Dia-Core is a newly devised core panel formed by gluing/welding of two same shaped panel pieces which have periodically indents. The basic model of Dia-core is based on Octet-Truss developed by Fuller, and it consists of tetrahedra and octahedra. It has good cost performance due to easy press forming. Therefore, it is expected to become new core materials which can compete with honeycomb panels from the total points of view. In this paper, by using experiments and numerical simulations, the bending rigidity, a representative propertie of Dia-Core is clarified. The results suggest that the bending rigidity of Dia-core is proportional to the initial thickness of panel pieces and the square of the panel height. These trends can be explained by the application of the theory of sandwich structures. And by using these results, the specific rigidity of Dia-core is calculated and compared with that of two typical honeycomb panels.

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Packaging is essential to most kinds of industries. But designing the forming collar which is the most important part of packaging machine is a difficult job. This paper presenting a flexible methodology for calculating the complete geometry of the collar, rather than the usually non-complete collar over which the film is formed. The collar geometry is calculated such that it has the minimum deformation energy. This enables right-first-time and repeatable collar production and reduces the time and cost for producing next generation packaging machines.

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In recent years, the structures which used origami engineering attract much attention. It can be applied in many fields, such as automobile, building, medical care and so on. In this paper, it is focused on the reversed spiral cylindrical (RSC) origami structure, which is designed by Nojima. This structure is expected to use in side member and beverage containers. An automatic crashworthiness analysis system is developed to generalize different types of RSC origami structures which can transform RSC origami structures from polygon thin wall structures with a group of parameters automatically.

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The purpose of this paper is to present generalized models of compact folding/wrapping method of flat membranes around a central hetero-hub using modified Archimedean spiral configurations. By using the formulated simple angle relations between fold-lines, various kinds of wrapping models are shown to be easily designed. The present models are expected not only to devise living goods but also to be used for instructional materials with edutainment.

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Some origami models related with golden mean/angle or silver ratio are described. One is related with phyllotaxis of plants and flowers, and another is related with unperiodic space filling models in geometry.

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In this paper, we present the results of applying the platonic solids for segmentation of the triangular surface mesh. Mesh segmentation has become an important step in model understanding and can be used as a useful tool for different applications, for instance, modeling and reverse engineering. Our approach is based on an idea to use of normal vectors of all faces of the selected platonic solid as the direction vectors for grouping the mesh elements. The selection of the best platonic solid for a given model by finding the optimum value of a cost function with many local minima is one part of our investigation. Each group of triangles (segment) can be used for local mesh denoising. Features of initial models can be restored during the denoising process. Also the platonic solids approach could be extended to extract features from a surface triangular mesh.

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NURBS surface generation from triangular meshes is the core part of reverse engineering. In this paper, a system for generating NURBS surface is proposed. First, a triangular mesh model is divided into several quad-like logical patches. Usually, the topology of each patch is arbitrary. To construct NURBS, however, structured mesh topology is necessary. The process of converting an arbitrary topological mesh to a structured one is called remeshing usually. A simple, efficient and novel remeshing method is presented. Then NURBS surface patches can be generated. Finally, several NURBS patches are connected in a smooth way.

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An automatic ball balancer is a unique vibration suppression device which can balance the rotor automatically. In the post critical speed, two balls in the rotor cavity locate at the appropriate positions in the opposite side of the unbalance and cancel the unbalance. This device has two malfunctions. One is the effect of friction. Due to the inevitable friction, balls stop near the optimal positions and do not balance the rotor perfectly. The other is the self-excited oscillation which occurs near the major critical speed. This paper introduces methods to eliminate these effects.

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On field balancing for rotating machine of rigid rotor, two trial runs with trial mass attached on the rotor are usually needed. This paper describes a possibility that the dynamic unbalance in rotor can be determined by the considered equations of motion and geometric vector calculation methods, by using the measurements of vibration displacement amplitudes for the initial run or the initial and one trial run attached with a trial mass.

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This paper proposes a balancing method of flexible rotor based on nonstationary data which the rotating speed of the rotor increases or decreases. The rotor/bearing system is modeled by FEM in order to obtain transient amplitude and phase angle and to confirm the exist of the point(fixed phase angle) which dose not change the phase angle when angular acceleration changes. Followings are concluded; transient balancing is possible for balancing of flexible rotor, the fixed phase angle exists any character of bearing and it is useful for the balancing of flexible rotor.

