Showing papers in "JSME international journal. Series 3, Vibration, control engineering, engineering for industry in 1989"

Nonstationary Vibration of a Rotating Shaft with Nonlinear Spring Characteristics During Acceleration Through a Critical Speed : A Critical Speed of a 1/2-Order Subharmonic Oscillation

Abstract: This paper deals with the nonstationary oscillations of a flexible rotating shaft with nonlinear spring characteristics. In particular, we investigate a phenomenon during constant acceleration and deceleration passing through a critical speed of a 1/2-order subharmonic oscillation of forward precession. In numerical simulations, we examined the influence of the angular acceleration λ and the initial angular position ψ0 of a rotor unbalance on the maximum amplitude of the subharmonic oscillation. As a result, the following points are clarified: (1) the maximum amplitude depends markedly on λ and ψ0; (2) in order to always pass through this critical speed with finite amplitude during acceleration, an angular acceleration greater than a certain value λ0 is necessary; and (3) when the angular acceleration is less than this critical value λ0 (0<λ<λ0), the shaft's ability to pass through this critical speed depends on ψ0. We ascertained the validity of these theoretical results by experiments.

Experimental Study of Free Vibration of Clamped Rectangular Plates with Straight Narrow Slits

Abstract: The real-time technique of time-averaged holographic interferometry is applied to determine the natural frequencies and corresponding mode shapes of clamped rectangular plates with straight narrow slits, and the effect of the lengths, positions and inclination angles of slits on the natural frequencies and corresponding mode shapes is investigated. Four types of slit locations for a slit parallel with respect to the sides of a plate and a slit having various inclination angles with respect to the longer sides are considered. The natural frequencies obtained experimentally are expressed in terms of a dimensionless frequency parameter, and the results are shown graphically as a function of dimensionless slit length and inclination angle. Several interesting findings are made.

A Study on Brake Noise : Drum Brake Squeal

Abstract: Recently, a theoretical analysis of drum brake squeal was presented by N. Millner. This report has been quoted in many papers. We considered an improved analytical model in order to clarify a practical method of eliminating brake squeal. We obtained an equation which represents E, the increase of kinetic energy during 1 cycle. The equation for E often becomes positive under the influence of coupled vibrations between radial and tangential directions in the brake shoe and brake drum. Brake squeal is generated under the condition E>0. The factors having an influence on brake squeal were clarified by considering the above equation for E. In accordance with the above considerations it is shown that adopting a material with a low coefficient of friction, varying the boundary conditions of the brake shoe, and changing the position of the lining are effective in eliminating brake noise.

The Effect of Shot Peening on the Bending Strength of Carburized Gear Teeth

Abstract: The quantitative effects of hardness and residual stress produced by shot peening on the bending strength of carburized spur gears of m=5 are investigated. The residual stress of every test tooth is measured by an X-ray diffraction method. The intensity of shot peening has little effect on the fatigue strength. The mean strength is about 1200 MPa, which is about 1.3 times that of carburized gears without shot peening. When a tooth surface is electropolished and a higher compressive residual stress is applied to the fillet, the fatigue strength is still 250 MPa higher than that of the shot-peened gears. In this study, the improvement of fatigue strength is assumed to be caused by an increase of both hardness and residual stress, and an experimental formula is proposed to estimate the fatigue strength.

High-Speed Contact Performance of a Catenary-Pantograph System : An Experimental Study Using a Dynamically Scaled Model

Abstract: A dynamically scaled model, which can quantitatively simulate a property at twice the testing speed, is used to clarify how the performance of the existing system deteriorates with an increase in speed, how it depends on the system parameters and how the system can be improved. The contact loss and stress of the contact wire become so large that it is considered impossible to realize a satisfactory current collection at a speed of 300 km/h without appropriate improvements. It is also found that these factors depend mainly on the wave propagating velocity of the contact wire and can be eliminated by introducing a higher-tensioned and/or a lighter contact wire.

Optimal dynamic vibration absorber for multi-degree-of-freedom systems. (Theoretical consideration in the case of random input).

