An accurate description of the tire characteristics is very important for vehicle dynamic analysis. However, the characteristics of a tire are very complex, and it is not easy to develop the analytical model of tire force. It is also well known that the actual tire force is greatly affected by the suspension properties. Therefore, it is necessary to evaluate the tire characteristics including the effects of the suspension system. In order to evaluate the effects of tire-suspension system on vehicle dynamics, we had developed a tire-suspension hardware-in-the-loop simulation (HILS) system. In this system, the various contact conditions of the tire can be realized. In addition, the tire-suspension HILS system enables us to carry out evaluation tests under constant condition in comparison with actual running tests. In previous study, we used roller rolling system to rotate the tire. However, contact conditions between the tire and the roller were estimated to be different from the conditions on the real road, which might cause different tire characteristics. In this study, we developed a flat belt rolling system to improve contact conditions. The effectiveness of the flat belt rolling system was evaluated by slip angle input test and slalom runnning test.

抄録全体を表示

This paper describes the development of an electromagnetic suspension system for an active control. Our system used a DC servo motor, and it realized various damping characteristics by controlling the torque of the motor. The generated damping force is calculated based on the state of the vehicle. The purpose of this study is to evaluate the effectiveness of the electromagnetic suspension system with the tire-suspension hardware-in-the-loop simulation (MILS) system. The tire-suspension HILS system was equipped with a tire-suspension system of an actual vehicle, and can realize various contact conditions of tire with a 6 degree-of-freedom (6-DOF) motion platform. With this system, virtual running tests with some steering inputs and road inputs were carried out. OpenCRG road profile data was used as road inputs. To evaluate the performance of the electromagnetic suspension system, we compared the test results between active control system and passive system.

抄録全体を表示

Common autovehicle suspension employs a hydro-pneumatic absorber mounted in parallel with a compression spring that provides for the necessary restoring force. Since the spring omission becomes possible, a compact and lighter design can be achieved by using the recently proposed colloidal suspensions. In this experimental work, frontal and rear colloidal suspensions were designed to replace the traditional suspensions of a real autovehicle, and travel tests on a normal road with a semi-sinusoidal asphalt step were performed. From the impulse response of tested autovehicle one evaluates its comfortableness, both based on the K factor method and based on the equivalent acceleration recommended by the ISO 2631 standard. Such experimental method allows comfortableness evaluation without using an expensive test rig on which the autovehicle is placed over four hydraulic actuators and excited to simulate the real road conditions. Results obtained are firstly validated in the case of classical suspensions consisted of oil dampers mounted in parallel with compression helical springs. Then, colloidal dampers with and without attached compression springs were evaluated. Relationship between the travel speed of the autovehicle and the level of vibration perception, as well as the influence on the sickness, concentration and health was obtained for various values of the tire inflation pressure. Ride-comfort decreases at augmentation of the travel speed and the tire inflation pressure. Although the colloidal suspension was found to provide inferior comfortableness than the classical suspension, results obtained so far are encouraging, since better performances are to be expected by softening the colloidal suspension.

抄録全体を表示

The rail is worn away by severe stress exerted by passing wheels. The worn shape of the rail is greatly different depending on track sites because the contact condition of rail/wheel is changed depending on the sites. Prediction of the worn shape of the rail accurately is a benefit not only for evaluating the vehicle running stability according to change of the rail shape but also for predicting the micro-crack propagation. In this research, we conducted wear test using rail and wheel material specified by Japanese Industrial Standard (JIS) by changing slide condition and contact pressure. Then, we calculated a wear coefficient by applying Archard's wear law that is one of the wear prediction laws already established. Finally, we suggested a wear law considering the nonlinearity of wear by sliding.

抄録全体を表示

In this investigation, a numerical procedure of multiple wheel/rail contacts for evaluating the curving performance and flange climb derailments of railroad vehicles is developed using constraint contact and elastic contact formulation. In the proposed approach, the location of flange contact is determined by using iterative contact serch with an initial estimate provided by 2-point contact table. This leads to a systematic and accurate prediction of contact points for severe flange contact scenarios encountered in curve negotiations on a small-radius curved track. It is demonstrated by several numerical examples that multiple wheel/rail contacts and the flange climb motion can be accurately predicted using a proposed approach. Furthermore, numerical results obtained using the prposed approach are in good agreements with those of a general-purpose multibody dynamics code, SIMPACK^<TM>.

抄録全体を表示

Upon a train derails, its dynamic motion should be affected by the change of running resistance when the wheels run over sleepers. Therefore, it is important to determine the change of running resistance experimentally and theoretically. Authors made a model vehicle of 1 to 10 scale, and carried out running tests under which the vehicle ran colliding against model iron sleepers varying the initial running speed of the vehicle and the width of model sleepers. We found from the tests that the running resistance increased during the vehicle speed from Okm/h to about 20km/h, once decreased during the vehicle speed from approximately 20km/h to 70km/h, increased again exceeding 70km/h with the increasing of the vehicle speed. Authors also constructed half car and full car dynamics models to describe the motion of the vehicle in which the force acting between wheels and sleepers when the both collide with each other was considered, and executed running simulations varying parameters considered in our wheels and sleepers collision model. The calculated results of running resistance were consistent with the test results satisfactorily regardless of the sleeper type, and indicated that the maximum contact force between wheels and sleepers was the most affective for the running resistance among three parameters considered in the collision model.