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This paper deals with the development of balance measurement system for solids of revolution such as wheel with medium size. The prototype system has been developed but its performance has been estimated by tests for a simple wheel with an unbalance mass. However, the signals of the displacement response of spindle, which were measured on the performance tests, included not only some noise but also some vibration by dynamic characteristics of the plate functioning as spring and it yields large errors on the measurement quantity of the unbalance. The dynamic characteristics of the system and spring plate should be investigated and the design of the system should be reconsidered in order to solve the problem. In this study, the dynamic characteristics will be proved by the experiments by driving tests of the balance measurement system and analysis by the simulations using FEM analysis model.

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The turbine generator, a major component of power plants, must have sufficient reliability. Since the natural frequency of a turbine blade decreases for longer blades, design of the turbine shaft and blade should take into account the coupling of the shaft vibration and the vibration modes of the blade for nodal diameters k = 0 and k = 1. The present work analyzes the resonance condition of the in-plane and out-of-plane blade. In-plane blade resonates at -ω_b = -Ω. due to gravity. Out-of-plane blade resonates at -ω_b = -2Ω due to unbalance and asymmetry of the bearing stiffness. Additionally, self-excited vibration is caused by fluid force, and entrainment may be considered.

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本論文では、シュラウドやスタブなどの連結部材で全周を結合された全周リング翼構造の翼・ディスク系において、初期欠陥など、何らかの理由で全周の1箇所においてシュラウドやスタブが喪失した時の振動応答特性、すなわち健全な全周リング構造に対して振動応答がどの程度増大するかを、簡便に予測する手法を検討する。まず、シュラウドやスタブが喪失した時の振動応答特性を定性的に検討するため、シュラウドやスタブの喪失により振動モードが規則的に変化することに着目し、振動応答を簡便に計算する理論式を導出する。つぎに、この理論式を使用してパラメータ計算を行い、シュラウドやスタブが喪失した時の振動応答特性を詳細に調査する。最後に、有限要素法で直接解析した結果と理論式で解析した結果を比較し、提案した予測式により、シュラウドやスタブが喪失した時の振動応答特性をどの程度予測できるかについて検討する。

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Centrifugal pendulum vibration absorbers are widely used as the vibration suppression devise for helicopters. The vibration characteristics of this absorber has been investigated by applying the linear theory on anti-resonance. However, the nonlinear characteristics appear when the pendulum swings with large amplitude. The authors studied vibration suppression characteristics of pendulum absorbers considering nonlinear characteristics of pendulums. In the first report, we investigated a two-degree-of-freedom system composed of a rigid rotor blade and a pendulum. In this system, the blade was excited by a harmonic deflection motion of the shaft. In the second report, we investigated a three-degree-of-freedom system composed of a fuselage, a rigid blade and a pendulum. In this paper, the model has three degrees of freedom and is composed of a blade, a pendulum and a rotor mount. The blade is flexible and only the first mode is considered. An aerodynamic excitation force applies to the blade. The vibration suppression characteristics of this system are investigated theoretically and experimentally.

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There are many harmonic components in the electromagnetic force caused by electrical motors. The harmonic components induce the structural vibration and noise. In the paper, electromagnetic vibration and noise from eccentric motor are experimentally discussed comparing with normal motor. As a result, maximum vibration is about 2 times and the noise is about 4 dB above comparing with those of normal motor.

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There are many harmonic components in the electromagnetic force caused by motors. The harmonic components induce the structural vibration and noise. In this paper, electromagnetic vibration and noise from motor with off-centered rotor are discussed comparing with normal motor in numerical analysis. As a result, harmonic components of odd-order, which do not appear in off-centered rotor, appear in eccentric rotor. And the vibration and noise depend on the eccentric direction and magnitude. In the case of eccentric magnitude 0.2mm, the maximum noise is about 4dB larger than that of the off-centered rotor.

