Vibration characteristics are determined for a previously unsolved class of problems, that of in-plane vibration of rectangular plates with mixed boundary conditions. The edges are partially clamped and other parts are free or simply supported. The solution procedure uses Ritz method with algebraic polynomial functions with boundary index to allow any sets of four different, in-plane boundary conditions. Partial clamp is approximated by applying partial elastic springs with high stiffness distributed along edges. Convergence studies are made, and accurate frequencies are presented for six various examples. The results are compared with FEM solutions, and good agreement is obtained.

In this research, the authors developed a simple health monitoring method by analyzing the frequency response of the observed structure using deep learning. The purpose of the developed method in this research is to estimate the presence or position of a loosened bolt from the vibration response where the loosened bolt is assumed as a defect. The test specimen with different bolt fastening states is excited using an impulse hammer and the frequency response is acquired using an acceleration sensor. The fastening state of the bolt is predicted by analyzing measured frequency response functions. Two kinds of methods are employed, a normal deep neural network and a convolutional neural network, to analyze the frequency response. In each method, some numbers of hidden layers, optimization algorithms, and activation functions are tested, and the accuracy is compared. As a result, the maximum accuracy of 98.7% is obtained. This demonstrate the applicability of deep learnings of frequency responses to the structural health monitoring.

An aboveground oil storage tank with fixed roof explodes when flammable vapor inside is ignited for some reason. All fixed roof tanks are designed as a frangible roof joint in which the sidewall-to-roof joint is ruptured before the sidewall-to-bottom joint is ruptured under over pressurization. API Standard 650 is the code for the frangible roof joint design. However the large number of explosion incidents have showed that API design method does not work for small diameter tanks. Buckling of both joints of the tank with fixed roof may occur under internal pressure, and is a bifurcation buckling with many circumferential wave numbers. The sidewall-to-bottom joint may uplift from the foundation under internal pressure even when liquid pressure is applied, and stresses in this joint may reach elastic-plastic state. In this study, an elastic-plastic bifurcation buckling analysis under internal pressure is carried out for the small diameter fixed roof tanks using the axisymmetric shell finite element method. This study clarifies which joint buckles depending on the liquid level.

A deployable membrane structure has been attractive attention to realize an ultra-lightweight structure in space. However, since the membrane is a flexible structure component, vibration easily occurs due to an external force such as an impulse force right after deployment. A membrane vibration affects operation function of the structure. Thus, it is important to understand its nonlinear membrane vibration behavior to improve the reliability of membrane structure. In this study, a full-field surface shape measurement system using grating projection method was newly constructed in order to capture a nonlinear membrane behavior with high-spatial resolution. Through the surface shape measurement of the vibration behaviors of the deployable membrane model, the effectiveness of the constructed measurement system is introduced for measuring the flexible membrane vibration behavior.

Our previous research found that CFRPs fabricated by the electrodeposition resin molding (ERM) method exhibited high damping properties. In this research, tailored fiber placement (TFP) was used to make curved fiber shapes, however, those shapes were limited to a parabola and a sine curve. Linear combination of radial basis functions (RBFs) were used to make more complex fiber shapes, and optimum fiber shapes are investigated to improve damping of CFRPs fabricated by the ERM method. Damping is modeled by the specific damping capacity (SDC) which is defined as the ratio of dissipated energy and maximum strain energy, and total damping properties of CFRPs are calculated using finite element analysis (FEA). Before optimization, material SDCs of a plain weave sheet and a TFP layer, which are compositions of CFRPs, are identified by particle swarm optimization (PSO) using the results of experimental modal analysis and FEA. Then, fiber shapes were optimized to maximize the first modal SDC of L-shaped and T-shaped plates using PSO with nonlinear dissipative term. Simultaneously, the thickness distribution which is caused by overlaps or gaps between curved fibers was estimated and applied to a finite element model for more accurate numerical estimation. The results showed that the present optimization of curved fiber shapes including estimation of thickness distribution improves the first modal SDC and decreases the volume of a TFP layer in comparison with unidirectional fiber shapes.

In this research, topology optimization is performed for each purpose on a simple 3D shape in order to find the optimal camera structure in terms of structural strength and natural frequency. When performing topology optimization, we investigate how the optimum structure changes by changing the optimization conditions, and what difference there is in the evaluation of the optimum structure. As a result, in the structural strength optimization, a trade-off relationship is confirmed when the weighting conditions are changed under multiple load conditions. In multi-objective optimization of structural strength and natural frequency, even if weighting is changed significantly and topology optimization is performed, there is no significant difference in evaluation values and there is no trade-off relationship. Further, it can be seen that the structural strength is not improved.

The purpose of this study is to improve the identification method of material properties using vibration characteristics of CFRP thin plate. This identification method selects five material properties by matching vibration modes and natural frequencies obtained from forced vibration experiment and analysis by Ritz method. In order to match vibration modes and natural frequencies, differential evolution method (DE) optimizes five material properties at the same time. Then an evaluation function is used to evaluate the matching degree between experimental results and analysis results. This optimization is repeated until terminal criteria is satisfied, and the individual with the highest matching degree is selected as identification result. In the previous study, identification results were unstable because of the inaccuracy of the evaluation function. Therefore, in this study, a new evaluation function was developed, and its accuracy was verified. In the identification using test pieces which have many aspect ratios and fiber orientation angles, material properties of simulation data are perfectly identified at almost all of the test pieces. As a result, it has been revealed that optimization method using new evaluation function is accurate and wide test pieces are suitable for identification.

