Combustion oscillations occur themselves as pressure and heat release oscillations in lean premixed combustors, and they may cause some unexpected damage. This paper proposes a design method of a reset controller to eliminate a combustion oscillation in a lean premixed combustor model. We consider a plant model consisting of a linear system with a nonlinear feedback element and a reset controller. We show parameter conditions of the reset controller for which limit cycles are eliminated, using flame describing functions of the nonlinear element. We apply the proposed design method of the reset controller to eliminate the combustion oscillation in the lean premixed combustor model and show its effectiveness appropriately.

Thin walled beams are utilized in the parts of automobiles and micro machines in order to erduce the weight and to keep high rigidity. However, under lateral periodic load, nonlinear vibrations may be generated in specific frequency domains. Therefore, it is important to analyze nonlinear vibrations of the beams with various distribution of cross section along its axis. In this study, analytical results is presented on nonlinear vibrations of a stepped beam considering effects of axial inertia force. The beam is divided into a few segments to express the geometry of the stepped beam. The deflection of the beam is expanded with the mode share function that is expressed with the product of truncated power series and trigonometric functions. Taking the axial displacements, the deflection, slopes, bending moments and shearing forces at the node of the segments as unknown variables, nonlinear coupled ordinary differential equations are dirived with Galerkin procedure. Different from previous analysis, the equation of motion of the beam is formulated as an expression including the axial inertia force of the end-mass. Nonlinear periodic response are calculated with the harmonic balance method, which are compared with the previous experimental results.

A rational method of dimensional reduction based on new type of complex nodal analysis is developed in order to analyze accurately a nonlinear vibration generated in a large-scale structure with locally strong nonlinearity, asymmetry and non-proportional damping. In the proposed method, the state variables of linear nodes are transformed into the modal coordinates by using the complex constrained modes that is obtained by fixing the nonlinear nodes. A small number of modal coordinates that have a significant effect on the computational accuracy of the solution are selected and utilized in the analysis by combining them with the state variables of nonlinear nodes that are expressed in the physical coordinates. The remaining modal coordinates that have little effect on the computational accuracy are appropriately approximated and are eliminated from the system. From the reduced model constructed by these procedures, the steady state periodic solution and the stability, the transient solution and the quasi-periodic solution can be computed with a very high degree of computational accuracy and at a high computational speed. The validity of the proposed method is verified by the numelical results obtained for a rotor model with nonlinear bearings.

In this study, steady-state collisional vibration for a continuous system subjected to periodic excitation is analysed. The analysis model is a simply-supported-beam composed of two different beams with additional mass at the middle position in the beam span. Each beam is modeled by young's modulus, second moment of area, area of cross section and degree of density. The added mass elastically collides with elastic bodies having certain spring constant and collision gap at the middle position. In the analysis, Fourier series method is applied, and an exact solution of response oscillation is proposed. Numerical calculations are performed from the exact solution of the response oscillation. The response vibration waveforms are obtained and resonance curves are created with the spring constant ratio of the collided spring, the added mass ratio, the excitation amplitude ratio of the collision gap, the bending stiffness ratio, the linear density ratio as a parameter. Furthermore, experiments are carried out to verify the effectiveness of this analysis.

The effect of perturbations in initial velocity form steady state of undamped vibro-impact 1DOF oscillation is studied under excitation from vibration manipulation function, which was designed in three-vibro-impact oscillator under Grover algorithm. Quasi-periodic impact oscillations or almost-periodic impact oscillations in simulations were explained as state transitions on circular orbit in Poincare map from analytic formula of operators in the three-vibro-impact oscillator. In simulations chaotic divergence from long quasi-period oscillation was observed in the perturbed system just after the occurrence of Graze, which was explained as the function of a mal operator without impact from Grover algorithm.

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 of stability analysis show that the low frequency vibration occurs in the parameter range where unstable periodic solutions exist. An analysis is also made on the relationship between the change in the mechanical energy and the behavior of the small variation of state variables, which demonstrates that the average value of the fluctuating mechanical energy increases with the low frequency vibration.