抄録全体を表示

In this paper, we proposed a method to introduce a fine unevenness on a part of a wheel tread in order to improve a curving performance without decreasing a hunting stability of railway vehicle, and verified a validity of this proposed method by applying a numerical analysis. Although a rolling radius difference of wheel tread with fine unevenness is the same as those without fine unevenness, a contact patch near the side other than the flange are different. When a railway vehicles run into a curved section, a contact point of inner wheel/rail shifts to the side other than the flange. At this time, if the creep coefficient of an inner rail side becomes small, the lateral force of inner and outer rail can become small, and thus the vehicle can pass the curve more smoothly. We showed that especially the wheel tread with fine unevenness has a large reduction effect of outer lateral force and derailment coefficient in cases where vehicles run on a small radius curved section with a large cant at a low speed by numerical analysis.

抄録全体を表示

Formation of undulating wear of overhead rigid conductor line causes extreme wear of contact lines and contact strips of a pantograph. Various methods have been carried out in order to prevent occurrence of the undulating wear. However, since undulating wear formation mechanism has not been clarified, undulating wear has not been extinguished. This paper describes the mechanism of the formation of the undulating wear based on the result of unevenness measurement of actual overhead rigid conductor lines and excitation tests of pantograph. It has been found out that the formation of the undulating wear is closely related with the dynamic characteristics, especially small accelerance, of the pantograph.

抄録全体を表示

The steering reactive torque of an automobile is one of the important information for a driver to estimate the road conditions. The characteristics of the reactive force depend on the stiffness property of mechanical components, layout of suspension links, and so on. In developing the automobile, it is desirable to realize an intuitive evaluation of operability before prototyping. For this purpose, we developed a steering torque simulator based on real-time multibody analysis in previous study. This paper describes method of enhancement of the reality of developed simulator by considering the influence of road roughness. To consider the influence of road roughness, we implemented OpenCRG, which is a open file formats and open source tools for the detailed description, creation and evaluation of road surface. Several kinds of road profiles were implemented in the steering torque simulator, and the generated torque was evaluated. In addition, the deformation of the contact patch was also considered by modifying the tire model.

抄録全体を表示

The purpose of this study is to evaluate strength of tapered roller bearing loaded vibrations. We modeled the tapered roller bearing to the flexible multi-body model, and calculated the stress of retainer by mechanical simulation. The simulation result shows that the stress of retainer became large when rollers vibrate in yaw motion, and the largest part of the stress was the root of retainer bridge. And we evaluated fatigue strength based on the calculated stress of retainer by this simulation. However, such a simulation using a flexible multi-body model had a problem to takes a lot of time. So, we could not calculate the stress in various conditions. For this problem, we confirmed that the major frequency of the stress in the root of the retainer bridge is below the first natural frequency of the retainer. We found that this simulation can be calculated by the solid body model to save time. And we calculated the stress in the root of bridge per unit force by the static analysis. Therefore, we became able to calculate this stress by the force calculated by the solid body model analysis. Using this solid body model, we calculated the force between the retainer and rollers in various conditions. We found this force increased depending on vibration acceleration, rotation speed of inner race, and radial force though it didn't increases depending on rotation direction of inner race. And we found the fatigue failure vibration acceleration of the tapered roller bearing.

抄録全体を表示

The gyroscopic exercise tool utilizes the gyroscopic effect caused by the whirling motion of the high speed rotating body to train the hand muscle. This tool utilizes the contact phenomenon between the rotor and the case. When the input motion with 3-5 Hz is added to the case, the rotor spins in thousands rpm whirling with the precession motion which is synchronous to the input case motion. Conventional studies on this tool assume the continuous rolling motion of the rotor to the case. This paper does not set this assumption, and investigates the dynamical modeling of this tool considering the contact/non-contact configurations and the slip between the rotor and the case. Two kinds of motions are observed in the numerical simulation, one is the uniform precession which was observed in the conventional studies and the other is the periodically reverse precession. These two motions are physically explained, and are also observed in the experiment.

抄録全体を表示

We study on the behavior of the granular bodies in a circular-cone-shaped vessel and transportation performance of a circular-cone-shaped vessel. In this paper, we call the vessel, that consists of two cylinders with different diameter conected by a circular cone such as a Hopper, as a circular-cone-shaped vessel. We assume that, granular bodies are made of elasto-plastic materials such as lead. The elasto-plastic behavior at the impact is modeled as a bilinear type force-displacement characteristics. Based on this assumption, we analyze the behavior of each sphere using Discrete Element Method (DEM). Here, the relationship between the relative velocity and coefficient of restitution for the elasto-plastic behavior at the impact is decided by the impact experiment using two spheres. In numerical analysis, we vary the initial position and the taper angle and study the effect on the transportation performance of a circular-cone-shaped vessel, i.e. the ejection time and stoppage. Finally, we conduct 3D analysis and study the difference between 2D analysis and 3D analysis. And in 3D analysis, we also study the effect of initial position of granular bodies.