Free vibration characteristics of the CFRTP rectangular plate printed by 3D-printer is studied in this paper. A CFRTP composite rectangular plate has been printed by a 3D-printer such as the Mark-Forged Mark Two printer. The vibration characteristics are measured by impulse vibration test, and then experimental modal analysis detects the natural frequencies, modal dumping ratios and natural vibration mode shapes. The numerical analysis is also carried out by using a commercial FEA software, ANSYS, to check the vibration characteristics of the plate obtained experimentally by impulsive vibration test.

Resent 3D printer can make a CFRTP (Carbon Fiber Reinforced Thermo Plastics) plate with continuous fiber reinforcement. The 3D printed CFRTP plate has various vibration modes depended on its anisotropy characteristic by carbon fiber direction. This paper deals with visualization of vibration mode and make a FEM model of 3D printed CFRTP plate to calculate the vibration mode. The time averaged digital holographic interferometry can visualize vibration modes of the plate on resonance situation. This method can visualize also high order mode of the plate. The FEM model of the 3D printed CFRTP plate is made used anisotropic elements with orientation angles same with fiber direction. The bended fiber part located at the plate diagonal is modeled 45deg direction elements. This FEM model can indicate almost same vibration mode with experimental results at some modal orders. But the result has indicated different natural frequencies with the experimental results.

Carbon fiber reinforced plastic’s performance is clearly different depending on the orientation type of the reinforcing fiber. Composite materials oriented from conventional straight lines are now widely used, but they are not optimal in situations where fiber damage or stress concentration occurs due to drilling. Therefore, attention has be attracted to the design of variable-stiffness composite structures that have been made by changing the orientation and volume fraction of reinforcing fibers in a curved line, which can be realized with continuous fiber reinforcing 3D printers. In this study, we propose a modeling and design proposal for variable-stiffness fiber reinforced composites with spline curved orientation and volume fraction of fibers as design variables.

The stick-slip vibration of violin string was formulated by using natural vibration functions. Stick mode is assumed to be velocity excitation condition at one end of the string, and slip mode is assumed to be Coulomb friction force excitation at the touching point of the bow. Stick and slip mode switches each other if shear force of the string at touching point is over static friction force. Displacement and velocity over string is taken over as the initial conditions when vibration mode switches. Present method is compared with CA method (Cellular Automaton method) with good agreement.

In the case of an automotive disk brake, squeal called in-plane squeal may be generated in which the disk vibrates in the in-plane direction. The disk has a structure called a hat and has a thin-walled cylindrical shape for supporting the friction portion. We consider that the hat has a natural vibration that vibrates in the plane and out of plane simultaneously, which leads to in-plane squeal. In this research, it is shown that in-plane squeal is reduced in a disk with a structure that retains the element that causes in-plane squeal as in the actual machine, in which only the in-plane and out-of-plane amplitude ratio of the natural vibration is changed from a specific ratio. First, in order to fabricate a squealing research disk that makes it easier to control the natural vibration by removing the vane part from the actual machine, the natural vibration mode is examined by finite element analysis of the disk and measurement of the all-round mode by impact vibration test. The squeal vibration mode is measured by a squeal test, and the relationship between the disk natural vibration and the squeal is clarified. Next, we considered that the in-plane and out-of-plane amplitude ratio of the natural vibration of the disk is important for the generation of in-plane squeal, and designed the disk by paying attention to the in-plane and out-of-plane amplitude ratio of the vibration mode, and tried to reduce the in-plane squeal. Finally, the noise reduction effect of the manufactured disk is measured by a noise test.

In fixing process of an image forming apparatus such as a printer fuser unit, the toner is fixed to a paper by heat and pressure. The printer fuser unit comprises a fixing sleeve, a heat source, a pressure roller including an elastic layer, and a pad. When a paper with toner passes through between the sleeve and the pressure roller, the toners are fused and fixed to the paper. The sleeve rotates following the pressure roller driven by a motor and is pressed against the roller through the pad in order to form a nip area which means a distributed contact area between the sleeve and the roller. The pad and the inner surface of the sleeve are in sliding contact via a sliding sheet impregnated with a lubricant. In some operational conditions, uncomfortable noise can occur by friction between the sleeve and the sliding sheet attached to the pad. The purpose of this study is to clarify the generation mechanism of friction-induced vibration and propose countermeasures against noise based on generation mechanism of friction-induced vibration. The present study investigates the relationship between the tendency of noise occurring and friction characteristics of the sliding part, the effect of the rotational direction on noise, and the actual operating vibration of the fixing sleeve and the pressure roller during noise generation. As a result, we identified that friction-induced vibration is caused by dry friction. Furthermore, we estimated the main vibration source by measuring the actual vibration of each member and the effect of damping. We also identified factors that affect the noise frequency. Finally, we proposed countermeasures against noise based on the generation mechanism of frictioninduced vibration generated in the printer fuser unit.

