It is investigated if it is effect that Truss-core panel can be used for vehicle body panel and Reversed Spiral Cylindrical Origami Structure (RSC) can be used for Vehicle member for vehicle weight reduction drastically. It is difficult that truss core panel is pressed homogeniously with simple press for the numerous arrangements of tetrahedral convex. For that reason, the multistage forming simulation method is developed and tested with many kinds of materials. The results of test suggest that the method has excellent characteristics. It was shown that RSC in simulation has the structure whose amount of energy absorption is larger than going side-member of rectangular section. The possibility of reducing greatly the weight of vehicle is expected in Origami Engineering by hydro forming test.

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In this study, we verified accuracies of two kinds of transfer path analysis methods by performing a simple structure test. Inverse matrix method using transfer functions and principal component analysis method using only running data were examined. As the result of experiments, the accuracies of these methods were clarified to drop occasionally in some frequencies, but the frequencies are different each other. These results indicate that it is necessary to select suitable transfer path analysis method according to the target frequency for obtaining contribution of noise and vibration accurately.

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In this study, we considered a calculation method to obtain accurately transfer functions employed in running transfer path analysis, and tried to reduce noise influence effectively in transfer functions by setting probability significance level of each input signal as noise reduction standard. Next, we verified the noise reduction performance through simple simulation and compared that with the conventional method in which size of input signal was employed as the standard. As results, the noise influence was reduced from calculated transfer function by using the new method effectively better than that of the conventional method.

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This paper presents two proposals in TPA using finite element model: 1) technique in contribution analysis to the structure with manifold and continuous transfer paths, 2) visualization technique of the influence degree for the reduction of the response of the structure. The influence degree is newly defined by the result of the contribution analysis and assists analysts to obtain measures more efficiently. These two techniques let the analysts easy to understand the vibration transmission by the visualization. The application to an automotive body structure validates the effectiveness and usefulness of the proposed approach.

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Transfer Path Analysis has well established in order to improve the noise and vibration quality of mechanical structures. However, the identification of input force is still difficult problem to solve and its accuracy has to be evaluated. This paper presents the evaluation method for the input identification error. In this study, traditional identification method based on accelerance matrix inversion is utilized. The identification error is estimated by evaluating variance of identified force spectra. Then, proposed methods are certified using FEM simulation and experimental approach.

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This paper describes a reciprocal panel acoustic contribution analysis for vehicle interior noise in the low frequency range. Reciprocal panel contributions are calculated from uncoupled structural transfer functions of body panels and coupled acoustic transfer functions between receiver point and body panels. Analysis results of a simple model are presented for comparison with ordinary panel contributions computed form coupled structural transfer functions and uncoupled acoustic transfer functions. Finally, applications of reciprocal panel contributions are shown to be useful tools in modifying structure design for interior noise improvement.

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The vehicle body and the enclosure are regarded as the vibro-acoustic coupling system. In order to reduce the noise of the vehicle cabin, characteristics estimation of the system is strongly required. This paper produced a small speaker to enlarge the coverage of acoustic excitation and evaluated it. And I examined mode identification method for characteristic grasp of vibro-acoustic coupling system.

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This paper describes the robust design method base on CAE. In initial design stage of mechanical design, the advantage of the conventional method, Monte-Carlo method, Taguchi Method etc, is limited. Because it is need to define the noise factors as a known quantity. In this paper, novel approach which can be applied to initial design stage is proposed. The basic idea is that the noise factor is not design parameter (ex, machine component shape, stiffness of weld), but characteristic of system (ex, the interference of sound, particle velocity). In this paper, the basic idea is applied to simple FE model.

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Mitsubishi Electric Corporation developed a compressor equipped with a concentrated winding motor that adopted a press-fitted segment core for the first time domestically. It was necessary to grasp the dynamic characteristics of the press-fitted segment core to establish the low noise design technique of the developed compressor. This paper proposes a method that a calculated natural frequency of (2, 2) mode was matched to the measured natural frequency based on the theoretical formula of the natural frequency of the ring to presume the equivalent stiffness coefficient needed for the vibration analysis. Afterwards, the noise analysis of the structure-changing model was carried out by using the equivalent stiffness coefficient. The calculated results agree well with the measured results. Therefore, it was clarified that the noise characteristics of a compressor equipped with a concentrated winding motor that adopted the press-fitted segment core could be predicted.

