• Journal of KSNVE
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• v.5 no.2
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• pp.247-256
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• 1995

In this paper, double exposure holographic interferometry using ruby pulse laser is formed in order to investigate the propagation of transient waves. The vibration characteristics according to the change of impact load direction, i.e., impacted in the shear direction and in the normal direction are analyzed. It was observed that the macroscopic trends of transient wave generation and propagation in the assembly of precipitator plates were almost similar regardless of the change of impact load direction. But the propagation and mixing of transient wave was advanced relatively slowly when impacted in the normal direction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.110-112
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• 2009

Transient acoustic pressure in the near field of an impacted plate carries information that can be utilized for recovering the impact force history. The inverse calculation approach using BEM-based NAH, which is conventionally used for time harmonic excitation, can be applied for reconstructing the transient waves using the principle of Fourier transform and spectral analysis. Then, using the recovered velocity in normal direction of the plate surface, the corresponding structural intensity can be obtained and the identification of input power can be performed. However, several manipulations should be given to overcome numerical artifacts, such as aliasing and erratic oscillation at discontinuity, and to suppress the effect of noise. Experiment using a simply supported plate is presented for demonstration purpose.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.52-56
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• 1993

An efficient method is presented for determining transient responses of locally nonlinear structures using substructure eigenproperties and Lagrange multiplier technique. The method is based upon the mode synthesis formulation procedure, but does not construct the equations of motion of the combined whole structure compared with the conventional methods. For modal bases of each linear substructure, either fixed or free interface modes can be employed. The transient analysis is based upon the recurrence discrete-time state equations and offers the simplicity of the Euler integration method without requiring small time increment and iterative solution procedure. Numerical examples reveal that the method is very accurate and efficient in calculating transient responses compared with the direct numerical integration method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.463-463
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• 2014

Multi-packet blade systems usually undergo multiple nozzle excitations during operation. For the design of multi-packet blade systems undergoing multiple nozzle excitations, transient characteristics around an operating frequency and resonance frequencies should be identified. In this study the equations of motion of multi-packet blade systems undergoes multiple nozzle excitations are derived. The reliability of the derived equations is verified by obtaining responses at resonance frequencies. Then, using the model, the effects of system parameters on the transient characteristics of the system are investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.298-299
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• 2014

The solution of transient response of complex stiffness system was obtained using a green function of this system. To derive the green function, governing equation of this systems was expressed in Steady Space and solved by the diagonalization. The solution of this system are written as a convolution integral form. The result that are calculated by the numerical integration process for transient responses was showed properly.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.9
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• pp.674-684
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• 2002

In order to decrease remarkably the computation time and storage used in the direct integration method without the loss of accuracy, authors suggest a new transient analysis algorithm. This algorithm is derived from the combination of three techniques, that is, the transfer technique of the transfer stiffness coefficient method, the modeling technique of the finite element method, and the numerical integration technique of the Newmark method. In this paper, the transient analysis algorithm of a frame structure is formulated by the proposed method. The accuracy and computation efficiency of the proposed method are demonstrated through the comparing with the computation results by the direct integration method for three computation models under various excitations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.269-272
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• 2005

In order to prevent a router machine feed drive system from transient operational vibration, this paper presents vibration analysis of a rack and pinion typed feed drive system for a router machine. The feed drive system was mathematically idealized as a 5-degree-of-freedom lumped parameter model. Stiffness parameters of motor-shaft, rack and pinion gears, and machine structure were appropriately considered in the modeling. Computational experiment was carried out to obtain vibrations of the feed drive system during its transient speed operation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.426-431
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• 1998

This, paper describes formulation for time historical response analysis of vibration for tree structure. This method is derived from a combination of the transfer stiffness coefficient method and the Newmark-.betha. method. And This present method improves the computational accuracy of the transient vibration response analysis remarkably owing to several advantages of the transfer stiffness coefficient method. We regarded the structure as a lumped mass system here. The analysis algorithm for the time historical response was formulated for the tree structure. The validity of the present method compared with the transfer matrix method and the FEM(Finite Element Method) for transient vibration analysis is demonstrated through the numerical computations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.590-595
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• 2001

Vibration transient generated by developing localized fault in gear can be used as indicators of condition monitoring in a gear. In this paper, we propose the phase map for a fault signal using continuous wavelet transform to detect this vibration transient. Local fault induces the abrupt fluctuation of load exciting tooth and phase lag in the vibration signal measured on the gearbox. The relatively large fault like "tip breakage" easily can be detected by the clear fluctuation of exciting load. However, minor fault like "initial pitting" cannot be detected using the load fluctuation. To detect this kind of minor fault, the phase map for a fault signal is taken into account. The phase lag by minor fault is observed well in the phase map.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.360.2-360
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• 2002

There was the transient vibration on $H_2$ piping system fer cooling the generator in a power plant. We found it was resulted from resonance between the natural vibration of the piping system and exciting force from the turbine rotor by measurement and simulation test. We verified it would be changed the mode shape of the piping system by several simulation test for the structural modification of the piping system. (omitted)