In this paper, we describe a method for vibration suppression of multi-mode vibration system. This is the method which combined a filter to pick signal of fixed transfer function out with a general differential controller. It's possible to pick only signal of fixed transfer function out from output signal and feedback it by this filter.In this paper, we indicate the algorithm of the proposed method, and confirm the effect of vibration suppression by simulations and experiments. We confirmed that the proposed method can suppress the first mode vibration of the plant by step response and disturbance response simulations. Further, we performed verification experiments and confirmed that it's possible that the proposed method suppresses the first mode vibration of the plant by measurement results of frequency response and step response. From these results, we showed the validity to the vibration suppression of the proposed method.

抄録全体を表示

In a high resolution observation satellite or an astronomy satellite, observation sensors need to be cooled down to reduce the thermal noise. Recently, a mechanical cryocooler is used to cool the sensors, though the mechanical cryocooler generates a small mechanical vibration with pistons of compressors. This small vibration degrades the resolution of a sensor or pointing accuracy. In this research, we propose an active disturbance reduction control with an adaptive filter for a mechanical cryocooler without any additional actuators.

抄録全体を表示

We applied a rotational vibration manipulation function (rVMF), which is a piecewise feedforward function of a 1DOF oscillator, for stability control of an inverted-pendulum-type vehicle. In intermittent feedforward control or discrete sampled-data control by rVMF, stable area of initial angle and angular velocity becomes narrower in case operational period (Δt) becomes larger. The stability control succeeds in case Δt is less than 1/10 of the natural period of the pendulum. By limiting the initial condition to the rest-inverted point, we design trajectories of the vehicle for stable rest-to-rest constant motion by using 2-staged sequential acceleration or deceleration method. Although an inverted pendulum has a negative spring constant, rVMF can manage its stability control, as far as Δt and initial condition are suitable.

抄録全体を表示

The dominant mechanism involved in patttern formation phenomena in contact rotating systems is considered to be unstable vibrations generated in linear time-delay systems due to processes such as viscoelastic deformation, wear, cutting and grinding. A number of countermeasures have been proposed to prevent the occurrence of these phenomena.In this report, we attempted energetic considerarion for the self excited vibration caused time delay. In equation of motion, we regarded damping term, damping term of time delay, and rigidity section of the time delay as external forces and used integral to get the energies these forces do. When the sum of these energies is positive value, the foerces do work of positive and the system must be unstable. On the other hand, when the sum of these energies is negative value, the forces do work of negative and the system must be stable. By the approach, we confirmed that a system is stable or not in terms of energy. In previous studies, stabilization of the system using a dynamic absorber was suggested as an effective preventative measure, and the validity of dynamic abosorber was confirmed by numerical analysis using stability analysis method. In this report, we considered for the operating principle of a dynamic absorber for pattern formation phenomena.

抄録全体を表示

Brake squeal often occurs in car disc brake. It is not only give discomfort for driver, but also mislead abnormal of the brake system. Disc brake squeal has several type. The in-plane squeal especially have become in recent issue. There are several reports that treat the in-plane squeal. But the mechanism of in-plane squeal is not yet fully understood. This paper investigated the characteristic of the in-plane squeal and effect of mass addition to the rotor by experiment and analysis. The actual disc brake system is used in the experiment, and the concentrated mass model is performed in the analysis. The vibration mode of in-plane squeal is investigated. Additionally, the frictional property of disc brake and effect of mass addition to the rotor on squeal are investigated. From these experiments, the generation mechanism of in-plane squeal is comfirmed. The simple analytical model is also set up. The analytical model was consisted of disc and brake pads which are express as beams with a concentrated mass model. Analytical model reappeared in-plane squeal of the floating type disc brake. 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. The effect of height of the hat of the disc brake and effect of mass addition to the rotor on squeal was analytically investigated.

抄録全体を表示

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 this study, the phenomenon of chatter vibration is elucidated and predicted. By chatter vibration measurement in several workpiece, chatter vibration frequency and chatter vibration mode in cutting workpiece were found out. Chatter vibration measurement was practiced with 24 displacement sensors to circumferential direction. It turned out chatter vibration is similar to the natural vibration of workpiece and self-excited vibration, which is caused by coupling two vibrations near the cutting tool position. To confirm the relationship between chatter vibration and natural vibration, natural vibration of several workpiece got. By impact test, workpiece’s natural frequency and natural vibration mode were found out. Modal analysis by impact test impacted 36 points of the test piece to circumferential direction. The measurement results turned out that chatter vibration in cutting come from workpiece’s natural vibration. It also turned out that chatter vibration is self-excited vibration, which is caused by coupling two natural vibration near the cutting tool position. From the above, chatter vibration model that include two transfer function and two feedback was created. Prediction of chatter vibration by open loop transfer function is possible by workpiece stiffness and damping by finite element method and experiment.

