Showing papers on "Vibration published in 1989"
TL;DR: These data confirm that vibration is able to preferentially activate the Ia afferent channel, even when the vibration amplitude is low, and show that the physiological messages triggered by ongoing motor activities undergo a series of changes during the exposure of muscles to vibration.
Abstract: The activities of single proprioceptive fibres were recorded from the lateral peroneal nerve using transcutaneously implanted tungsten microelectrodes. Unitary discharges originating from muscle spindle primary and secondary endings and Golgi tendon organs were identified by means of various physiological tests. The sensitivity of proprioceptors to mechanical vibrations with a constant low amplitude (0.2–0.5 mm) applied at various frequencies to the tendon of the receptor-bearing muscle was studied. Muscle spindle primary endings (Ia fibres) were found to be the most sensitive to this mechanical stimulus. In some cases their discharge could be driven in a one-to-one manner up to 180 Hz. Most of them also fired harmonically with the vibration up to 80 Hz and then discharged in a subharmonic manner (1/2–1/3) with increasing vibration frequencies. Muscle spindle secondary endings (II fibres) and Golgi tendon organs (Ib fibres) were found to be either insensitive or only slightly sensitive to tendon vibration in relaxed muscles. The effects of tendon vibration on muscle spindle sensory endings response to muscle lengthening and shortening induced by imposed constant velocity or sinusoidal movements of the ankle joint were studied. Modulation of the proprioceptive discharge frequency coding the various joint movement parameters was either completely or partly masked by the receptor response to vibration, depending on the vibration frequency. Moreover, vibrations combined with sinusoidal joint movements elicited quantitatively erroneous proprioceptive messages concerning the movement parameters (amplitude, velocity). The sensitivity of the Golgi tendon organs to vibration increased greatly when the receptor-bearing muscle was tonically contracted. These data confirm that vibration is able to preferentially activate the Ia afferent channel, even when the vibration amplitude is low. They define the frequency sensitivity of the muscle spindle primary and secondary endings and the Golgi tendon organs. They also show that the physiological messages triggered by ongoing motor activities undergo a series of changes during the exposure of muscles to vibration.
804 citations
TL;DR: The entropy and the free energy associated with these degrees of freedom can be calculated with high precision for simple molecules in the gas phase under certain conditions to larger molecules and to proteins.
Abstract: Molecules in solution have degrees of freedom representing overall movements of translation and rotation, internal vibrations and rotations about single bonds. The entropy and the free energy associated with these degrees of freedom can be calculated with high precision for simple molecules in the gas phase. The calculation can be extended under certain conditions to larger molecules and to proteins
317 citations
TL;DR: In this paper, the buckling and free-vibration behavior of cross-ply rectangular composite laminates under various boundary conditions was studied. But the bucklings and free vibration properties were not investigated.
Abstract: Analytical and finite-element solutions of the classical, first-order, and third-order laminate theories are developed to study the buckling and free-vibration behavior of cross-ply rectangular composite laminates under various boundary conditions
252 citations
Book•
01 Oct 1989
TL;DR: In this article, a single-degree-of-freedom (SDF) dynamic system is considered, and the effect of different degrees of freedom on the dynamics of the system is investigated.
