Most of the materials used for manufacture, such as wooden boards, metal sheets, and paper, are planar and nearly inextensible. Bending this kind of material is a method to form objects that avoids waste and reduces gluing costs. However, the resulting shape is limited to developable surfaces. Due to this limitation, this method lacks flexibility in design. This problem can be addressed by adding slits to the material, allowing the conformation of a single sheet into expressive surfaces with high flexibility. In this paper, we propose an interactive design system for this kind of geometry. The material used in this work is a rectangle containing parallel slits. The regions between slits are called strips, and by bending them, we can simulate the desired shape. Both flexibility and the geometric constraints were satisfied by a numerical optimization approach. The proposed system computes the better bending shape of strips considering smoothness of surface and user input. We show the effectiveness of our system with evaluation experiments.

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In this paper we carried out the simulation for controlling the resonance frequency of a Helmholtz resonator, which is used for the reduction of noise. The resonance frequency is designed to the desired value by PID control of the acoustical boundary condition of the Helmholtz resonator. The resonator like this is called Smart Helmholtz Resonator. At first the gains of PID controller is changed to several values and it is confirmed that the resonance frequency is varied. In order to realize the desired resonance frequency the gains of PID controller are determined by the response surface method. By using the response surface method the determination of the optimal gains are possible for a lower frequency region quite accurately. It is shown that this method is effective for designing the resonance frequency of Smart Helmholtz Resonator.

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The noise of vehicles such as exhaust noise has become a important problem in modern society. Noise is uncomfortable for human beings and it is one of the seven typical pollution defined in the social law. The noise of frequencies less than 100Hz exerts bad influence to human body. A truss core panel proposed in this study is excellent in the interception, absorbing and radiation of noise. So, in this study the simulation on the interception performance of a truss core panel which has high strength, high rigidity and low cost is carried out.

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Dealing with car frontal crash, previous research has indicated that front side member plays major role in energy absorption. For protecting the passengers, the front side member is expected to absorb crash energy as much as possible. In this study, the front side member with half cut type is studied by parameter study and optimum design method. An optimal design system of the half cut type side member is developed, in which the objective function is to maximize the absorbed energy of side member structure; the design variables are structural parameters, number of edges of polygonal cross section; spot welding pitch length; and thickness of thin-walled side member structure; the constrained condition is that the mass of optimal side member must be less than the allowed value. The parameter study and optimum design results are then discussed. The effect of absorbed energy with each design variable is studied. And the optimal side member structure is capable of absorbing energy 17.01% more than that of original half cut type of box-shaped cross sectional side member structure which is generally used.

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Nowadays the earth has been affected and polluted by various environmental problems, therefore reducing CO_2 emission for protecting environment, particular for emission of automobile has became an important issue. There are certain reports have confirmed that lightweight of vehicle had been able to contribute for reducing the CO_2 emission. So we direct our attention to Truss Core Panel as less weighty structure from the engineering application prospect of origami-engineering. The Truss Core Panel has better advantages in bending stiffness and in shear strength aspects. However, so far there are no studies of Truss Core Panel that apply the technology on the aspects of the shear stress and heat. In this study, we evaluate its shear and heat characteristics with Honeycomb Panel through the shear and heat simulation by utilizing multi-purpose analysis software of Nastran. And then we select design variable of Truss Core Panel to examine how the variable affects its shear and heat characteristics.

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The natural frequency calculated by a conventional beam theory technique of a stepped rotor whose diameter is not constant has a tendency to become high. For this subject, the shaft stiffness evaluation method which uses a stepped rotor shape was proposed. Concretely, after generating a solid model from the shape data of a stepped rotor, stiffness of the solid model is calculated, next, all degree of freedom of the solid model is reduced to the degree of freedom of the contact face, and high accuracy equivalent reduced model stiffness is introduced by the technique reducing the degree of freedom of the contact face to the degree of freedom of the beam model. After the verification result of a simple model by this method is described, the comparison of the numerical natural frequency and the measured result of a turbine rotor is reported.

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The gyroscopic exercise tool which utilizes the gyroscopic effect caused by the whirling motion of the high speed rotating body to train the hand muscle is considered. When the input motion with 3-5 Hz is added to the case, the rotor spins in thousands rpm whirling with the precession motion which is synchronous to the input case motion. This tool utilizes the contact phenomenon between the rotor and the case. This paper develops its dynamical model considering the transition among non-contacting, rolling, and sliding conditions. The dynamical characteristics of its motions are numerically investigated, and are also confirmed in the experiment.