抄録全体を表示

This paper describes the characteristics of a pendulum which consists of a container having a liquid and a thin rod. From the bottom of the container, the liquid is discharged as waterdrop. We investigated the effects of liquid discharged from the bottom of the container on oscillation of the system. The oscillation is measured by high speed camera while discharging liquid. While the period of the falling waterdrop was the same and twice the period of the pendulum, a growth of oscillation was observed.

抄録全体を表示

In this paper, the three-dimensional nonlinear characteristics of multi-surface liquid motion in a rectangular tank are investigated. The rectangular tank is divided into two parts by the baffle, which is perpendicular to the bottom of the tank and does not reach the bottom. The liquid oscillation subject to the horizontal excitation parallel to the baffle is focused on. The nonlinear ordinary differential equations governing the liquid oscillation are derived by using the Galerkin method. The admissible functions are assumed to be combinations of the modal functions. The modal functions are obtained by the boundary element method. It is pointed that the two modes, one of which oscillates in phase on both sides of the baffle and another oscillates in anti-phase, appear. The nonlinear coupling characteristics of those two dominant modes are discussed. It is noted that the mode, which does not directly excited by the excitation, is parametrically excited by the directly excited mode and that the three-dimensional liquid surface oscillation occurs as a result of parametric resonance. Frequency responses are obtained by applying the shooting method to the derived equations and stability analysis is conducted. Experiments were conducted by using a model tank. The occurrence of three-dimensional liquid surface oscillation in the narrow frequency range near the natural frequencies of the in-phase mode and the anti-phase mode is confirmed in both analytical and experimental results. It is shown that the amplitude of the three-dimensional liquid surface oscillation is larger than that of two-dimensional liquid surface oscillation.

抄録全体を表示

The finite element method is applied to buckling analysis of cylindrical shells subjected to asymmetric external and axisymmetric internal liquid pressures. The axisymmetric shell element is used and the load distribution, prebuckling and buckling displacements are represented by Fourier series expansion in the circumferential angle. The approximate treatment of tsunami pressure acting on tanks is proposed and the accuracy of the treatment is investigated. The asymmetric analysis considering the above treatment and axisymmetric analysis and the previously proposed simplified equations are applied to the model storage tanks under tsunami and axisymmetric internal liquid pressures. The validity and effectiveness of the axisymmetric analysis and the simplified equations are demonstrated.

抄録全体を表示

Powerful tsunami attacked to the northeast coast of Japan due to the Great East Japan Earthquake occurred on March 11, 2011. Some aboveground oil storage tanks (ASTs) were subjected to external pressure due to the tsunami. Wind giarders are installed to the shell plates in AST for the prevention of buckling by wind pressure. Although many researches on the buckling of ASTs or cylinder shells concerning tsunami were made, the effect as reinforced rings of the wind guarders was not taken into consideration in them. This paper presents the bifurcation buckling of shell plates in 10,000 m³ AST under both internal and external liquid pressure using the axisymmetric shell finite element method. The buckling external liquid height of AST with wind girder is compared with that without wind girder. As a result, the effect of the wind girder on buckling liquid pressure is small.

抄録全体を表示

CFRP (Carbon fiber reinforced plastics) have several advantages over conventional structural materials such as steel and aluminum alloy, as for instance, light-weight, high stiffness and strength and so on. But, generally speaking, CFRP laminates are said to have relatively low vibration damping. For solving this damping issue, damped CFRP laminates with damping sheets inserted at their interlamination have been proposed. If one wants to effectively utilize these kinds of CFRP technologies, precise identification of mechanical properties of CFRP lamina and damping sheet is necessary. In the present study, materials properties identification for damped CFRP laminates was conducted by combining the modal test with impulse hammering and finite element method (FEM) numerical analysis. From fitting FEM numerical results to the experimental ones for the first few modes of bending, some of the elastic and damping properties could be identified, leaving a few more unidentified materials properties which will need higher order modes.

抄録全体を表示

A novel composite structure arm for astronautical development by using CFRP and honeycomb core is already presented. Materials used in astronautical development should be compact and lightweight in order to save the launch cost. Honeycomb structure is one of lightweight material, and already used in astronautical field mainly for large panels. Besides, Carbon-Fiber Reinforced Plastic (CFRP) is known to be a lightweight and strong material. In this study, experimental evaluation of the presented arm is carried out. As superiority in parallel core bending specific stiffness is already presented in previous studies, cross core bending and torsional specific stiffness is investigated in this study.