抄録全体を表示

Recently, inverted pendulum vehicle controlled by movement of driver's center of gravity, such as Winglet or Segway. These vehicles are called as "Personal Mobility Vehicle (PMV)". They are believed to be used widely from now on, because they are expected to move in pedestrian space differently from automobiles. But the PMV, an inverted pendulum vehicle, hasn't been studied enough compared with automobiles and bicycles. In this study, coupling model between a vehicle and a human are built using Multibody Dynamics. The vehicle is expressed by 2 rigid bodies (tire and body) and a human is expressed by 8 rigid links (foot, lower leg, femoral, body, head, upper arm, lower arm, hand). 2 type of impulses external forces are applied to the different part of the coupling model (vehicle body, human body, and head). We investigate the behaviors of a human model, especially the motion of human model's center of gravity. And we consider the differences in the responses for 2 types impulse external forces.

抄録全体を表示

Quadruped animals switch gait patterns with speed for energy-effective movement. This is similar to the phenomenon that excited natural vibration modes switch with drive frequency in a multi-degree-of-freedom system. Therefore, in this paper, it is assumed that quadruped animal move by using the natural vibration of their own musculoskeletal system. First, experimental apparatus consists of a body, a shoulder / waist and four legs. Four legs are attached to four DC motors fixed at the shoulder / waist. It is verified that there are natural vibration modes look like the trot, pace, and gallop by free vibration. Next, the transfer function is measured in order to design local feed back controller. The transfer function is from the excitation to the vibration detection at right front. There are natural vibration frequencies of trot, pace, and gallop modes in the gain characteristics of the transfer functions. When the excitation point corresponds to the vibration detection point in the multi-degree-of-freedom system, the phase lag becomes 90° at all the resonance frequencies. Therefore, the controller that has a phase lag of 90° is designed. Finally, self-excitation at natural vibration is generated by using four DC motors with local feed back controller. Natural vibration modes look like the trot, pace, and gallop are excited. Efficient driving at resonance point is indicated by measuring current in DC motor.

抄録全体を表示

Quadruped animals switch gait patterns with speed for energy-effective movement. An experimental apparatus which has a simple structure modeled after the actual musculoskeletal system of a quadruped animal was made, and it was shown that the apparatus has natural vibration modes similar to the gait patterns of quadruped animals by a past study. However, it swings to the back and forth symmetry because the leg of the experimental apparatus was considered to be rigid pendulum. Quadruped animals walk by alternately repeating a different movement in the swing phase and the stance phase. To clarify this phenomenon, an experimental apparatus which has a simple structure modeled after the leg of a quadruped animal is made. And it is shown that the apparatus has natural vibration modes similar to the movement of leg when quadruped animals walk. Next, the apparatus is driven at natural frequency by decentralized control. Finally, the relationship between the energy consumption and driven frequency is examined by using apparatus.

抄録全体を表示

An optimization method for a locally reinforced CFRP/Al hybrid plate is proposed to maximize the fundamental frequency. The hybrid plate consists of aluminum core plate and locally installed CFRP patches, and their optimum placements are searched in the optimization problem to reinforce the plate effectively. A finite element analysis code with four-node rectangular ACM elements is employed to calculate frequencies of the hybrid plate, and the result is validated by comparing with the experimental result. Optimum positions and a fiber orientation angle of CFRP patches are used as design variable, and designed simultaneously by the simple genetic algorithm method under the constraint of number limitation of reinforcing elements. Numerical results show that the plate with optimum placements of CFRP patches and fiber orientation angle indicates higher fundamental frequency than the plate with general placements of CFRP patches and fiber orientation angle.

抄録全体を表示

In this study, new effective combination units of visco-elastic and piezo-electric films were proposed for FRP laminated beams and shells to improve their damping and damage tolerance performances. In the present report, a case study of numerical analysis using the general purpose finite element method (FEM) code, ANSYS ED ver.10, was conducted to a case of two-ply CFRP laminate (TYPE A) and two cases of CFRP laminates with visco-elastic and piezo-electric damping units (TYPE B and C) and then their natural frequencies and modal loss factors were numerically obtained. From the present numerical results, it was found that damping performances could be certainly improved when visco-elastic (VE) layers were inserted between the stiff CFRP layers. Piezo-electric (PZ) films, on the other hand, were found to be able to slightly increase the transverse shear deformations of visco-elastic layers, which were one of the main mechanisms of energy dissipations during vibrations, but further optimizations should be done for piezo-electric films.

抄録全体を表示

This paper presents the free vibration characteristics of the sandwich plates composed of isotropic material and viscoelastic material. For this purpose, the parameter identification of the stress-strain relationship for two kinds of viscoelastic materials is carried out first by using fractional derivative model, and then natural frequencies and specific damping capacities of the sandwich plates are obtained numerically by using the Ritz's method based on the Discrete-Layer Theory (DLT), Higher-order Shear Deformation Theory (HSDT) and Classical Lamination Theory (CLT). Finally, the experimental study is also carried out by using the experimental model analysis, and the accuracy of identified models is discussed from the comparisons of numerical and experimental results.