The occurrence of the low frequency vibration in vibroimpact systems such as vibrating filters and vibratory feeders reduces the reliability of the system and precludes normal operation when its amplitude is excessive. For suppressing the low frequency vibration, this paper investigates the effects of a dynamic absorber on vibration characteristics. The apparatus used in the experiment has two degrees of freedom, where the lower mass is supported by a spring and excited by an external periodic force whose frequency is much higher than the natural frequency of the system. The upper mass bounces on the lower mass under the action of gravity. In this system, the low frequency vibration occurs when the frequency of the external force exceeds a particular value. The dynamic absorber consists of a weight, a leaf spring and damping material. The experimental results demonstrate the change in vibration characteristics of the system due to the dynamic absorber, showing that the dynamic absorber is able to suppress the low frequency vibration.

Rail corrugation is a phenomenon in which roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running, and causes the vibration and the noise. Therefore, in this paper, we analyze the amplification factor of roughness amplitude using a model that takes into consideration the interaction between the track and the vehicle, and clarify the growth mechanism and the wavelength determination mechanism of the rail corrugation. As a result of the theoretical analyses, it is indicated that the essential factors of growth of the corrugation are (1) interference of rail wave motion between the front and the rear wheels of a bogie of the vehicle, (2) anti-resonance phenomenon of the elastic support of the track system, (3) anti-resonance phenomenon of the total system of the track and the vehicle, and (4) anti-resonance phenomenon of the vehicle system. In addition, as a result of examing the rail corrugation measured on the commercial lines, it is confirmed that the causes of the corrugation occurrence are the above mentioned (1),(2) and (3) factors, and that the measured wavelengths almost agree with the theoretical values.

In this paper, we analyzed the frequency characteristic of rail surface roughness data of the rail corrugation in detail measured in a few commercial lines of railway. At first, based on a result of the theoretical analysis that estimated of the rail corrugation, and based on the occurrence situation of the rail corrugation in the lines, we made the classification map of pattern formations of the rail corrugation. As a result of the analysis of rail surface roughness data in the lines, we confirmed a rail corrugation roughly corresponding to theoretical values of (1) interference of rail wave motion between the wheelbase of vehicle, (2) anti-resonance phenomenon at the elastic support in track system, and (3) anti-resonance phenomenon at the total system of track and vehicle.

Reaming is a finishing process to be performed in order to improve the accuracy of the prepared hole drilled. In this process, a chatter vibration often occurs and the drilled hole is deformed in a polygonal shape. This polygonal deformation phenomenon becomes a problem, because of decrease in the precision of the hole. The generating mechanism of the polygonal deformation is considered to be a self-excited vibration caused by time delay. In the previous study, a simple analytical model is proposed in order to study the basic characteristic of the phenomenon. In this study, an analytical model taking into account bending vibration of tool is proposed in order to investigate the higher order polygonal deformation phenomenon at the entry of the hole. Also, the stability analysis is performed numerically.

The dominant mechanism involved in pattern formation phenomena in contact rotating systems is considered to be unstable vibrations generated in linear time-delay systems due to processes such as viscoelastic deformation, wear, cutting and grinding. A number of countermeasures have been proposed to prevent the occurrence of these formation phenomena. In this report, using a new type of complex modal analysis method for two degree of freedom system, the author seeks the approximately characteristic solution. The result shows the validly of the approximately characteristic solution by comparing to the exact characteristic solution. In addition, an optimization procedure for the dynamic absorber is considered, using this method.

BTA(boring trepanning association) deep hole drilling is widely used for producing deep holes with high aspect ratio. Since the cutting chips are discharged together with the cutting oil through the boring bar, the finished surface becomes smooth. However, self-excited vibration, called rifling mark, occurs during the operation. Then finished surface of the rifling mark is polygon. When a rifling mark occurs, various problems such as deterioration of product precision and reduction of tool life occur. This phenomenon is called pattern formation, and the similar phenomena occurs in drilling, reaming and lathe turning. In the case of BTA deep hole drilling, it is very difficult to detect the occurrence of rifling mark in the early stage, because the BTA tool locates deeply inside the work. In this paper, the detection method of the rifling mark in BTA deep hole drilling process is discussed.