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In this study, the simulation model presented and validated in a previous study, Link-Spring model, is used to describe the foil structure of bump-type foil bearing. A theoretical analysis is presented to investigate the nonlinear dynamic behavior, i.e., the stability and unbalance response of bump-type foil bearings. The trajectory of shaft is simulated with the iteration calculation of shaft motion equation at each time step, which is coupled with the Reynolds' equation and the foil structure model. Parametric studies of number of bump, size of bump, thickness of foil and material of foil are presented based on the bearing load prediction and the nonlinear orbit simulations.

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Non-contacting seal is used to prevent leakage flow for turbomachineries, such as gas turbines and compressors. Since these turbomachineries tend to be operated under high pressure and power, the fluid forces induced at the seal is one of the causes of instability. One way to reduce this instability is to use inlet swirl injection against rotation. In this research, we found the distribution of circumferential velocity and pressure at the inlet of the seal and the effect of injection of inlet swirl on the static and dynamic characteristics.

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Many rotors are supported by an oil film bearing which has high stiffness. Since the gap of an oil film bearing is very small, we must suppress vibration as much as possible to prevent metal contact by an oil membrane break. Therefore the damping ratio is an important index to use when evaluating the rotor system stability. However it is difficult to identify the damping ratio under various conditions. In this paper, the damping ratio of oil film bearing rotor system is evaluated by using the tracking solver. This solver provides a continuous solution of damping ratio during rotation. We evaluate the damping ratio of the oil film bearing with a dynamic vibration absorber which is developed for suppression of oil whip instability.

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Recently, the research and development of micro machines that move with fluid in a small diameter tube has been performed enthusiastically. It is important to clarify the fluid-solid interaction in case of small clearance between a micro machine and the wall to design micro machines with enough reliability. This research investigates the fluid flow characteristics around the body when the body is influenced by pressure force from upstream along center axis as a basic system that moves with fluid in a small diameter tube.

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This paper presents a flow-induced vibration of guide plates with a large tilt angle in relation to the flow direction. A wind tunnel tests are carried out for measurement of the vibration and pressure characteristics of the guide plates. The measured data of pressure include random and acoustic resonance components. The vibration of the guide plates includes the components both with the natural frequencies of the plates and the acoustic resonance frequency. We have proposed a vibration response analysis technique for an FE model, considering both the spatial correlation and phase delay characteristics defined by the measured pressure. It is verified that the present technique is valid for the experimental results.

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In this paper, we propose a new concept of tuned sloshing damper with two immiscible fluids of different densities. This concept uses sloshing which occurs at the interface between two fluids to suppress a vibration of structure. In theoretical analysis, governing equations of interfacial sloshing-structure interaction system are derived by Hamilton's principle. Coupled natural frequencies and frequency responses are calculated by these equations. On the other hand, the suppression characteristics of proposed method is researched by analysis and experiment. As a result, it was found that the vibration of structure is effectively suppressed by tuning the natural frequencies of coupled vibration modes.

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To predict natural frequencies of high-pressure centrifugal compressor impellers accurately, we measured the natural frequencies of an equivalent disc vibrating in a high-pressure gas environment. It is known that natural frequencies of pump impellers in water decrease compared with their natural frequencies in air due to the add mass effect. However, in our experiments in a high-pressure gas environment, the natural frequencies of the disc not only decreased but also increased compared with those operating under atmospheric condition. In order to clarify the effect of axial gap length and gaseous species, we set three ways of the axial gap length of our test apparatus and used four different gasses as the surrounding gas.

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This paper deals with a theoretical stability analysis of a web flutter generated to a thin film subjected to fluid flow in a narrow passage. In the stability analysis, the structural equation of the thin film in the transverse motion is based on the Kirchhoff-Love's thin-plate model and the basic equations of fluid flow around the thin film are based on Navier-Stokes equations. The governing equations of the thin film motion coupled with fluid flow are obtained. As a results, the analytical results show that the traveling wave mode flutter occurs to the thin film due to the fluid flow in the narrow passage when the flow velocity becomes high, and clarify the dispersion relation of the wave motion, wave velocity (phase velocity) and growth rate of the wave.

