• Transactions of the Korean Society of Mechanical Engineers
• /
• v.13 no.3
• /
• pp.385-396
• /
• 1989

In this paper, using by the orthogonalities of modes for trainwheel (as Mindlin's annular plate and rail (as Timoshenko beam), the frequency equation of the coupled system are induced. It is convinced that the natural frequencies of coupled system are distributed to be about quadratic order function examined through the experimental and numerical analysis. The natural frequencies of the system coupled by both creep force and creep moment are composed of the natural frequencies of the system coupled by creep force and the natural frequencies of the system coupled by creep moment . And it is shown that the coupled natural frequencies up to 3rd do not make much difference from the values of the system coupled by individual creep force of creep moment. But the coupled natural frequencies higher than the 3rd are quite different from those of individual case.

• Structural Engineering and Mechanics
• /
• v.18 no.6
• /
• pp.709-729
• /
• 2004

This paper presents numerical and experimental investigations on damage detection of mono-coupled multistory buildings using natural frequency as only diagnostic parameter. Frequency equation of a mono-coupled multistory building is first derived using the transfer matrix method. Closed-form sensitivity equation is established to relate the relative change in the stiffness of each story to the relative changes in the natural frequencies of the building. Damage detection is then performed using the sensitivity equation with its special features and minimizing the norm of an objective function with an inequality constraint. Numerical and experimental investigations are finally conducted on a mono-coupled 3-story building model as an application of the proposed algorithm, in which the influence of modeling error on the degree of accuracy of damage detection is discussed. A mono-coupled 10-story building is further used to examine the capability of the proposed algorithm against measurement noise and incomplete measured natural frequencies. The results obtained demonstrate that changes in story stiffness can be satisfactorily detected, located, and quantified if all sensitive natural frequencies to damaged stories are available. The proposed damage detection algorithm is not sensitive to measurement noise and modeling error.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.10 no.4
• /
• pp.8-15
• /
• 2011

In this paper, the influence of a crack on the natural frequency of cracked cantilever L-shaped beam with coupled bending and torsional vibrations by analytically and experimentally is analyzed. The L-shaped beam with a crack is modeled by Hamilton's principle with consideration of bending and torsional energy. The two coupled governing differential equations are reduced to one sixth-order ordinary differential equation in terms of the flexural displacement. The crack is assumed to be in the first, second and third mode of fracture and to be always opened during the vibrations. The theoretical results are validated by a comparison with experimental measurements. The maximal difference between the theoretical results and experimental measurements of the natural frequency is less than 7.5% in the second vibration mode.

• Coupled systems mechanics
• /
• v.5 no.3
• /
• pp.223-234
• /
• 2016

The main purpose of current study is to find the soil effects on natural period of elevated tank. The coupled analytical method is used to assess in this study. The current study presented models which are capable to consider the soil dynamic stiffness changes and fluid- structure interaction effects on natural period of elevated tanks. The basic of mentioned models is extracted from elastic beam and lumped mass theory. The finite element is used to verify the results. It is observed that, external excitation can change the natural period of elevated tanks. Considering the increase of excitation frequency, the natural period will be decreased. The concluded values of natural period in case of soft and very soft soil are more affected from excitation frequency values. The high range of excitation frequency may reduce the natural period values. In addition it is observed that the excitation frequency has no significant effect on convective period compare with impulsive period.

• Structural Engineering and Mechanics
• /
• v.22 no.6
• /
• pp.719-739
• /
• 2006

An analytical method for the free vibration of two circular plates coupled with an inviscid and compressible fluid is developed by the Rayleigh-Ritz method. The fluid is bounded by a rigid cylindrical vessel and two circular plates with an unequal thickness and diameter. It was found that the theoretical results could predict well the fluid-coupled natural frequencies with an excellent accuracy when compared with the finite element analysis results. As the fluid thickness increases or the plate thickness difference increases, an abrupt curve veering in the natural frequency loci of the neighboring modes and drastic changes in the corresponding mode shapes are observed. The mode localization frequently appears in the higher modes and in the wide gap between the plates because of a decrease in the fluid coupling owing to the fluid dispersion effect.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1998.04a
• /
• pp.45-50
• /
• 1998

The coupled vibration occurs between traveling vehicle and bridge, when vehicle runs on it. The natural frequency of this coupled system is dependent on the contact position of vehicle and bridge, that is, time-varying system. The calculations of these natural frequencies are very complicated, and often carried out by using Green function theory, series. But, these methods have any limitations, such as, supporting condition, boundary condition. In this paper, on the coupled system constructed by the concentrated mass and elastically supported beam, an analytical method of natural frequency is proposed by using Fourier sine transformation. The results are compared and discussed with numerically calculated ones.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.21 no.2
• /
• pp.169-177
• /
• 2011

In this paper, the natural frequency of a cracked cantilever L-beams with a coupled bending and torsional vibrations is investigate by theory and experiment. In addition, a method for detection of crack in a cantilever L-beams is presented based on natural frequency measurements. The governing differential equations of a cracked L-beam are derived via Hamilton's principle. The two coupled governing differential equations are reduced to one sixth order ordinary differential equation in terms of the flexural displacement. Futher, the dynamic transfer matrix method is used for calculation of a exact natural frequencies of L-beams. The crack is assumed to be in the first mode of fracture and to be always opened during vibrations. In this study, the differences between the actual and predicted positions and sizes of crack are less than about 10 % and 39.5 % respectively.

• Journal of Industrial Technology
• /
• v.16
• /
• pp.239-245
• /
• 1996

Modal parameters determine the frequency response characteristics of vibration system or acoustic system. When the two systems are fully coupled, however, coupling changes the vibrational and acoustic model parameters into those of the coupled system. In this case, it is very difficult to obtain the modified model parameters and response characteristics. In this paper, coupling effect is analytically investigated on the natural frequency, mode and frequency response characteristics. The result can be applied to understand and to design the frequency response characteristics of the vehicle passenger compartment.

• Coupled systems mechanics
• /
• v.2 no.4
• /
• pp.303-327
• /
• 2013

The coupled free vibration of flexible structures and on-board liquid in zero gravity space was analyzed, considering the spacecraft main body as a rigid mass, the flexible appendages as two elastic beams, and the on-board liquid as a "spring-mass" system. Using the Lagrangians of a rigid mass (spacecraft main body), "spring-mass" (liquid), and two beams (flexible appendages), as well as assuming symmetric motion of the system, we obtained the frequency equations of the coupled system by applying Rayleigh-Ritz method. Solving these frequency equations, which are governed by three system parameters, as an eigenvalue problem, we obtained the coupled natural frequencies and vibration modes. We define the parameter for evaluating the magnitudes of coupled motions of the added mass (liquid) and beam (appendages). It was found that when varying one system parameter, the frequency curves veer, vibration modes exchange, and the significant coupling occurs not in the region closest to the two frequency curves but in the two regions separate from that region.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.900-903
• /
• 2002

This study dealt with the experimental modal analysis of the perforated rectangular plate coupled with fluid. The natural frequencies of the perforated plate and solid plate in air were obtained by the analytical method based on the relation between the reference kinetic and maximum potential energy and compared with the experimental results. Good agreement between the results was found for the natural frequencies of the perforated plate in air. It was empirically found the natural frequencies of the perforated plate coupled with fluid. The transverse vibration modes, in-phase and out-of-phase, were observed alternately in the fluid-coupled system. Additionally, the effect of distance between perforated plate and solid plate on the fluid-coupled natural frequency was investigated.