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The predictive accuracy for the dynamic behaviour of a rotor under conditions of high-speed spinning depends on the accuracy for the analytical model of the rotor, the dynamic characteristics of the bearings and the seals, and the external force. In the present study, we propose a method to identify all characteristic matrices in the vibration equation of a rotor based on the information on rigid and elastic properties which can be obtained by a vibration test without spinning. The rotor is assumed to be composed of a shaft which can be modeled as beam elements and rigid discs. The proposed method can be applied for model reduction in which the reduced number of beam elements is feasible to calculate the dynamic behaviour of the rotor.

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Industrial turbo machines such as the centrifugal compressor show a tendency toward speedup and the downsizing. If a speedup technology to pass high order critical speed with active magnetic bearings can be established, the downsizing of the train will be enabled because of increasing the number of the impeller stages per 1 case. As fundamental researches of this speedup technology development, we produced the high-speed balancing machine for the flexible rotor supported by AMB and tested it. As a result, in the design of the flexible rotor, we showed that we could regulate critical speed by mass distribution intentionally. In addition, we performed modal balancing method in high order critical speed and succeeded in the passage of the sixth order critical speed. Furthermore, we showed that N-cut and N-cross control was effective in the high order critical speed to the third bending mode.

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A rotating shaft supported by a repulsive magnetic bearing may contact with a backup bearing during the passage of the critical speed as a damping coefficient of the repulsive magnetic bearing is small. This paper introduced the freedom of inner ring rotation of the backup bearing and developed a model of contact whirling motion between the shaft and the backup bearing which considers both slipping and rolling conditions and transition between them. The contact vibration is investigated and it is clarified that the slipping forward whirling motion occurs in the case that the inner ring is not rotatable, the rolling forward whirling motion occurs in the case that a damping of the inner ring rotation is small. On the other hand, in the case that a damping of the inner ring rotation is large, the rolling backward whirling motion occurs with high whirling speed, and this backward whirling motion keeps existing when the rotational speed reaches to the lower side of the critical speed during deceleration. This result is validated experimentally. Furthermore, it is clarified that the rotational speeds of the escapement from the contact vibration change along with an axial displacement of the repulsive magnetic bearing.

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This study investigates the nonlinear vibration of the flexible rotor supported by the journal bearing. The numerical simulation method, so called shooting method, is utilized to investigate both stable and unstable solution. Both the synchronous and asynchronous vibrations are analyzed. Because the shooting method is available only for the periodic vibration, the investigation of the asynchronous vibration can be performed only for the case without unbalance of the rotor system. To investigate the asynchronous vibration in the case with unbalance, an approximated force model of the journal bearing is developed. The validity of the proposed model is discussed by the numerical simulation and clarified.

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Recently flywheel energy storage systems using superconducting magnetic bearings have reached its validation phase. And varied combinations of magnetic bearings have been used in this system. However, increasing in amplitude has become a problem because of its low damping. Also nonlinear phenomena can occur in such low-damping systems using an electromagnetic force. This study investigates vibration reduction of a rotor system with an electromagnet. The nonlinearity of magnetic force is taken into consideration in the case. First of all, we developed an essential model of a rotor supported by a superconducting bulk, a permanent magnet and an electromagnet. Equations were derived by taking into account the nonlinearity of the electromagnetic force. Nonlinear analyses were conducted about these equations of motion of the rotor. These equations were then calculated by using the Runge-Kutta method. Numerical results show vibration reduction of a rotor by changing electromagnetic force at appropriate rotating speed. Good agreements were obtained between experimental results and numerical results. As summary, changing of not only linear stiffness but also nonlinear stiffness affects vibration reduction of a rotor supported by superconducting bulk, a permanent magnet and an electromagnet.

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It is well known that asymmetric vane spacing can result in decreased levels of the excitation at specific frequencies. In the previous paper, the resonant response reduction of mistuned bladed disks due to asymmetric vane spacing was studied by use of the equivalent spring-mass model. Although the mistuned bladed disk should be analyzed by FEA to accurately evaluate the resonant response reduction effect of asymmetric vane spacing, it is unrealistic due to enormous computational time. Therefore, in this study, the mistuned bladed disk is modeled by use of FMM (Fundamental Mistuning Model) to evaluate the resonant response reduction effect of asymmetric vane spacing accurately and practically. First, the frequency response analysis of a simple mistuned bladed disk consisting of flat plate blades is carried out for symmetric vane spacing, using both of FMM and the direct FE model, and the calculated results are compared to confirm the validity of FMM. Second, the frequency response analysis of a realistic bladed disk is carried out for asymmetric vane spacing, using FMM, to examine the effect of resonant response reduction effect.