Abstract: TABLE OF CONTENTS PREFACE 1 INTRODUCTION 1.1 Objectives of the Study of Structural Dynamics 1.2 Importance of Vibration Analysis 1.3 Nature of Exciting Forces 1.4 Mathematical Modeling of Dynamic Systems 1.5 Systems of Units 1.6 Organization of the Text PART I 2 FORMULATION OF THE EQUATIONS OF MOTION: SINGLE-DEGREE-OF-FREEDOM SYSTEMS 2.1 Introduction 2.2 Inertia Forces 2.3 Resultants of Inertia Forces on a Rigid Body 2.4 Spring Forces 2.5 Damping Forces 2.6 Principle of Virtual Displacement 2.7 Formulation of the Equations of Motion 2.8 Modeling of Multi Degree-of-Freedom Discrete Parameter System 2.9 Effect of Gravity Load 2.10 Axial Force Effect 2.11 Effect of Support Motion 3 FORMULATION OF THE EQUATIONS OF MOTION: MULTI-DEGREE-OF-FREEDOM SYSTEMS 3.1 Introduction 3.2 Principal Forces in Multi Degree-of-freedom Dynamic System 3.3 Formulation of the Equations of Motion 3.4 Transformation of Coordinates 3.5 Static Condensation of Stiffness matrix 3.6 Application of Ritz Method to Discrete Systems 4 PRINCIPLES OF ANALYTICAL MECHANICS 4.1 Introduction 4.2 Generalized coordinates 4.3 Constraints 4.4 Virtual Work 4.5 Generalized Forces 4.6 Conservative Forces and Potential Energy 4.7 Work Function 4.8 Lagrangian Multipliers 4.9 Virtual Work Equation For Dynamical Systems 4.10 Hamilton's Equation 4.11 Lagrange's Equation 4.12 Constraint Conditions and Lagrangian Multipliers 4.13 Lagrange's Equations for Discrete Multi-Degree-of-Freedom Systems 4.14 Rayleigh's Dissipation Function PART II 5 FREE VIBRATION RESPONSE: SINGLE-DEGREE-OF-FREEDOM SYSTEM 5.1 Introduction 5.2 Undamped Free Vibration 5.3 Free Vibrations with Viscous Damping 5.4 Damped Free vibration with Hysteretic Damping 5.5 Damped Free vibration with Coulomb Damping 6 FORCED HARMONIC VIBRATIONS: SINGLE-DEGREE-OF-FREEDOM SYSTEM 6.1 Introduction 6.2 Procedures for the Solution of Forced Vibration Equation 6.3 Undamped Harmonic Vibration 6.4 Resonant Response of an Undamped System 6.5 Damped Harmonic Vibration 6.6 Complex Frequency Response 6.7 Resonant Response of a Damped System 6.8 Rotating Unbalanced Force 6.9 Transmitted Motion due to Support Movement 6.10 Transmissibility and Vibration Isolation 6.11 Vibration Measuring Instruments 6.12 Energy Dissipated in Viscous Damping 6.13 Hysteretic Damping 6.14 Complex Stiffness 6.15 Coulomb Damping 6.16 Measurement of Damping 7 RESPONSE TO GENERAL DYNAMIC LOADING AND TRANSIENT RESPONSE 7.1 Introduction 7.2 Response to an Impulsive force 7.3 Response to General Dynamic Loading 7.4 Response to a Step Function Load 7.5 Response to a Ramp Function Load 7.6 Response to a Step Function Load With Rise Time 7.7 Response to Shock Loading 7.8 Response to a Ground Motion Pulse 7.9 Analysis of Response by the Phase Plane Diagram 8 ANALYSIS OF SINGLE-DEGREE-OF-FREEDOM SYSTEMS: APPROXIMATE AND NUMERICAL METHODS 8.1 Introduction 8.2 Conservation of Energy 8.3 Application of Rayleigh Method to Multi Degree of Freedom Systems 8.4 Improved Rayleigh Method 8.5 Selection of an Appropriate Vibration Shape 8.6 Systems with Distributed Mass and Stiffness: Analysis of Internal Forces 8.7 Numerical Evaluation of Duhamel's Integral 8.8 Direct Integration of the Equations of Motion 8.9 Integration Based on Piece-wise Linear Representation of the Excitation 8.10 Derivation of General Formulae 8.11 Constant Acceleration Method 8.12 Newmark's beta Method 8.13 Wilson-theta Method 8.14 Methods Based on Difference Expressions 8.15 Errors involved in Numerical Integration 8.16 Stability of