Abstract: This study deals with the optimization problem of a dynamic vibration absorber (DVA) for multi-degree-of-freedom systems subjected to random input with a dominant frequency. A new design method, which optimizes the parameter of DVA composed of such passive elements as a spring and a damper, is proposed. In this method, a suboptimization method based on the optimal control theory is applied for the optimization problem with control structure constraints due to passive elements. This method can consider the input information and the constraints on the stroke of DVAs. The vibration control performance of this method is investigated and is compared with the previous method, in numerical calculations. As a result, the usefulness of the present method is verified.

A Nonparametric Identification Technique for Nonlinear Vibratory Systems : Proposition of the Technique

Abstract: A new technique for identifying nonlinear systems is proposed. The basic procedures of this technique include (1) dividing the regions of displacement and/or velocity into small subdomains, and expressing the restoring force or damping force in a piecewise manner over each subdomain, (2) gathering dynamical data of a periodic external force applied to the system as well as those of periodic oscillations induced by it and (3) applying the principle of harmonic balance. To evaluate the applicability of the proposed technique, we applied it to some typical nonlinear systems with smooth nonlinearity as well as nonsmooth nonlinearity. In application of the technique, the dynamical data are generated numerically from the equation of motion of these systems. It has been shown that the proposed technique identifies the systems very well.

Finite Element Analysis of an Electromagnetic Damper Taking into Account the Reaction of the Magnetic Field

Abstract: In this paper, the fundamental characteristics of the electromagnetic damper are investigated by the finite element method. The reaction of the magnetic field excited by the eddy current is considered in the formulation. Firstly, the eddy current in the conductor slab is calculated for a slab moving at a constant velocity perpendicular to the magnetic flux density, and the attenuation coefficients are evaluated in accordance with the calculated values of the eddy current. Secondly, the effects of the reaction of the magnetic field are analyzed by the finite element method and Runge-Kutta method in a couple problem involving the magnetic field and the vibration of the slab. Thirdly, the numerical results are verified through experimentation.

Dynamical Behavior of a Levitated Body with Magnetic Guides : Parametrically Excitation of the Subharmonic Type Due to the Vertical Motion of Levitated Body

Abstract: Nonlinear oscillations of a levitated body, which is moved in a horizontal plane and is guided by magnetic forces on both sides, are examined theoretically and experimentally. The magnetic forces acting on the body are calculated exactly by applying Coulomb's law over an infinitely small area of magnets, and by integrating about four magnetic poles of two magnetic plates. The parametrically excited oscillations of the body, due to the relative vertical motion between the body and the magnetic guides, are studied theoretically by using the above magnetic forces. The experiments are performed with a simple experimental apparatus. As a main result, the oscillation with a fractional-harmonic pair, as predicted by the theory, is shown experimentally in the special case when two natural frequencies of the body are nearly commensurable.

The Safety Assessment of Human-Robot Systems : Architectonic Principles of Hazard-Control Systems

Abstract: As robotics consists of overall engineering systems, it is necessary for the improvement of robot safety that a systematic plan be executed. The examination and designing of safety measures is an important stage of the safety plan. It is essential to establish a systematic methodology for planning and designing safety measures for the effective practice of this stage in individual systems. first, the hazard-restraint process is generalized as four hazard-restraint principles, based on the A-C model hazard-production theory. Next, the architectonics of the final defense line of the hazard-restraint process is established in terms of a dissociation of action linkage by a hazard-control system. Last, the architecture of the hazard-control systems is demonstrated by examples for systems involving a robot following its course, rescue robot, or surgery robot, and the applicability of safety confirmation sensors or controllers is defined clearly.

A study on the running accuracy of an externally pressurized gas thrust bearing. Bearing stiffness and damping coefficient.

Abstract: The bearing characteristics, such as bearing stiffness and damping coefficient, of an externally pressurized gas-lubricated thrust collar bearing with multiple supply holes are analyzed theoretically. A point-source solution is applied to strictly evaluate the bearing characteristics. The dispersion effects due to the discrete location of the supply holes are discussed by comparing the point-source solutions with the solutions obtained under the line-source assumption. The effects of the deviation of bearing forms, such as the perpendicularity of the rotor end surface, size deviation of the supply holes and flatness of the bearing plate, on the bearing characteristics are also discussed.