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The evaluation methodologies for the flow-induced vibration instability of a long flexible beam due to the axial flow in confined narrow passage are reported. So far, we have proposed original analytical method for the flow-induced vibration instability of elastic beam subjected to axial flow in confined narrow passage. In this paper, by using this proposed analytical method, we have performed the parameter-studies on the dynamic stability of elastic beam subjected to axial flow in confined narrow passage. And we clarify the effects of support conditions of structures, structural damping, and fluid characteristics on the dynamic stability for safety dynamic design in industries.

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This paper deals with an experimental study of active feedback control of one dimensional leakage-flow-induced vibration. We proposed the non-contact active feedback control method by flow injection and suction from slits. This control method has two suppression effects, the one is caused by flow control and the other is caused by changing the pressure in the passage. For the flow control at inlet, the vibration is efficiently suppressed when the phase-shift, which is between vibration displacement and flow injection from the slit, is positive. For flow control at the outlet, the vibration is suppressed when the phase-shift is negative. In the case of narrower gap, the vibration is suppressed by the changing the pressure in the passage when the phase-shift is negative. The vibration is effectively suppressed in the case of outlet control with horizontal slit.

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Transonic flow vibrations in a main flow control valve for nuclear and thermal power plants are investigated. In the steam control valve, flow becomes supersonic around the valve head. Shock waves appears and cause flow separations. As a result, serious pressure fluctuations appear. In the present study, experimental and numerical simulations are carried out in order to clarify the cause of a flow induced vibration of the valve head. Unsteady fluid forces are examined with exciting the valve head. Results show that the unsteady fluid force acts as a negative damping force at certain operating conditions and a self-excited oscillation with large amplitude appears.

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In order to prevent the brain blood vessel system disease, recently, arteriosclerosis index of the pulse wave capable of examining the degree of the arteriosclerosis invasively and safely is noticed. This index second derivative of pulse wave with time is called the acceleration pulse wave and is started to use in the clinical feild, however, scientific verification is not yet made. In this study, the usefulness of the acceleration pulse wave is clarified by experiment and numerical simulations based on mathematical modeling.

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In the previous report, the concentrated mass model was proposed to analyze a nonlinear pressure wave phenomenon in a cylindrical straight tube. In this paper, we apply the model to a branch element. To confirm the validity of the proposed branch model, we perform experiments on a sound tube with a branch pipe, compare the experimental results with the numerical results. The numerical computational results agree very well with the experimental results. Therefore, it is concluded that the proposed branch model is valid for the numerical analysis of nonlinear pressure wave problem in a tube with a branch pipe.

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Vibration experiments were performed using an actual mock-up piping by sweep test and steady operations of pump. At a time, numerical simulations for the experiments were performed, and the simulation results were good agreement with the experiment ones. From both the experiment and simulation results, it was shown that the valve opening had much effect on the boundary condition to define the acoustic resonance frequency.

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The acoustic attenuation in the piping taking into consideration the effect of the gas flow was investigated. In this study, the acoustic attenuation by the energy loss due to the friction of the pipe was added to the acoustic attenuation in the static fluid. As a result, acoustic attenuation in the pipe is increased with increasing the gas flow, and the effect of the gas flow to the acoustic attenuation can be well evaluated by this model.

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An air conditioning equipment is usually set in a rail vehicle in order to keep comfortable However the noise is offensive to the ear especially when the rail vehicle is under suspension. Then the noise reduction is very important from the point of view of keeping the car room comfortable and one of the distinguished techniques. This paper describes acoustic and flow noise characteristics of the bending duct The experiments were carried out in various parameters such as the absorbing ability, bending numbers and flow velocities by use of the bending duct As a result it was clarified that the noise reduction effect due to the bending is proportional to the number of times of bending. Moreover the reduction of pressure fosses by use of the guide and the airfoil is very effective to the noise reduction.v

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In the present paper the attention is focused on effect of arrangement of in-line tube banks on acoustic resonance which occurred in the two-dimensional model of boiler. We have examined the characteristics of acoustic resonance generated from in-line tube banks with tube pitch ratio of 1.33, 1.44, 1.56 and 2.0 in the flow direction. As the tube pitch ratio in the flow direction increased, the acoustic resonance of low order mode in the transverse direction was generated, and the resonance onset velocity in the transverse mode was fairly slower than that of small tube pitch ratio. It was easy to generate acoustic resonance of transverse mode as the tube pitch ratio in the flow direction increased.