抄録全体を表示

This paper studies the analytical models for of damped free vibration characteristics of FRP laminated composite plates. For this purpose, the strain energy and the kinetic energy are formulated for the rectangular plate based on Discrete-Layer Theory (DLT), Higher-order Shear Deformation Theory (HSDT) and Classical Lamination Theory (CLT), respectively. The frequency equations are derived for the freely-supported plate at all edges by using the Ritz's procedure. In the numerical examples, natural frequencies and specific damping capacities are calculated numerically for the plates by assuming complex elastic modulus. Furthermore natural frequencies and modal damping ratios are obtained experimentally by experimental modal analysis. Finally the applicability of each analytical model for damping vibration analysis is studied by comparing with numerical and experimental results.

抄録全体を表示

Since composite materials are known to have high specific stiffness and strength, they have been widely used many industrial fields, including windmill turbine blades. Such light-weight composite structures under body forces are required to study their vibration characteristics to prevent fatigue failure or noise. In this report, the effect of centrifugal forces is studied on natural frequencies of composite laminated plates as a model of blade. The stress distribution of plates under centrifugal forces is first solved by the Ritz method, and natural frequencies under in-plane stresses are calculated by the Ritz method using in-plane stress distributions found in the first problem. The numerical results obtained by the present method are compared with those from the calculation assuming the stresses distributed uni-directionally. It is found that for the plate with high aspect ratio, both results agree well and this validates the present calculation method. Next, lay-up configurations of composite laminated plates are optimized to maximize the fundamental frequency under centrifugal forces by a layerwise optimization (LO) method. The optimum lay-up configuration determined by the LO method with both the present and the simple uni-directional stress models results in higher fundamental frequencies than plates with typical lay-up configurations.

抄録全体を表示

In the design of the structural elements on the machine and the construction engineering, the resonance measures are important problems, and a vibration control and high structural material is required. Laminating a metallic material and the viscoelastic material is effective for improvement of strength and damping of the structural elements. In present study, the experiment is executed based on "US K 7391 Test methods for vibration-damping property in damped composite beam of unconstrained type". The damping ratio of the laminated beam is evaluated from the time series vibration waveform obtained by the measurement. The concept of damping patch design such as location and length of the viscoelastic material are considered.

抄録全体を表示

National agency for security of aircraft such as Federal Aviation Administration (FAA) and Ministry of Land, Infrastructure, Transport and Tourism (MLIT) of Japan, establishes regulations which demand to conduct a dynamic test for safety of aircraft seats under a certain acceleration-time history. And a drop impact test is one of the ways to conduct the test. In this test, a test object dropped from a drop tower impacts decelerator which is piled up honeycomb sandwich panels. For realizing the desired "acceleration-time" history accurately, the decelerator design method is needed. In this research, quasi-static compression test of paper honeycomb sandwich panels was conducted to examine the "displacement-load" curve and energy absorption. The layup configuration of decelerators was designed by two kinds of approaches: (i) a method without considering the dynamic effect of paper honeycomb sandwich panel, and (ii) a method with considering the dynamic effect of the panel based on Harrigan's shock theory. In the second approach, the "acceleration-time" history of the designed decelerator was calculated by Harrigan's shock theory and compared with the required "acceleration-time" history. Finally, these approaches were compared with the design methods suggested by shoji et al. which uses dynamic energy absorption of honeycomb panels.

抄録全体を表示

This paper proposes a method to identify the location and force history of an impact force acting on CFRP laminated plates using the radiated sound. Sound pressure measured with microphones is used to identify the impact force. The impact location is identified using arrival times of the sound wave at the sensors. Experimental transfer matrices, which relate the impact force and the measured sound pressures, are used to identify the force history. In order to verify the validity of the proposed method, impact force identification of a CFRP laminated plate is performed experimentally, and the identification results are compared with the measured ones. In addition, the effect of the stiffness of the impactor on the accuracy of identification results is examined by conducting experiments using two impulse hammer tips, one made of rubber and the other made of hard plastic. Moreover, the effect of noise on the accuracy is also examined. The experimental results reveal that the location and force history identified using the proposed method show good agreement with the measured ones. In order to identify the force history accurately, experimental transfer matrices should be constructed with an impulse hammer tip which can excite a wide frequency range.

抄録全体を表示

Recently, DS (Directionally Solidified) and SC (Single Crystal) alloys have been widely applied for gas turbine blades instead of CC (Conventionally Casting) alloys to meet the requirement of the high temperature operation and to improve the thermal efficiency. The SC blade consists of one columnar grain, and the DS blade consists of several columnar grains where the growing direction of the columnar crystal is set to the direction of the centrifugal force. Therefore, the vibration analysis of the SC and DS blades has to be carried out, taking account of the anisotropy. In this study, first, the effect of the anisotropy of elastic constants on the vibration characteristics of the SC and DS blade is investigated in detail. Second, the validity of the assumption of the transverse isotropy for the DS blade is examined, carrying out the Monte Carlo simulation. From these results, it is concluded that the actual DS blade can be treated as a transversely isotropic material.

