Recently, workpiece such as jet engine turbine case has been lightened and thinned for low fuel consumption. However, the parts such as jet engine turbine case reduce heat resistance for thinning. So it has been required thinning with heat resistance material. However, cutting heat resistance workpiece of low stiffness that thinning causes contributes chatter vibration. In order to understand chatter vibration characteristics, chatter vibration measurement was made in the circumferential direction using 24 displacement sensors. In order to clarify the relationship between the natural vibration and the generated chatter vibration, a striking vibration test was conducted. From the measurement results, it is anticipated that the chatter vibration model is a self-excited vibration oscillating by coupling two natural vibrations of the cosine mode and the sine mode by tool contact and demonstrated. Then, based on the magnitude of the open loop transfer function at the phase crossover frequency of the chatter vibration model, the occurrence of chatter vibration was predicted. In order to estimate the magnitude of the loop transfer function at the phase crossover frequency during cutting, first, a loop transfer function in the static state that is not affected by tool contact is obtained. Next, since the frequency near the phase intersection frequency is near the natural frequency of the workpiece, the magnitude of the open loop transfer function increases. This increase rate (gain amplification factor) is determined by the natural frequency difference between the cosine mode and the sine mode due to tool contact, and the workpiece attenuation. The influence by which a tool gives it to an occurrence prediction is checked. Therefore, the influence by which nose radius of a tool gives it to the natural frequency difference between the cosine mode and the sine mode.

In this report, for the forced synchronization of a standing wave thermoacoustic engine, hysteresis in the synchronous / asynchronous region was investigated by changing the external frequency near the branch point from both inside and outside of the branch. The experiment was performed by using a linear motor to input an external force to the standing wave thermoacoustic engine. In the experiment, the difference between the external frequency of the linear motor and the self-sustained oscillation frequency of the standing wave thermoacoustic engine Δf is used as a change parameter. Δf is changed in two patterns: (a) the external force frequency is increased so that Δf changes from negative to positive direction(Δf⁺), (b) the external force frequency is decreased so that Δf changes from positive to negative direction(Δf⁻). The region of the synchronous / asynchronous according to the way that change the external force frequency was compared. Under the condition of this report, in the region where Δf is positive, the synchronous / asynchronous region were alomost same for regardless of Δf⁻ and Δf⁺. On the other hand, in the region where Δf is negative, the result of the hysteresis in the synchronous / asynchronous region was obtained depending on Δf⁻ and Δf⁺.

It is important to investigate the mechanism of fluid transportations, for example, in order to estimate the diffusion of contaminants in the environment or to efficiently mix up different kinds of liquid in a chemical plant. On the other hand, it is known that fluid particles are transported chaotically in Lagrangian description even when the flow is seen to be stable in Eulerian description. In this paper, we investigate such a chaotic mixing of the two-dimensional Rayleigh-Benard convection with some periodic perturbations in Lagrangian description by focusing on the invariant structures such as KAM tori and Lagrangian coherent structures (LCSs). We numerically show that the topological structure of LCSs comes to resemble that of Poincare maps when the integration time for LCS is large enough, though they do not have a clear relationship when the integration time is small enough. In addition, we show that the fluid particles at the center of KAM tori are transported periodically inside the convection. In particular, we illustrate that the quasi-periodic regions themselves rotate around the center of KAM tori and are transported periodically, even though each particle inside quasi-periodic regions is transported quasi-periodically. This implies that KAM tori have a twisted structure in state space. Finally we clarify the bifurcation diagram of the periodic orbits at the center of KAM tori by varying the amplitude of the perturbation of the convection.

The transient response moment analysis of a linear system subjected to non-Gaussian random excitation is carried out by using the equivalent non-Gaussian excitation method. The non-Gaussian excitation is prescribed by both probability density function and power spectrum. Since the excitation is described by the Ito stochastic differential^ equation, moment equations for the system response can be derived from governing equations for the excitation and the system. However, the moment equations are generally not closed due to the complex nonlinearity of the diffusion coefficient in the governing equation for the excitation. Therefore, using the equivalent non-Gaussian excitation method, the diffusion coefficient is replaced by the equivalent one, which is expressed by a quadratic polynomial. After the replacement of the diffusion coefficient, we can derive a closed set of the moment equations and obtain the time evolution of the response moments by solving the moment equations. In numerical examples, the analytical method is applied to a linear system under non-Gaussian excitation with the widely different probability distributions and bandwidth. Comparison between the analytical results and Monte Carlo simulation results illustrates the effectiveness of the equivalent non-Gaussian excitation method in transient response analysis.

In recent years, random response analysis of a system modeled by fractional derivatives has attracted attention. On the other hand, due to the complexity of the mathematical handling of fractional derivatives, in most cases, analysis has been conducted assuming that the input to the system is white noise. In the previous study, as the moment equation method is effective and useful in random response analysis of an integer-order-derivative system, the method was extended. The moment equations corresponding to the system with fractional-order derivative of order 1/2 was derived and the effectiveness to systems under non-white random excitation was verified. In this paper, we extend the method of moment equation proposed in the previous study to a system with fractional derivatives of a wide range of order. Then, we discuss the class of order in which the proposed method can be directly applied or not . Futhermore, for the latter case, we will propose a solution to make it possible to apply the proposed method. Finally, the effectiveness of the method is demonstrated.