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

In the vibration cutting system, the recommended cutting speed range is about one third or less of the critical cutting speed. Over the recommended cutting speed range, the processing accuracy will easily deteriorate due to abnormal vibration. On the other hand, in the field of electric circuits, researches are under way to suppress the generation region of chaotic vibration by applying weak harmonic perturbation to fundamental vibration. In this research, we try to suppress abnormal vibration by applying weak harmonic perturbation on vibration cutting system. Specifically, we develop an experimental device capable of superimposing harmonic components on tool vibration of vibration cutting, and we confirm the effectiveness of harmonic by examining the surface roughness and the workpiece displacement. We carry out experiments with varying the cutting speed, and show that the deterioration in surface roughness are suppressed by weak harmonic perturbation. That is, it is considered that abnormal vibrations occurring in the machining region exceeding the recommended cutting speed in the vibration cutting system could be suppressed by harmonics.

Passive dynamic walking is a gait on a shallow slope without actuation and 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 analytical model of a straight-legged biped passive walker taking into account the motion in coronal plane as well as sagittal plane. Also, the steady state solution is investigated numerically. Furthermore, the effect of ankle springs on the stability of walking is studied.

The effects of parameters on the driving mechanism using swing motion are investigated. The system comprises a body and a rod which have two and one freely rotating wheels, respectively. The rod is pinned to the body so that it is able to swing like a pendulum about the pinned joint by a servo motor. Experiments and numerical simulations are carried out in order to clarify the effects of swing amplitude, rod length, distance between rear wheels and radius of gyration of the body on the propulsion characteristics. The results demonstrate that the propulsion speed increases with increasing swing amplitude, rod length and radius of gyration, whereas it is hardly affected by distance between rear wheels.

By using piecewise sampled-data control with deadbeat function, we try to swing up pendulum with trolley in simulation. We use vibration manipulation function as deadbeat control to determined acceleration of the trolley. We use two or three operations for swing up. In case of raid control, whose first operational period, Δt₁, is as fast as 5% of the natural period of the pendulum, τ, swing-up control was succeeded. Or in case Δt₁≦τ/4 or Δt₁= τ, it can be done by choosing small angular velocity. In case τ/2≦Δt₁>τ, swing-up control is associated with cyclic rotations. Or in case proper angular velocity was chosen, swing-up control can be made. Although rapid swing up requires high acceleration of the trolley, it can be done easily with different angular velocities.

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 iron-gallium alloy (Galfenol) has received much attention in recent years. A bending force applied at the tip of the cantilever yields a flux change due to tensile or compression stress, and the flux variation leads to the generation of voltage on the wound coils. This energy harvesting technology has advantages over conventional types, with respect to size 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 constituted a two-degree-of-freedom vibration system. Using DE, we numerically explored the best combination of spring constants and masses of the vibration system that maximized the electric power generation.

This paper deals with the vibration quenching problem of the single-degree-of-freedom system with a limited power supply. This system is forced by the centrifugal force of rotating unbalance, and the system is quenched using a Hula-Hoop and displacement magnification mechanism even if the displacement of the main system is small. The vibration quenching of the system are studied from the numerical integration of the equation of motion obtained using Lagrange equation and the experiment. Following was made clear: (1) By enlarging the displacement at the position of Hula-Hoop using displacement magnification mechanism, vibration quenching became possible even when the displacement amplitude of the main system is small. (2) Although the system becomes two-degree-of-freedom system by the proposed displacement magnification mechanism, by designing so that the second resonance frequency becomes high, it is possible to widen the frequency range where vibration can be quenched. (3) The characteristics of the approximate solutions obtained by the numerical integration method coincide with those of the results obtained by the experiment.

The aim of this study is to develop a systematic method to suppress residual vibration in overhead cranes that lowers operating performance and prevents automation of the system. In the previous paper, we proposed a control method which 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. The proposed method introduces the concept of the apparent external force which includes the influence of nonlinearity and damping, making it applicable to single pendulum type nonlinear damped systems as well as linear undamped ones. However, if mass of the hook is too large to be neglected, the single pendulum type system is not suitable to model cranes. Therefore, this paper uses double pendulum type system model of crane, and suppressing the residual vibration by eliminating two natural frequency components from each the apparent external force. Numerical simulations demonstrate that this method can suppress the residual vibration of the double pendulum type system. Furthermore, optimizing trajectory decreases the maximum swing angle of the hook and the cargo during transportation and makes transition of the maximum swing angle with control time smoothly.