抄録全体を表示

This paper presents theoretical results on nonlinear vibrations of a rectangular plate subjected to gravitational and periodic acceleration laterally. The rectangular plate is simply supported at all edges, which are surrounded with an elastic material. Both uniform in-plane displacements and asymmetric in-plane displacements act as in-plane constraints on the opposite edges via the elastic material. Other opposite edges are compressed with uniform in-plane displacements. Restricting nonlinear vibrations of a thin plate in lower frequency range where bending vibrations are dominant, the effects of in-plane inertia forces can be neglected in the analysis. The Karman type equation modified with lateral inertia is applied as the governing equations of the plate. The response of lateral deflection is assumed with multiple natural modes of linear vibration including unknown time functions. Stress function including nonlinear coupling of the deflection is derived from the compatibility equation. The stress function satisfies both equilibrium conditions of in-plane forces and in-plane moments of forces at the corresponding boundaries. Substituting the deflection and the stress function to the governing equation, a set of nonlinear ordinary differential equations is derived with the Galerkin procedure. Characteristics of restoring force of the post-buckled plate, due to gravity and the in-plane constraints, show the type of a softening-and-hardening spring. Periodic responses are calculated by the harmonic balance method. Non-periodic responses are integrated numerically by the Runge-Kutta-Gill method. Frequency response curves including responses of multiple modes are obtained. Increasing the in-plane asymmetric constraints at the boundaries, responses of the plate are inspected. The amplitude of the principal response corresponding to the lowest mode of vibration is affected by the in-plane constraint. The in-plane asymmetric constraint generates a stretched area and a compressed area in the plate. Within the relatively small amplitude of response, which corresponds to the characteristic of a softening spring, the response shifts to the higher frequency region, as the asymmetric constraint is increased. On the other hand, within the relatively large amplitude of response, which corresponds to the characteristic of a hardening spring, the response becomes smaller at the stretched area, and becomes larger at the compressed area. Moreover principal resonance of the 3rd mode of vibration appears more remarkably with asymmetric constraints.

抄録全体を表示

It is well known in the fields of nuclear and chemical plants that various pipes conveying liquids and gasses should be safe and reliable against excitation by earthquakes. This study proposes an effective use of the flexible pipe system, consisting of a double-walled pipes and infilling materials, to increase the bending rigidities and robustness to excitation. In particular, the vibration properties of such double-walled flexible pipe are examined in terms of changes of infilling rates. Aluminum pipes and glass beads are employed in the experiment to assemble the flexible pipe, and the natural frequencies and damping ratios are measured by using an experimental modal analysis technique with an impulse hammer. The present double-walled pipe system with beads successfully results in higher damping ratios than the pipe without beads. To reveal further relationship between infilling rates and damping ratios, experiments for the single-walled pipe with different filling rates are also conducted. It becomes then clear that there is a moderate filling rate to improve the damping properties of the flexible pipe.

抄録全体を表示

The floating roofs are widely used to prevent evaporation of content in the large oil storage tanks. The 2003 Tokachi-Oki Earthquake caused severe damage to the floating roofs due to liquid sloshing. This accident becomes a cause and the structural integrity of the floating roofs for the sloshing has been actively studied. This paper presents the axisymmetric finite element analysis for the sloshing response of floating roofs in cylindrical storage tanks. The hydrodynamic coupling of fluid and floating roof under seismic excitation is taken into consideration in the analysis. It is assumed that the fluid is compressive and inviscid, and the roof is linear elastic while the sidewall and the bottom are rigid. The fluid behavior is formulated in terms of displacement as the Lagrangian approach. In order to remove the spurious modes, the free vibration analysis is carried out. The highly precise response solutions are given if the effective modes are only taken into consideration in the modal composition.

抄録全体を表示

The elastic buckling mechanism and its adoption in the form of a design procedure are investigated for orthotropic roof shells with square plans. The nature of the imperfection sensitivity of these structures is for the first time discussed in this paper. This allows the development of the reduced stiffness buckling analytical concept for the sphericalshells based upon the introduction of a simple lower bound estimation equation. The elastic buckling load estimation using an alternative buckling mode factor has been proposed.

抄録全体を表示

We suggested a Higher Order Spectra (HOS) as new identification technique in the non-linear vibration system to receive irregularity input, we carry out an experiment non-linear vibration using the HOS and analyzed it and produce the improvement model with the magnet as an experiment model, and we performed the examination, and these are the main point of this report.

抄録全体を表示

The purpose of this paper is to develop a new analysis method, called Three Dimensional Time-Frequency Analysis, based on the well-known digital filter methodology. Using the method, we introduce the algorithm to analyze the sampled signal input, i.e. impulse and swept-sine signals. Second, we apply our method to forced vibrations of weakly nonlinear systems, described by the Duffing equation, to examine the difference between nonlinear and linear systems. Some typical examples were analyzed for the case of a primary and a secondary resonances, and then jump phenomena for primary resonance of the Duffing equation, and superharmonic resonance under the influence of monofrequency excitations are discussed. As a result, the effectiveness of our proposal method is confirmed.