the Integration Method 8.17 Selection of a Numerical Integration Method 8.18 Selection of Time Step 9 ANALYSIS OF RESPONSE IN THE FREQUENCY DOMAIN 9.1 Transform Methods of Analysis 9.2 Fourier Series Representation of a Periodic Function 9.3 Response to a Periodically Applied Load 9.4 Exponential Form of Fourier Series 9.5 Complex Frequency Response Function 9.6 Fourier Integral Representation of a Nonperiodic Load 9.7 Response to a Nonperiodic Load 9.8 Convolution Integral and Convolution Theorem 9.9 Discrete Fourier Transform 9.10 Discrete Convolution and Discrete Convolution Theorem 9.11 Comparison of Continuous and Discrete Fourier Transforms 9.12 Application of Discrete Inverse Transform 9.13 Comparison Between Continuous and Discrete Convolution 9.14 Discrete Convolution of an Infnite and a Finite duration Waveform 9.15 Corrective Response Superposition Methods 9.16 Exponential Window Method 9.17 The Fast Fourier Transform 9.18 Theoretical Background to Fast Fourier Transform 9.19 Computing Speed of FFT Convolution 9.16 Exponential Window Method 9.17 The Fast Fourier Transform 9.18 Theoretical Background to Fast Fourier Transform 9.19 Computing Speed of FFT Convolution PART III 10 FREE VIBRATION RESPONSE: MULTI-DEGREE-OF-FREEDOM SYSTEM 10.1 Introduction 10.2 Standard Eigenvalue Problem 10.3 Linearized Eigenvalue Problem and its Properties 10.4 Expansion Theorem 10.5 Rayleigh Quotient 10.6 Solution of the Undamped Free-Vibration Problem 10.7 Mode Superposition Analysis of Free-Vibration Response 10.8 Solution of the Damped Free-Vibration Problem 10.9 Additional Orthogonality Conditions 10.10 Damping Orthogonality 11 NUMERICAL SOLUTION OF THE EIGENPROBLEM 11.1 Introduction 11.2 Properties of Standard Eigenvalues and Eigenvectors 11.3 Transformation of a Linearized Eigenvalue Problem to the Standard Form 11.4 Transformation Methods 11.5 Iteration Methods 11.6 Determinant Search Method 11.7 Numerical Solution of Complex Eigenvalue Problem 11.8 Semi-definite or Unrestrained Systems 11.9 Selection of a Method for the Determination of Eigenvalues 12 FORCED DYNAMIC RESPONSE: MULTI-DEGREE-OF-FREEDOM SYSTEMS 12.1 Introduction 12.2 Normal Coordinate Transformation 12.3 Summary of Mode Superposition Method 12.4 Complex Frequency Response 12.5 Vibration Absorbers 12.6 Effect of Support Excitation 12.7 Forced Vibration of Unrestrained System 13 ANALYSIS OF MULTI-DEGREE-OF-FREEDOM SYSTEMS: APPROXIMATE AND NUMERICAL METHODS 13.1 Introduction 13.2 Rayleigh-Ritz Method 13.3 Application of Ritz Method to Forced Vibration Response 13.4 Direct Integration of the Equations of Motion 13.5 Analysis in the Frequency Domain PART IV 14 FORMULATION OF THE EQUATIONS OF MOTION: CONTINUOUS SYSTEMS 14.1 Introduction 14.2 Transverse Vibrations of a Beam 14.3 Transverse Vibrations of a Beam: Variational Formulation 14.4 Effect of Damping Resistance on Transverse Vibrations of a Beam 14.5 Effect of Shear Deformation and Rotatory Inertia on the Flexural Vibrations of a Beam 14.6 Axial Vibrations of a Bar 14.7 Torsional Vibrations of a Bar 14.8 Transverse Vibrations of a String 14.9 Transverse Vibration of a Shear Beam 14.10 Transverse Vibrations of a Beam Excited by Support Motion 14.11 Effect of Axial Force on Transverse Vibrations of a Beam 15 CONTINUOUS SYSTEMS: FREE VIBRATION RESPONSE 15.1 Introduction 15.2 Eigenvalue Problem for the Transverse Vibrations of a Beam 15.3 General Eigenvalue Problem for a Continuous System 15.4 Expansion Theorem 15.5 Frequencies and Mode Shapes for Lateral