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Combustion oscillation in burning appliances such as gas turbines and boilers is often appeared as a fluctuation of pressure, flow velocity and heat release and causes damage and performance degradation of apparatus. The lean premix combustion considering recent regulation on NOx emission often brings combustion oscillation. So, it is necessary to find suppression methods of these oscillations. In this study, we express combustion oscillation as one-dimensional phenomena, and analyze pressure and flow velocity fluctuations. By varying parameters such as combustion chamber length, position of reacting zone, preheat temperature and equivalent ratio, the insta- bility conditions are evaluated based on eigenfrequency analysis. Furthermore, the experimental apparatus is set up to investigate combustion oscillation.

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The present study intended that clarification of generating mechanism of blade passing frequency (BPF) noise in wing profile centrifugal blower. First, flow in the vicinity of cut-off in generation source of BPF noise visualized brought out relation between blade passing and flow. Next, probe microphone measured fluctuating pressure source of BPF noise in cut-off surface. Distribution of fluctuating pressure pinpointed major source of BPF noise. Measurement of wind position just as fluctuating pressure brought out relation between blade passing and fluctuating pressure.

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In this study, the authors have investigated how non-structural members in the carbody influence on the rigidity and the vibration characteristics of a commuter type railway vehicle. Additional ceiling frames, instead of the whole "inner ring" sub-structures, which are composed of reinforcing beams on the floor, side and roof structures and evaluated in the previous study, are attached to "Rigidity Test Car", which have been designed and manufactured for above purpose. Excitation tests have been performed, and the results have shown that the proposed ceiling frames have largely affected the natural frequencies, vibration shapes and response accelerations of the carbody, nevertheless of the additional mass of the ceiling frames are much smaller than that of the whole inner ring. It have been verified that the rails for hand straps are also effective to improve the rigidity of the carbody when these are properly attached to the carbody.

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When a railway vehicle overturns in accidents, the shape of cross section of the carbody is likely to be transformed to the parallelogram by the side impact. In the case, the survival space for passengers and crews may be decreased by the deformation. To secure the survival space, the "ring structure" is composed by uniting sub-frames attached inside the carbody as non-structural members together. Empirical tests and FE analyses were performed to verify the possibility of improving the rail carbody strength against the load from the body side.

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This paper deals with transportation using travelling space generated between two resonantly-driven plates, which are excited at an eigenfrequency of fiexural vibration mode. This transportation machine mainly aimed to achieve a feed of particles and fluid. The advantage of this transportation machine is that the energy efficiency, because of the resonance driving. Firstly we theoretically proposed the generation of travelling space between two plates and then the realization method of this theory was proposed. Finally it was experimentally shown that this machine can transport such particles as styrene foam.

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A cleaning system for removing lunar dust from the surfaces of solar panels and optical lenses will be of great use for lunar exploration. Hence, we are developing a cleaning system based on electrostatic force generated by the electrostatic traveling-wave for removing lunar dust. We have developed an electrostatic cleaning plate with transparent ITO (Indium Tin Oxide) electrodes and demonstrated using lunar dust simulant that the decrease in the transmission rate of light is only by several percent by the application of ultrasonic vibrations in a vacuum even if lunar dust was initially charged. Based on these investigations, we have successfully demonstrated the electrostatic cleaning of real lunar dust returned by the Apollo 11 lunar surface mission. Finally, we have carried out a numerical simulation and proven that the performance of the system will improve in the low-gravity environment on the moon.

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This paper presents design method of a spatial filter for suppressing modal observation spill over and the measures of modal observability is introduced as criteria for designing the optimal filter in an engineering sense. In the spatial filter design by using multiple sensors, sensor positions including sensor's position error are obtained by using the measure of modal observability. The workability of the measure of modal observability is investigated by experimental application to a cantilever beam. The validity of the adjusting of optimal sensor position is carried out by the measures of modal observability. Health monitoring of the structure based on the spatial filter is investigated in vibration testing.