抄録全体を表示

Automatically grasping the parameters of golf clubs is necessary for the swing of golf robot to adjust. We suggest to an algorithm for automatic estimation of properties of golf-clubs by system identification using force sensor. In the first step of this algorithm, substituting initial values to unknown parameters of the club and calculating vibration modes of it. In the next step, the unknown parameters of club are estimated by the least squares method using the vibration modes and the data from static test and acceleration test. The third step is calculating vibration modes by substituting the estimated parameters again. By calculating second and third steps recursively, the unknown parameters converge to actual parameters. However, in some cases of initial parameters, identification is failed due to divergence or converge to local minimum parameters on calculation process. This study investigates the condition to estimate correct results by simulation.

抄録全体を表示

When using natural frequencies as observation data and performing a multiple damage identification analysis, as many degrees of natural frequencies as possible must be measured in order to perform precise identification calculations. However, it is difficult to experimentally measure a large number of degrees of natural frequencies accurately for a large scale structure. Our research thus proposes a multiple damage identification analysis method that uses a modified structure model based on the methods described above. Instead of measuring a large number of degrees of natural frequencies, this method would use measurements of low numbers of degrees of natural frequencies taken from each of several modified structure models made after one part of the target of analysis as observation data. In this report, we have focused on the problem of multiple damage identification in frame structures by formulating an analytical algorithm based on the generalized transfer stiffness coefficient method and filtering theory, and validated this method based on the results of concrete numerical calculations.

抄録全体を表示

In this paper, the effect of dither control on multiple simultaneous squeal generated in the disk brake is experimentally investigated. Dither control is a method to control unstable vibration by applying a low amplitude and a frequency significantly higher than a frequency of unstable vibration. In this paper, a dither device consists of a piezoelectric element and a load cell and is placed between a piston of a caliper and a pad to impose a small periodic variation on the mean clamping force in braking. It is shown that even though the excitation frequency of dither control is lower than squeal frequency, the amplitude of squeal decreases as the excitation amplitude of dither control is increased above a critical level. And furthermore, it is made clear that dither control introducing a periodic fluctuation to the braking force is effective against squeal concerned with out of plane vibration mode of a rotor and is not effective against the other squeal mode at a high frequency.

抄録全体を表示

Suppression effect of multiple dynamic absorbers on chatter in end milling process is investigated. Stability analysis with a simple analytical model is conducted to clarify the relationships between chatter-free depth of cut, spindle speed, tuning parameters (natural frequencies and damping ratios) and total number of dynamic absorbers. First, the suppression effect is examined for the case which all dynamic absorbers are tuned to an identical parameter. The tuning parameters with the largest suppression effect are determined for spindle speeds at the local minimal and the local maximal values on the stability lobe of chatter without dynamic absorbers. It is shown that the influence of the changes of the tuning parameters on the suppression effect varies according to spindle speed. The asymptotic borderline of stability and the maximal axial depth of cut are improved substantially with dynamic absorbers tuned to the derived parameters. Next, the suppression effect is discussed for the case which each dynamic absorber is tuned to different natural frequencies. It is noted that further improvement in the suppression effect is possible compared to the former case.

抄録全体を表示

Brake squeal is a serious problem of automobile brake noise. It is uncomfortable sound appearing sometimes when driver uses brakes. The brake squeal is too complex phenomenon to find out effective solution for preventing the noise. It has been said long time that one of dominant factor causing brake squeal is velocity dependence of friction coefficient between pad and disk, so called "dμ/dV". There is one of theories that a system become unstable dynamically when dμ/dV<0 and then brake squeal occurs. Many researchers reported about measurement results of dμ/dV, obtained by calculating friction coefficient gradient for sliding velocity. Although the sliding velocity is generally measured at steady sliding condition, it is seemed to be including minute vibration when brake squeal is occurring. In this paper, dμ/dV value was calculated by measured friction coefficient and sliding velocity between pad and disk including minute vibration at brake squeal frequency. The results indicated difference of dμ/dV between steady sliding condition and minute vibrating condition. Additionally, tendency of dμ/dV gradient variation differs by each brake pad.

抄録全体を表示

Magnitude and pressure dependency of dynamic stiffness of disk brake pad influence squeal frequency, sound pressure level and squeal generation. The past researches clarified that dynamic stiffness is affected by surface textures. The smoother the surface texture of pad is, the larger dynamic stiffness is. However, frictional contact interface between disk and pad has been sticking at past dynamic stiffness measurement. Slipping between disk and pad affect pad texture. In this study, relation between dynamic stiffness and slipping at contact frictional interface is measured. We made apparatus for dynamic stiffness measuring at slipping between disk and pad. At slipping, dynamic stiffness is decreased. As the slip velocity is large, dynamic stiffness is decrease. If pad stiffness assume series coupling of surface stiffness and base material stiffness, decrease of dynamic stiffness can express that surface stiffness decrease at slipping. In designing squeal-less brake pad, slipping between disk and pad should be considered.