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In a variable speed engine, it is impossible to avoid the resonance during operation. In a constant speed engine, the resonance during start-up or shut-down also cannot be avoided. Therefore, the increase of the acceleration rate passing through the resonance is considered as one of the effective methods for reducing the vibratory stress of the blade and increasing the reliability of the turbo-machinery. In this study, the transient vibration analysis of the mistuned bladed disk passing through the resonance is carried out, using the conventional modal analysis method and the numerical integration. First, the mistuned bladed disk is modeled by the equivalent spring-mass model, and the steady frequency response analysis is carried out by the Monte Carlo simulation, in order to obtain the worst mistuning. Second, for the mistuned bladed disk of the worst mistuning, the transient vibration analysis in passing through the resonance is carried out, and the effect of the acceleration rate and the blade damping on the transient vibration response is examined in detail. From these results, it is concluded that the larger the acceleration rate is, the smaller the mistuning effect is.

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Vibration characteristics of two-blade and three-blade wind turbines are investigated. The system is modeled by a coupled system of the flexible tower (consisting of a mass and a spring) with two degrees of freedom and the blades with a single degree of freedom, and these blades are subjected to wind pressure which varies depending on the height from the ground. The vibrations of the two-blade and three-blade wind turbines are theoretically analyzed to determine the natural frequency diagrams, frequency responses, stationary time histories and their FFT results. It is found that several response peaks appear at the lower range of the rotational speed ω because of both the wind pressure and the parametric excitation terms. The vibrations at these peaks include multiple frequencies consisting of higher harmonics. The response curves near the highest peak exhibit soft spring types due to the nonlinearities of the restoring moments of the blades, and they predominantly include 2ω and 3ω and their higher harmonics in two-blade and three-blade wind turbines, respectively. The number of blades influences the frequencies of vibrations. In the numerical simulation, "localization phenomena" in the blades, which vibrate at different amplitudes, are observed.

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This paper develops the 1 dimensional finite element rotating shaft model with a breathing crack which is concise and general purpose oriented model. The transition of open/closed conditions of a breathing crack is represented in terms of the deference of rotational displacements of both ends of the element at the crack position. Then, the variation of the area moment of inertia due to crack is represented by using the sigmoid function. The numerical simulation is performed for the various values of the depth of the crack, and the occurrence of the sub-resonance at the expected rotational speed are confirmed. Furthermore, the occurrence of each sub-resonance for the depth of the breathing crack are investigated and explained.

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Vibration control of floating platforms utilizing gyroscopes is theoretically investigated. The platform is modeled as a structure supported by springs and dashpots. Gyroscopes with brake drums are installed on the platform to suppress the resonance of the structure. Two kinds of platforms are considered: (a) a rectangular floating platform where the roll motion is controlled by a single gyroscope and (b) a square floating platform where the roll and pitch motions are controlled by two gyroscopes. In the theoretical analyses, the natural frequencies and the frequency response curves are calculated. The influences of the rotational speed of the gyroscope, the damping coefficient of the brake drum in the gyroscope and the distance between the center of gravity of the gyroscope and the gimbal axis on the frequency response curves are examined. The gyroscope shows the effectiveness in the vibration controls in both (a) and (b) cases. It is also found that the natural frequencies of the system change depending on the rotational speed of the gyroscope, and that the peaks of the frequency response curves are suppressed at low amplitudes by adjusting the value of the damping coefficient of the brake drum.

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Campbell diagrams are commonly used for designing rotating machinery to avoid resonance frequencies. Authors have proposed improved Campbell diagrams, of which the indication is modified to be more intuitive. A signal processing, which distinguishes between forced vibration and free vibration, has been applied to diagnosis of blade-shaft coupled vibration. In this paper, case studies of vibration diagnosis of rotating machinery using the improved Campbell diagrams are introduced: vibration of flexible rotor supported by active magnetic bearings, blade vibration of steam turbine-generator set, blade-shaft coupled resonance and abnormal blade vibrations of blade-shaft coupled system. For example, in the case of abnormal blade vibrations of blade-shaft coupled system, the improved Campbell diagram allows for detailed nonlinear analysis of entrainment phenomenon of forced self-excited system by separating it to forced vibration and self-excited vibration. Through these case studies, we report effectiveness of the use of our improved Campbell diagrams.

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Concerned with the flow oscillations in a collapsible tube, Starling resistor type oscillations have been widely investigated. This report describes the flow vibrations in the rubber tube which is locally squeezed by a kind of clamp. The phenomena, such as the change of tube cross section, the flow rate characteristics, and the fluid vibration behavior are explained under the conditions of the negative transmural (internal minus external (atmosphere)) pressure difference. The changes of the pressure and the cross section in the tube are measured in the decompression process of the reservoir. Some wave forms with flat phase in the pressure variations are related with those characteristics.