This paper discusses a new identification method of linear single-degree-of-freedom system using Gaussian random vibration response. The propose method is based on the method of Maximum Likelihood Estimation (MLE). The likelihood function of proposed method is composed from the analytical solution of Fokker-Planck equation. The estimation formulas of unknown parameter are obtained by maximization of the original likelihood function. The obtained estimators correspond with population variance estimation of multivariate Gaussian model. Furthermore, the numerical identifications are conducted using the random vibration response by calculation result of 4th Runge-Kutta method. In the result, the estimation performance of the propose method is confirmed in terms of dependency of sample number and dependency of damping coefficient. Especially, the proposed method is implied the application to identification problem of large damping system. Quantification of large damping characteristic is important problem, because it is very difficult problem in conventional identification method. Moreover, the benchmark tests are conducted with Half-Power Method (HPM) based on the spectral analysis and Auto-Regressive Method (ARM) based on the time series analysis, respectively. The results of benchmark are shown in the accuracy of propose method is higher than its of HPM and ARM, respectively.

In the previous report, we propose modeling focusing on "sigmoid function" as an attenuation model combining viscous damping and Coulomb friction characteristics, and conduct numerical simulation on higher-order spectra (HOS) analysis and higher-order frequency response analysis in that model was carried out. In order to further model various characteristics, we focused on "continuously differentiable friction model" proposed by Makkar et al. Numerical simulation analysis on higher order spectra(HOS) such as tri-spectrum was performed in these attenuation models. Effectiveness of the proposed method is presented and examined. These are the main points of this research.

This paper shows a fundamental study to apply the principle of metamaterial to solid waves of 2D/3D structures. A method of making the effective mass negative and an effect of the negative mass for a lumped parameter system in which the governing equation is isomorphic to the central difference approximation formula of the wave equation are investigated from the viewpoint of damping / vibration isolation. The results are as follows: 1) The effective mass can be negative by adding the dynamic damper-like systems in two-dimensional and three-dimensional structures. 2) It is important to make all natural frequencies of the one-degree-of-freedom system consisting of the mass of the main system and springs of the additional structures the same and to make all natural frequencies of the additional structures the same.

Many phenomena existing in mechanical structures have nonlinear characteristics such as play and friction, the response characteristic of the vibration system subjected to random input is a so-called non-gaussian random process. For the handling of these data, it is essential to apply statistical methods and analyze using higher-order statistics considering non-gaussian. The purpose of this research is to apply statistical method in higher-order frequency response analysis in asymmetric nonlinear vibration system using higher-order spectra (HOS) and present the effectiveness of this method. In this report, following the previous report, we focus on the repulsion characteristics of the magnetic force, perform experimental analysis and numerical simulation analysis on the "magnetic spring" model with non-linear characteristics, and perform cross-bispectral analysis considering input and output Applied. While evaluating the subharmonic vibration, the effectiveness of this method is examined.

Rotating machines are widely used in industry and therefore improvement of their efficiency through weight reduction and high-speed operation is always one of the most important tasks. However, such attempts run the risk of generating self-excited vibrations, since it is difficult to accurately predict the vibration characteristics of the high-precision large scale model which closely reflects the effects of shaft asymmetry and anisotropic bearing properties. In order to overcome this problem, this paper proposes a novel technique to construct a reduced model that accurately predicts the stability characteristics of the original large scale model. The effectiveness of the proposed technique is verified by comparing the results of stability analysis between the reduced and full models.

In this paper, the forced response analysis of two degrees of freedom (DOF) piecewise-linear nonlinear oscillators that are subjected to harmonic excitation and contact between the oscillators. our study shows investigation of the forced response of a two DOF PWL nonlinear system is with experiments and numerical analyses. First, experiments have been setup that are capable of simulating and measuring the dynamics of PWL nonlinear systems. With this experimental setup, forced response tests have been conducted with swept-sine base excitation. To ensure that the components collide with each other during the oscillation, masses of the components have been adjusted such that their natural frequencies differ from each other. As a result, clear features of nonlinearity are observed. In particular, the skewness of the signal envelops of the measured time histories of the displacements have been observed. Second, numerical analyses have been conducted by solving the nonlinear equations of motion of the two DOF PWL nonlinear systems, which contains nonlinear contact forces generated at the contact surfaces. Some discrepancies between experimental and numerical results are found in the frequency range where intermittent contacts between the oscillators occur, i.e., the response is nonlinear. Overall, however, it is observed that the numerical results agree well with the measured results for the frequency range of interest

The stick-slip vibration of violin string was completely formulated by using CA method (Cellular Automaton method) in time history analysis. The local neighborhood rule of the CA method was derived for the travelling wave along the string, both ends of string, and the bow point. The key point in success is that the bow point is to be fixed point and also to be velocity excited point at the same time. This means that reflected wave velocity consist of the incidental wave velocity and bow velocity. The above formulation results in reproducing the perfect Helmholtz waves.