Long term efforts have been poured to the dynamics of a spring supported pipe conveying fluid. One of the reasons why this problem attracts the interest of many researchers is that this system shows the doubly degeneracy, pitchfork and Hopf bifurcations. At the point of double degeneracy, the buckling and the self-excited vibration in a certain mode occur simultaneously. It can be considered that such instability is widely existed in the non-self-adjoint systems. Up-standing pipe is typical example of such systems. In this study, we investigate the unstable phenomena of an up-standing pipe conveying fluid. First, we theoretically investigate the linear stability of an up-standing pipe conveying fluid. In case the gravitational force acting on the pipe becomes so large that it can overcome the flexural restoring forces, the first instability of this system is buckling in the first mode. When the flow velocity is over a certain value, the first mode gains the stability. As the flow velocity increases further, the self-excited vibration in a certain mode can be produced. Second, we conducted the experiments to confirm the steady state of the system. In particular, we conducted three dimensional quantitative measurements of the pipe motions. We observed some interesting motions.

Passive dynamic walking is a gait on a shallow slope without active control. The walking cycle is generated by the dynamics and action of gravity only. A natural motion like a human walking and high efficiency are its merits. Passive dynamic walking is considered as a kind of self-excited vibration in which continuous motion governed by a nonlinear equation of motion and impact motion at switching of legs are repeated alternately. Many kinds of nonlinear phenomena are observed in this walk. In this paper, we propose an analysis model of straight-legged biped passive walker considering the motion of upper body in sagittal plane. Also, the steady state solution is investigated numerically.

In end milling, chatter vibration generated during processing becomes a problem in processing accuracy. Chatter vibration is classified into forced chatter and self-excited chatter depending on the cause of the vibration. The chatter vibration phenomenon in end milling is modeled as a forced self-excited system considering the time delay. Steady-state solutions and its stability are essential for the analysis of this kind of vibration phenomenon, but analysis methods have not been established. In this study, the harmonic balance method was applied to the analysis of the steady vibration solution and stability of the forced self-excited system considering the time delay in the equal pitch end mill. Furthermore, the validity of the calculation results was verified by comparing the harmonic balance method and numerical simulation

Pattern formation phenomena in contact rotating systems are caused by self-excited vibrations due to time-delay characteristics of the system. Since the ranges of rotational speed where the self-excited vibration occurs are close to those where resonance occurs due to unevenness of the roll surface or nonlinearity, it is difficult to determine in practical situations whether the self-excited vibration occurs or not, especially when its amplitude is small and the frequency resolution is low. One possible approach is to use the time-varying phase difference between the self-excited vibration and the roll rotation that is observed when frequency analyses are conducted with a low frequency resolution. This paper derives an analytical expression describing the relationship between the temporal variation of the phase difference and the actual frequency difference for two signals with close frequencies, verifying its effectiveness both theoretically and experimentally.

This paper describes chatter vibration generated in a thin rectangular plate at end milling. When end milling the thin rectangular plate, the end mill does not vibrate, and chatter vibration is generated in which the rectangular plate deforms in the out-of-plane direction. The frequency of chatter vibration generated is low near the edge of the rectangular plate and high near the center of the rectangular plate. The vibration mode of chatter vibration when the tool position is near the edge of the rectangular plate is the antiphase mode with the tool position as a node. The vibration mode of chatter vibration when the tool position is near the center of the rectangular plate is the in-phase mode in which both ends of the rectangular plate vibrate in the same phase. The frequency and vibration mode of this chatter vibration agree with the

An author proposed a new identification method of linear 1-dof system using Gaussian random vibration response in a previous study. However, there is a problem that conventional research in terms of experimental validation. In this paper, we conducted the experimental study of our propose identification method. At first, the single degree-of-freedom system is fabricated using the concentration mass and compression coil spring. Moreover, experimental modal analysis is conducted in order to obtain the eigen frequency and quality factor. Furthermore, noise source in order to realize the white noise excitation is established using vibration speaker. Gaussian characteristics of excitation source is confirmed using Kolmogorov-Smirnov test. The stochastic displacement response is obtained using the above experimental setup (i.e. white noise excitation source and single degree-of-freedom system). As the result, the response distribution contains the unnecessary noise response. In order to eliminate the unnecessary response, band-pass filter is applied the observed displacement signal. Furthermore, identification experiment of un-known parameter (i.e. spring constant, ratio between diffusion coefficient and damping constant and eigen frequency, and so on) is conducted based on propose algorithm. As the result, the estimate operation of propose identification method is confirmed. Furthermore, the estimation values using the filtered displacement data were good agreement with the results using the experimental modal analysis.