Overhead cranes are widely used and play a significant role for mass transportation in factories. One of the main problems in operating an overhead crane is the residual vibration which often decreases efficiency and safety of the operation. 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. The authors have applied this property to a nonlinear damped system and developed an efficient method to derive an adequate trajectory of the trolley of the overhead crane which enables complete prevention of the residual vibration of the cargo. This paper proposes a systematic method for designing path of the trolley whereby the trolley and the cargo are both able to avoid obstacles while minimizing the path as well as keeping the residual vibration suppressed. The effectiveness of the proposed method is examined by numerical simulations.

Improvement of the sound quality is an everlasting problem in the audio system industry. As one method to improve sound quality, an audio rack is used. An audio rack is the rack which was developed to install an audio equipment. Sound quality improves by enclosing granular materials in an audio rack. As this reason, granular materials effects as the damper, and sound quality improves to suppress the vibration of the audio equipment. In this study, suppression effect of the granular materials which are enclosed within the high grade audio rack board is investigated from a vibration engineering.

The present work proposed the dynamic absorber for very low frequency structures using magnetic springs and magnetic dampers. The application of the magnetic springs and magnetic dampers allow the absorber to eliminate the influence of friction and to easily change the natural frequency and the damping ratio of the absorber. In the present work, the very low frequency structures composed of a pendulum and the absorber with two magnetic springs and two magnetic dampers have been constructed. Two optimum parameters of the absorber for the steady state vibration response and the transient vibration reduction of the very low frequency structures were derived analytically. The time response analysis using the numerical integration compared the effect of the two optimum parameters on the transient vibration. Furthermore, it was revealed that the vibration reduction effect by the absorber increased further by selecting the initial conditions of the main structure and the absorber properly. Next, the free vibration tests with the experimental apparatus were carried out, and it was confirmed that the experimental results agreed qualitatively with the numerical analysis results. In addition, it was confirmed that the application of the absorber properly tuned to the natural frequency and the damping ratio according to the initial conditions provided excellent vibration reduction effect.

This research deals with rebound vibration behavior of movin mirror inside a SLR camera. The differences of the mirror vibration phenomena is tested by using the two-rectangular-metal-plates model, which is bonded by double-sided tape. By changing the pasting position, the mirror part functions as a damper and the rebound amount is reduced. When the frequency ratio between the mirror part and the body part was 1.0 times, the rebound amount is not reduced. On the other hand, the frequency ratio between the mirror part and the body part is 0.5 times, the rebound amount is suppressed.

This paper deals with the quenching problem of electromagnetic vibration of the motor stator in the wide frequency region around the natural frequency using two dynamic absorbers. The iron stator of motor is modeled by circular ring, and a pair of dynamic absorbers are installed on the outside of iron stator to quench the forced vibration caused by the rotating distributed electromagnetic force. The solutions of forced vibration are obtained by the theoretical analysis, and those are compared with the solutions obtained by the finite element method and numerical integration. Following was made clear: (1) By installing two dynamic absorbers which have not only different natural frequencies and different damping ratios but also different masses each other, the iron stator is quenched better than by installing the same dynamic absorbers. (2) The mechanism of the above-mentioned vibration quenching method using two different dynamic absorbers is made clear. (3) In the case using the dynamic absorbers those have realistic values of damping ratios, about 25 degrees is better as angle made by the two dynamic absorbers. (4) The characteristics of resonance curves obtained by the theoretical analysis using ring theory and those obtained by the finite element method and numerical integration agreed well each other.

In this study, we devised an active device in order to suppress the essential tremor in human limb. The tremor is observed in most human arms even at physically well condition that is derived from excessive stress or chills, therefore, it may cause anyone bad effect on precise operation such as welding and surgery. In this work, experiments are performed where the simulated microscopic surgery is imposed on subjects whose fingers are equipped with the active mass damper attenuating the tremor in their hands. The damper is actively driven according to the state feedback controller designed by the linear two-degrees-of-freedom vibration system model. Subjects were asked to grip a needle having a relatively small diameter using tweezers, and were also asked to insert it in a needle with a larger diameter. Tremors were measured while the subjects keep the tip of the needle in place. It is shown that the damper can attenuate vibration in human fingers.