The vibrations of a bowed violin string have been studied since the 19th century. The string was found to oscillate in a simple triangular pattern described by Helmholtz. Today these vibrations are known as stick and slip vibrations caused by friction and have been studied by many researchers. Stick-slip vibrations are self-sustained oscillations induced by dry friction. The theoretical analysis of stick-slip vibrations was solved by Cellular Automaton Method during prior research. However, it is not solved by Modal Analysis Method. In this research, stick-slip vibration is solved by Modal Analysis Method. At the time of slip, as a result of the simulation, it was possible to obtain results by Modal Analysis Method which is reasonable compared with Cellular Automaton Method and at the time of stick, it was possible to obtain reasonable calculation results only for displacement.

In the case of an automotive disk brake, squeal called in-plane squeal may be generated in which the disk vibrates in the in-plane direction. The disk has a structure called a hat and has a thin-walled cylindrical shape for supporting the friction portion. In this paper, we consider that the hat has a natural vibration that vibrates in the plane and out of plane simultaneously, which leads to in-plane squeal. Therefore, a disk which has hat is manufactured and a squealing test machine that generates stable in-plane squeal is used to measure squealing vibrations in and out of the surface of the disk. And it becomes clear by squeeze mode measurement that such natural vibration causes in-plane squeal. Concretely, the disks from which the vane part was removed were manufactured with other material, and the transfer function was measured. Next, a squeal tester with a simple structure consisting of these disks and a simplified brake pad was fabricated, and a stable in-plane squeal was generated, and the in-plane and out-of-plane vibrations were simultaneously measured. Then, the disk vibrates in the in-plane direction and has an inherent vibration that vibrates in the out-of-plane direction, and it is shown that the squeal vibrates simultaneously in the in-plane direction and the out-of-plane direction.

Squeal often generates in car disc brakes. Brake squeal gives discomfort for driver. Also, it is misunderstood abnormality of the system, therefore car maker has many troubles with claims from customers. Recently, further improvement of quietness is expected due to the development of electric vehicles and hybrid vehicles. Disc brake squeal is classified in terms of its generation mechanism. It has been found in previous studies that two types of squeal exist in disc brakes. One is called out-of-plane squeal, and the other is called in-plane squeal. Recently, the occurrence of in-plane squeal has been increasing, and the mechanism of in-plane squeal is not yet fully understood. In the experiment of this research, the in-plane squeal was reproduced the actual disc brake system. And it is confirmed that the characteristics of the unstable vibration agree well with those of the in-plane squeal generated in the floating type disc brake. This paper investigated the characteristic of the in-plane squeal and effect of mass addition to the rotor by analysis. The analytical model was consisted of disc and brake pads which are express as beams with a concentrated mass model. Analytical model reproduced in-plane squeal of the floating type disc brake. In addition, this paper investigates how mass addition of the rotor affects in-plane squeal and consideres the optimal position of adding mass.

Electrostatic cleaning equipment has been developed to remove dust from the surface of solar panels installed in an arid region. When a high AC voltage is applied to the parallel screen electrodes placed on a solar panel, the resultant electrostatic force acts on the particles near the electrodes. The reciprocatory motion of the particles between the electrodes is due to the alternating electrostatic force, where some particles pass through the openings of the upper screen electrode and fall downward along the inclined panel owing to the gravitational force. We demonstrated that the dust is removed efficiently from the panel surface. The power consumption of this system is negligibly low. This technology is expected to increase the effective efficiency of mega solar power plants constructed in deserts.

A self-standing support has been developed with the aim of developing a compressor that can operate in a low rotation range. It was considered that the drive unit in the shell deviates from the equilibrium position when disturbance is applied to the compressor because it was supported by a spherical surface. In order to improve the practicability of the compressor that applies the self-standing support, the supporting method was examined to prevent the drive unit from slipping from the equilibrium position. First, a one point support, a two points support, and a four points support is proposed for simple models, and verified their effectiveness. As a result, it was confirmed that the four points support was the best support since the vibration transmitted from the drive unit to the plate was small and the drive unit can maintain its original equilibrium position even when an impact force is applied. Next, a five points support similar to the four points support was applied to the prototype of self-standing support, and it was verified whether the same results as the simple model could be obtained. As a result, it was revealed that the vibration transmitted from the drive unit to the plate was small, and the drive unit could maintain its original equilibrium position even if an impact force was applied. Therefore, it can be said that the five points support is effective for a compressor.

From the viewpoint of energy efficiency, it is necessary to set the operating rotation range of a reciprocating compressor mounted on a household refrigerator low. On the other hand, there is a problem that when the reciprocating compressor is operated in a low rotational speed region, large vibration is generated by resonance. Therefore, in order to suppress the vibration transmitted from the reciprocating compressor to the refrigerator, the method of changing the natural frequency of the compressor to a frequency lower than the operating speed range was examined. Among them, a support element using a nonlinear spring was proposed, and the effectiveness of the new support element was verified by actually supporting the reciprocating compressor and performing drive experiments. As a result, with the support element using a nonlinear spring, although it was possible to reduce the natural frequency of the compressor, it was not possible to exclude all the natural frequencies from the operating region. However, even if resonance occurs in the compressor, the vibration transmission to the base is very small, and it is confirmed that the vibration reduction effect is high in the operating rotational speed region lower than that when supported by the rubber bush. In the future, in order to clarify the mechanism by which the vibration is reduced, it is planned to study the influence of the rigidity of the support element on the vibration mode by investigating the vibration mode generated between the compressor and the base in detail.