In the previous study, the stationary and transient response distribution of a linear system subjected to non-Gaussian random excitation with a symmetric probability distribution was investigated. It was revealed that the response distribution is strongly dependent upon the bandwidth of the power spectrum of the non-Gaussian excitation. Furthermore, it was also found that in the transient response distribution, some characteristics not observed in the stationary one exist. On the other hand, in real engineering fields, there are many excitations with an asymmetric distribution such as road roughness and shallow water wave. Therefore, in this research, in the case of non-Gaussian random excitation with an asymmetric probability distribution, the transient response distribution and moment are examined by using Monte Carlo Simulation. As the probability distributions of non-Gaussian excitations, gamma and lognormal distributions are adopted because the shape of these distributions is much different from a Gaussian distribution and is also different from each other. For these excitation distributions, the characteristics of the response distribution are examined. In addition, we observe variance,skewness and kurtosis of the response to investigate the time variation of the response distribution in more detail.

There are three typical criteria for design of dynamic vibration absorbers (DVAs): the H_¥ optimization, H₂ optimization,and stability maximization criteria. When single-mass, parallel-type double-mass, and series-type double-mass DVAs are optimized using these criteria, it has already been clarified that the effect of vibration suppression by the DVAs improves in the listed order. More specifically, if the vibration suppression performance of the parallel-type double-mass DVA is evaluated based on the H_¥ and H₂ optimization criteria, then it will be midway between the performances of the singlemass and series-type double-mass DVAs. However, if performance is evaluated by the stability criterion, that of the parallel-type double-mass DVA is only slightly improved relative to the single-mass DVA. Because the stability criterion for DVAs is a criterion for searching for the condition under which the characteristic equation of the vibratory system takes a repeated root, the characteristic root trajectories for the parallel-type double-mass DVA are compared with those for the series-type DVA in this paper.

This paper investigates the vibration control of a structure using a roller-type vibration absorber (RVA) with a rolling elliptic surface. The RVA is attached to the structure which is modeled as a single-degree-of-freedom system, subjected to harmonic excitation. The equations of motion of the structure with the RVA are derived, and they include nonlinear terms of the inertia and restoring moment. Frequency response curves are theoretically determined. The natural frequency of the RVA with a rolling elliptic surface depends on the radius of a roller and the lengths of horizontal and vertical axes of the rolling elliptic surface. Therefore, there exist some pairs of the lengths of the horizontal and vertical axes of the rolling elliptic surface in such a manner that the tuning condition holds, that is, p₀ = p₁ , where p₀ and p₁ are the natural frequencies of the structure and the RVA, respectively. The influences of the shape of the rolling surface on vibration suppression by the RVA are investigated. It is shown that the RVA with a laterally-long rolling elliptic surface is more effective for suppression of the resonance peaks than that with a vertically-long rolling elliptic surface.

In the latest trend in engine technology, high-power engines and low cylinder engines are widely used. These engines contribute to strong torsional vibration due to engine combustion within the powertrain systems. On the other hand, automatic transmission (AT) is required to use a lock-up clutch system which links engine and gear train directly from vibration low engine rotation speed. Lock-up damper, torsional spring in torque converter, is not enough to absorb the torsional vibration .Therefore, the centrifugal pendulum vibration absorber(CPVA)is developed to suppress the torsional vibration .The natural frequency of CPVA is proportional to engine rotation speed. Then it is expected to suppress torsional vibration in wide range of the engine rotation speed .However, the natural frequency of the CPVA varies due to the nonlinear when the vibration amplitude of CPVA is large. There is a space limitation problem to install larger size of CPVA to suppress the strong torsional vibration. To overcome these problem, a new centrifugal pendulum type dynamic vibration absorber with slider crank chain is invented. In this study, the optimal design for the centrifugal pendulum type dynamic vibration absorber with slider crank chain is discussed.

The dynamic absorber must have the desired natural frequency which is determined by the condition of vibration suppression. For example, the Frahm damper has the natural frequency which is just same as the target frequency for vibration suppression. For two DOF system, we have shown that there are two combination of the parameters for specified natural frequencies. In the vibration theory of MDOF system, natural frequency and modal vector are a set and inseparable. Then, there is the question whether modal vector determines the parameters of two DOF system. In this study, we pick up mass ratio and stiffness ratio as parameters of two DOF system. and examine the relationship between these parameters and their modal vectors. It is shown that each of the mass ratio and the stiffness ratio mainly affects the second and the first modal vector, respectively. The transition of natural frequencies by the mass ratio and the stiffness ratio is also considered. Moreover, the mass ratio and the stiffness ratio from modal vectors are successfully derived. The modal vectors affect the mass ratio and the stiffness ratio in the almost similar way. In addition, the relationship between the modal vectors and natural frequencies are almost same as the mass ratio and the stiffness ratio.

This study aims at applying linear quadratic regulator (LQR) theory to control a vibratory system modelled by a fractional-order differential equation. First, an iteration-based method for solving the algebraic Riccati equation is proposed to obtain a fractional-order LQR. Next, Newmark-𝛽method is modified to be able to simulate a fractional-order differential equation. Finally, as an example, a vibration control problem is considered for a generalized Voigt model. Numerical calculations demonstrate that the Fractional-order LQR control can suppress vibrations occurring in the vibratory system with viscoelastic damping.