The objective of this study is to clarify the vibration generation mechanism of agricultural machinery caused by the interaction between the tire lugs and the road surface. It is important to investigate the lug excitation force occurring on a rolling agricultural tire in order to clarify the vibration generation mechanism. In our previous study, we modelled the agricultural tire as a three-dimensional rigid ring model (SWIFT model). Further, the frequency equations of SWIFT model are derived and the model parameters are identified by minimizing the difference between measured and calculated natural frequencies. In order to identify lug excitation force, shaft displacement and shaft force during rolling motion are measured three-dimensionally by rolling test and lug excitation force in longitudinal, vertical and lateral direction are identified. From the obtained results, shaft force characteristics and lug excitation force characteristics are investigated. As a result, there is a correlation between shaft force and lug excitation force and it has been confirmed that both characteristics are influenced by the vibration characteristics of the tire. However, the transfer characteristics with lug excitation force as input and shaft force as output are not investigated. In this study, amplitude magnification and phase difference are analyzed as the transfer characteristics of lug excitation force and shaft force. From the obtained results, the influence of vibration characteristics of the tire on transfer characteristic are investigated.

In this study, analysis is conducted on behavior of an electromagnetic reciprocating vibratory swing compressor. The governing equations of the swing compressor is derived in terms of motions of piston with coil and motor assembly and current induced in the electric circuit. Electromagnetic coupling is also considered between the vibrations of a spring-piston system and the electric circuit which consists of a coil and a resistance. First, the analytical model is introduced with the vibration system with two degrees of freedom. The parameters such as spring constants, damping, and iron loss coefficients are obtained and identified by preliminary experiments. Time responses of motion and current of the swing compressor are calculated with direct time integration. Frequency responses of these variables are also obtained. Next, the numerical results are compared with the experimental results to verify the analysis presented in this study. The experiments were held under the condition without compressive load and that under compression of air as refrigerant. Very good agreements are found between numerical and experimental results in the condition without compressive load, which verify our analysis. Although, damping is uncertain and leakage of refrigerant is not considered in the analysis in the condition of air compression, the analysis agrees qualitatively with the experiment.

This research investigates with rebound vibration behavior of mirror inside a DSLR camera. The differences of the mirror vibration phenomena are tested by using the rectangular-metal-plates model. This aluminum alloys mirror model is fixed by a bolt and a nut on the horizontal rotatable shaft. In collision experiment, the bonded mirror model swings down freely and rotates about a shaft. Vibration behavior of mirror models is measured by laser displacement meter. As a result, the variation of maximum rebound angles has relationship with left and right stopper positions which manipulated by vertical and horizontal axis. The rebound angle is suppressed by changing the stoppers position in controlled behavior. In the experiment condition which is measured the lowest rebound angle, the vertical axis position-controlled stopper is at its optimum potential at 0.5[mm] height difference in regard to its opposite stopper position.

The shutter of the camera is a device for controlling the exposure to the image pickup element, and the focal plane shutter is used in the DSLR camera. Rare uneven exposure occurs in the focal plane shutter at the manufacturing stage. The cause of uneven exposure is considered to be the vibration of the shutter blades constituting the shutter. In this research, we focused attention on the hole shape connecting the links. Transient motion characteristics are evaluated by an experiment in which a pin is inserted into a blade model having a hole and is operated. As a result, the rebound amount was suppressed by changing the hole shape from a circle to an ellipse. Also, if the hole shape is elliptical from moving image analysis, the direction of exercise was restricted.

In this study, impulse-hammering vibration measurements of carbon fiber reinforced plastic (CFRP) composite laminates with or without flexible sheets (PIEZON-PP) inserted at central interlaminars were carried out and then finite element method (FEM) numerical analysis by using general purpose code, ANSYS, was applied to identify elastic properties of CFRP and flexible sheet (PIEZON). For the present material properties identification for CFRP layers and flexible sheets, the first order Newton’s method was used to seek optimum elastic properties which minimized errors between the impulse-hammering measurement results and the FEM numerical results in terms of natural frequencies of the five lowest bending modes of three different unidirectional carbon fiber orientations, that is, unidirectional (0°) CFRP, transverse (90°) CFRP and 25° CFRP with and without flexible sheet. Good elastic properties identifications could be conducted and these properties will be able to be used for any further optimization problems such as topology optimization for CFRP structures with flexible damping sheets.