抄録全体を表示

This study performed to measure the vibration mode of thin CFRP plate by time averaged pulse stroboscopic digital holographic interferometry. In order to confirm the amount of amplitude of the vibration, the laser doppler velocimeter (LDV) and a time-averaged digital holographic interference device with a light chopping device are produced. The light chopping device can make pulse stroboscopic light and it can vary the duty ratio of the light intensity. This device produce time averaged pulse stroboscopic digital holographic interferometry. LDV and holographic interferometry method measurement measured an amplitude amount of a cantilever plate vibration. The measurement results indicate the same value by each method. The time averaged pulse stroboscopic digital holographic interferometry can visualize vibration amplitude of the plate quantitatively. At the duty ratio is 50%, the measurement amount becomes maximum or minimum amplitude, at due to phase angle difference between the light and the vibration. This method can visualize the vibration mode of thin CFRP plates.

抄録全体を表示

Carbon fiber reinforced plastic (hereinafter referred to as CFRP) has excellent characteristics, so application to aerospace and automotive fields and the like is increasingly in full swing today. However, as compared with structural materials such as aluminum alloys, the damaged form is complicated, and it is important to correctly estimate the strength reduction and structural strength reliability due to the introduction of damage. Therefore, in this study, we investigated how the natural frequency and the loss coefficient of the CFRP orthogonally symmetrical laminated material are changed by introducing in-layer resin cracking damage by measuring the mechanical impedance by the central vibration tests.

抄録全体を表示

This study aims to design optimum partial reinforcement with curvilinear fibers to maximize natural frequencies of laminated composites. The test specimens are fabricated by the tailored fiber placement machine and VaRTM method, where two kinds of test specimens are prepared based on the optimum design obtained by the numerical calculation. The first one has the fiber shapes which reproduces the curvilinear partial reinforcement shape, and the other has the approximated fiber shapes by the straight segment. The numerical results indicate that the laminates with curvilinear partial reinforcements have higher natural frequencies than those without reinforcements. The experimental results successfully validate the numerical results, and it is conformed that there is an advantage for the laminate with curvilinear patricidal reinforcement over those with approximated straight reinforcement.

抄録全体を表示

Free vibration characteristics of the FRP plate printed by 3D-printer is studied in this paper. A square FRP composite plate is printed by a 3D-printer, the Mark-Forged Mark Two printer. The vibration characteristics are measured by impulse vibration test and acoustic vibration test. Experimental modal analysis detects the natural frequencies, modal dumping ratios and natural mode shapes. The time averaged digital holography interference method visualizes the vibration modes of the plate with different fiber direction angle against boundary condition. The numerical analysis is also carried out by using a commercial FEA software, ANSYS, to study the vibration mode shapes obtained by vibration test.

抄録全体を表示

The present study proposes a new fabrication method of carbon fiber reinforced thermos-plastic (CFRTP) laminates with curvilinear fiber shapes. Preforms with curved fibers are fabricated by using a tailored fiber placement (TFP) machine which is an application of embroidering technique and enables us to change the fiber orientation angles continuously during placement process. In the manufacturing process, carbon fibers are first fasted with stiches on a thin thermoplastic sheet by the TFP machine in the arbitral shape. Then, the sheet is impregnated into preforms by a hot press molding. Observation of cross sectional areas and fracture surfaces of test specimens by a microscope and SEM reveals that the thermoplastic resin materials are impregnated well into the carbon fibers. Measured and calculated vibration characteristics agree well for the plates with quadratic fibers as well as unidirectional reinforcing fibers.

抄録全体を表示

Experimental result are presented on nonlinear vibrations of a bi-stable CFRP laminated curved plate. The CFRP plate is fixed at center with bolts. The CFRP plate has two equilibrium configurations which is an upward convex and a downward convex. The characteristics of restoring force are measured in which asymmetric configurations appears in the transition between two stable equilibrium position.The natural frequencies are measured by impulse force. Moreover, natural modes of vibration are measured applying infinitesimal acoustic pressure. Next, the CFRP plate is exited with periodic acceleration by the electromagnetic shaker. Sweeping the excitation frequency, responses of the plate are measured by laser displacement sensors. Under uniform lateral periodic excitation, principal resonance with higher harmonics components is observed in large amplitude showing the characteristics of softening spring. Furthermore, sub-harmonic resonance of 1/2 order is generated when a concentrated mass is attached at a corner of the plate in downward convex which induces an asymmetric deformation.

抄録全体を表示

In this study, topology optimization were numerically applied to structural shape optimization problems under static loads for CFRP composite structures. General-purpose finite element analysis code, ANSYS 18.1, was used in the present study, in which the density method (SIMP method), one of the most popular numerical approaches in the structural optimization discipline, was employed for seeking the most efficient structural patterns of the present CFRP under certain fixed weight reduction constrains. From the results of the present study, certain optimal structural patterns or morphologies could be found out for each set of structural and material configurations.