抄録全体を表示

Machines and structures are generally constructed with many parts and the bolted joint is often used to joint some parts. The static property of the jointed part was relatively well proved, for example, Rotscher cone of influence, while the dynamic property has not been cleared yet. In this study, a simple model of bolted joint with high accuracy was proposed by using the finite element method. The object was a set of frame structures and they were jointed by tap bolts or through bolts. In the finite element model, the bolt axis, bolt head and nut were modeled by beam elements and rigid ones to construct a simple finite element model. The first natural frequency was measured by impact test and the fixation area of the contact surface in the finite element model was adjusted to agree the calculated natural frequency with the measured one.

抄録全体を表示

The influence of the positioning error, the eccentricity or shape error, which is made during the milling process, at the planetary gear center or the internal gear of the star type planetary gear trains to the torsional resonance are discussed using the simulating program. The program was previously confirmed that it can sufficiently simulate the vibration occurrence speed of the rotational shaft and the vibration orbit of the floating sun gear. In the conclusion, the position error of the internal gear center and the planetary gear center make the change of the self-centering position of the floating sun gear and the shape of the movable area of the sun gear. But they are not the cause of the resonance, because the resonance does not occur without the forced torque. The eccentricity of the planetary gear can be the cause of the resonance when the rotation speed of the planetary gear becomes the natural frequency of the rotating shaft. But the eccentricity of the internal gear is not the cause of the resonance. The triangle shape error of the internal gear, which is measured in the experiment, also simulated. And it is made clear that the shape error can be the cause of the resonance. This can be considered that the transmission error can be made by the coincidence of the shape and the number of planetary gears.

抄録全体を表示

Numerical simulation program based on the finite difference method (FDM) to analyze two-dimensional dynamic behavior of pantograph/catenary system has been being used for researches, developments, and operations of electric railways for a long time. However, the finite element method (FEM) is more suitable to care its three-dimensional dynamic behavior with large displacement. Therefore, the author newly developed a new simulation program based on FEM, which can analyze dynamic behavior of catenary with three-dimensional configuration, such as inclined catenary system.

抄録全体を表示

In this report, we considered that the effects of in-plane stress of disk for the changes of modal shape analytically. The purpose of this report is to confirm whether the modal shapes change according to the change of in-plane stress. The results clarify the in-plane stress changes the modal shape. The curvature of the modal shape is proportional to reciprocal number of the bending stiffness. The in-plane stress has the effect to change the bending stiffness distributions on disk. Moreover, the natural frequencies of disk are evaluated by two energy methods in which the variations of modal shapes are considered or not. The difference of natural frequencies from two methods shows the effect of the changes of modal shape of disk for difference of results of the energy method is small (the maximum difference of strain energy is 7.1 %).

抄録全体を表示

In a previous paper, the authors proposed a new transfer matrix method for analyzing steady state responses of a nonlinear multi-degree-of-freedom system. In this paper, as a basis for generalizing it to be applicable to a continuous system, the method is revised so that it can be applied to a nonlinear beam. As numerical examples, harmonic as well as superharmonic oscillations of a beam are analyzed. By comparing the results of the method with those of numerical integration of the equations of motion, the validity of the proposed method is confirmed.

抄録全体を表示

Nonlinear vibrations of the multiple beams which are fixed at their both ends to elastic structures under harmonic excitation are investigated. Van der Pol's method is used to determine the frequency resonance curves. The shape of response curves are hard spring types. Although there exist stable branches near the right hand side in the response curves for the system with a single beam, the corresponding branches become unstable for the system with multiple beams. In addition, additional branches appear, because the multiple beams are coupled with the structure. As the number of the beams increases, the number of these additional branches also increases. The beams vibrate at different amplitudes at the excitation frequency range where a sort of the autoparametric resonance occurs. The system may encounter fold bifurcations, pitchfork bifurcations and Hopf bifurcations depending on the values of the system parameters. Amplitude modulated motions, including chaotic vibrations, are observed in the numerical simulation. Corresponding to the unstable branches, each beam vibrates at different amplitudes; this means "localization phenomena."

抄録全体を表示

In this research, numerical results are presented on nonlinear transient responses of beams and arches with a spring-mass system. The governing equation of the arch with the spring-mass system is transformed to a set of ordinary differential equations by the Galerkin method. Nonlinear transient responses of the arches and mass are calculated with numerical integration, applying initial velocity on the mass of the spring-mass system. Based on the numerical results of transient responses, effects of characteristics of nonlinear restoring force of arches on impact force of an object, which collides with arches, are investigated. As the curvature of the arch is increased, impact force is decreased comparing with the result when an object collides with a rigid wall. When the initial velocity of the mass is relatively small, where the deflection of the arch is included in the region of a softening spring, the impact force is efficiently decreased.

抄録全体を表示

A waveform of a water surface caused by water sloshing in a rectangle tank often changes because of nonlinear effect of fluid. In the case of a small water depth, shallow water wave theory can be applied to this phenomenon. When Tsunami propagates on a sloping beach, soliton wave is generated because of nonlinear effect of fluid. This Tsunami phenomenon also can be evaluated based on shallow water wave theory. The purpose of this study is to establish a practical analytical model to analyze these phenomena. This model consists of masses, connecting nonlinear springs, connecting dampers, base support dampers, and base support springs. The characteristic of connecting nonlinear spring is derived from the gravitational pressure, and the base support damper and the base support spring are derived from the shear stress on a bottom. Water waves generated in a rectangle tank, on a sloping beach are analyzed numerically by using the proposed model in order to confirm the validity of the model. All numerical computational results agree very well with the experimental results carried out by Shimizu and Tsuruya. Especially, the phenomena that the distorted waves are generated by the nonlinear effect of fluid are numerically reproduced. Therefore, it is concluded that the proposed model is valid for the numerical analysis of nonlinear pressure wave problem.