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A waveform of a pulse wave in a blood vessel often changes because of nonlinear effect. Analyzing this nonlinear phenomenon by the finite difference method requires high computational cost, and the treatment of the method is cumbersome. In order to overcome these problems, we propose a concentrated mass model to analyze the nonlinear pulse wave problems. This model consists of masses, connecting nonlinear springs, connecting dampers, base support dampers, and base support springs. The characteristic of connecting nonlinear spring is derived from the relationship between pressure and diameter of a blood vessel, and the base support damper and the base support spring are derived from the shear stress from a wall of a blood vessel. The pulse waves in the blood vessel of the dog measured by Laszt are analyzed numerically by using the proposed model in order to confirm the validity of the model. Numerical computational results agree very well with the experimental results. Especially, "steepening phenomenon" generated by the nonlinear effect of fluid is numerically reproduced. Therefore, it is concluded that the proposed model is valid for the numerical analysis of nonlinear pulse wave problem.

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Our final target of this study is developing a simulation package for predicting the pressure pulsation inside automotive exhausting system. In the simulation technique the pulsations of pressure and flow are assumed to be governed by one-dimensional wave equation and the method of characteristic is used. The exhaust system is modeled by the combination of three fundamental elements (pipe, volume and orifice). This paper discusses the effect of both temperature variations and gas composition inside the system. As a result, the effect of temperature variations and gas composition is so large. Consequently, the temperature difference in the position should be taken into consideration.

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A pressure wave propagating in a tube often changes to a shock wave because of the nonlinear effect of the fluid it is traveling through. The purpose of this study is to establish a practical analytical model to analyze this phenomenon. In this paper, the modeling of pressure wave propagating in turbulent flow and two-phase flow is proposed. Each model consists of masses, nonlinear spring, connecting dampers, and base support nonlinear dampers. To confirm the validity of the proposed model, an experiment on an air-conditioner piping system and contractions is performed and the experimental result is compared with the numerical result obtained by the concentrated mass model. All numerical computational results agree very well with the experimental results. Therefore, it is concluded that the proposed model is valid for the numerical analysis of nonlinear pressure wave problem on real piping system in single and two-phase flow.

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In this paper, vibration mitigation of combustion oscillation using several resonators is investigated. First, test apparatus are made. Using the apparatus, the frequencies and mode shapes of the combustion oscillation are checked. Then based on the result, the positions of the resonators are determined. Second, the combustion oscillation is produced for various conditions. Then, we attempt to mitigate the vibration by using two Helmholtz resonators and one side branch resonator. The effects of the resonators on equivalent ratio and combustion chamber length are investigated. We investigate the relation between the volume of the capacities of the resonators and the frequencies of the combustion oscillation. Possibility of the automatic tuning of the combustion oscillation is discussed.

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This paper discusses developments in two-phase flow induced vibrations research particularly recent findings within the Ecole Polytechnique FSI Chair. Two-phase flow excitation mechanisms include fluidelastic instability, turbulence and quasi-periodic excitation. The latter is a newly discovered phenomenon which is yet to be fully understood; high frequency quasi-periodic behavior may turn out to be important in practice. Significant progress has been made in understanding fluidelastic instability. In particular it has been shown that existing single phase flow based models may be applicable if used with care. Other important developments include better understanding of two-phase damping and as well as the development of a void fraction model which makes it possible to quantify two-phase flows in tube bundles with very good accuracy. Many of these developments remain, however, at the research stage and are yet to make it to practical application.

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Recent technological developments have resulted in various high quality products. Since the functionality and quality of the products are almost equivalent, the functions should be differentiated based on the sensibility thereof. Thus, we focused on push-button sounds. To estimate the quality of sounds, auditory experiments can be undertaken as a subjective evaluation, but this requires a great deal of time and a number of participants. To solve these problems, a psychoacoustic index has been proposed, although it cannot adapt to the objective evaluation of time-varying sounds such as push-button sounds. In our previous work, push-button sounds were represented in the time-frequency plane using a continuous wavelet transform, and combined with the results of the semantic differential method. From these results, the relationships between the physical properties and the auditory impressions were clarified. In this study, we propose feature extraction using triangular biorthogonal wavelets. The aim of the automated sound quality evaluation is to obtain an auditory impression score extracted by the semantic differential method without auditory experiments. Triangular biorthogonal wavelets are two-dimensional non-separable wavelets defined on a triangular lattice, allowing for multi-scale isotropic signal decomposition. The extracted features describe well the distinctive characteristics of push-button sounds. Evaluation of the automated evaluation was carried out using the sum of the squared difference and using dynamic programming matching. High recognition results were achieved with coarse features decomposed using triangular biorthogonal wavelets and dynamic programming matching. These results suggest the possibility of automated evaluation.