抄録全体を表示

The present study fabricates fibrous composite with curvilinear fiber shape by using tailored fiber placement machine which is an application of embroidering machine. The composite with curved fibers has variable mechanical properties depending on fiber curvature. Due to this curvature, the overlapping of fiber tows often occurs. First the relationships among fiber density, thickness and overlap rate are revealed by experimental study with test specimens that have various curvatures or overlap rates. Then, regression equations for stiffness in terms of overlap rate are estimated for various fiber shapes. Finally, natural frequencies and mode shapes are calculated by finite element analysis with estimated mechanical properties, and those are compared with experimental results. The present calculated results indicated good agreement with experimental results. Therefore, it was found that the obtained regression equation is effective to predict mechanical behavior of composite with curvilinear fiber.

抄録全体を表示

This study investigated the material properties identification method of a single layer CFRP plate. This identification method is comparing between the vibration mode measurement results obtained from anisotropic materials with vibration analysis results of a single layer CFRP plate. In particular, genetic algorithm was used to identify multiple material properties at the same time. The usefulness of the identification method was confirmed by using simulation data. It turned out that it is necessary to include the high order mode in vibration mode used for genetic algorithm. Although there is variability, the possibility of identifying multiple material properties at the same time is suggested. If it can be identified by using experimental data including high order mode, material properties identification method of anisotropic material is established in the future.

抄録全体を表示

Self-synchronized phenomena have drawn great attention in engineering as potential mechanism which automatically creates pattern of vibration or rotation suited for machine operation. While many researches have been made on the selfsynchronized phenomena from the viewpoint of appropriate design of an individual system, the mechanism has not been clarified enough to realize a system which makes optimum use of advantageous features of the phenomena. The aim of this research is to clarify the effect of degrees of freedom of the system on the stability of synchronization which has crucial importance for clarification of the mechanism. This paper examines and compares characteristics of self-synchronized phenomena in several systems by the analysis using the shooting method, demonstrating the effect of translational and rotational degrees of freedom on the synchronized pattern as well as its stability.

抄録全体を表示

In this study, it was discussed theoretically about the function of a planetary gear inerter from the view point of the influence to the frequency characteristics of vibration system which it incorporated. In the previous paper, we performed formulation of the dynamic characteristics and investigation of function of a planetary gear inerter which is one of the practical inerter. According to this investigation, we found out that the planetary gear inerter could be interpreted to having the combination of three different functions, ideal inerter function, moment of inertia redistribution function, and directly connected moment of inertia. In this paper, we aimed to clarify the influences of each function of planetary gear inerter on dynamic characteristics of torsional vibration system. In order to achieve that, we formulated the 2 types of 1DOF torsional vibration system which the planetary gear inerter incorporated and investigate these functions analytically. As the result, we found out that the ideal inerter function which is one of the function of planetary gear inerter could be interpreted as negative stiffness between two terminals which is proportional to the excitation frequency. Because of this study, it could be expected to utilize inerter for vibration system design at the view point of new function.

抄録全体を表示

This paper investigates intrinsic localized modes (ILMs) in a system where N nonlinear oscillators are arranged in a circle and connected by weak springs when the system is subjected to sinusoidal, harmonic excitation torque. These oscillators consist of point masses at the tip of pinned, massless rigid rods, nonlinear springs, and dashpots. In the theoretical analysis, van der Pol’s method is employed to determine the expressions for the frequency response curves for fundamental harmonic oscillations. In the numerical calculations, the frequency response curves for N=3 are shown in the cases of both soft-spring and hard-spring nonlinear arrays and compared with the results of the numerical simulations. As a result, in the case of the soft-spring nonlinear arrays, eight stable oscillation patterns may appear when the connecting spring constants are comparatively small, and ILMs appear in six patterns depending on the initial conditions and the excitation frequency. The number of the oscillation patterns decreases as the connecting spring constants are increased. Comparatively, small values of the connecting spring constants may cause Hopf bifurcation to appear followed by amplitude modulated motions (AMMs), including regular ILMs, moving ILMs, and chaotic vibrations. In the case of the hard-spring nonlinear arrays, similar phenomena are observed except for moving ILMs. ILMs do not appear when the values of connecting springs exceed specific values in the both cases.

抄録全体を表示

Recently, various method of robotic locomotion is studied. This paper presents a promotion mechanism using vibration and investigates a condition of resonance point drive. In this study, the locomotion device consists of some carts connected in series by springs added the friction mechanism is proposed. This mechanism occurs a different frictional force between forward traveling and backward traveling. This device obtains propulsion by vibration. Therefore, the driving condition using natural vibration is high efficiency. At first, the driving condition of the fastest promotion is investigated by experiment using two carts connected in series by single spring. Next, the effect for promotion velocity of vibration mode is investigated by experiment using some carts connected in series by springs. As results, the promotion in the condition of natural vibration frequency is the fastest, and the driving condition which use higher order mode including the reverse phase between carts is the most efficient. This is a result when damping is low enough. However, damping acts under influence exterior module of apparatus when vibration propulsion is used. Therefore, we investigate the effect of damping on propulsion characteristics. As results, velocity of higher order mode greatly decrease when damping acted, and the most efficient vibration mode changed.