The particle damper has a simple structure and can be applied in special environments, and its use in various fields such as railway vehicles is considered. The particle damper is a damper that uses the kinetic energy of particles and consumes the energy by collision or friction energy between a vibrating body and particles. Particle dampers are extremely simple and inexpensive, and unlike general viscous damping and active dampers, they have the advantages that they do not age, do not require maintenance, and do not depend on temperature. Currently, it is used in tennis rackets, shockless hammers, main engines of space shuttles, etc., but it is not many cases in industries. There have been many examples of studies on particle dampers, but many studies have focused on vibrations of 100 Hz or less, and many studies have focused on particles with a particle size exceeding 1 mm. The cast iron powder treated in this study has a particle size much smaller than the particle dampers used so far, and it is currently used in high-grade audio racks, and its damping effect is very excellent, but its damping mechanism is unsolved. In this study, we conducted a test on a high grade audio rack and a speaker stand in which cast iron powder was enclosed, and vibration characteristics of cast iron powder are clarified by comparing vibration characteristics with those of steel balls.

In the situation where the crane operator population is decreasing, development of techniques for efficient crane operations is desired. One of the means to make them efficient is the automation, where the challenge is how to suppress the residual vibration. In order to deal with this problem, the authors proposed a new type of open-loop control method for suppressing the residual vibration by eliminating natural frequency component. This method is based on the fact that residual vibration is completely suppressed in a linear undamped system excited by an external force that does not contain the natural frequency component of the system. This paper applies the method to the control of a rotary crane model consisting of an arm which rotates in the turning and the derricking directions, and a cargo suspended from the arm. In order to examine the effectiveness of the proposed method, numerical simulations are conducted for three cases of crane operations. The results show that the proposed method is able to move the arm to the target position, preventing the residual vibration of cargo in all cases considered.

Vocal cord vibration is self-excited vibration due to the interaction between structure and fluid. So far, several models have been proposed as analytical models for vocal cord vibration that represent the vocal cord by mass-spring systems. However, these models have a problem that it is difficult to determine the parameters of the analytical model (mass, spring constant, etc.). There are also studies that analyze vocal cord vibration using the Finite Element Method (FEM) or the Finite Volume Method (FVM), etc. However, large-scale Fluid-Structure Interaction (FSI) analysis has a problem of high computational cost. In order to solve these problems, we propose a vocal cord analysis model using modal analysis. Modes of the vocal cord are obtained by FEM, and vocal cord motion is represented as a superposition of modes. Fluid analysis is performed by one-dimensional Bernoulli's equation. The vocal cord vibration is calculated by coupling the vocal cord motion model and the fluid calculation model. In this method, since the mode obtained from structural analysis is used, analysis based on actual physical properties can be performed. The mode equation is a superposition of onedegree-of-freedom equations, and the fluid equation is a one-dimensional equation, therefore the calculation cost is low. The validation of the proposed method is performed by comparing the proposed method with ANSYS and the experiment. Moreover, the self-excited vibration condition of the vocal cords is mathematically derived. By applying the shooting method to the proposed method, the change of self-excited vibration due to the difference of conditions is examined.

This paper proposes the method that obtain a reduced-order model using sampled data. The outline of the method is as follows. First, after coordinate transformation from the displacement coordinate system to the modal coordinate system,the sample data is projected onto the space that the 1st mode is excluded. Next, the proper orthogonal decomposition (POD) is applied to the projected data to obtain the POMs in the space that the 1st mode is excluded. The obtained POMs are expanded to the whole mode space and the correction bases are obtained by transforming the coordinate to the displacement coordinate system. Finally, a reduced-order model is obtained by using the 1st mode and the correction bases. The results are as follows: 1) This paper proposed the method for simultaneously obtaining the correction bases for obtaining a reduced-order model using sample data of the solution space. 2) At least in the calculation example of this paper, it is shown that the obtained reduced-order model has sufficient accuracy. 3) The relationship between the characteristics of the sample data and the accuracy (applicability range) of the reduced-order model is a future subject.

Recently, washing machines are demanded to reduce noise and vibration due to the changes of lifestyle such as the number of people who both work increased and other various reasons that the laundry can only be washed at night. To avoid serious troubles by noise in the neighborhood, especially the vibration in dehydration process in a washing machine has to be reduced. Vibration and noise of a washing machine are caused by unbalanced mass of clothes being washed on one side in the washing tub. To resolve this problem, it is important to research vibration characteristics of washing machine. Therefore, the purpose in this paper is to create the vibration analysis model of a tilted type washing machine considering the influence of fluid balancer. The mechanism of the balancer is that the working fluid in the balancer is automatically moved to a position against the unbalanced mass during drying process (high speed rotation) to cancel the unbalanced load. In this model, the fluid inside the fluid balancer is expressed as 36 balls with 6 baffle boards. These baffle boards are installed to prevent the fluid from being too biased to one side. This model is created by using ADAMS. First, verification is performed with an eccentric load of 300g. After that, the model is tested at an eccentric load of 500g to verify whether the model is effective under other conditions. As a result, it was found that this model is effective at certain eccentric loads and rotational speeds.