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An automatically performing bell system, which informed the specified time with music, has many types of bell configuration and arrangement. The first requirement for the bell system is to tune the fundamental resonance frequencies of each bell to an equal temperament of scale. Finite Element Method was used to determine the natural frequency and mode shape of the axisymmetric bell. Experimental evaluation was also carried out to examine the existence of the orthogonal mode which frequency is close to the fundamental frequency. Boundary Element Method(BEM) was applied to investigate the acoustic radiation properties of bell's eigen mode. Based on this results, bell is approximated by the point sound source with specific radiation directivity. Moreover, wave form of sound pressure radiated from the vibrating bell is calculated by this point sound source approximation and compared with the detailed BEM analysis.

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This paper presents the noise reduction of the machine product with fan noise by reducing structure-borne sound. Also we propose a new method for identifying the contributions of air- and structure-borne sounds in machinery noise. The contribution analysis method is based on the estimation of the structure-borne sound which is predicted by using experimental SEA. Firstly, the contribution analysis method is newly introduced. Next we apply the method to identifying the sound contribution of a breast milk warm machine which has a motor and a sirocco fan for blowing hot air circulated inside of the machine. The contribution analysis results are verified by the comparison with the measurement results in which the structure-borne sound is less generated. Finally it is shown that the noise level can be reduced by controlling the structure-borne sound.

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In these years, drive-system noise generating from motor vehicles on meter-gauged railways is decreased by employing fully enclosed type traction motors. However, the sound level of a gear noise is still remained high relatively. Our purpose is to develop a low noise gear systems by changing gear materials. In this paper, We carry out the running test and analysis of low noise gear made by ductile cast iron(FCD900), using mechanical dynamic behavior analysis, FEM analysis and BEM analysis to predict the vibration and sound power reductions of the gear systems. Consequently, we found that the gear which added to the materials has the lowest sound level by the improvement effect of the gear contact surface, compared to conventional one.

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As the diesel engine used for the forklift and construction machineries is operated in the continuous heavy duty condition, it employs the gear train to drive the fuel injection pump and valve train. When the driving torque acting on the rotating shaft is decreased in the idling condition, separation of gear tooth and rattle noise are induced. Moreover, torsional vibration of crankshaft increases the impact vibration between the gear train. This gear train is commonly installed at the pulley side of the crankshaft and the gear casing is attached to an engine block to cover the gear train. Vibration level of this gear casing is often magnified due to the engine block vibration and the engine noise is increased at the pulley side. Modal synthesis method is applied to reveal this phenomenon and to lead to a low noise design of the gear casing. This method employs the vibratory characteristics of engine block and gear casing and its static deflection induced by engine block vibration. In this paper, the combination of vibration mode of each structure to enlarge the gear casing vibration is discussed. This method reveals that similarity of static deflection and eigen mode shape of the gear casing is the major factor of the large vibration response of the gear casing and the separation of the these two natural frequencies is essential to reduce the radiated noise from the gear casing.

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Since structure-borne noise is generated by vibration of members of the structure, it is demanded to reduce the vibration and noise around the railway viaducts. To develop a countermeasure to reduce the vibration and noise effectively, it is necessary to predict them based on the analysis for the mechanism of them. We have therefore developed a new method of vibration analysis based on a flexural vibration analysis extended to the whole of structure, and a method to calculate the structure-borne noise by using the solution given by the vibration analysis as above mentioned. As the result of the calculation and measurement of the noise near the floor slab of a concrete viaduct constructed on Shinkansen line, it was revealed that the developed method has an acceptable accuracy. Then, we tried to evaluate the effect of two representative countermeasures to reduce the structure-borne noise, one is to apply an elastically supporting system, and the other is to modify the specification of floor slab by the developed analysis method, and revealed the effects of them quantitatively.

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As a means of reducing noises in a closed space, Helmholtz resonators are often used. Depending on how they are used, Helmholtz resonators are classified into a single resonator, parallel resonators and series resonators. Here with the purpose of proposing an optimal design technique, a single resonator and dual parallel resonators are considered. First a technique based on the fixed points theory, widely used for designing dynamic dampers, is developed. It is found that the technique can be applied to a single resonator but cannot to dual resonators. So a new iteration method, aiming to equalizing maximum values of sound pressure is proposed. It is found that the technique is applicable to both single and dual resonators.