抄録全体を表示

Carbon nanotubes are made of carbon atoms, which are light weight and have high rigidity, flexibility and, high conductivity. But they are very small objects, so it is difficult to study through experiments, and physical properties and vibrations mode. By molecular dynamics method, which can analyze atomic motion of small scale atomic level, we visualize the behavior of the single wall carbon nanotube, whose layer is single layer, change frequency and direction of external force, Twist, bending, expansion and contraction, breathing mode are observed.

抄録全体を表示

Usually, when examining the behavior of system, different disciplines such as mechanical, electrical, and fluid mechanical area are separated. However, nowadays different and wide range systems are needed. Therefore, simulation by using Bond graph is effective as it treats several disciplines and achieves ideal synthesis. In this study a Bernoulli Euler beam, which does not treats the rotational inertia and shear deformation, is investigated. We carried out the optimization analysis and design the beam which has the desired natural frequency.

抄録全体を表示

As a basic study to estimate dynamic characteristics of structures such as carbody of railway vehicles and in order to improve their vibration characteristics, this study is aiming to identify mass, stiffness and damping matrices (called characteristic matrices) from frequency response function obtained by some realistic excitation testing of target structures. In this report, a theoretical procedure to estimate those matrices from frequency response functions obtained by single driving point is firstly described. Then the procedure is validated numerically using a nine degrees of freedom kinetic model. To improve the accuracy of identified characteristic matrices, using foresight information concerning with mass matrix are proposed. It has been demonstrated that introducing the foresight information is effective and good agreement has also been observed between exact and identified FRFs (Frequency Response Functions). In addition, the influence of the noise contamination in measured data is discussed. Although this proposed method is relatively robust against noise contamination, it has been found that accurate modal characteristics estimation of the target structure is important to identify characteristics matrices successfully.

抄録全体を表示

Whereas the natural frequencies of the bending vibration for plate are derived analytically, the natural frequencies of the torsional vibration can be calculated only approximately. In the previous researches, the natural frequencies for the specified shape of plate are studied, but the relationship between the natural frequencies and the aspect ratio of plate seems not to be investigated. In this paper, the natural frequencies of the plate are calculated by Rayleigh and Ritz method and the relationship between the natural frequencies and the aspect ratio of plate are illustrated. The results shows that the natural frequencies of torsional vibration arise between the natural frequencies of lower order bending vibration for the wide range of the aspect ratio.

抄録全体を表示

This paper examines the characteristics of the low frequency vibration which occurs in a vibroimpact system. The system investigated comprises two masses which can move only in the vertical direction under gravity. The lower mass is supported by a spring and subjected to a periodic exciting force whereas the upper mass bounces freely on the lower mass. The results show that the induced frequency is close to the natural frequency of the whole system when the ratio of the upper mass to the total mass is small, and gradually decreases with the increasing mass ratio. In order to clarify the mechanism of the frequency decrease, the analysis is made on the behavior of the variation, demonstrating that the collision between masses induces the instantaneous phase delay of free vibration component and its effect increases with the mass ratio.

抄録全体を表示

Magnetic Resonance Elastgraphy is one of the method for early diagnosis for cancers in which elastic modulus is measured by visualizing propagation of waves in the body with MRI. In this study, aiming to establish a remote generation method of wave in a human body for an inspection of a focus, a fundamental mechanism of remote-vibration generation is investigated. We introduced a model that consists of a mass-damper-spring system subjected to periodic force and a bar in which wave propagates from the mass-spring system to a flexible body in which wave is generated. Based on the analytical result, it was found that wave can be generated robustly with relatively large amplitude under the conditions that the dimension of the vibrating plate, which radiates the wave, is larger enough than the wavelength, and that the product of natural sound impedance of a bar and cross-sectional area is equivalent to the damping coefficient of wave radiation, and that the resonance of spring-mass system is induced which generates vibration, and that the damping coefficient of the spring-mass system is chosen as same value as the equivalent damping coefficient of the wave radiation.

抄録全体を表示

This paper proposes the method that obtain a reduced-order model using sampled data. The method is similar to the proper orthogonal decomposition (POD). POD determines the base vectors based on the concept of maximizing the variance of the data. On the other hand, this method determines the base vectors based on the concept of minimizing the sum of the distance between the space spanned by the base vectors and the data. In this paper, a relation between a number of sampled data and a accuracy of the obtained model is investigated. The results are as follows: 1) At least in the calculation example of this paper, the number of sampled data is sufficiently the same as the number of dimensions required for solution space approximation. 2) Generalization of conditions to be satisfied by data, such as number, characteristics, etc., is a future task.