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To properly evaluate the tensioning effect for a circular sawblade, it is essential to use the change in natural frequencies of the roll tensioned sawblade. We present a spatial filtering technique called the modal filter to easily measure the natural frequencies for only the modes necessary for the evaluation of the tensioning effect. The information on disk nodal diameters allows to easily design the modal filter for disk. The examples show that the natural frequencies for the modes with nodal diameters 0, 1 and 2 are necessary for the evaluation. In addition, the modal filter designed extracts the three modes necessary separately.

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

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This paper proposes a vibration testing system based on an impulse response excited by a laser ablation. In conventional vibration testing using an impulse hammer, the excitation force hardly includes high frequency element over tens of kilohertz. High power YAG pulse laser is used in this system for producing an ideal impulse force on structural surface. It is possible to measure high frequency FRF (Frequency Response Function) in this system. And water droplet overlay on the metal is used to adjust the force magnitude in laser excitation. The system is validated by comparing an aluminum block's FRFs that are obtained by laser excitation, impulse hammer and FEM.

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A vibro-acoustic coupling system is defined as the coupling between the structural dynamic behavior of a system and its interior acoustical characteristics. This paper focuses on the experimental analysis of coupling systems. The NLS is presented as a reliable tool for identifying modal parameters of a coupling system. The acquired results tell us the reliability of NLS with a coupling system. Recommendations for experimental analysis are also summarized.

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For considering countermeasure of the noise in vehicle cabin, structure-acoustic coupling analysis needs to be conducted. Conventionally, the input identification under operational condition has been the first step to tackle with the problem. However, the input identification is usually time-consuming and needs practical skills. This paper proposes a new sensitivity analysis for the noise reduction under operational condition without using input identification. The structure modification is investigated based on the operational response. The proposed method is applied to the mass-added structure modification. It is confirmed that the noise level decreases as it was predicted based on the proposed approach.

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This paper investigates the application of Statistical Energy Analysis model (SEA model) and Energy Distribution Model (ED model) to a rotary machinery system with subsystems having low modal densities. First, the SEA and ED models are summarized and are compared by using the simple beam structure numerically. It is shown that the ED model can be identified the SEA applicapability to all kinds of systems. Then the complement of a process based on SEA model for solving structure-borne sound problems on machinery is expanded by replacing the SEA model to the ED model. The process based on ED model is discussed to be applied to the rotary machinery.

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This paper presents a method for identifying the input power to structure in machine operation using experimental SEA. The basis of the method is that the vibrational energies of the respective subsystems during working can be measured using the velocimeter or accelerometer at the same measuring positions of constructing the SEA model. The accuracy of the identified input power is investigated through the use of the sensitivity of the input power with respect to the change of loss factors and energy for subsystem. This method is applied to two kinds of different structures. One is a simple plate structure composed of two subdivisions for impulsive testing. Another is a complicated structure composed of eight subdivisions for steady state testing. The estimated results show that the method has excellent performance to identify the input power during working.

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The new input identification method of Apparent-Mass Method was proposed by the authors in D&D2008. The proposed method utilizes apparent-mass matrix in order to avoid accelerance matrix inversion, and the apparent-mass matrix is calculated by minimizing measurement error included in excitation force signals. In this paper, variance estimation methodology for identified force is proposed. The random noise included in the excitation force and operational measurement induces variation in the identified force. Then the validity of proposed method is confirmed using numerical simulation and excitation test.

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This paper deals with strength design and motional analysis of a machine structure by 3D Computer Aided Design (3DCAD) and Computer Aided Engineering (CAE). Cost, rigidity, etc. are raised as a point that should be taken into consideration in designing a machine structure. Holding down productive energy and cost low relates to earth environment in that resources are utilized effectively. This research examines the improved model using 3DCAD and motional analysis.

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Transfer Path Analysis (TPA) is a key technology for solving the noise and vibration problems. Identification of excitation force is an essential part in TPA. For the identification of input force, Direct measurement, Mount Stiffness method and Matrix Inversion Method are commonly used. Recently, as a faster and easier approach, Operational Path Analysis (OPA) has been proposed. Firstly, this paper examines advantages and disadvantages of each TPA method. Secondly, we propose a new TPA method using Principal Component Analysis (PCA). This method does not obtain contributions of excitation points but contributions of excitation areas. The proposed method is superior to traditional method at its accuracy where the method obtains PCA Virtual Force and PCA Transfer Function.

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