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In the paper, we propose a concentrated mass model to perform a two-dimensional acoustic analysis. This model consists of masses, connecting springs, connecting dampers, and base support dampers. The characteristic of connecting spring is derived from the condition of adiabatic change of air, and the equivalent mass and the equivalent damping coefficient of the base support damper are derived from the shear stress from the wall. To confirm the validity of the proposed model, the numerical results obtained by the concentrated mass model are compared with the theoretical value of traveling wave, and with the theoretical value of the natural frequency. All numerical computational results agree very well with the theoretical values. Therefore, it is concluded that the proposed model is valid for the two-dimensional acoustic analysis.

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This paper discusses analytical Statistical Energy Analysis (SEA) applicability to structural-acoustic coupling systems by means of Finite Elemental Method (FEM) calculation. At first, we summarize analytical equations about SEA primary parameters (power input, subsystem's energy, and coupling loss factor). Next, we calculate these parameters by using analytical SEA and FEM calculation in order to verify the equations for these parameters. FEM calculations are performed to compare power input, subsystem energies, and coupling loss factors on structural-acoustic coupling system. The analytical SEA predictions are also compared with FEM calculation results.

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Aiming to estimate sound radiation power and to optimize vibrating structure, this paper proposes the virtual exciting force. The virtual exciting force can generate the vibration accelerations measured at several reference points and will be used instead of unknown actual exciting force. By using natural frequencies and eigenfunctions at virtual exciting points and reference points, frequency spectra of the virtual exciting forces can be formulated. The proposed method is applied to one side clamped rectangular plate. Numerical simulations validate that virtual exciting force is effective and useful to estimate vibration accelerations.

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The internal combustion engine sometimes encounters the cavitation erosion induced by piston slap. The impact vibration between the piston and cylinder liner generates the pressure fluctuation on the coolant side of the liner and leads to occur the cavitation in the case that dynamic pressure falls below its vapor pressure. Authors have already developed the analytical method to predict the liner vibration caused by the piston slap. In the previous paper, the acoustic characteristic of the water coolant passage of the actual diesel engine in vacuum condition was analyzed and compared with the measured result. In this paper, theoretical method to determine the coupled vibratory characteristics of structure and water acoustic field is developed. This method employs Finite Element Method and modal analysis technique. Calculated results of vibro-acoustic characteristics of the rectangular tank is compared with the measured ones and the effect of the heavy fluid loading is discussed.

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Bolted joints are widely used in mechanical and architectural structures. However, many serious accidents occur because of loosening in bolted joints. The conventional methods of the bolt loosening inspection require the use of special measurement equipment and human operation. It is difficult to conduct inspections in dangerous places, such as atomic power plants, space stations and bridges. In this study, a smart washer was proposed to detect the bolt loosening without human involvement and to achieve continuous monitoring. The smart washer that consists of the flexible cantilever enables to detect bolt loosening by using self-sensing and actuation functions of piezoelectric material. The remote health monitoring system using the smart washer. The subject of this paper is the energy harvesting method for the health monitoring system by using the smart washer. This paper describes a design method of the smart washer in consideration for piezoelectric vibration power generation by using flutter phenomenon.

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A wide-band vibration energy harvester using a nonlinear hardening oscillator with self-excitation circuit is presented. For the conventional linear vibration energy harvester, the resonance frequency is matched to the source frequency, and the mechanical Q factor is designed as large as possible to maximize the oscillator's amplitude. The large Q factor, however, bounds the resonance in a narrow frequency band, and the performance of the vibration energy harvester can become extremely worth when the frequency of the vibration source fluctuates. As is well known, the resonance frequency band can be expanded by introducing a hardening (or softening) nonlinear oscillator. However, it is difficult for the nonlinear vibration energy harvester to maintain the regenerated power constant because such nonlinear oscillator can have multiple stable steady-state solutions in the resonance band. In this paper, a control law that switches the load resistance between positive and negative values according to the instantaneous displacement and the velocity is proposed to give the oscillator a self-excitation capability, which ensures the oscillator entrained by the excitation only in the largest amplitude solution. Moreover, an adaptive adjustment of the control law is proposed to quicken the entrainment process. Numerical analysis shows that the nonlinear vibration energy harvester with resistance switching can maintain the large amplitude response even when the excitation frequency abruptly changes.

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Magneto-Rheological Grease (MR Grease) is one of functional fluids whose yield shear stress can be controlled reversibly by the applied magnetic field strength. Grease is known as lubricant widely used in mechanical components. It is composed of base oil and thickener which has 3-dimensional structure. Micron-size iron particles are dispersed in grease, and the thickener is expected to prevent iron particles from settling out caused by density difference of compositions. In this study, a model of MR Grease clutch was constructed and its performance was investigated as an application study of MR Grease. The effect of centrifugal force to MR Grease was also studied.