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This paper presents a method for identifying the input power to structure in machine operation using energy analysis model such as Statistical Energy Analysis (SEA) and Energy Distribution (ED). The basis of the method is that the vibrational energies of the respective subsystems during working can be measured using the velocimeter or accelerometer at the same measuring positions of constructing the SEA and ED model. In this paper, the method is applied to three series coupled plates. It is shown that the accuracy of the identified input power using SEA and ED model are compared by applying two approaches to FEM analysis and a experimental test. The estimated results show that the method has excellent performance to identify the input power during working.

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Air blower using travelling space generated between two resonantly-driven plates, which are excited at an eigenfrequency of flexural vibration mode has been developed. This air blower suite for a cool down device of compact device, because this air blower has a thin configuration. The advantage of this air blower is energy efficiency, because of the resonance driving. This paper experimentally verified the principle of air blower. Then, a new compact machine was developed to excite desired operating deflection shapes, and consequently a desired sine-shaped mode was obtained.

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This paper discuses the way to reduce the noise and vibration of thin plate structures. This paper focuses on the musical saw, a kind of musical instrument. The musical saw is thin plate and it is need to bend the saw as S-curve, to play the instrument. Thin plate structures used for various products. In some case, curvature is laid on thin plate structures to enhance the rigidity. If musical saw and thin plate structures conditions are matched, it will be noise problem. Investigating that the relationship between the sound pressure, S-curve, boundary condition, and aspect ratio of the saw by experiment and FEA, it is discussed to apply the investigation result to the thin plate structures.

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For the forced excitation of a large structure such as airplanes using one actuator, natural vibration mode cannot be excited because the vibration doesn't spread in the entire structure. On the other hand, when a lot of actuator is used, the excitation frequencies of the actuators must coincide and the magnitude and phase of the excitation force must be minutely adjusted for every vibration mode. Thus, we used a method for driving at resonance point by using the self-excited vibration generated by the local feedback control. A desired mode of vibration can be excited by adding a sine wave signal within the local feedback controller.

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This paper verifies the expressions for power input and subsystem energy by modal density of subsystem in Statistical Energy Analysis (SEA) by means of FEM calculation. First, it is shown that the SEA main parameters which include power input, energy of the subsystem and coupling loss factor can be expressed mainly by the modal density. In order to verify their modal density descriptions, FEM calculations are performed to compute subsystem energies, power input and coupling loss factors on four kinds of structures with different non-uniform shapes with the equivalent modal densities. The analytical SEA predictions are also compared with the FEM calculation results.

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This article proposes a new experimental procedure that achieves accurate measurements of rigid body properties in approximately 60 seconds. The experimenter intervenes only in placing the test structure onto a softly suspended platform. The platform is equipped with simple unbalance actuators, which simultaneously excite the structure, and with accelerometers, which measure the vibration response. The rigid body properties of a given test structure can be determined by fitting a theoretical model of the acceleration response to the measured response data.

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Accurate rigid body property (RBP) identification is desired in various industrial fields such as aerospace and automotive engineering. In a past study, we developed a new method based on a model using suspension on a single elastic wire. However, it is often impractical to suspend the test structure on only a single wire. Therefore, to facilitate practical testing, this paper proposes a multi-wire suspension model. In addition, a method that combines the suspension model with modal curve fitting is proposed in order to identify accurate RBP of low-rigidity structures. The effectiveness is demonstrated using two experimental structures.

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The crack position in a cantilever beam is identified. The vibration experiment is conducted and the eigenfrequency data is obtained by measuring the acceleration of the beam tip. The extended finite element method is used to analyze the vibration problem. The evaluation function is calculated using the eigenvalues of both experimental and numerical simulation, and the identification is conducted based on the gradient of the evaluation function. The accuracy of longitudinal direction is much more higher than that of thickness direction. That difference is caused by the characteristic distribution of eigenvalues.

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In is very important to understand the dynamic characteristics to control vibrations of machinery. Generally, the conventional identification methods for experimental modal analysis are employed to time-invariant systems. However, there are a lot of requirements to extract modal parameters of time-varying systems. It is hard to implement the vibration testing for time-varying systems, because of excitation difficulties, boundary conditions, etc. In this paper, the subspace algorithm is proposed to obtain natural frequencies of time-varying systems. Then, a combination procedure of SVD and QR decomposition is proposed for the identification algorithm to improve computational load. The effectiveness of the proposed time-varying identification algorithm is verified by numerical results. Finally, the procedure is applied to an experimental manipulator model.