Expanding degrees of freedom in vibration systems is an effective way to improve the power generation efficiency of energy-harvesting devices from the vibrating source, since the system becomes responsive for a wide frequency range due to the appearance of multiple resonant peaks. A magnetostrictive-type vibration energy harvester that uses an irongallium alloy (Galfenol) has received much attention in recent years. This energy harvesting technology has advantages over conventional types with respect to the compactness and efficiency, and it is extremely robust and has low electrical impedance. In this study, the differential evolution (DE), known as a kind of global optimization techniques, was introduced for the parameter design of the harvester that comprised a primary structure with an extended two-degrees-offreedom substructure connected to the end. Using DE, we numerically explored the best combination of the mass and dimension of the extended part that minimized the difference between the dominant frequency components in ambient vibration and the natural frequencies of the generator. The proposed design was found to improve the device's electric power generation efficiency.

This paper describes the wind wave energy harvesting using a rigid pendulum and a DC motor. Many types of energy harvesting techniques have been studied thus far. These methods extract vibration energy as electrical energy through electromechanical transducers. In this research, a DC motor was used as an electromechanical transducer. In previous studies on the wind wave energy harvesting using a rigid pendulum and a DC motor, the amount of generated power has been evaluated experimentally and the optimum values of the electrical circuit that maximizes the amount of power generation has not been theoretically derived. On the other hand, in energy harvesting using electromagnetic induction, the optimum values of the device have been derived; however, the effect of the characteristic impedance of water has not been considered. Therefore, we obtained the optimum values of the device considering the effect of the characteristic impedance of water. We derived the optimum values in two cases: one is the case where the frequency of the wind wave is constant, and the other is the case of random excitation. The power consumption of the resistor was regarded as the harvested energy in this research. The optimum values of the resistive circuit that maximizes the amount of the harvested energy were derived in two cases, and the effectiveness was verified through simulations and experiments.

The superharmonic resonance of a cantilever beam subject to mechanical ball impacts is investigated numerically for potential vibration energy harvesting. In our device, a multipole magnet array attached on the cantilever moves above a planar coil array fixed on the baseplate of the device, leading to power generation through electromagnetic induction. In the numerical model, the cantilever is assumed to be a single DOF damped mass-spring system, which is coupled with the translational motion of a point mass through the classical collision model. The Fourier amplitudes of the cantilever’s displacement have been obtained and compared with the experimental results. It is found that the numerical solution of the superharmonic components shows quantitative agreement with the experiment in the low-frequency range associated with human-induced motions. The excitation region of the superharmonics has been represented as a function of the excitation frequency and the gap distance of the ball motion.

An audible warning device (AWD) is a device which generates sound by impact vibrations. The behavior of AWD is a kind of self-inducted vibration in which the suction behavior in AWD depends on its own motion. In specific conditions, period doubling bifurcation occurs and behavior of AWD becomes unstable. Therefore, the bifurcation behavior is investigated by a simple model. We introduced an analytical model which consists of two rigid bodies for a shaft and a pole, two beams for a stay and a sub stay, a diaphragm, and an annular plate for a resonator. The pole and the shaft are accompanied by impacts, and suction force between the pole and the shaft is modeled as a ramp function which starts to increase from zero-value at the time of an impact to those at the next impact. Fixed points of the map and their stabilities are numerically calculated, and arc-length continuation method is used to obtain those. It was found that curve veering is occurred between the two natural vibration modes when length of the sub stay is sufficiently long. Furthermore, the result of bifurcation diagrams has shown that the region of period-1 stable response, which corresponding to the normal condition, becomes narrower when the length of sub stay approaches to the length at which curve veering occurs.

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 mechanical energy of the small variation increases with the low frequency vibration. An analysis is also made on the relationship between the time-phase-averaged and the phase-averaged mechanical energy of the small variation, which demonstrates that the phase-averaged one is usable for evaluating the development of the low frequency vibration. 九州大学 Kyushu University

The occurrence of the low frequency vibration in vibroimpact systems such as vibrating sieve reduces the reliability f the system and precludes normal operation when its amplitude is excessive. In order to establish guidelines to suppress e low frequency vibration, this paper derives analytical expressions for optimal parameter values of a dynamic absorber or a free vibration model and compares them with numerically obtained optimal parameter values of a dynamic absorber or the vibroimpact system. The results demonstrate that the two sets of optimal values are close to each other, which uggests the effectiveness of the design of a dynamic absorber to suppress the low frequency vibration through the optimal esign for the free vibration model.

A railway current collection system mainly consists of a pantograph and a conductor line. Pantograph in a railway current collection system sometimes separates from the conductor line. This phenomenon is called contact loss. At the contact loss, the contact force is lost. Contact loss is not desirable from the view points of operation and maintenance. It has been reported that the contact loss occurred in a rigid conductor line system. The contact loss in this system is well modeled as an impact oscillation between a mass-spring system and a vibrating plate. In the previous study, we investigated the effects of an additional mass on the impact oscillations between a single degree of mass-spring system and a sinusoidal vibrating plate. When the excitation frequency of the vibrating plate is near the natural frequency of the second mode, the system shows the strong suppression effects on the impact oscillation. Therefore, the additional mass and the semi-active control of the spring stiffness can prevent the occurrence of the impact oscillations. In this study, we propose the two degrees of freedom mass-spring system. In particular, we conducted the experiments to confirm the suppression of impact oscillations and verify the theoretical predictions.