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Piezoelectric shunt damping is a damping technique using a piezoelectric element which can act both a sensor and an actuator. A circuit attached to the piezoelectric element is called the shunt circuit, and has the characteristics of the absorber. Many studies use the circuits with linear characteristics, but it becomes possible to have more complex characteristics by virtual admittance. In this paper, the nonlinear absorber called autoparametric vibration absorber is realized by piezoelectric shunt damping with the virtual admittance.

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Smart micro composites are designed optimally for the vibration suppression. The present smart structures are composed of graphite/epoxy (CFRP) composites and PZT actuators. Performance of vibration control strongly depends on actuator placements and modal shapes of structure. It is possible to specify vibration mode shapes for laminated composites by varying stacking combinations of angles of reinforcing fibers. In this paper, vibration control performance is maximized by optimizing fiber orientation angle, PZT actuator placement, and weight parameters in the control system simultaneously. A simple genetic algorithm method with modal database is used as an optimizer. Based on the numerical results, the experimental verification is conducted with an innovative excitation method using a laser abrasion technique. Since the pulse laser is irradiated precisely at the same position with same power repeatedly, this method makes it possible to excite micro structures with high reproducibility. Calculated results show that the optimized smart micro composite has superior performance of vibration suppression to some representative ones, and experimental results validate the present multidisciplinary optimization technique.

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To achieve an effective vibration attenuation of vibrating structures, a novel integrated active-passive control is presented. The integrated method is composed of two approaches; tuned electrical resonance and bang-bang active. Based on the interactive relations between mechanical and electrical vibrations, switching logics are devised for the integrated control. The paper presents the relative phase-shift of electrical resonance in non-stationary excitation, which cannot be found in stationary excitation. This phase-shift has been ignored although it is an essential factor for integrated systems. We demonstrated that the integrated active-passive control enhances vibration attenuation of conventional bang-bang active systems by using experiments on a 10-bay truss structure.

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In the piezoelectric shunt damping technique, active shunt circuits play an essential role for realizing an advanced sensor-less piezoelectric vibration control system. This paper discusses the stability margin of the piezoelectric shunt damping system using the virtual admittance also known as the synthetic admittance. From the analysis of the stability-margin of the open-loop transfer function, it is shown that the virtual admittance is suitable for simulating the inductive shunt such as a series LR circuit.

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Vibration control of smart structures using piezoelectric actuators have been studied widely. Saturation of the piezoelectric actuators and the amplifiers for driving the actuators is an important practical problem. However, the problem has not been studied enough. On the other hand, if the input voltage amplitude of the actuators in operating conditions are smaller than the maximum voltage limits of the actuators and the amplifiers, the feedback gains of the controller can be increased and the control performance can be improved. Model predictive control method is a method that can treat the above mentioned problems. However, the computational load of the method is much larger than conventional linear controllers because the method requires to solve the optimization problem with constraints in each time step. The large computational load causes large energy consumption and heat generation of controllers. It may prevent integration of structures and controllers of smart structure systems. In this paper, two adaptive gain feedback methods are proposed as the methods can treat the problems with smaller computational load. The performance of the two methods are examined by numerical simulations and compared each other.

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A rational method of dimensional reduction, which is proposed for vibration analysis of a large-scale structure with locally strong nonlinearity, is applied to a gear-shaft system. A pair of gears has some significant nonlinear behaviors. The meshing force stiffness between a pair of gears changes periodically because of the change of the number of the pairs of teeth which touch each other and the move of the contact point between the teeth. In addition, the pair of gears has the backlash and it has nonlinear dynamic behavior come of gear rattle. The analytical model for the coupled bending torsional vibration of the gear-shaft system is derived considering the nonlinearity described above. Furthermore, the rational method of dimensional reduction use complex constrained modes to consider the gyro effect of the system, and the effect of global nonlinearity of the system is unconsidered. The effectiveness of the method is verified by the numerical vibration analysis of the gear-shaft system.

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There are many papers treating problems of vibration analysis of a beam with breathing cracks, which open and close during vibration. The opening and closing of the breathing crack depends on the sign of bending moment at the crack position. Since the bending moment is not the primary variable in the usual analysis method, efficient and accurate analysis is difficult. In a previous paper one of the authors presented an analysis method of nonlinear vibration of a beam with breathing cracks, which is based on the mixed variational principle. In the paper characteristics of the nonlinear vibration of a beam with breathing cracks is also presented. In this report, experiment is conducted to verify the characteristics of the nonlinear vibration of a beam with a breathing crack.