This paper is a study on Tailless Quad Tilt Rotor VTOL UAV which is designed and demonstrated by our team. For the practical use of proposed VTOL system, it is necessary to achieve a long distance and a long time in level flight. This paper discusses the induced drag at wing tip of tailless wing which is a main wing of UAV. For the conventional aircrafts winglets are used to reduce the induced drag. By our experimental flight of small tailless wing with winglets, the flight stability was found that easy to lose in gust wind. So this paper is selected to optimize the shape of wing tip for reducing induced drag of tailless wing. Experimental results in wind tunnel and calculated results using CFD software are shown by incorporating several types of wing tips.

Multistage tensegric robot arm is already presented to realize gigantic robot over 10m height. In the previous research, advantage of multistage robot to ease stress is confirmed and its control algorithm is discussed. However, its mechanical property has not been investigated yet. This paper discusses about bending to occur to a robot arm unit as a continuation of mechanical analysis. These results would be useful to design real gigantic multi-stage robot arm.

Flexural vibrations of railway vehicle car bodies around 10 Hz negatively affect ride comfort because humans are sensitive to this frequency range. Therefore, these vibrations should be reduced to improve ride comfort. The purpose of this study is to develop a new vibration reduction device which can reduce flexural vibrations of railway vehicle car bodies. In this study, we designed and developed a multi-axis dynamic vibration absorber (called MADVA in this report), which consists of a mass, a housing, presser plates, and elastic materials. Multiple pairs of oppositely directed elastic materials are connected between the mass and the housing, and the mass and the presser plates to permit the mass to move along primary axes. The multidirectional motion of the mass is expected to reduce three-dimensional flexural vibrations. The MADVA has a frequency adjustment mechanism for application to various types of car bodies which have different natural frequencies. We conducted some excitation tests of the MADVA to evaluate its characteristics and confirmed that its vertical and lateral peak frequencies can be adjusted to dampen the 10 Hz range. Furthermore, we built a numerical model of the MADVA for finite element method (FEM) simulation and predicted the vibration reduction effect on a Shinkansen-type test vehicle.

It has been shown that passengers have large reduction effect on the elastic vibration of a railway vehicle carbody. That effect is considered due to the viscoelastic motion and multi-directional motion of a human body. This study focuses on the latter one and aims to develop a new vibration reduction device to mimic the multi-directional motion of passengers. The study so far, an experimented multi-directional dynamic vibration absorber (called MDDVA in this report) is developed. The MDDVA consists of a steel ball supported resiliently by elastic balls bottled in a rigid cylindrical vessel. The steel ball can vibrate multi-directionally in the vessel and is expected to work as an MDDVA. In addition, the natural frequency of the MDDVA can be changed by pressing the elastic balls from the top. To evaluate the effectiveness of the MDDVA, excitation tests by means of a scale model of a railway vehicle is conducted. As a result, the MDDVA can reduce the elastic vibration by adjusting the natural frequency of MDDVA to that of the scale model, and multi-modal vibration reduction effect is successfully observed. And then, FEM models of the MDDVA and a scale model are constructed to verify the mechanism of the multi-modal vibration reduction. As a result of the FEM analysis, it is confirmed that the multi-directional motion of the steel ball produces the multi-modal vibration reduction effect. This paper aims to construct FEM models of the MDDVA to be used for design. New FEM models of the MDDVA, which the elastic balls can be pressed from the top as with the actual MDDVA, are constructed. As a result of the FEM analysis with level changes of pressing the elastic balls, it is confirmed that a tendency of test accords that of FEM analysis. However, improvement is necessary to design the MDDVA quantitively.

A 3-Directionally Supported Dynamic Vibration Absorber（called 3DSDVA in this report）has been developed in this study. The 3DSDVA, which is consists of viscoelastic supported an iron cube auxiliary mass with circular low hardness rubbers, can vibrate in multiple directions. By compressing the rubbers, the supporting rigidity of the auxiliary mass is increased, and the natural frequency of the 3DSDVA can be adjusted. The natural frequency adjustment mechanism was confirmed by the excitation test in the vertical direction. In order to examine the damping ability of the 3DSDVA, an excitation test was conducted using a 1:10 scale railway under frame model. As a result of the test, a large vibration reduction effect has been observed successfully.

Recently, we have proposed an active vibration control system by using synchronization properties of non-linear oscillators. In this system, a single oscillator has the role as amplifier that emphasizes the vibration response of target structures. However, to generate various vibration patterns for the structures’ multiple vibration mode, using networks consisting of a number of oscillators is effective. Therefore, in this paper discusses a relationship between a distribution of oscillators and a noise reduction.