Vibrations of a Beam 15.6 Effect of Shear Deformation and Rotatory Inertia on the Frequencies of Flexural Vibrations 15.7 Frequencies and Mode Shapes for the Axial Vibrations of a Bar 15.8 Frequencies and Mode Shapes for the Transverse Vibration of a String 15.9 Boundary Conditions Containing the 15.10 Free-Vibration Response of a Continuous System 15.11 Undamped Free Transverse Vibrations of a Beam 15.12 Damped Free Transverse Vibrations of a Beam 16 CONTINUOUS SYSTEMS: FORCED-VIBRATION RESPONSE 16.1 Introduction 16.2 Normal Coordinate Transformation: General Case of an Undamped System 16.3 Forced Lateral Vibration of a Beam 16.4 Transverse Vibrations of a Beam Under Traveling Load 16.5 Forced Axial Vibrations of a Uniform Bar 16.6 Normal Coordinate Transformation, Damped Case 17 WAVE PROPAGATION ANALYSIS 17.1 Introduction 17.2 The Phenomenon of Wave Propagation 17.3 Harmonic Waves 17.4 One Dimensional Wave Equation and its Solution 17.5 Propagation of Waves in Systems of Finite Extent 17.6 Reection and Refraction of Waves at a Discontinuity in the System Properties 17.7 Characteristics of the Wave Equation 17.8 Wave Dispersion PART V 18 FINITE ELEMENT METHOD 18.1 Introduction 18.2 Formulation of the Finite Element Equations 18.3 Selection of Shape Functions 18.4 Advantages of the Finite Element Method 18.5 Element Shapes 18.6 One-dimensional Bar Element 18.7 Flexural Vibrations of a Beam 18.8 Stress-strain Relationship for a Continuum 18.9 Triangular Element in Plane Stress and Plane Strain 18.10 Natural Coordinates 19 COMPONENT MODE SYNTHESIS 19.1 Introduction 19.2 Fixed Interface Methods 19.3 Free Interface Method 19.4 Hybrid Method 20 ANALYSIS OF NONLINEAR RESPONSE 20.1 Introduction 20.2 Single-degree-of-freedom System 20.3 Errors involved in Numerical Integration of Nonlinear Systems 20.4 Multiple Degree-of-freedom System ANSWERS TO SELECTED PROBLEMS INDEX
248 citations
Book•
01 Jan 1989
TL;DR: In this article, the effect of changes in running condition on the noise of rotating electrical machines was investigated and applied to assessing the technical condition of rotating machines and to scheduling their maintenance.
Abstract: A. Generation and Elimination of Noise and Vibration. 1. Basic acoustic terms. 2. Generation process of noise and vibration in electrical machines. 3. Electromagnetic noise and causes of vibration. 4. Vibration of rotating electrical machines. 5. Generation of airborne noise in electrical machines. 6. The effect of changes in running condition on the noise of rotating electrical machines. 7. Design considerations to reduce noise and vibration of electromagnetic origin. 8. Mechanical noise and vibrations. 9. Noises of aerodynamic origin. 10. Secondary noise reducing measures. B. Experimental Investigation of Noise and Vibration Phenomena. 11. Measuring noise and vibration phenomena. 12. Measuring the steady-state vibrations of electrical machines. 13. Noise measurements on electrical machines under steady-state operating conditions. 14. Measuring transient noise phenomena. 15. Measuring techniques of transient vibroacoustic signals. 16. Indirect measuring of transient vibroacoustic signals. C. Some Practical Applications of Vibroacoustic Methods in the Testing of Rotating Electrical Machines. 17. Noise and vibration testing in practice. 18. Applying vibration measurement to assessing the technical condition of rotating machines and to scheduling their maintenance. Epilogue with economic considerations. Appendices. References. Subject Index.