Railway wheel squeal. Squeal of a rotating disk.

Abstract: A steel rod was rubbed against the circumference of a thin steel rotating disk in its axial direction. A rotating disk serving as a railway wheel was clamped at the inner radius and free at the outer radius. A squeal occurred at low rotational speeds, when a nodal diameter mode of the disk was stationary in the space-fixed coordinated system. At relatively high rotational speeds, a squeal with a forward or a backward traveling wave was generated. Either of the two waves may occur depending on the vibration of the steel rod. Analytical responses of the rotating disk in both the disk-fixed and the space-fixed coordinate systems agreed with the experimental ones.

Study of the fitting strength between ceramic and metal elements with the use of a shrink fitter at elevated temperature. Proposal of the shrink-fit method with the use of a shrink fitter and experimental results.

Abstract: A new method of obtaining shrink fir between a ceramic shaft and an outer metal ring by means of a shrink fitter is reported in this paper. This shrink fitter, which is ring-shaped and has a higher coefficient of thermal expansion than the outer ring does, was inserted between the ceramic shaft and the outer ring. The shrink fitter was cut in the radial direction into several pieces. The fitting strengths of these shrink-fitted assemblies were measured from room temperature up to 600°C°C. The effect of the number of cuttings in the shrink fitter on the fitting strength at elevated temperatures was researched. It was revealed that the cutting of the shrink fitter into three pieces or more was requisite to ensure the fitting strength at elevated temperatures. It was possible to design the fitting strength-temperature relationships by changing the thickness of the shrink fitter in the radial direction. For example, the fitting strength would increase with temperature when the shrink fitter was sufficiently thick, and the fitting strength would decrease with temperature when the shrink fitter was sufficiently thin. Expressions which estimate the fitting strengths of the shrink-fitted assemblies are also developed in this paper.

Experimental identification of mechanical structure with characteristic matrices. (Proposition of curve fitting in the frequency domain and MCK identification using curve fitting).

Abstract: It is not always possible to obtain characteristic matrices from modal parameters obtained by experimental modal analyses, such as curve fitting. If the degrees of freedom of the mathematical model are different from those of the structure identified, which occurs in almost all cases, contradiction occurs between the modal parameters when transformed to physical parameters. This paper proposes certain constraints that modal parameters must satisfy in order to be transformed to mass, stiffness and damping matrices without contradiction. A nonlinear optimization technique is used to solve these contraints. A new multireference curve fitting method in the frequency domain is also proposed. The number of unknown parameter depend only on the number of degrees of freedom identified, regardless of the number of response points. This method is effective when there are a number of response points. some experimental models are examined to validate this method.

An active tilting system for railway cars.

Abstract: Negotiation curves at speeds higher than normal is desired. for the purpose of improving ride quality on curved tracks, an active tilting system for railway cars is studied. This system is composed a curve detector, curve data memories, microcomputers for making control signals, feedback circuits of swing angles, and air servomechanisms. The whole construction of the system is described as well as the method of detecting the entrances of curved tracks, the contents of the objective control signals made by microcomputers, the criteria for ride quality, and the system optimization through running tests.

An improvement of the tooth profile accuracy of a hobbed gear by adjusting the hob eccentricity.

Abstract: Recent studies have shown that the tooth profile errors of hobbed gears were mainly caused by geometrical error and eccentricity of the hob under good cutting conditions. Because manufacturing a highly accurate hob is very difficult and a highly accurate gear may not be obtained, even though a highly accurate hob is used, it is very important to investigate how to improve the actual meshing accuracy of the hob in the cutting process. In general, the meshing error of the edges caused by the hob eccentricity is nearly sinusoidal and the geometrical errors often contain sinusoidal components. On the basis of these facts, this report proposes a method which makes both of the sinusoidal error components cancel each other out in order to obtain an accurately hobbed gear. The test results clearly show the method's effectiveness in improving the tooth profile accuracy of gears.