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This study is related with an approach for the diagnosis of defects or peculiar on structures using hammering test that is one of the non-destruction inspection methods of the structure. In this paper, the detection method of the defects as a non-destruction inspection method has been suggested and the efficiency of the diagnosis method based on the hammering sounds has been estimated in a simple structure model, an aluminum bar with free end. According to the simulation by FEM model, it became obvious that the natural frequencies for the relating vibration mode of the aluminum bar decrease when the crack is at the abdomen of the vibration mode. On the contrary, the natural frequencies may not be changed or the change may be small when the crack is at near the nodes of natural vibration mode. The diagnosis of the existence of the defect was done from the correlation of the Wavelet coefficient between the two sound signals from aluminum bar without and with crack. The rough position of the crack is estimated from the relationship among the natural frequencies.

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In the experimental modal analysis, the treatment device has to be fixed on the target structure in order to obtain the vibration response to the moment excitation. However, if the treatment device is used, the vibration property must be changed because of the additional mass of the device. In this study, a new moment excitation device that a step moment can be impacted on the structure without using treatment device is proposed. The proposed device is easy to handle and realizes the accurate measurement without additional weight. The experimental results are shown to confirm the validity of the proposed technique.

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This paper proposes a method that makes it possible to analyze FRF by only measuring the output (acceleration response) in a laser excitation experiment. First, the laser excitation force is systemized by Newton's second law using a rigid block. Next, the laser excitation experiment with an object structure having a natural frequency within the high frequency region is conducted. Complex Fourier spectrum obtained by Fourier transforming the measured response is divided by the estimated laser excitation force. Finally, since the trigger position of the response and the time the impulse input is actually applied have errors, phase characteristics of the force-regulated complex Fourier transform is modified by taking the dead time included in the response into account, resulting in the FRF of the structure.

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This paper proposes a method for estimating auto FRF (frequency response function) using additional masses. In FRF measurement, impact hammer are generally used to measure the excitation force to structure, but the case of object's shape is complex, actual user often can't measure auto FRF. In the proposal method, inertia force of additional mass is presumed external forces. In this paper, accuracy of the method is validated by applying it to a beam structure if case auto FRF is unmeasured at some point.

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Bending vibration characteristics of railway vehicles have been investigated in general under excitation tests, in which a carbody was directly excited by a shaker. It is however very difficult with their results to evaluate the ride comfort of passengers under a condition that the vehicle runs on a certain track. The authors are therefore developing a "vertical vibration simulator" for railway vehicles. The simulator consists of a excitation system equipped with linear actuators, the elastic supporting device installed between wheels and rails, and analytical techniques to estimate the power spectral density (PSD) and the ride comfort level (LT) which feature the ride comfort. In this paper, we describe the excitation tests performed using an actual commuter car and the estimated PSD and LT are compared with what measured under the running conditions.

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This paper deals with development of tuned mass damper for vibration isolation table. If the honeycomb vibration isolation table has the experimental equipment including the vibration resource and the vibration frequency of the resource is identical with the natural frequency of the isolation table, resonance will be occurred between the resource and the table, and it makes large influence on the measurement accuracy. This study has been carried out in order to realize an optimum design to satisfy the requirements for vibration isolation table with high performance. Based on the finite element model by NASTRAN, the simulation were executed to estimate the influence to the natural frequencies and the compliance of the vibration isolation table by changing mass or damping of TMD.

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We deal with finite element modeling techniques for the dynamic behavior of sheet metal structures jointed by spot welds. A major requirement of spot weld finite element models is to accurately predict the dynamic characteristics of welded structures with a small number of degrees of freedom. In addition, spot weld models are easy to generate for non-congruent meshes of the jointed metal sheets. For this purpose, a model using multi-point constraint (MPC) is widely used in the automotive industry. For the model using MPC, we investigate the effect of element size in the area of the spot weld (patch area) on the modal properties. An example structure consists of two steel plates jointed by three spot welds. The results indicate that the proper shell element size in the patch area is dependent on the solid element size determined from the diameter of a weld nugget.