抄録全体を表示

In recent years, nonlinear ultrasonic methods, owing to contact acoustic nonlinearity (CAN) and material nonlinearity, are counted on more sensitive non-destructive testing (NDT). Also, ultrasonic guided wave propagating over long distances can be applied to NDT for long structures. Therefore, nonlinear guided wave methods attract attention and are researched. In particular, the cumulative nonlinear guided waves caused by internal resonance are expected as possessing merits of nonlinear ultrasonics and guided waves. However, in previous researches, the area inspected by the cumulative nonlinear guided wave method are as large as that inspected by the conventional guided wave method. Therefore, we propose the method of using autoparametrically excited guided waves in order to expand the inspective area. In this study, nonlinearity and excitation are given only to one of the boundaries for simplicity. We theoretically investigated autoparametrically excited guided waves using the method of multiple scales (MMS).

抄録全体を表示

To examine the rotating speed variation caused by roller slipping and the horizontal acceleration vibration of the rotating roller, we altered the experimental equipment so that reduction could be made about rigidity of the roller supporting part. The change of the structure enables us to measure structural vibration occurring in the rolling experiments on a fine coal. As a result, the higher natural frequencies about the structural system have changed into the lower. To investigate dynamic responses of the rolling roller, the rotating velocity of the roller, acceleration at the axis of rollers, the generated forced and etc. were measured. As a result, both the rotating speed variation and the horizontal vibration acceleration gradually increased in accordance with the running velocity of increase before decreasing at higher running velocity. In order to clarify the causes, we obtained the relation between the apparent friction coefficient and the slip ratio between the roller and the fine coal, from 0.10 [m/s] to 0.50 [m/s] at a running velocity. It is found that the dependency of the friction coefficient and the slip ratio is not remarkable. Extracting the frequency components around the natural frequencies of the experimental equipment, we calculated the RMS values for each running velocity. As a result, it is found that the lower natural frequency could be excited when the roller is rolling on a fine coal and the excited frequency components changed to higher according to the running speed.

抄録全体を表示

The objective of this study is to clarify the vibration generation mechanism of agricultural machinery caused by the interaction between the tire lugs and the road surface. It is important to investigate the lug excitation force occurring on a rolling agricultural tire in order to clarify the vibration generation mechanism. In our previous study, it is confirmed that the dynamic behavior of rolling tire is influenced by the vibration characteristics of the tire and only the rigid modes can affect the rolling tire behavior. Therefore, we modeled the tire as in-plane rigid ring model and the lug excitation force in longitudinal and vertical direction are identified. However, as for an agricultural tire, lateral direction lug excitation force also generates due to cross-stich lugs. In order to estimate lateral force, the rigid ring model to describe the out-of-plane tire dynamics is required. The three-dimensional rigid ring model (SWIFT model) is able to describe not only the in-plane tire dynamic but also the out-of-plane tire dynamics. So, the frequency equations of SWIFT model are derived and the model parameters are identified by minimizing the difference between measured and calculated natural frequencies. In this study, the shaft displacement and the shaft force during rolling motion are measured three-dimensionally by rolling test. From the measured data, the lug excitation force in longitudinal, vertical and lateral direction are identified by using SWIFT model.

抄録全体を表示

This paper proposes a transfer function of rotating shaft system considering both an open crack and anisotropy in bearing support stiffness. Due to the interaction of anisotropy in support bearing and rotor crack, vibration component is generated without limitation. In this paper, a transfer function focusing on five vibration components is derived. Then, the experimental system of the rotating shaft supported by the bearing with anisotropic support stiffness is developed, and the harmonic excitation was added to this system by active magnetic bearing. Several harmonic excitation experiments were carried out. These experimental results clarified the usefulness of the derived transfer function.

抄録全体を表示

We introduce about study of low noise gear system technique of Sinkansen. First, we made a simulation model for the purpose of evaluating the dynamic behavior of the Shinkansen gear device. and evaluate influence on vibration by Miss-alignment between a pinion and gear. Second, we describe about FCD material technique. The spheroidal graphite cast iron gear aimed at the decreased of the vibration from the meshing vibration of the gear of the driveline system in the railway vehicle and the noise source. The spheroidal graphite cast iron is excellent in the vibration damping capability and the gear meshing face roughness compared with the steel materials. In the noise testing result of the driveline system gear reduced model that used the spheroidal graphite cast iron, the meshing volume of the gear of 20-25% was reduced. In addition, the gear cutting cost reduction is effective compared with the steel materials. However, rolling fatigue strength and the bending fatigue strength of spheroidal graphite cast iron material is low from the steel materials. It is necessary to improve the fatigue strength of the spheroidal graphite cast iron. And, heat treatment and surface treatment were done to the high strength spheroidal graphite cast iron. This report is a heat treatment of the high strength spheroidal graphite cast iron and introduces of the fatigue strength improvement effect by the surface treatment.