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This paper presents analytical results on chaotic vibrations of a rectangular shell-panel under in-plane asymmetric constraints. The shell-panel with initial deflections is simply supported at all edges and also subjected to gravitational and periodic acceleration laterally. The boundary of the shell-panel is attached with an elastic material represented with distributed linear-springs in the in-plane directions. The outer sides of the springs are constrained by both uniform and asymmetric in-plane displacements. Neglecting the effect of inertia force along in-plane direction, the Donnell type equations modified with lateral inertia are applied as the governing equations of the shell-panel. The response of lateral deflection is assumed with multiple modes of vibration including unknown time functions. Stress function related with nonlinear coupling of the deflection is derived to satisfy the compatibility equation. The stress function satisfies both equilibrium conditions of in-plane forces and in-plane moments of forces at the boundaries. Applying the Galerkin procedure, equation of motion is reduced to a set of nonlinear ordinary differential equations. Characteristics of restoring force, linear vibrations and nonlinear responses are calculated on the shell-panel. The characteristics of restoring force show the type of a sofitening-and-hardening spring with a negative gradient. Nonlinear periodic responses are calculated with the harmonic balance method. Non-periodic responses are integrated numerically with the Runge-Kutta-Gill method. It is found that chaotic responses are generated in specific frequency regions. The chaotic responses are inspected with the Fourier spectra, the Poincare projections and the maximum Lyapunov exponents. The chaotic responses involve the sub-harmonic resonance response of 1/3 order corresponding to the lowest mode of vibration. Increasing the in-plane asymmetric constraints at the boundaries, contribution ratio of the mode of vibration that has a nodal line perpendicularly to the asymmetric constraints increases on the chaotic response.

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Recently, many researchers of space structures are focused on large deployable membrane structures which are lightweight and can be stowed in small volumes. One of the basic deployment methods of membrane structures is centrifugal deployment. The method unfurls and stabilizes the structure only by centrifugal force. Therefore, understanding the dynamic property of rotating membranes has been an important subject. In this study, vibration modes of a rotating circular membrane were investigated by forced excitation experiment. An experimental equipment which could rotate and shake a membrane simultaneously in vacuum were created by utilizing a rotary ball spline and a small shaker. Excitation experiment was performed with a wide range of rotation and excitation frequencies. Some resonance phenomena were observed and modal frequencies and shapes of several vibration modes were obtained. The experimental results were compared with analytical results which were obtained by the author employing the membrane theory of shell of revolution and taking account of buckling of thin membrane to examine the correlation between them.

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Triboelectric charging on micro-particles is studied analytically and experimentally. The contact analyses on particle-and-particle or particle-and-wall are calculated by using the distinct element method (DEM). To determine amount of charge on all particles contacting with the wall, an equation of triboelectrostatic charging as a function of time is used. In particular, to simplify the charge calculation algorithm, the triboelectric charge between particles is not considered. In experiments, both single particle and multiple particles' triboelectrification cases are conducted, and amount of charge on the particles is measured at each elapsed time. Charge constants of generating or decreasing in the theoretical equation are approximated with the experiment data by the least-square method. The above referenced equation is employed to numerically calculating the multiple particles' charging, and the calculated results are compared with experimental ones in order to verify the validity of the numerical method.

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Motion of a foreign object on a relay electrode is investigated numerically and experimentally. In the numerical approach, the motions of the foreign object and the relay electrode are analyzed the discrete element method (DEM) and the finite element method (FEM), respectively. The impulse force which a relay electrode gives to the foreign object is calculated by using the theory of elasticity. The charge simulation method is used for calculating electric field between relay electrodes. In the experimental approach, and the motion of the charged foreign object is tracked with a video camera. The foreign object is beforehand charged using a corona charging device and the electric charge was measured with an electrometer. As a result, the negatively charged foreign object bounds considerably compared with positively one. The adequacy of the analysis method is justified by comparing with the experimental results.

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To realize reliable regolith sampling for autonomous operation in space, the authors have developed a new sampling system that employs electrostatic force. This system employs a combination of electrostatic capture and transport of particles. High voltage is applied between parallel screen electrodes of the sampling device. Owing to electrostatic force, particles are captured at the screen electrode of the device. The captured particles are then transported by an electrostatic traveling wave and transferred to a collection capsule. It has been demonstrated that lunar soil simulant can be sampled if the end of the screen electrode is in touch with the regolith for short period, within one second. Because gravity is extremely low on small asteroids, the process of sampling particles on asteroids will be easier than that on the Earth.

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