235 citations
Book•
01 Jan 1989
207 citations
01 Jan 1989
206 citations
Dissertation•
01 Feb 1989
193 citations
TL;DR: In this article, a deformable shear deformable theory of cross-ply laminated composite shallow shells is presented, which is further employed in the analysis of the eigenvibration and static buckling problems of doubly curved shallow panels.
Abstract: This paper deals with the substantiation of a shear deformable theory of cross-ply laminated composite shallow shells. While the developed theory preserves all the advantages of the first order transverse shear deformation theory it succeeds in eliminating some of its basic shortcomings. The theory is further employed in the analysis of the eigenvibration and static buckling problems of doubly curved shallow panels. In this context, the state space concept is used in conjunction with the Levy method, allowing one to analyze these problems in a unified manner, for a variety of boundary conditions. Numerical results are presented and some pertinent conclusions are formulated.
138 citations
TL;DR: In this article, the authors used harmonic balance to develop approximate analytical solutions to the equations of motion of a single impact pair including a general discussion of the existence and stability of these solutions Nonlinear frequency response characteristics are obtained for a single frequency excitation and primary resonance (no subharmonic or superharmonic response) and the results are validated using an analog computer simulation.
TL;DR: In this article, a simple mechanical impact (hammering) model for brake noise generation is proposed, which is independent of friction variation during the period of decreasing sliding speed, and can explain the noise excitation phenomenon.
TL;DR: In this article, the authors presented a model for the reaction of the air on a vibrating circular plate, showing that reaction to be equivalent to a virtual mass and radiation damping, to be added to the plate mass and the mechanical damping.
TL;DR: In this paper, a modal technique was used to predict the flutter speed of suspension bridges based on a selection of the lowest vertical and torsional natural mode shapes, which yields an unsymmetric matrix eigenvalue problem.
TL;DR: Interpolation by digital computer provides an alternative to the phase-locked frequency multiplier for the calculation of the time domain average of gear vibration signals as discussed by the authors, but it requires longer calculation times.
Patent•
12 May 1989
TL;DR: In this article, a vehicle with a fork structural vibration type angular velocity sensor, a supersonic road sensor and a car speed sensor is used to detect horizontal and vertical displacement of the vehicle.
Abstract: PURPOSE: To perform much better control with yet fewer sensors by detecting each displacement in both horizontal and vertical directions and so on of a vehicle with a fork structural vibration type angular velocity sensor, a supersonic road sensor and a car speed sensor, and thereby controlling a suspension. CONSTITUTION: Horizontal displacement of a vehicle is detected by a fork structural type angular velocity sensor 11, and vertical displacement of the vehicle is detected by a supersonic road sensor 12, while vehicle speed is detected by a car speed sensor 13. Then, on the basis of each detection signal of these sensors 11-13, a specified arithmetic process is performed with an electronic controller 14, while damping force of a shock absorber is regulated by an actuator 15. At this time, the angular velocity sensor 11 connects a vibration unit 109 joining a drive element 101 and a detecting element 104 with a joint 105 and another vibration unit 110 connecting a monitor element 102 and a detecting element 104 with a joint 106 through a connecting plate 107, and it is made up of supporting this connecting plate 107 at one point by a support rod 108. COPYRIGHT: (C)1990,JPO&Japio
TL;DR: In this paper, the steady state vibrations of a non-linear dynamic vibration absorber are studied using the method of multiple scales, in conjunction with digital simulations, and the main results are concerned with certain dynamic instabilities which can occur if the absorber is designed such that the desired operating frequency is approximately the mean of the two linearized natural frequencies of the system.
Abstract: The steady state vibrations of a non-linear dynamic vibration absorber are studied using the method of multiple scales, in conjunction with digital simulations. The main results are concerned with certain dynamic instabilities which can occur if the absorber is designed such that the desired operating frequency is approximately the mean of the two linearized natural frequencies of the system. A combination resonance can occur in this case, resulting in large amplitude almost-periodic vibrations. This motion destroys the effectiveness of the absorber and can coexist with the desired low-amplitude periodic response, which leads to initial condition dependent dynamics.