抄録全体を表示

In this paper, we propose ta method to reduce noise globally in a certain area based on wavefront synthesis. In this method, multi-channel active noise control is used that is divided into two parts. One sub-system is to reproduce the same shape of wavefront of the noise into the target area. The other is to adjust the amplitude and phase of reproduced wavefront to be the anti-noise with Filtered-x LMS algorithm. The effectiveness of the proposed approach is verified by numerical simulation and experiment.

抄録全体を表示

This study aims on to clarify characteristics of Shamisen (Japanese traditional guitar) in terms of energy propagation by using statistical energy analysis (SEA). Firstly, Experimental SEA model of a shamisen is constructed with impulsive excitation test; influence of internal cavity between surface skins is also investigated. Secondly, vibration energy propagation is evaluated with coupling loss factor (CLF) and internal loss factor (ILF), and it is shown that energy propagation from body to skin is remarkable than opposite direction especially in the frequency of shamisen sound range. Also, it is clarified that ILF of body is higher than that of skin, and they are almost consistent regardless of location. ILF of skin above 500 Hz is at the same level. Then, power flow is investigated and it is clarified that vibration of string is transmitted to the front skin through the bridge, and the vibration is transmitted to the back skin through internal cavity; the mechanism is the same as drum. Based on the result, Using the perturbation method, examined how to transfer energy to the surface leather and back leather where there is main energy exchange. Other than energy transmission between the surface leather and the back leather. Transmission from the front side to the back side via a neck to increase the vibration energy propagation to the back leather. Then, the exchange of energy between the surface leather and the back leather increases. This is thought to be a suitable energy propagation path to excitation the surface leather and the back leather more in the shamisen.

抄録全体を表示

Against a noise problem, it is important to comprehend the acoustic characteristics at a receive point that transmitted from the noise source. The acoustic characteristics at any point is expressed by the acoustic particle velocity on the noise source and Green function. Although the acoustic particle velocity has calculated by the integration of the acceleration on the noise source and Green function has gained based on the reciprocity theorem, we propose a method using a piezoelectric loudspeaker and acoustic particle velocity sensor. The acoustic particle velocity is directly measured by the sensor, and the Green function, which is a frequency response function, is gained by the emission noise from a piezoelectric loudspeaker on the noise source. This paper describes the fundamental method to estimate the acoustic transmission characteristics and a result of a verification test. Furthermore, we demonstrate the contribution ratio of the noise sources to the sound pressure at receive point on the premise that the sound pressure is dealt with as the vector and complex number.

抄録全体を表示

Frequency response of the modal sound transmission coefficient is explained by taking into account the generalized force induced by the incident acoustic wave, the radiation efficiency, and the natural frequency of the structural mode. Since the interaction among the structural modes is not considered in the three parameters, the behavior of the modal sound transmission coefficient can be partially explained by these parameters. The modal sound transmission coefficient is thought to be high if the amplitude of the generalized force and the radiation efficiency are high and the natural frequency is close to the frequency of interest. The numerical example showed that it is true.

抄録全体を表示

To estimate the sound radiation power as an objective function in noise reduction design, vibration characteristics of the structure and the force exciting it need estimating. However, as the vibration characteristics of the structure change, the exciting force also changes, therefore the estimated exciting force cannot be directly applied to the structure after it changed for noise reduction design. In this paper, we propose a method to estimate the response of the structure after its vibration characteristics are changed considering the change of exciting force. By introducing an exciting source that generates exciting force, the excitation force is expressed using the frequency response function of the structure. The exciting source is modeled as having a vibration system showing a linear response to the input, and the number of points connected to the structure is not limited. We can identify the vibration characteristics of the exciting source and the input applied to it by measuring the response with a known structural change. In experiments on cantilevered flat plates, changing structure by adding mass to several different positions, identify characteristics of the exciting source and estimate the responses considering the exciting force change. Moreover, applying this method to the search for the attachment position of the rib which minimizes the sound radiation power, we verify the validity of the method.

抄録全体を表示

The quietness of mechanical products is an important product value. In the future, it is considered that the target frequency band will be higher and wider. The vibration problem in the high frequency range is affected by multiple natural frequencies. It is difficult to take measures only by paying attention to single peak. Therefore, a design method effective for broadband vibration problems is necessary. We propose a two-step design as a design method effective for broadband vibration problem. This paper is shown application examples of two-step design using both wave motion and mode viewpoint. For the first step of the research, the concept of two step design, perspective and detailed design is proposed in this paper. Perspective design means based on wave theory and it grasps global tendency of the structure with Analytical Statistical Energy Analysis. On the other hand, detailed design more focus on modal shape to reduce vibration at specific frequencies with Finite Element Method. To demonstrate the feasibility of proposed method, vibration energy propagation analysis of coupled suspension cross member is performed through numerical simulation. As a result, the two-step design shows that the vibration of the object can be further reduced in addition to the broadband vibration.