This paper presents a new analytical procedure on bending vibrations of an annular plate. The procedure is composed with modal expansion with mode shape functions and a finite element analysis. The plate is divided into finite number of segments. The mode shape function is introduced with the product of power series and trigonometric function. The unknown coefficients of the mode shape function are substituted by the deflection and its higher derivatives at each mode of the segments, which enables to satisfy the continuity of slope, bending moment, torsional moment, equivalent shear force at the node of segment. Discretized equations of motion of the plate are derived with Galerkin method. Natural frequencies and mode of vibrations are calculated and are compared with the exact results. Changing the ratio of inner radius to outer radius and division ratio of segment in radial direction, natural frequencies are calculated. Good agreements are obtained between the computed results and exact results of natural frequencies. In the future, this analytical procedure is expected to be applied to nonlinear vibration analysis which is sensitive to boundary condition and the continuity of deflection and its higher derivatives at segment boundaries.

A simplified calculation method for in-plane and out-of-plane coupled vibration occurred in thin curved panels is presented in this report. In order to treat such vibration motions simply, a structure consist of straight and curved beams is proposed and the connecting conditions of these beams are satisfied by means of artificial springs introduced at their joints. The analytical procedure to obtain vibration response versus harmonic displacement excitation applied into the basement of the supports of the coupled system is described in detail. Vibration responses for the different bending rigidities and loss factors in the beams are calculated as numerical examples. The influence of the loss factors in the curved beams is observed upon the vibration response of floor section, particularly for the motion with large relative displacement between roof and floor.

In this study, the present authors propose a new concept in solid, plate and shell numerical modeling, that is, material-properties-graded modeling, which may be a kind of extension of well-known functionally-graded material (FGM) modeling. This has recently been motivated by today's vital research and development activities in the field of additive manufacturing (AM) or 3D printing of complicated structures posed by topology optimization design, where more rational material properties with density or microscopic porosity varied or graded in the structures can be designed by density-based topology optimization (SIMP method) and then manufactured by various additive manufacturing or 3D printing methods such as fused deposition modeling (FDM). In this article, we try to explicate the present numerical modeling based on the well-verified plate/shell theories with transverse-shear-deformable higher-order displacement assumptions.

Powerful tsunami attacked to the northeast coast of Japan due to the Great East Japan Earthquake occurred on March 11, 2011. Some aboveground oil storage tanks (ASTs) were subjected to external liquid pressure of the tsunami. An effective method to prevent the buckling of existing ASTs under external liquid pressure is to install ring stiffeners on the shell plate. In this paper, the approximate minimum required number of ring stiffeners and their installed location of ASTs are determined. The optimum design method which repeats the procedure to increase the buckling liquid height by installing a ring stiffener at the peak location of buckling mode is used. This method was proposed in the author's previous paper. The bifurcation buckling analysis is the axisymmetric shell finite element method. As a result, the two ASTs of 10,000 m3 and 90,000 m3 require 14 ring stiffeners in each case when external liquid height is set to the same as the design internal liquid height.

In this study, topology optimization techniques were numerically applied to eigen-frequency structural optimization problems of composite sandwich structures with CF/PA6I-6T skin layers and PA6 core layer. General-purpose finite element analysis code, ANSYS and its structural optimization option were used in the present study, in which the density method (SIMP method), one of the numerical approaches in the structural optimization discipline, was employed for seeking the most efficient internal structural forms of core layers for eigen-frequency maximization under certain fixed weight reduction constrains. From the results of the present study, certain optimal inner structures or morphologies could be found out for each set of structural and material configurations for each vibration mode, which makes engineers and researchers of the composite material field have a future prospect of the present attempts.

This study investigated the material properties identification method of a single layer CFRP plate. This identification method is comparing between the vibration mode measurement results obtained from anisotropic materials with vibration analysis results of a single layer CFRP plate. In particular, genetic algorithm was used to identify multiple material properties at the same time. The usefulness of the identification method was confirmed by using simulation data and experimental data. When the evaluation function is raised to the power, the variation is reduced. Also, it was found that taking an average value results in a reasonable value. In the experimental data, it was possible to identify with a goodness of fit of 95%.

The finite element method is applied to buckling analysis of cylindrical shells subjected to axisymmetric external and internal liquid pressures. The axisymmetric shell element is used and buckling displacements are represented by Fourier series expansion in the circumferential angle. The linear and nonlinear buckling analyses are performed for cylindrical shells and model tanks. The results of linear and nonlinear buckling analyses are compared and the effects of geometric nonlinearity are investigated.