TL;DR: In this paper, the free vibration characteristics of laminated composite shells are presented using an isoparametric doubly curved quadrilateral shear flexible element and first-order shear deformation theory is accounted for using an extension of Sanders' shell theory.
TL;DR: In this article, a refined higher-order theory for free vibration analysis of unsymmetricaliy laminated multilayered plates is presented, which accounts for parabolic distribution of the transverse shear strains through the thickness of the plate and rotary inertia effects.
TL;DR: In this paper, a vibration damper includes two materials, each being formed of a metal sheet having a rubber- or synthetic resin-base viscoelastic polymeric layer or layers formed on one or both sides, which are arranged in opposition to each other through said vicoelastic layers and bonded together with the use of a hot-melt-adhesive synthetic resin layer having a high melting point.
Abstract: A vibration damper includes two materials, each being formed of a metal sheet having a rubber- or synthetic resin-base viscoelastic polymeric layer or layers formed on one or both sides, which are arranged in opposition to each other through said viscoelastic layers and bonded together with the use of a hot-melt-adhesive synthetic resin layer having a high melting point. Alternatively, one of said materials is arranged in opposition to another metal sheet through said vicoelastic layer or layers and bonded thereto with the use of said hot-melt-adhesive synthetic resin layer. A soundproofing structure using such a vibration damper is also provided.
Patent•
21 Nov 1989TL;DR: An elasto-plastic damper is adapted to be used in a structure such as a building and other facilities, for absorbing vibration energy created by earthquake tremors and other ground vibrations.
Abstract: An elasto-plastic damper is adapted to be used in a structure, such as a building and other facilities, for absorbing vibration energy created by earthquake tremors and other ground vibrations. The damper is a centrally bulged and generally cone-shaped hollow body of revolution so that its section modulus changes substantially porportional to a bending moment created in the damper body due to horizontal stresses, thus permitting a maximum degree of deformability. This elasto-plastic damper is compact in size and demonstrates a high degree of vibrational energy absorbability.
TL;DR: In this paper, a theoretical framework for analyzing and classifying actuators that generate their output by rectifying small-amplitude mechanical vibrations, such as might be generated by piezoelectric elements, is established.
TL;DR: In this article, the available empirical relationships for maximum dynamic shear modulus (Gmax) and dynamic longitudinal damping (Dl) at low strain amplitudes for sands are reviewed.
TL;DR: In this article, phase velocity and damping of waves along the circumference of a stationary tire are compared with a two-dimensional model, called the circular ring model, and the influence of the area on which the force operates is analysed with respect to the admittance.
TL;DR: In this article, the Coriolis mass flowmeter is modelled by using the theory of vibrating beams and tube deformations for the fundamental mode and for the next two modes of natural (out-of-plane) vibration are worked out for a U-tube configuration.
TL;DR: A review of the literature concerned with experimental studies of the effects of translational whole-body vibration on continuous manual control performance is presented in this article, which emphasizes the adaptive ability of the human operator.
TL;DR: Whole-body vibrations were measured at the seatpan of load-haul-dump vehicles of 3.5-, 5-, 6- and 8-yard capacity at two underground mines and acceleration exposure ratios calculated using resultant acceleration vectors were found to exceed the ISO exposure limit for health or safety in all 22 cases.