In this study, we propose a frequency estimation method based on an adaptive line enhancer (ALE) algorithm to be used for changing property of the frequency-tunable dynamic vibration absorber (DVA). This method estimates the frequency from the time series of the delayed input signal, focusing on the fact that the autocorrelation function of noise converges rapidly to zero when the phase difference for several sampling periods is set. An elastomer composite with controllable stiffness, known as a magnetorheological elastomer (MRE), is used in a dynamic vibration absorber whose natural frequency is tuned adaptively to the disturbance frequency through the application of an external magnetic field. Firstly, we explain the structure of a variable stiffness DVA and the mechanism of the proposed frequency tuning algorithm. Secondly, the test result of the DVA properties, namely, the natural frequency and damping ratio is shown. By taking full advantage of the frequency adjustability of the proposed DVA, we then evaluated the real-time vibration control performance for an acoustically excited plate having multiple resonant peaks. The sweep excitation tests show that the vibration of the structure can be effectively reduced with an improved performance by using the adaptive-tuned DVA to be used with the proposed frequency estimation algorithm.

A viscoelastic material is sometimes applied to the damping element of a dynamic absorber. However, since the dynamic characteristics of a viscoelastic material are temperature dependent, it is considered that the vibration damping performance may deteriorate due to changes in the natural frequency and damping ratio. This paper proposes a structure for a dynamic absorber capable of suppressing the temperature-dependent change in vibratory characteristics. The dynamic absorber is a cantilever type which consists of two plate springs, and a viscoelastic material which is placed between these plate springs. The plate springs are bimetal which have the property of bending in response to temperature change. By means of this structure, the stiffness change of the viscoelastic material due to the temperature dependence is mitigated by the shape change of the viscoelastic material due to the bending of the bimetal. The validity of the proposed structure was confirmed theoretically and also in practice by a vibration test using a shaker.

In the optimization of dynamic vibration absorbers (DVAs), it is generally assumed that the damping force changes in proportion to the velocity of the object; this damping is called viscous damping. On the other hand, many DVAs used for practical use are made of polymeric rubber materials having both restorative and damping effects. The damping force of this polymer material is considered to have a hysteretic type damping characteristic that is proportional to the displacement, not the velocity of the object. However, there are very few studies on the optimal design of this hysteretic damped DVA, and at present the design formula of the well-known general viscous damped DVA is used for design of this type of DVA. This article reports the optimal solution of this hysteretic damped DVA. For generality, it is assumed that the primary system also has a structural damping that can be treated as a hysteretic damping. Two criteria, namely H∞ and H criteria, are adopted for the optimization of DVA. For the former, we succeeded in deriving an exact algebraic solution, and for the latter we showed the simultaneous equations and its numerical solution.

A dynamic vibration absorber using a pendulum can tune its natural frequency by the length of the pendulum. However, in the case where the rotation angle of the pendulum is large, the natural frequency deviates from the optimum value because of the nonlinearity of the restoring force of the pendulum. Therefore, this paper proposes a new mechanism to reduce the nonlinearity of the dynamic vibration absorber. The pendulum length increases as the rotation angle of the pendulum increases when the proposed mechanism is used. This paper also proposes the method to reduce the number of the nonlinear terms in the equation of motions. This method makes the directions of motions of the pendulum and cart perpendicular. The effectiveness of the proposed methods and theoretical analysis is verified through simulations and experiments.

In this study, the maximum amplitude magnification factor for a linear system equipped with a three-element dynamic vibration absorber (DVA) is exactly minimized for a given mass ratio using a numerical approach. The frequency response curve is assumed to have two resonance peaks, and the parameters for the two springs and one viscous damper in the DVA are optimized by minimizing the resonance amplitudes. A generalized optimality criteria approach is adopted for the derivation of the simultaneous equations for this design problem. The solution of the simultaneous equations precisely equalizes the heights of the two peaks in the resonance curve and achieves a minimum amplitude magnification factor. The simultaneous equations are solvable using the standard built-in functions of numerical computing software. The performance improvement of the three-element DVA compared to the standard Voigt type is evaluated based on the equivalent mass ratios. The advantages of the three-element type DVA have been made clearer.

It is known that the dynamic absorber is affective at the specific frequency, but is ineffective in the other frequency band. Taking advantage of the fact that the natural frequency is determined by the stiffness of the dynamic absorber, switching of the stiffness is performed to change the stiffness of the dynamic absorber to prevent resonance and device semi-active control that suppresses the vibration. In prior research, the mechanism of the variable stiffness was achieved by combination and the release of two pairs of springs with a rack gear, however, there was a problem of "the occurrence of acceleration disturbance." In order to improve the problem, a variable stiffness mechanism is realized by using an elastic body instead of the rack gear. For the semi-active control on the bases of the frequency of the structure, the measurement of the vibration frequency in the real time was necessary. It was measured by a suitable filter in prior research. In this paper, the time response of the structure of the several steps ahead is predicted and semi-active control is realized by choosing the stiffness with much dissipation of the kinetic energy. The effect of the proposed semi-active control is verified by simulation and an experiment.

