computations using the two-dimensional. unsteady, compressible, Euler equations are carried out to represent the experimented impulse waves. Computed Schlieren images predict the experimented impulse waves with a good accuracy. The results obtained show that for the radial direction the peak pressure of the impulse wave discharged depends upon the Inclined angle of the exit of the pipe. but for the axial direction it is almost constant regardless of the inclined angle of the pipe exit.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.1148-1158
• /
• 2005

This work reports results of our study on the dynamic responses of the buried pipelines both along the axial and the transverse directions under various boundary end conditions. We have considered three cases, i.e., the free ends, the fixed ends, and the fixed-free ends. We have studied the seismic responses of the buried pipelines with the various boundary end conditions both along the axial and the transverse direction. We have considered three cases, i.e., the free ends, the fixed ends, and the fixed-free ends for the axial direction, and three more cases including the guided ends, the simply supported ends, and the supported-guided ends for the transverse direction. The buried pipelines are modeled as beams on elastic foundation while the seismic waves as a ground displacement in the form of a sinusoidal wave. The natural frequency and its mode, and the effect of parameters have been interpreted in terms of free vibration. The natural frequency varies most significantly by the soil stiffness and the length of the buried pipelines in the case of free vibration, which increases with increasing soil stiffness and decreases with increasing length of the buried pipeline. Such a behavior appears most prominently along the axial rather than the transverse direction of the buried pipelines. The resulting frequencies and the mode shapes obtained from the free vibration for the various boundary end conditions of the pipelines have been utilized to derive the mathematical formulae for the displacements and the strains along the axial direction, and the displacements and the bending strains along the transverse direction in case of the forced vibration. The negligibly small difference of 6.2% between our result and that of Ogawa et. al. (2001) for the axial strain with a one second period confirms the accuracy of our approach in this study.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.18 no.6
• /
• pp.69-75
• /
• 2019

In recent years, the driving performance and exhaust sound quality in automobiles have been recognized as important factors, as they maximize the driving fun to fulfil the demands of customers. Therefore, many automobile manufacturers are studying various exhaust pipe shapes to improve sound quality and optimize exhaust pressure. The objective of the exhaust pipe design is to maximize the engine efficiency using optimal exhaust pressure settings. In this study, an exhaust system was fabricated with different junction shapes, and the results were analyzed through various experiments. The exhaust gas pressure acting inside the exhaust pipe was measured using a pressure transducer. Meanwhile, the vibration generated in the vehicle was measured in three axial directions and analyzed. The ground noise generated in the indoor and outdoor of the vehicle was measured, and the noise generated at the maximum output was measured and analyzed.

• Journal of Ocean Engineering and Technology
• /
• v.19 no.2 s.63
• /
• pp.47-52
• /
• 2005

This paper introduces a procedure for free span and fatigue analysis of offshore pipelines per DNV-RP-F105, 2002. The new method includes the axial force and deflection load in pipelines. The screening criteria were established to calculate the allowable span lengths in the new design codes. The screening criteria allows a certain amount of vortex-induced vibration due to wave and current loading. However, the induced pipe stresses are very small and usually below the limit stresess of typical S-N curves. In contrast, the conventional criteria did not allow any vortex-induced vibration in the free span of pipelines. Thus, the screening criteria yields reduced allowable span lengths. A simplified procedure was established to calculate the fatigue damage due to long-term current distribution. The long-term current statistics was assumed with a 3-parameter Weibull distribution. The fatigue damage was estimated for the span lengths obtained from the screening criteria for various conditions. Sample calculations show the effect of axial force for various boundary conditions. Comparisons with conventional criteria are included.

• Journal of KSNVE
• /
• v.11 no.1
• /
• pp.57-67
• /
• 2001

Proposed in this paper is a method of measurement of the flow rate in a pipe. The sound waves which are propagated within a pipe are characterized by that the wavenumber in the axial direction is changed according to the flow rate, and these characteristics are used in the present method of measurement of the flow rate. The amount of change in wavenumber of sound waves according to the flow rate can be obtained from the relationship among acoustic pressure signals within a pipe, which are measured by using a microphone array. The flow rate can be obtained by using the amount of change in wavenumber of sound waves and the relational equation of the flow rate. With respect to errors that can occur during the measurement of the flow rate, the types of errors and the method of correction of those errors are presented. This method of measurement of the flow rate has application limitation conditions due to the sensor interval, assumption of sound waves as plane waves, etc. The numerical simulation and experiments for measuring the flow rate of air in a pipe are performed in order to verify the applicability of this method of measurement of the flow rate. The experimental results are shown to be similar to those of the numerical simulation. And the flow rate measured is shown to be consistent with the actual value within 5% error bound.

• Journal of KSNVE
• /
• v.6 no.6
• /
• pp.827-834
• /
• 1996

The effect of pipe breaks in the secondary side is investigated as a part of the fuel assembly qualification program. Using the detailed dynamic analysis of a reactor core, peak responses for the motions induced from pipe breaks are obtained for a detailed core model. The secondary side pipe breaks such as main steam line and economizer feedwater line braksare considered because leak-before-break methodology has provided a technical basis for the elimination of double ended guillotine breaks of all high energy piping systems with a diameter of 10 inches or over in the primary side from the design basis. The dynamic responses such as fuel assembly shear force, bending moment, axial force and displacement, and spacer grid impact loads are carefully investigated. Also, the stress analysis is performed and the effect of the secondary side pipe breaks on the fuel assembly structural integrity under the faulted condition is addressed.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.24 no.4
• /
• pp.307-314
• /
• 2004

A circumferential guided wave method was developed to detect the axial crack on the bent feeder pipe. Dispersion curves of circumferential guided waves were calculated as a function of curvature of the pipe. In the case of thin plate, i.e. infinite curvature, as the frequency increases, the $S_0$ and $A_0$ mode coincide and eventually become Rayleigh wave mode. In the case of pipe, however, as the curvature increases, the lowest modes do not coincide even in the high frequencies. Based on the analysis, a rocking technique using angle beam transducer was applied to detect an axial defect in the bent region of PHWR feeder pipe. Based on the analysis of experimenal data for artificial notches, the vibration modes of each signal were identified. It was found that the notches with the depth of )0% of wall thickness can be detected with the method.