抄録全体を表示

Squeal and chatter phenomena were generated in bicycle disc brake. In this report, the authors deal analytically with a simple coupled in-plane and out-of-plane vibration system with three degree of freedom subject to the friction in order to make clear the essence of such phenomena generated in bicycle disc brake system. In this model, two kinds of squeal were generated in the nonlinear analysis, the squeal generated in the linear analysis and the internal resonance phenomena were also generated in the nonlinear analysis. The squeal was in-plane unstable vibration in the disc surface direction, caused by the dry friction with negative slope with respect to the relative velocity. The internal resonance phenomena, that is, the chatter was the other frictional nonlinear vibration in which the squeal and the out-of-plane unstable vibration due to Coulomb friction were combine together through the internal resonance relationship between out-of-plane and in-plane vibrations caused by increasing of moment spring constant. And, a dynamic absorber which is one degree of freedom and can be vibrate in the in-plane direction was applied to the block. The dynamic absorber works effectively to the the unstable vibration which vibrate in the in-plane direction mainly but does not work effectively to the internal rsonance phenomena.

抄録全体を表示

This study presents Active Wheel Damper (AWD) unit which can be fixed on the flexible structures such as cantilever beam with ease. The AWD use a gyro sensor to measure the absolute angular velocity due to the deflective vibration of the structure directly, and can construct sky-hook control with no difficulty by direct feedback of the angular velocity. In this study, sky-hook control with Adaptive Disturbance Cancellation control (SWADC), which is constructed as combined control system of sky-hook control and adaptive disturbance cancellation control, is also proposed to enhance the performance of vibration suppression of AWD unit. Adaptive algorithm, which can estimate the frequency of the vibration of the structure in real-time, is derived based on adaptive notch filter algorithm and estimated frequency is used for the model of disturbance observer which estimates harmonic disturbance. Performance of vibration suppression of AWD is confirmed by simulation and experiment in this study.

抄録全体を表示

Vibration control of an elastic structure subjected to horizontal harmonic excitation by using a nearly square liquid tank is investigated. When the tuning condition, a ratio 1:1:1, is satisfied among the natural frequencies of the structure and two sloshing modes (1,0) and (0,1) in the tank, the performance of the tuned liquid damper can be improved because autoparametric resonance occurs. In the theoretical analysis, the equation of motion for the structure and the modal equations for sloshing are derived considering the nonlinearity of sloshing. Then, van der Pol's method is employed to determine the frequency response curves. The influences of the system parameters, such as the aspect ratio of the tank cross-section and the installation angle of the tank, on the response curves are examined. As a result, the optimal values of these parameters are determined. Hopf bifurcations occur and amplitude modulated motions appear depending on the system parameters. The validity of the theoretical results was confirmed by the experimental data.

抄録全体を表示

Stochastic jump phenomena in the random responses of a Duffing oscillator subjected to the harmonic excitation with random perturbation are investigated. The stochastic jump phenomena correspond to the existence of multiple stationary responses, which differ in phase angle to the excitation. In our previous research, the product of complex wavelet transform of the response and the complex conjugate of that of the excitation has been proposed as the phase angle of each frequency. In this paper, we introduce several thresholds for the argument of this product to distinguish the state of the response. These thresholds are determined from the approximate frequency response function to harmonic excitation. Numerical examples show that there is the optimal threshold, and the optimal value can successfully classify the states of the response.

抄録全体を表示

Response distribution of a nonlinear system subjected to non-Gaussian excitation is investigated. The excitation is represented by its probability density and the auto-correlation function whose characteristic is governed by the correlation time. Both bimodal and Laplace distributions are considered as the non-Gaussianity of the excitation. In order to examine the influence of the non-Gaussianity and the length of correlation time of the excitation on the response, stationary response distributions of a Duffing system are simulated. It is shown that the response distribution is similar to the non-Gaussian distribution of the excitaiton when the correlation time is long.

抄録全体を表示

Impact vibrations of cantilever beam that has very narrow clearance between a beam and an impact wall, and that is excited around 2nd natural frequency, was investigated from the point of view of the sub-harmonic vibration of 1st mode. The followings are made clear. (1) A widely spread attractor with the bending type impact vibration, i.e. the beam bend like a clamped - simply supported beam while the beam is almost contact with the wall, is caused by a nonlinearity that the system is piecewise linear. (2) It is suggested that an essential mechanism of the bending type impact vibration is explained by a model using relatively a few modes. It is also made clear that even if a system is piecewise linear, i.e. the system is consisted of several linear systems, and each systems has linear modes, an analytical model using linear modes for each systems have inappropriate restrictions caused by characteristics of linear modes at connections of each linear systems.

抄録全体を表示