Vibration control devices, such as a semiactive damper, are common use for vibration reduction. In general, many of them have a controllable flexibility, damping and friction. The authors have developed variable inertia damper by using Magneto-Rheological (MR) fluid with long by-pass pipe in a previous study. In this study a new type vibration control device which is having variable moment of inertia by the MR fluid inside a flywheel is developed. The moment of inertia of a rotating body is depended on own mass and a radius of gyration. The MR fluid is filled into the flywheel, and magnetic field is applied to the flywheel by electromagnets. If the radius of gyration is switched because ferrite particles of the fluid are clustered when magnetic field is applied, the vibration control device can have a variable moment of inertia effect. In order to confirm the effect, resisting force characteristics of the vibration control device were investigated, and to confirm validity of the vibration suppression, vibration tests of one degree-of-freedom system with the vibration control device were carried out. Finally, feasibility study and the effect of variable moment of inertia for vibration suppression were confirmed.

In this study, we conducted a shaking table test using a three-story building model with the aim of suppressing damage to buildings by combining multiple damping mechanisms of viscous systems, friction systems, and fluid inertia mass systems. First of all, basic structural characteristics consisting of cold-formed steel frame shear wall with friction mechanisms are studied. Next, we examined basic response characteristics to some strong seismic waves. The shear wall energy absorption capacity increased by tightening the high-strength bolt between the frame and the face material. This shear wall can exhibit stable bilinear-type restoring force characteristics having an arbitrary yield strength by changing the tightening force of the bolt. By changing the tightening force of the bolt, it is possible to provide the test frame with any yield strength distribution to these shear walls. In the shaking table tests, it was found that this basic structure showed stable bilinear restoring force characteristics and exhibited a high response suppressing effect.

This study is on a shaking table test of Light-gauge Cold-formed Steel Frame. The test frame is a three-story frame scaled to nearly 1/2. In this paper, we show the test results and seismic response control effect using the friction damper and Linked Fluid Inertia Mass Damper (LFIMD). The friction damper is installed in the shear wall, and the LFIMD is installed between the adjacent floors. We designed a LFIMD that is constructed by three cylinders connected with link tubes, to simultaneously control story deflection of a three-story frame.

In this paper, we conduct shake table tests on the two-story light-gauge cold-formed steel structure with a sliding base system and linked fluid inertia mass dampers (LFIMDs). The sliding base proposed in this paper consists of an alloy plated steel and cross laminated timber (CLT), and has the friction coefficient of about 0.4 in order to slide when subjected to strong earthquake ground motions. The LFIMDs are installed to the test frame to equalize the story drift of all the story and to enhance the energy dissipation capacity. The result of the shake table test shows that the sliding base system is effective in terms of the reduction of the story drift, and shows that the LFIMDs work to further reduce the story drift and the acceleration response. We also conduct time history response analysis of two-story wooden houses using a massive amount of strong ground motion records and confirm the excellent seismic performance of the proposed structural system.

In this report, we investigate the effectiveness of a nonlinear passive vibration isolator using multiple G-shaped beams. One of the characteristics of the vibration isolator using single G-shaped beam is that the isolation frequency range exists in the frequency range beyond the second natural frequency, so the vibration isolation performance was limited owing to the second natural frequency. In the previous report, we tried to reduce the influence of the second order vibration mode in the low frequency range by introducing an isolator using multiple G-shaped beams. In this study, static and dynamic characteristics of a vibration isolator using multiple G-shaped beams numerically and experimentally.

This paper deals with the control system design for active isolation table that loads a dynamical object. When elastic loads are put on the isolation table, vibration modes of the table are changed. Therefore, the controllers for the active isolation table should be designed taking account of elastic loads.

In this research, an experimental active isolation table with an elastic load is built. Previous controller was designed to suppress horizontal vibration in addition to vertical vibration simultaneously. However, the performance of the previous controller was worse than the controller designed to suppress only horizontal vibration. The reason is estimated as the coupled vibration between the horizontal direction and the vertical direction is relatively low. In this research, focusing on the rotational motion appeared on the experimental apparatus, new controller to suppress rotational vibration is designed and its performance is examined. The presented controller showed good performance.

The number of injured people transported by ambulance in H 28 is 5.62 million, of which the number of seriously ill patients is 470,000, and the average time of transportation is also 39.3 minutes, which is on an increasing trend. Vibration during transportation may worsen the symptoms of seriously ill patients, so a vibration isolation bed is used to attenuate vertical vibration, front and rear inertial forces. However, existing vibration isolation bed resonate with the vibration on the floor during running of the ambulance and the burden on the injured people increases. The goal of this research is to evaluate the vibration characteristics of existing vibration isolation mounts and to elucidate the cause of resonance. In this research, we perform eigenvalue analysis and eigenvalue experiment to evaluate vibration characteristics. An analysis model is created in 3DCAD, specific analysis is performed, and in eigenvalue experiments, a hammering test is performed to find natural frequencies and specific modes to clarify the cause of resonance. Also, the existing vibration isolation bed is placed on a vibration table, the vibration characteristics are evaluated by a sweep test, running experiments are carried out on a car, and vibration characteristics are evaluated