Measurement of Actual Stress and Temperature on the Roll Surface During Rolling : Frictional Stress Distribution and Pressure Distribution in Cold Rolling

Abstract: Pressure, and frictional stress in both rolling and width directions have been measured in the cold rolling of aluminum strip and billet by a new stress sensor developed by the authors. Characteristics of the frictional stress distribution in cold rolling have been elucidated. Frictional stress in the rolling direction is almost constant from the entrance to the neutral point in the contacting arc, both in strip and billet rolling. by contrast, frictional stress in the width direction increases from the center line to the edge part and its peak lies in the central part of the contacting arc in strip rolling. However, in billet rolling, it has two peaks along the contacting arc and its value does not vary from the center line to the edge part. This may be connected with the metal flow in the width direction in billet rolling.

Modeling and Analysis of a Production Line Operated According to Demand

Abstract: We shall consider a production line which is operated according to demand for products so as to minimize product shortages and excesses of inventory. In our model, the capacities of buffer storages and a warehouse are adjusted according to demand, and the blocking of each stage plays an essential role in reducing unnecessary inventories. The efficiency of the line is measured by the sum of the average shortage of products and the average inventory of in-process and finished products in the steady state. We propose two efficient approximate solution methods evaluating the line efficiency in terms of configuration parameters. Of these two methods, the second method requires more tedious calculations, but is more accurate. We confirm the validity of the approaches by comparing the solutions for many example problems obtained by our methods with those obtained by computer simulation.

Free Vibration Analysis of a Multiple Straight Line Structure Regarded as a Discrete System by the Transfer Influence Coefficient Method

Abstract: This paper describes the general formulation for the in-plane flexural free vibration analysis of a multiple-layered straight-line structure by the transfer influence coefficient method. The structure is modeled as a distributed mass system with lumped masses and lumped inertia moments, and massless linear and rotational springs. The results of the simple numerical computational examples demonstrate the validity of the present method giving the numerical high accuracy and the numerical high speed, compared with the transfer matrix method on a personal computer. The main features of this method are the unification of the frequency equation for all boundary conditions, and the elimination method of the false roots when the bisection method is used for solving the frequency equation. The cancelling attributable to the adding and subtracting of hyperbolic and trigonometric functions is overcome by partitioning the uniformly distributed beams.

Development of an oil-air lubrication system with a piezoelectric nozzle for machine tool spindles

Abstract: Oil-air lubrication is an effective lubrication method for the high-speed spindle of machine tools. However, the rate of oil supply to the bearing fluctuates markedly due to intermittent oil supply from the oil-air mixing valves. In this study, a new oil-air mixing apparatus is developed by applying a piezoelectric nozzle which has been used to the printing head of ink-jet printers. By using the piezoelectric nozzle instead of the conventional mixing valve, fluctuation of the oil supply is successfully controlled. Further, it becomes possible to attach the oil-air mixing equipment in the vicinity of the bearings. The oil supply rate can be, therefore, quickly changed in response to changes in the running condition of the bearing.

Head Slider Flying Height Measurement Using a Color Image Processing Technique

Abstract: A new method was developed to measure the head slider flying height in magnetic disk devices. The interference color fringe created in the clearance between slider and the glass disk was characterized by using a color image processing technique. The relation between hue and the flying height was obtained within a 0.0073 micrometer error. The presented method makes use of the phase difference among RGB signals, so it does not depend on the light intensity distribution in the TV field, which comes from optical devices. In addition, the presented method gives spatially continuous flying height attitude with a high resolution over a wide range.

Static and dynamic characteristics of porous journal bearings with nonuniform permeability.

Abstract: The present study is a theoretical analysis to evaluate the static and dynamic characteristics of oil-filled porous journal bearings with nonuniform permeability. Three types of nonuniform distributions of permeability are analyzed. For the first type, the permeability of the inside is lower than that of the outside. For the second type, the permeability of the loaded part is lower than that of the unloaded part. For the third type, the permeability of the bearing ends is lower than that of the middle. It is found that all nonuniform type bearings have a higher load carrying capacity, lower total side leakage flow, larger oil film coefficients, and higher stability threshold speed compared with the corresponding values of uniform type bearings, in which permeability is equal to the higher of nonuniform type bearings. Furthermore, the second nonuniform type has a higher load carrying capacity and a lower total side leakage flow than the other nonuniform types.