Abstract: Whole-body vibrations (WBV) were measured at the seatpan of load-haul-dump (LHD) vehicles of 3.5-, 5-, 6- and 8-yard capacity at two underground mines. Twenty-two sets of measurements were made involving 11 vehicles, 8 operators and 4 work locations. In each set frequency-weighted rms and peak accelerations were measured in the x, y and z directions, as defined by the ISO (1982), during mucking, driving full, dumping and driving empty. Significant differences in rms accelerations were found between vehicle sizes and between operational tasks (less than or equal to 0.05). The smallest (3.5 yd) vehicle produced the greatest accelerations in the x and z directions. Accelerations in the x and z directions were also greater when driving full and empty than when mucking and dumping. The highest frequency-weighted rms accelerations of 2.0 to 2.8 m/s-2 were recorded in the z (longitudinal) direction. Peak accelerations ranged from 1.2 to greater than or equal to 20 m/s2, resulting in crest-factor ratios in excess of six. The exposure periods for each task were used to calculate mean daily acceleration exposures (m/s2). Of the 22 sets of measurements, 20 exceeded the International Standards Organization (ISO) six-hour daily exposure limit in the z direction of acceleration, and 9 exceeded the six-hour daily exposure limits in all three directions. Acceleration exposure ratios calculated using resultant acceleration vectors as described in ISO (1982), were found to exceed the ISO exposure limit for health or safety in all 22 cases. One-third octave band frequency analysis of the weighted signals indicated that the dominant frequencies were usually 1.6 to 3.15 Hz, except when the vehicles were idling and higher frequencies predominated.
TL;DR: In this article, an analytical model for determining the free vibration characteristics of advanced composite turbopropellers (prop-fans) is presented, where the blade is modeled using a number of straight beam-type finite elements, and the elastic axis of each element is a piecewise straight representation of the curved line of shear centers of the swept blade.
Abstract: An analytical model for determining the free vibration characteristics of advanced composite turbopropellers (prop-fans) is presented. The blade is modeled using a number of straight beam-type finite elements, where the elastic axis of each element is a piecewise straight representation of the curved line of shear centers of the swept blade. The finite-element model is obtained from Hamilton's principle with allowances for: generally anisotropic material behavior, arbitrary cross-sectional properties, large pretwist angles, out-of-plane cross-section warping, and geometrically nonlinear behavior based upon moderate deflection theory. The natural frequencies and mode shapes of the rotating blade are calculated assuming linear perturbations about the nonlinear static equilibrium position of the blade. This model is sufficiently general to analyze other advanced composite aerospace structures. Numerical results are presented to illustrate the versatility of the method by applying it to 1) a conventional propeller (TRW-Hartzell 101/16) and 2) a highly swept and pretwisted isotropic turbopropeller (NASA SR-3). Excellent agreement with experimental test results is obtained for the lower modes of both the conventional propeller and the advanced turbopropeller.
TL;DR: In this paper, a single magnetic actuator is used to estimate system characteristics and apply the optimum control force needed to minimize synchronous vibration, without prior knowledge of bearing or rotor characteristics or the distribution of out-of-balance forces.
Abstract: This paper develops the authors' earlier work on vibration control of multi-mode rotor-bearing systems. It shows how a single magnetic actuator can be used to estimate system characteristics and apply the optimum control force needed to minimize synchronous vibration. In the application considered here, a rotor is supported on oil-film bearings. The algorithm determines the optimum control force without prior knowledge of the bearing or rotor characteristics or the distribution of out-of-balance forces. A rig is described and used to illustrate the application of the theoretical work.
01 Apr 1989-Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology
TL;DR: In this article, it is shown that the precision machining of cermaics can be achieved using ultrasonic superposition vibration cutting of ultrasonically vibrated ceramics (USVC).
Abstract: In this report, it is shown that the precision machining of cermaics can be achieved using ultrasonic superposition vibration cutting of ultrasonically vibrated ceramics (USVC). Analytical results are confirmed by experiments using a new 50 Hz vibration cutting device with an ultrasonically vibrated tool on ceramic surfaces. By using this new cutting process, a cutting volume of 25 mm2 × 0.02 mm per 6 is obtained, and a cutting surface roughness of 1–6 μm Rmax is achieved. In addition, it is found that tool and machined surface temperatures do not rise, owing to the low load and speed. It is proposed that adding high frequency vibration stress to ceramics, which have a tensile stress weakness, is the basis for the precise and efficient cutting of ceramics.