In Japan, the number of the sick and wounded transported by ambulances and their transport time are increasing year by year. Traveling vibration caused by transportation of a ambulance is transmitted to the sick and wounded, and may cause sickness and disease deterioration. Current ambulances are equipped with a vibration isolation bed, which is a vibration reduction device, as a measure against that vibration. I did a vibration experiment of the existing vibration isolation bed. As a result, the vibration isolation bed reduced the head vibration but not the leg vibration. The purpose of this research is to manufacture a new type of vibration isolation bed using high damping material at present research stage. The high damping material pipe is made by braiding glass fiber on a core material similar to polystyrene foam, and impregnating the resin from above. When the pipe deforms in a bending direction, the fibers rub against each other, converting the kinetic energy of vibration into thermal energy and damping the vibration. In vibration experiments assuming that the pipe is used as a suspended ceiling, the pipe showed a high damping factor. A prototype of a vibration isolation bed using a pipe was created. We carried out a loading test on one pipe to find the Young's modulus of the pipe. As a result of the experiment, it was found that the pipe can bear a weight of up to 8 kg. It was found that the number of required pipes was 182, assuming that it was used as a vibration isolation bed. Therefore, it is thought that this pipe is not suitable for the vibration isolation bed.

Considering the vibration velocity criterion in the ASME OM code, it was shown that the CAV in each cycle corresponds to the stress amplitude since the CAV in each cycle corresponds to the vibration velocity amplitude. From this, a method was developed, which can calculate stress amplitude from CAV per cycle and calculate cumulative fatigue damage value from Miner's law. The vibration response of the cantilever piping was calculated for four earthquakes, the cumulative fatigue damage value was calculated using the rain flow method, and the results were compared with the developed method to confirm the performance. Both results agreed well. According to the method developed in this paper, when there are a lot of pipes of various shapes with different natural frequencies, it has been shown that the cumulative fatigue damage value of each pipe element is lowered by -2.39th power of the frequency as a general tendency. This suggests that the effect of the acceleration excitation with a high frequency component can be small.

Some topics on the earthquake demand reduction to mechanical components due to inelastic energy absorption are discussed analytically with one-degree-of- freedom bilinear model response under the relatively small ductility factor region. Comparing with usual building structures, mechanical components tend to have higher natural frequencies and lower damping values in seismic design practices in Japan, therefore, so-called “Inelastic Energy Absorption Factor” tries to be analyzed with elastic damping factors of 0.02 and 0.05, and with natural frequencies ranged from 1 to 30 Hz, assuming more than fifty strong earthquake motions recorded in Japan as inputs. Finally, the U.S. seismic design practice for mechanical components considering in inelastic energy absorption effects can be reasonably applied to those in Japan, with some notes on the application of “property of energy conservation” rule in the relatively higher frequency region, because it may estimate overly the demand reduction effects under those conditions.

Experimental investigation on failure behaviors of piping systems were conducted with elbow pipes made of simulation materials to clarify the possible failure modes under the beyond design level seismic loads. In this study, lead-antimony (Pb-Sb) alloy was adopted as the simulation material, and shaking table tests on piping system models were conducted. The piping system model were composed by two elbows made of Pb-Sb alloy, one additional mass, and steel bars. Input motions were sinusoidal wave. Shaking table tests were conducted on several test conditions by varying the additional mass and frequency of the input sinusoidal wave. From the experiments, it was shown that the failure mode was the ratchet and subsequent collapse, and it seemed that the occurrence of failure mode depended on the frequency ratio and the mass ratio, similar to the results on the single-elbow piping system model conducted in the previous studies. It was also shown that the investigation procedure using simulation materials was effective to investigate the ultimate behavior of piping systems.

In this study, static load tests and high acceleration sinusoidal vibration tests of braced piping supports were conducted. The shape of the piping support was a frame type. A square steel tube was used for the member of the piping support. In the static load test, the buckling occurred at the brace member and the frame member. In the vibration test, the buckling occurred only the brace member. In addition, the fatigue crack occurred at welding heat affected zone of supporting part. The elastic-plastic behavior of the specimen after the buckling was stable in the vibration test. The fatigue crack was not observed until 20 cycle after buckling, and occurred during additional vibration. The primary failure mode of the vibration test was buckling, which was consistent with that of the static load test. The skeleton curve of the load-displacement relationship obtained from the vibration test were in good agreement with that obtained from the static load test. The damping factors of the specimen were calculated from load-displacement loops before and after buckling in the vibration test. The elastic-plastic behavior of the braced piping support with buckling under dynamic load were clarified. In addition, the example of the stable behavior of the braced piping support with buckling under dynamic load was given.

Two kinds of functions are required for the elastic-plastic pipe supports which can be used within plastic region; One is to enhance the design bearing capacity and the other is to provide damping using the seismic energy absorption due to elastic-plastic hysteresis. The effectiveness evaluation for the elastic-plastic design of the piping systems with elastic-plastic pipe supports was done within the limit of no plastic failure by comparing with the allowable load at the Level-D. The comparison results revealed that the traditional elastic-plastic pipe supports could increase the design bearing capacity, but they could not always provide the larger damping effect because of the dependence of hysteresis shapes on the support geometries. These results were thought to be due to the combination of the two function requirements in the same steel member. Therefore, the design idea of the elastic-plastic pipe supports with independent design of the two functions was proposed. The effectiveness was proven by the seismic response analysis.