When self-synchronization occurs in a system where multiple nonlinear self-excited oscillators with different natural frequencies are coupled, all oscillators vibrate at one specific frequency due to their interaction. While many researchers have examined characteristics of this phenomenon, the mechanism has not been completely clarified. In order to obtain new comprehensions into the occurrence mechanism, this paper considers a system consisting of two DC motors, and analyzes the energy condition necessary for synchronization, for the two cases of 4 DOF and 3 DOF model. It is seen that the derived condition is able to predict the range of synchronized frequency and the applied voltage where synchronization occurs, providing a better understanding of the effect of DOF on synchronization from the energetic point of view.

This paper deals with the entrainment phenomenon by forced displacement excitation in vortex induced vibration of structures. This phenomenon can occur when a long-period earthquake occurs in a super high-rise structure that may have vortex induced vibration and can occur also when an offshore floating wind turbine is affected by wind and swell simultaneously. Moreover, it is important to examine this phenomenon from the viewpoint of the multi-degree-of- freedom forced self-excited system. By the experiment using wind tunnel and the numerical analysis using shooting method and ordinally numerical integration, following was made clear: (1) Entrainment phenomenon was confirmed in the excitation frequency region including the natural frequency of the cylinder. (2) The entrainment region is wider at the higher wind speed than at the wind speed with the largest amplitude by vortex excitation. (3) Regarding the resonance amplitude in entrainment region, its amplitude is slightly larger at the higher wind speed than that at the wind speed when the amplitude by the vortex excitation is the largest. (4) The largest vibration amplitude at entrainment is a value almost close to the sum of the largest amplitude at the time of only the vortex excitation and that at the time of only the forced displacement excitation. (5) The experimental results and the numerical analysis results were almost qualitatively consistent.

In this paper, we deal with the vibration control problem by a Hula-Hoop in a two-degree-of-freedom system that is an example of a multi-degree-of-freedom system. The vibration control effect was investigated by changing the installation position of the Hula-Hoop, the mass point to be controlled, and the effective frequency range. From the numerical integration of the equations of motion and the experiments, the following was found. (1) By installing the Hula- Hoop in the lower structure, it is possible to suppress the entire system in the frequency region from the first resonance point to the anti-resonance point and in the frequency region higher than the second resonance point. (2) When the Hula-Hoop is installed in the upper structure, only one of the lower structure and the upper one can be controlled in the same frequency ranges mentioned above. (3) The conditions for optimal vibration control using the Hula-Hoop in a two-degree-of-freedom system are clarified. (4) The characteristics of the solutions obtained by the numerical integration method coincide qualitatively with those of the results obtained by the experiment.

When a structure with a movable additional mass is periodically excited, the additional mass moves due to the vibration of the structure. As a result, the system can resonate by changing the natural frequency of a certain natural vibration mode including the added mass so that it approaches the excitation frequency. This phenomenon, called passive self-tuning resonance, is expected to be applied to the field of energy harvesting by vibration in terms of broadening the resonance frequency of the system. In this study, a simple system consisting of a beam and a slider was used to observe the dynamic behavior of the system by experiments and its characteristics were investigated. Experimental results show that, once the slider moves toward the antinode of one vibration mode of the system, and that mode resonates, the dominant mode eventually switches to another mode, and the slider moves to the antinode of that mode, and this series of movements is repeated. Numerical integration based on theoretical study gives results similar to the above experimental results, showing nonlinear coupling between the slider and the beam's multiple vibration modes.

In our previous study, stiffness proportional damping is used, and the nonlinear characteristics appears only near the first resonance frequency. To investigate nonlinear property of higher order mode, mass proportional damping is considered because the modal damping coefficients decrease as mode order increases. In this paper, we use two combinations of the stiffnesses. These combinations of the stiffnesses have same natural frequencies, but differ in the localization of linear modal vectors. Frequency response curves are calculated by harmonic balance method. Numerical results show that the nonlinear characteristics appears only near the second resonance frequency in both combinations of stiffnesses. But there is difference in the ratios of the peak values of amplitudes of first and second resonance for two combinations of stiffnesses. The system with localized modal vectors has larger ratio of peak values of amplitudes than the system with un-localized ones. In addition, modal coordinates are calculated by multiplying the displacements by linear modal vectors. Although the modal vectors are calculated for the corresponding linear system, the modal coordinates can mostly decouple first and second modes. Frequency response curves of the modal coordinate for two combinations of stiffness system become almost same.