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In order to suppress vibration, sensitivity analysis is conducted to find an appropritate structure change. For panel structures it is necessary to obtain sensitivity on bending stiffness for the modification. However, it is difficult to estimate experimentally. For this purpose we use a scanning laser doppler vibrometer in this study, and estimate response of the rotational degree of freedom by interpolating the translational responses in many points. We derive the sensitivity on bending stiffness from the rotational responses. The validity of the proposed method is confirmed by numerical simulation and experimentally by using the scanning laser doppler vibrometer.

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This paper describes vibration analysis using finite element method for elastic frames with a panel connected by nonlinear concentrated springs under impact load. The restoring force of the spring has cubic nonlinearity and linear hysterisis damping. Finite element for the nonlinear spring is expressed and is connected to the elastic frames with the panel modeled by linear solid finite elements in consideration of complex modulus of elasticity. Further, the discretized equations in physical coordinate are transformed into the nonlinear ordinary coupled equations using normal coordinate corresponding to linear natural modes. This transformation yields computation efficiency. Influences of vibration damping and rigidity of the frame are clarified on the nonlinear impact responses.

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This paper developed simplification method of wave propagation modeling for discontinuous structure by using reflection and transmission coefficients. The discontinuity was replaced with reflection and transmission coefficients that were identified with measured data beforehand. Then new spectral element which includes reflection and transmission coefficients was derived. The element was based on the elementary theory of a bar, except for the modeling of a discontinuity part. Spectral element method based wave analysis was also performed to show the validity of the modeling. The behavior of resultant wave showed good agreement with the assumed frequency characteristic on reflection and transmission coefficients.

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The wave analysis efficiently elucidates wave propagation on mechanical structures. Medium of wave propagation is called waveguide. The waveguide which has complicated configurations are generally modelled by a finite element method. Whereas modelling technique for vibration analysis using finite element method is practical, that for wave analysis is behind in technology. The wave propagation characteristics (e.g. phase velocity and group velocity) maybe represent by a wavenumber. In this paper, the influence of a model reduction was investigated in analytical accuracy in terms of wavenumber.

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This paper presents the formula of sensitivity in structural intensity in modal form. The sensitivities of natural modes and cross-modal functions are derived by the perturbation method. The perturbated results are compared with the deteministic results in order to verify the formula. Finally the variation of structural intensity, weight function and cross-modal function are discussed for the control of structural intensity by the structural modification.

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This paper discusses a new method for structural intensity measurement based on the modal expansion of structural intensity for flexural vibration on beams. The intensity field indicates the magnitude and the direction of vibratory energy flows at any point in a structure. The sensor array which is composed of two or four accelerometers is often used to measure the intensity vector at any point. On the other hand, we had proposed the modal expansion of intensity. The expansion can be used to estimate the intensity field from the modal properties evaluated by the experimental modal analysis. In this paper, we propose a new measurement method for intensity on beam and discuss the detail condition of the method. Then the numerical and experimental demonstrations are carried out to show the usefulness of the proposed method.

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Light weight structure made of fiber reinforced plastics (FRP) is manufactured by several forming types. In this study, circular cylindrical shells are formed by FW forming unit which has been designed by this lab.. Natural frequency and mode measured by the modal test are compare to the analytical result based on homogeneous method. The result shows the simply supported condition (SS) setted in this test is convenient for measuring vibration characteristics as the natural frequency and mode.

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Composite materials (fiber reinforced plastics: FRP) present the excellent possibility of design for changing in structural stiffness with tailoring the fiber-direction or ply-orientation. In this study, the Ritz method has been employed for different length to width ratio and fiber orientation angles within code-wise plate bending deformation. In applying the Ritz method, the frequency and its mode pattern is calculated and studied as the cantilevered (CFFF boundary condition) unbalanced laminated FRP plates with bend/twist cross-coupling parameter. Obtained result is follows. The first, the nodal lines are skewed with respect to the plate axis. The second, bend/twist mode is controlled with coupling parameter Ψ.