It has been clarified from observation of the seismic ground motions by the density array that the seismic ground motions acting on structures are spatially scattering and become incoherent caused by the variation of soil properties, delay or differences path of wave propagation. In this study, to grasp the effect of the seismic ground motion incoherency on the seismic response of a deeply embedment structure, structure-soil interaction analysis by dynamic substruction method were performed and in-structure response spectra which referred to as the seismic condition of the equipment installed in the structure were evaluated. As a result of the seismic analysis of Advanced Boiling Water Reactor Building with deeply embedding located at the hard rock site, it was confirmed that the response acceleration of the frequency component over 8 Hz decreases due to the ground motion incoherency, and that the tendency becomes remarkable at 20~50 Hz with large amplitude in the seismic ground motion. From comparison of the seismic response of the deeply embedment structure and the surface mounted structure excited by coherent and incoherent seismic ground motion, it was confirmed that the reduction of the response acceleration amplitude at the high frequency range due to the seismic ground motion incoherency was equivalent in both situation.

After the Great East Japan Earthquake of 2011 and the Kumamoto Great Earthquake of 2016, it is becoming necessary to upgrade earthquake countermeasure technology for further infrastructure conservation. We have been developing a high-performance three-dimensional seismic isolation system. This paper describes the full-scale seismic excitation experiments on a new three-dimensional seismic isolation device using coil springs and the negative stiffness linkages in parallel on the air levitation pads. As a result of the excitation experiment by using the seismic waves of KiKnet Mashiki-Machi (the Kumamoto Earthquake), the acceleration responses of the seismic isolation system were reduced to 1/10 in the horizontal direction and 1/3 in the vertical direction. Air levitation pads were designed by the fluid bearing formula and confirmed its validity by an experiment. The levitation height during excitation was monitored and we found that there was no contact with the floor surface even at high acceleration.

This paper deals with the response behavior of the high-speed-moving connected vehicles considering the running road subjected to seismic excitation. The high-speed-moving connected vehicles are modeled by a set of vehicle model that have 21 degree of freedoms. The running road is modeled by spring, mass and damper system that have 1 degree of freedom in each direction. We assumed bridge as the running road. We investigated the effect of the running road on the behavior of the vehicle by getting response behavior of the vehicle. As a result, seismic waves’ predominant frequency changed through the running road and the response behavior of the vehicle changed, too. Also, if we calculate the behavior of the connected vehicles, calculation cost and degree of freedom considerably increase. So, it is necessary to construct the reduced order model. So far, we constructed the reduced order model using modal analysis by repeating try and error. However, it was difficult to select vibration modes which influenced the safety of the vehicle on the running road during the earthquake. So, we propose the method that can select the vibration modes which influenced the safety of the vehicle on the running road during the earthquake automatically. The method adopted the theory of sparse estimation. As a result, the reduced order model using sparse estimation can reproduce the original model enough. In addition, the reduction of calculation cost and vibration modes can be expected very much, so we can simulate efficiently by using the reduced order model.

It is important to understand characteristics of rocking vibration related to overturning small structures inside buildings. In order to understand the overturning of the structure due to rocking vibration by numerical analysis, numerical analysis considering energy loss in a collision and duration of collision is performed by using a quadrilateral hysteresis loop characteristic in which repulsive force is a function of speed as a hysteresis loop characteristic. As a result, since the maximum rotation angle and response waveform at the non-linear state of structure due to rocking almost agreed, indicating the effectiveness of numerical analysis in this research.

In this study, we present theoretical and analytical results of damping force induced by stirring in granular materials. In the experiment, a vertical cylinder stirred by a vertical blade was used and it was partially filled with granular materials made of PMMA. The torque induced by stirring and the blade angle were measured with a torque sensor and an angle sensor, respectively. The angular amplitude of the stirring blade was fixed at 30 degrees and the vibration frequency was changed from 1 Hz to 5 Hz. In addition, the behavior of granular materials was calculated using the discrete element method. The validity of using the numerical method to determine the relationship between the blade angle and the torque was examined by comparison with experimental results. It was found that the numerical approach is effective for estimating the relationship between the blade angle and the torque.

We have investigated the damping mechanism of the granular material damper when a structure having a relatively high natural frequency and small vibration displacement is used as a vibration damping target. In the granular material damper, the motion of the granular material is the basic principle of attenuation occurrence. Focusing on the energy of the granular material damper, the movement of the main system is determined by the energy to be consumed, the energy consumed by the collision of the granular bodies on the left and right container walls and the friction between the granular bodies on the bottom of the container. By using these quantities, it is possible to quantitatively evaluate the damping characteristics of the granular damper. In this research, we studied the high attenuation of the granular material damper by calculation using this evaluation method. We investigated the influence of both Young's modulus and moment of inertia of granular material on damping characteristics. Next, we tested the granular material damper using rubber ball with iron core to verify calculation results.

In this study, influence that the damping force properties of the particles damper received from inflow of the air were investigated experimentally. Zirconia balls of 0.5 mm in diameter were prepared as the particles. Damping forces were measured under constant piston speed conditions by the load cell. The damping forces increased as the displacement is increased. The gradient of the damping force changed to three phases. In the all phases, the damping forces decreased as the air weight flow is increased. On the other hand, under constant air weight flow conditions, the damping forces did not change with displacement speed.