On heat-balance of gear-meshing apparatus (Experimental and analytical heat transfer coefficient on tooth faces).

Abstract: The heat transfer coefficient on tooth faces must be known when calculating temperature rise on tooth faces. Though analytical fling-off cooling of gear teeth and experimental results about the adhesive amount of oil have been already reported, there have been few reports about heat transfer coefficients on tooth faces based on experiments and calculated from actual conditions. In this paper, the temperatures of the tooth faces and of the oil were measured, so the heat transfer coefficient was evaluated based on the temperature difference between the tooth face and the oil. The heat transfer coefficient concerning two conditions was evaluated analytically.

A Study on The Numerical Analysis of Fluid Film Lubrication by the Boundary-Fitted Coordinates System : The Case of Steady Gas-Lubrication

Abstract: A new method on the discretization of the steady gas-lubricated Reynolds equation is presented. The present method is derived by applying the boundary-ditted coordinates system to the divergence formulation method. Generalized algebraic equations for node pressures derived from the present method can be widely used to represent arbitrary film configuration and arbitrary bearing shape. This algebraic equation is shown by the separation of three components: the Poiseuille flow; the Couette flow; the correcting component of slip flow by rarefaction of the gas. The Couette flow component is discretized by a new upstream scheme derived from an extension of the simple upstream scheme, and the other components are discretized by an approximation of linearized distribution. Discretization of four representative boundary conditions are shown. Examples on a herringbone grooved journal bearing used in a misaligned large eccentricity and a small number of grooves are shown.

A study of a servodamper with preview action. (An optimal design for impact vibration control).

Abstract: This paper presents an active control method for suppressing impact vibration using a servodamper with a preview action. It is also the purpose of this paper to establish the optimal design procedure for the servodamper system. First, from the viewpoint of preview control method, this paper describes system equations of the servodamper system. Then, by using a parameter optimization technique, the optimal conditions for the preview servodamper control system are derived. Using a design procedure based upon the optimal conditions, the optimal servodamper system is constructed, and the influence of both preview control and feedback control on the effectiveness of the optimal servodamper system is investigated. Furthermore, aiming to pursue a simple servodamper control system, a reduced order control compensator is presented. Finally, the robustness of the servodamper system is discussed and a general method for designing a servodamper system with preview action is also discussed.

The Hydraulic Tube Bulging of a Tube-Attached Lining Rubber Membrane with Axial Compressive Force

Abstract: The authors have developed a new machine for tube bulging which initially puts a deflated rubber membrane into a work tube and drives the internal pressure through a membrane after the initial settingup. Using this new machine, the effects of the tube end condition and tube length on the deformed shaped and the strain distribution are examined experimentally. Three cases of the tube end conditions, (A) axially fixed, (B) axially free and (C) axially compressed by force, are parametrically investigated. The results are as follows: (1) comparing at the same bulge height, the internal pressure is lower with the longer tube and also lower with the end condition changing from case A to C, (2) when the tube is short and/or the axial compressive force is small, the deformed shape appears as a barrel, and when the tube is long and/or the axial force is large, it has a cylindrical region uniformly expanded at its center, and (3) the axial compressive force tends to prevent thickness reduction of the tube.

Vibration Reduction of a Railway Wheel by Cantilever-Type Dynamic Absorbers : Optimal Adjustment of Absorbers and Experiment

Abstract: In this paper, the optimal tuning of the natural frequency and the optimal damping parameter of a cantilever-type dynamic vibration absorber attached to a railway wheel are derived. An index, the equivalent mass ratio, with which the effectiveness of absorbers can be estimated and evaluated easily, is defined. It is found that the cantilever-type absorber can be more effective than the conventional mass-spring absorber. When N absorbers are attached to a wheel and N/2 is different form the number of nodal diameters, the effectiveness of the vibration reduction does not decrease, even though the wheel is rotating.