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The vibration characteristics of the composite plate model with curvilinear fibers are investigated in this study. The curvilinear fiber is realized by the plastic deformation of steel wires and the present composite model is composed of the curved steel wires and epoxy resin. The natural frequency and mode shape are obtained by the experimental modal analysis method where the plate is excited by the impulse hammer and acceleration response is measured. The experimental results showed that the present model has the specific skewed mode shape and it agrees well with the finite element analysis result in terms of the frequency and mode shape. Then the curvilinear fiber shape is optimized for the maximum fundamental frequency by using the genetic algorithm method. The numerical results showed that the optimum curvilinear fiber results in the higher fundamental frequency than the plate with typical curvilinear fibers.

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Shapes and lay-up configurations of composite laminated shallow shells are optimized simultaneously to maximize the fundamental frequency by a simple genetic algorithm method with the elitist tactics. The shell shape is defined by a cubic polynomial and various shapes of shells with inconstant curvature radii can be expressed by varying the value of coefficient for each term. The coefficients and the lay-up configuration of the laminated shell are directly employed as design variables, and constraints are imposed on the coefficients and curvature radii to keep shells shallow. The frequencies are calculated by using the Ritz method due to its flexibleness for shell shapes. Results of the present analysis technique agreed well with experimental and finite element analysis results in terms of frequencies and mode shapes, obtained optimum solutions resulted in higher fundamental frequencies than the shells with general shapes and lay-up configurations.

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Composite materials such as sandwich panels have been employed in many structural applications. The elastic parameters of sandwich panels are essential for the structural analysis. Also, an inverse analysis method has already been proposed by one of the authors to identify the core elastic parameters of sandwich panels using the FEM eigenvalue analysis and the sensitivity analysis. The purpose of this study is to present the analytical model of a sandwich panel that has core of strict geometrical shape and to identify the equivalent elastic parameters of a core material. First, by applying the experimental modal analysis technique to a sandwich panels with free boundary conditions, natural frequencies and mode shapes are obtained. Next, considering the obtained natural frequencies and mode shapes of the sandwich panel, the elastic parameters of the core material are identified using the presented analytical model of the sandwich panel and the inverse analysis method.

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Composite laminates have some problems, such as damage tolerance and delamination resistance etc. To overcome these problems, reinforcement fiber is distributed in the direction of thickness of composite laminates. This technique improves some properties, but reduces in-plane mechanical properties of plate. Present study focuses on the change of natural frequencies caused by decrease of elastic modulus using some plate theories. Reinforcement fiber was found to make decrease in natural frequencies depending on fiber orientation and vibration mode.

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The FRP composite which has a lightweight and durability is used as a truss component of a FRP footbridge. In order to use FRP composite further in the industrial fields, such as engineering works, machinery, and construction, more the survey data of the vibration characteristic are required. In this research, the experimental modal analysis of the box-shaped FRP composite is carried out by using the impact hammering test, and the vibration characteristics (natural frequencies and vibration modes) are clarified. Furthermore, the theoretical modal analysis is carried out by using the general-purpose FEM (Finite element method) structural analysis tool (3D-CAD/CAE). Finally, the modal parameters of the box-shaped FRP composite are identified by performing comparison between theoretical data and experimental one.

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In this study, vibrating energy dissipation pathways in carbon fiber reinforced plastic (CFRP) laminates with two different kinds of damage, that is, delaminations and transverse matrix cracks were respectively studied by using both experimental and numerical methods to investigate the effect of damage introduction into CFRP laminates on their vibration properties changes. This kind of study will be useful, for instance, for non-destructive damage inspections and health monitoring of composite laminated structures. From the results obtained in this study, natural frequencies for the bending first mode of vibration of simply-supported beams were found to be insensitive to the introduction of both types of damages, while damping ratios were nearly proportional to the increase of the degrees of both damages, which implies that damping measurement could be an effective means to detect damages in composite laminates. From the numerical (Finite element method) analysis were also conducted, and it was shown that transverse shear strain energy and contact frictions on the damage surfaces would play important roles in the energy dissipation of damaged composite laminates.

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The Vibration Intensity (VI) method is one of the techniques to visualize vibration transmission paths. In actual structures, multiple waves exist at the same time because of reflection waves at boundaries or multiple excitation sources. If VI method is applied to the vibration field with multiple waves, VI method may detect different vibration energy flow from vibration energy flow in actual phenomena. The purpose of the present research is to investigate the influence of superposition of multiple waves on VI measurement in simple flat plate by FEM analysis.