Many phenomena existing in mechanical structures have nonlinear characteristics such as play and friction, the response characteristic of the vibration system subjected to random input is a socalled non-gaussian random process. For the handling of these data, it is essential to apply statistical methods and analyze using higher-order statistics considering non-gaussian. The purpose of this research is to apply statistical method in higher-order frequency response analysis in asymmetric nonlinear vibration system using higher-order spectra and present the effectiveness of this method. In this report, following the previous report, we understood the vibration characteristics by modifying the restoring force characteristics and damping characteristics of the magnetic spring model. In addition, we carried out experimental analysis and numerical simulation , and applied cross-bispectral analysis to understand the mutual transfer characteristics of nonlinear systems considering input and output. The subharmonic and higher harmonic vibrations caused by the nonlinear vibration characteristics were evaluated and the effectiveness of this method was examined.

Continuing from the previous report, we focus on the “continuously differentiable damping model” proposed by Makkar et al. Focusing on the symmetric nonlinear characteristics, we performed a numerical simulation analysis of trispectrum, which is one of the higher-order spectral analyses, and supplemented it. As for the identification method, the identification method using UKF, which is one of the nonlinear Kalman filters, was used. It was shown that it is possible to estimate the coefficient based on this modeling by performing simultaneous estimation of displacement, velocity and damping coefficient.

Elastic wave propagation caused by a plane motion of a uniform beam is theoretically investigated. The vibration in a transverse direction of the beam induces a dispersion effect of waves. In this paper, we focus on a geometrical nonlinearity as the finite deformation, the equation of motion based on the special Cosserrat theory is utilized. For simplicity, the shear strain, body force, and damping are ignored. From the approximation up to the third order of approximation of the displacement in a reductive perturbation method, the Korteweg–de Vries (KdV) equation for a long wave and the nonlinear Schrödinger (NLS) equation for a slowly varying envelope wave of the quasi-monochromatic short carrier wave are derived. The nonlinear term is affected by the axial stiffness and the dispersion term is by the rotational inertia and the bending stiffness for the case of the KdV equation. On the other hand, both the dispersion and nonlinear terms are affected by the axial stiffness, rotational inertia, and bending stiffness for the case of the NLS equation.

A rational dimensional reduction method based on a new type of complex modal analysis is developed for the accurate analysis of a nonlinear vibration generated in a large scale structure with locally strong nonlinearity. The proposed method uses the complex constrained modes obtained by fixing the nonlinear nodes to convert the state variables of linear nodes into the modal coordinates. A small number of modal coordinates which have a significant effect on the computational accuracy of the solution are selected and used for analysis in combination with the state variables of nonlinear nodes expressed in the physical coordinates. The remaining modal coordinates which have a little effect on the computational accuracy are appropriately approximated and eliminated from the system. By using the reduced model derived by this method, not only the solution but also the stability of the solution can be computed with high speed and accurately. In this paper, in order to improve the practicality of the method, the effectiveness of the method is confirmed by applying it to a non-linearity that has not yet been applied.

A rational dimensional reduction method based on a new type of complex modal analysis is developed for the accurate analysis of a nonlinear vibration generated in a large scale structure with locally strong nonlinearity. The proposed method uses the complex constrained modes obtained by fixing the nonlinear nodes to convert the state variables of linear nodes into the modal coordinates. A small number of modal coordinates which have a significant effect on the computational accuracy of the solution are selected and used for analysis in combination with the state variables of nonlinear nodes expressed in the physical coordinates. The remaining modal coordinates which have a little effect on the computational accuracy are appropriately approximated and eliminated from the system. By using the reduced model derived by this method, not only the solution but also the stability of the solution can be computed with high speed and accurately. In the previous papers, the effectiveness of the proposed method has been verified for basic models such as a beam structure and a rotor model. In this paper, in order to improve the versatility of the method, the effectiveness of the method is confirmed by applying it to a thin plate structure of the consistent mass matrix model.

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. Introducing 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, which corresponds to a human body, output power of wave generation is analyzed and discussed in detail. As a result, it was found that when the damping ratio of the input is same as the output one, the output power becomes the maximum when the input and the output impedances match to that of the bar. Moreover, when the input damping is different from the output one, the output power becomes the maximum under the condition the length of the bar is sum of integer multiple of the half wavelength and quarter of the wavelength.

In this paper, a reset controller is applied to suppress chaos occurred in the brushless DC motor (BLDCM), a type of permanent magnet synchronous motor (PMSM). That is, the parameter region of the reset controller that suppresses chaos is obtained for the model of the BLDCM in which chaos is occurred by simulation.

Ultrasonic levitation is technology that can levitate small objects with ultrasonic. In this technology, levitated objects do not have any material restrictions, and not only a solid substance but also liquid substance can be levitated. Therefore, this technology is expected to have various industrial applications, for instance, drop mixing experiment and material experiment in zero gravity. Although there are some methods of ultrasonic levitation, in this study, we use method of using Langevin-type transducer. This method is simple and inexpensive, consequently we can easily apply it to industrial use. This paper describes consideration of levitation principle according to the theory of acoustic radiation force on spheres suggested by L.V.King. In particular, we calculated acoustic radiation force and natural frequency of levitation object when it vibrates freely, using actual specifications. In order to verify the theory of King, we compared the theoretical value of natural frequency with the experimental value of it. Furthermore, we calculated two-dimensional sound pressure distribution in the sound field to determine where levitated objects will be trapped.