The present study proposes a new fabrication method for Carbon Fiber Reinforced Thermo-Plastic (CFRTP) by using a Tailored Fiber Placement (TFP) machine. Instead of the CF or glass plain weaves, the thermoplastic sheets are used as a base layer for the TFP fabrication. That is, Carbon Fiber (CF) tows are sewn on a Polypropylene (PP) sheet directly, and the PP sheet is impregnated into CF tows by using a hot-pressing machine as a matrix material of composites. This avoids remaining the base sheet as a layer of laminated composites. After the CFRTP flat sheet are fabricated, they are drawn deeply to cylindrical shapes by using a hot servo-pressing machine. Flat CFRTP sheets have spiral or radial fiber shapes and they becomes hoop or straight layers for the sidewall of cylinder after the drawing process. Due to these reinforcement, the fabricated works result in higher rigidity for compression. This is also validated by linear buckling analysis by using finite element analyses.

Free vibration characteristics of the FRTP rectangular plate printed by 3D-printer is studied in this paper. A FRTP composite plate is printed by a 3D-printer, the Mark-Forged Mark Two printer. The vibration characteristics are measured by impulse vibration test. 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.

A novel composite structure arm for astronautical development by using CFRP and honeycomb core is already presented. In previous studies, the superiority of the presented arm is theoretically confirmed while experimental results possessed far below stiffness. The reason is estimated to be the failure in adhesion. To avoid this, solid shaping of the arm by using 3D printer is presented. In this study theoretical and experimental evaluation of the presented arm is carried out and their difference are examined.-

Variable stiffness composites induced by the curvilinear reinforcing fibers came to be able to be manufactured by using a tailored fiber placement (TFP) machine. Since variable stiffness composites have high flexibility for design, it is known that variable stiffness composites indicate excellent mechanical properties compared to constant stiffness composites. In this study, vibration characteristics of variable stiffness composites reinforced along principal stress direction are evaluated numerically and experimentally. First, a modal analysis for an isotropic plate is performed and shapes of modal deformation are estimated. Then, the principal stress direction is calculated by performing static analysis under forced displacements which reproduce the modal deformation. Referring to these directions, variable stiffness composites with fibers along principal stress directions are designed, and natural frequencies of those plates are computed. The numerical results revealed that orientation of fibers along principal stress directions improved natural frequencies for the most of boundary conditions. Next, experimental modal analyses are performed in order to confirm the validity of the calculated results. The experimental results showed that more information including variable thicknesses, fiber densities is necessary to improve the accuracy of numerical analysis.

Since the size and weight of spacecraft structures installed on the spacecrafts are strictly limited, various types of extendable booms have been developed. To devise the weight reduction and simplification of the mechanisms, recent extendable booms can be stowed by elastically flattening the cross sections and wrapping around hubs and can be deployed by the restoring forces. These booms exhibit nonlinearity due to large deflections as well as nonlinearity in bending stiffness due to the changes of the cross-sections. In this paper, examples of space lightweight extendable booms are briefly explained and braided bi-convex booms developed in Japan and examined in this study are introduced. Then the results of measurements of the nonlinear bending stiffness and nonlinear vibration characteristics and the deployment experiment of the booms wrapped around a hub are summarized. Then the modeling of the nonlinear bending stiffness and deployment simulation employing the multiple particle approximation method are explained.

This paper deals with the point-to-point (PTP) motion control of a flexible manipulator, in which we attempt to suppress simultaneously the residual vibration and driving energy. The driving energy of the PTP motion of a flexible manipulator depends on the initial deflection. We consider the physical phenomenon and then propose a novel trajectory planning method of the joint angle of a flexible manipulator. The effectiveness of the proposed method is demonstrated through simulations and experiments.

There are various types of rope models to simulate vibration of rope as previous papers have been proposed. Although these models are able to simulate rope vibration excited by measured or known force, it is impossible to simulate the vibration caused by indeterminate force, which is difficult to measure, such as the force related to contact situation between rope and pulley. Additionally these models do not take into account contact between rope and pulley. In this paper, we propose a practical model which enables us to analyze the contact under winch operation. As an initial test of simulation accuracy, we measure rope vibration excited by pulley with small protrusion on rope groove, and simulate same condition to compare the results. Finally, this paper describes the mechanism of rope vibration from the protrusion.