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This paper presents a new analytical procedure on bending vibrations of a beam subjected to an axial force. The procedure combines the procedures of modal expansion with finite element analysis. The beam is divided into finite number of segments. The mode shape function is introduced with the product of truncated power series and trigonometric function which is proposed by the senior author. The function is differentiable continuously with infinite times. The unknown coefficients of the mode shape function satisfy both the geometric and dynamical boundary conditions at the node of segment. Discretized equations of motion of the beam are derived from the Galerkin method. We call the analytical procedure as the Finite Segment Analysis (FSA). Based on the FSA, linear natural frequencies of a pre-buckled beam subjected to an axial force are calculated. Increasing the number of segments, the results by FSA are compared with the exact results and with the results of conventional Finite Element Method (FEM). Under the calculation with two segments by FSA, the natural frequencies from the lowest mode to the fourth mode coincide with five digits to the exact results.

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Experimental results are presented on effects of a concentrated mass on chaotic vibrations of a clamped circular plate. The plate has the characteristics of a softening-and-hardening spring with snap-through. Under periodic excitation, predominant chaotic response with dynamic snap-trough is generated in a typical frequency region. The response is inspected by the Fourier spectrum, the Poincare projection, the maximum Lyapunov exponents and the principal component analysis. As the effects of the mass, the chaotic response is generated in the lower frequency region. Furthermore, the contribution ratio of the modal configuration, which corresponds to the lowest mode of vibration, shows slight increase.

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This paper presents the evaluation of the approximate equivalent stiffness for structural optimization of double-skin hollow plates. For this purpose, the equivalent stiffness of the plate is given first in the second-order polynomial form with respect to design parameters by using the Response Surface Method. Finite element analysis for bending problem is formulated by using the ACM rectangular element, and then FEA program is developed by incorporating the equivalent stiffness. Finally the numerical results by the present FEA are compared with the ones by a commercial FEA code, and the applicability of the stiffness and the present FEA are studied

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This paper presents the vibration response analysis of double-walled pipe models subjected to external excitation. The governing equations of motion are introduced in general form to comprehend different shell theories of Flugge, Love and Donnell by use of tracing parameters, and an approximate solution for the frequency response is derived for the pipe system problem. The modeling of filling material between two walls is considered, and the coupling effect of two shells through the filling material is discussed.

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The input/output performance of a hard disk drive (HDD) decreases when the HDD operates in rotational vibration (RV) environments found in servers. Understanding the vibration characteristics of components in the server and the amount of excitation forces is therefore needed to maintain a high performance level. We developed a prediction method that calculates the rotational vibration of HDDs caused by operational vibration of cooling fans in a rack mount server. The proposed method consists of a finite element model of the server and a fan excitation force model. The calculated overall values of the HDD RV agree with measured results.

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This study deals with a control of sound directivity by using a piezoelectric speaker, which is thin and lightweight with a simple structure. Influences of the design factors, the shape of vibration board and the position of vibrator, are experimentally investigated. Cylindrical shell structure is applied to the vibration board in order to increase the rigidity. In the experiment, sound directivity of the speaker models is evaluated from the sound pressure contour of axial transverse section by which the frequency response of radiated sound was measured at each angle. The experimental results show that the sound directivity at long side of the rectangle became sharp by using the shell type of piezoelectric speakers. In the high frequency band, especially, the sound directivity had significant changes by the attached position.

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Theoretical studies were conducted to clarify hydroelastic vibrations of a cylindrical tank filled with liquid under low-gravity. The liquid, which was treated as "potential flow", has a static configuration as an equilibrium interface between a liquid and a gas due to the surface tension in low-gravity field. Assuming free vibration of the system in the axial direction of tank, we derived the frequency equation by using Rayleigh-Ritz method. Coupled natural frequencies were obtained as an eigenvalue. In the vicinity where the natural frequencies of rigid tank and elastic beams intersect with the natural frequencies of liquid, frequency curve veering phenomena was observed.

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Some sloshing response analyses of floating roofs using commercial code LS-DYNA have been reported thus far, but there are unknown factors like the damping ratio in the analyses. In this paper, the effects of several parameters which are considered to have influence on damping in the analyses are investigated. On that basis, several earthquake response analyses were performed and the results were compared with the ones which have been already reported. Because the results of LS-DYNA give smaller response, some precautions when applying LS-DYNA to sloshing analyses are shown.

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