抄録全体を表示

The performance enhancement of the acoustic insulation is demanded for the high frequency for interior noise of automobile. We took a waffle shape on the urethane surface to improve sound insulation in the acoustic insulation of the type that laminated a rubber sheet to urethane and examined a change of the acoustic. We tested it using a simple sound insulation performance measurement device and compared it with the vibration sound analysis result using the finite element model. Urethane used Biot model and used the parameter that I measured separately by the calculation. In addition, it was and, in the case of sound input and vibration input, calculated a change of the sound performance by difference in waffle shape (rib width, rib interval). As a result, in a certain frequency band, We were able to confirm that sound insulation performance improved.

抄録全体を表示

In order to suppress the resonance sound from a Helmholtz resonator by installing a baffle plate into its opening, the sound pressure measurements and the flow visualization were performed. In the sound pressure measurements, it was found that the sound pressure with the baffle plate was much lower than that without the baffle plate. The effect of the baffle plate on the reduction of sound pressure depended on the installation position and angle. In the flow visualization, it was found that the baffle palate made the size of the vortex smaller than that without the baffle plate.

抄録全体を表示

This paper describes numerical simulation of dynamic characteristics of the L shaped angle equipped with a new vibration damping device. The device includes blocks of viscoelastic gels and a constraint layer having a box cross section. The gel blocks are sandwiched between the constraint layer and the test structure. Damping performances are investigated by the numerical computation using the finite element method and modal strain energy method. We evaluate the influences of the new vibration damping device on the oscillation characteristics of the L shaped angle bar using eigen modes, modal loss factors and resonance frequencies

抄録全体を表示

A breathable trim which compressed felt for light weighting has begun to be used by car. In this study, the panel was excited and assumed that the noise occurred in the compartment that was the closed space where a breathable trim was located. We made a simple model and calculated with an experiment. An acrylic pipe of 150mm in length and in 100mm in diameter was placed the parting strip that there was the hole. This was input the iron plate which it located in the base with a hammer. We measured a sound pressure level with the microphone which it was installed in an iron plate and the other side, made similar FE model and calculated. In addition, it was located the felt which assumed a trim in the hole minute of the parting strip. The felt used Miki model. The experimental results and the calculation results showed good agreement. Furthermore, this paper introduce a calculation result about the change of the sound pressure level when it changed flow resistivity of the felt.

抄録全体を表示

In this research, theoretical transmission losses (TL) of finite flat plate with simple support, clamped, and free boundary condition are derived considering eigenmodes of the plate by modal expansions. Theoretical TLs are demonstrated to agree well with those obtained by numerical approach. Compared with TL by mass law, TL decrease at eigen frequencies of the panel and exhibits almost constant value at certain frequency range below coincidence frequency. This frequency band ranges from the frequency where the radiation efficiency exceeds 1 to the coincidence frequency.

抄録全体を表示

This research shows a fundamental study for the design of acoustic metasurface composed of acoustic media and multi-elastic-material. Topology optimization method that can deal with multi-material distribution is incorporated into two-phase material model that can express acoustic-elastic coupled system uniformly without imposing coupling boundary conditions. The proposed method is applied to the design problem of acoustic metasurface that exhibits negative mass density. First, the two-phase material model is introduced. Next, level-set based topology optimization and topology optimization based on Multi-Material Level Set (MM-LS) method are introduced. The design problem of acoustic metasurface is defined and objective functional, effective mass density of acoustic metasurface, is formulated using Sparameter-based method. Sensitivity analysis is conducted based on the concept of topological derivative and adjoint variable method, and sensitivity of each level set function that are used in MM-LS method is obtained. The optimization algorithm is constructed, and finally two-dimensional numerical example shows that our approach successfully achieves the optimal design of the metasurface.

抄録全体を表示

In this paper, we apply the multi-scale analysis developed by one of the author and predict sound absorption coefficients for normal incidence from the microscopic structures. Poroelastic sound absorbing media are generally classified into foam material and fibrous material. Here we capture the characteristics of micro structure of polyurethane foam and fibrous felt from the observation by SEM such as the pore size, thin membranes of polygonal faces and fiber diameter, and construct unit cell models assuming that sound absorbing materials have a geometric periodicity in microscopic point of view. We obtained practically good agreements between measured and calculated sound absorption coefficients.

抄録全体を表示