Coal thermal power stations occupy for approximately 40% in the world. It is required that the efficiency of the station would be improved in order to prevent environmental pollution. Then, it is important to pulverizing a large amount of coal in the vertical roller mill. However, self-excited vibration might occur as most of coal become final. It is unclear that what kinds of friction property could be related to be self-excited vibration, as one of the causes self-excited vibration in the negative friction properties were suspection. In this paper, we examine the rotating speed variation caused by roller slipping and the horizontal acceleration vibration of the rotating roller about 3type of coal. We use experimental equipment a specific vibration characteristic, where the occurred vibration could be observed. As a result, the higher natural frequencies about the structural system have changed into the lower. To investigate dynamic responses of the rolling roller, the rotating velocity of the roller, acceleration at the axis of rollers, the generated forced and etc. were measured. As a result, both the rotating speed variation and the horizontal vibration acceleration gradually increased in accordance with the running velocity of increase before decreasing at higher running velocity about 3type of coal.

The closely spaced eigenvalue system is observed in a lot of coupled structures. In this system, there is difficulty of system identification in order to contain the beating wave. In this paper, system identification method of the closely spaced eigenvalue system is investigated. The algorithm of system identification is derived using the virtual symmetry two-degree-of-freedom model. In particular, the update algorithm is derived multi-variable Newton method, using the objective function based on the impulse response function of auto-frequency response function. The numerical simulations are conducted in terms of the observation noise. As a result, our proposed algorithm showed the robustness against the measurement noise and the noise of the initial values. Moreover, experimental identification is conducted using the actual pipeline rig. The estimation result of auto-frequency function denotes the good agreement with the experimental result.

This paper investigates the internal resonances of two vibration modes in a nonlinear double-beam system. Two identical beams, simply supported at the both ends, are discretely connected by a set of a spring and dashpot, and one of the beams is subjected to sinusoidal, harmonic excitation. Nonlinearity of the beams comes from a change in tension due to the stretch of the beams. In the theoretical analysis, modal equations of motion for the two, adjacent vibration modes of the system are derived. Then, van der Pol’s method is applied to the modal equations of motion in order to determine the expressions for the frequency response curves. In the numerical calculations, the frequency response curves are shown when the natural frequency of the second vibration mode is close to that of the first vibration mode. The first and second vibration modes of the system are nonlinearly coupled, and internal resonances occur. The time histories of the first and second vibration modes, and the time histories of the displacements of the beams at specific positions are also shown. When the connecting spring stiffness is comparatively small, the first and second vibration modes significantly interact with each other, and the amplitude of the vibration of the beam, which is excited, is larger than that of the other beam at a specific excitation frequency range. The opposite is true at a specific excitation frequency range when the connecting spring stiffness is increased. For a specific value of the connecting spring stiffness, Hopf bifurcation may occur, followed by amplitude modulated motions (AMMs).

The effectiveness of a dynamic absorber for self-excited vibration has been known for several years. However, in the case of self-excited vibration, the operating mechanism of a dynamic absorber is still poorly understood. In this paper, a simple and fundamental model with three degrees of freedom (DOFs), which is consisted of a two-DOF system with an asymmetric stiffness matrix and a single dynamic absorber, are considered and the operating mechanism is investigated. As an analytical tool to clarify the operating mechanism, a new type of complex modal analysis is developed for accurately evaluating the energy for each mode. By applying the new method, the damping matrix can be diagonalized exactly in addition to the symmetric mass and stiffness matrices of the system, and the equation of motion for a multi-DOF system can be converted into modal equations for a single-DOF system in the form of real second-order differential equations. From the modal equation, we derive the approximate solutions of the coupled vibration of two modes. However, these approximate solutions are not accurate due to the other modal coupling. In this paper, we derive the more accurate approximate solutions by considering effects of modal coupling.

Many phenomena existing in mechanical structures have nonlinear characteristics such as play and friction, the response characteristic of the vibration system subjected to random input is a so-called non-gaussian random process. For the handling of these data, it is essential to apply statistical methods and analyze using higher-order statistics considering non-gaussian. The purpose of this research is to apply statistical method in higher-order frequency response analysis in asymmetric nonlinear vibration system using higher-order spectra (HOS) and present the effectiveness of this method. In this report, experimental analysis by magnetic spring model is carried out, and higher-order spectral analysis considering input/output is studies.