bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic Behavior of a Drillstring: Presentation and Validation of the Experimental Set-Up
Authors: Berlioz Alain , Hagopian Johan Der , Dufour Régis , Draoui Elyés 
Published: March 2021

Abstract
As part of a large study on oil drilling vibrations involving, theory, laboratory tests and development of computer code, the present paper focuses on the effects of the tangential solicitations on the lateral behavior of a rod, representative of drillstring. The lateral behavior of the drillstring is governed by time-varying parameter equations. The torsion-lateral and longitudinal-lateral couplings are both experimentally and numerically studied and particular attention is paid to lateral instabilities. The effect of the curvature of the rod, mud, stabilisers and rotation are taken into account.
Nonstationary Vibration of a Rotating Shaft With Nonlinear Spring Characteristics During Acceleration Through a Major Critical Speed: A Discussion by the Asymptotic Method and the FFT Method
Authors: Ishida Yukio , Yasuda Kimihiko , Murakami Shin 
Published: March 2021

Abstract
Nonstationary vibrations at the major critical speed of a rotating shaft with nonlinear spring characteristics are discussced. Firstly, the first order approximate solutions of steady-state and nonstationary oscillations are obtained by the asymptotic method. The relations between these approximate solutions and the nonlinear components in the polar coordinate expression are investigated. It is clarified that, similar to the case of the stationary oscillations, only the isotropic nonlinear component has influence on nonstationary oscillations in the first order approximation. Secondly, the complex-FFT method where non-stationary time histories obtained by numerical integrations of the equations of motion are treated as complex numbers in the complex plane which coincides with the whirling plane are proposed. By this method, the amplitude variation curves of each vibration component are obtained. From the comparison of the amplitude variation curves of the first approximation of the asymptotic method, the solution of the complex-FFT method, and direct numerical integration, it is clarified that, although all these solutions coincide well in the case of stationary solutions, the first approximation of the asymptotic method has comparatively large quantitative error in the case of nonstationary solutions. In addition, the influences of the anisotropic nonlinear components which do not appear in the first approximation of the asymptotic method are investigated.
Response of a Parametrically-Excited System to a Nonstationary Excitation
Authors: Neal H. L. , Nayfeh A. H. 
Published: March 2021

Abstract
The response of a single-degree-of-freedom system to a nonstationary excitation is investigated by using the method of multiple scales as well as analog- and digital-computer simulations. The unexcited system has one focus and two saddle points. The system can be used to model rolling of ships in head or follower seas. The method of multiple scales is used to derive equations governing the modulation of the amplitude and phase of the response. The modulation equations are used to find the stationary solutions and their stability. The response to nonstationary excitations is found by integrating the original governing equation as well as the modulation equations. There is good agreement between the results of both approaches. For some frequency and amplitude sweeps, the nonstationary response found from integrating the original governing equation exhibits behaviors that are analogous to symmetry-breaking bifurcations, period-doubling bifurcations, chaos, and unboundedness present in the stationary case. The maximum response amplitude and the excitation amplitude or frequency at which the response becomes unbounded are found as functions of the sweep rate. The results of the digital-computer simulations are verified with an analog computer.
Perturbation Solution of an Oscillator With Periodic van der Pol Damping
Authors: Storti Duane W. , Nevrinceanu Cornelius , Reinhall Per G. 
Published: March 2021

Abstract
We present a perturbation solution for a linear oscillator with a variable damping coefficient involving the limit cycle of the van der Pol equation (van der Pol 1926). This equation arises as the variational equation governing the stability of in-phase vibration in a pair of identical van der Pol oscillators with linear coupling. The van der Pol oscillator has served as the classic example of a limit cycle oscillator, and coupled limit cycle oscillators appear in mathematical models of self-excited systems ranging from tube rows in cross flow heat exchangers to arrays of stomates in plant leaves.
As in many systems modeled by coupled oscillators, criteria for phase-locking or synchronization are of fundamental importance in understanding the dynamics. In this paper we study a simple but interesting problem consisting of a pair of identical van der Pol oscillators with linear diffusive coupling which corresponds, in the mechanical analogy, to a spring connecting the masses of the two oscillators. Intuition and earlier first-order analyses suggest that the spring will pull the two masses together causing stable in-phase locking. However, previous results of a relaxation limit study (Storti and Rand 1986) indicate that the in-phase mode is not always stable and suggest the existence of an additional stability boundary.
To resolve the apparent discrepancy, we obtain a new periodic solution of the variational equation as a power series in ε, the small parameter in the sinusoidal van de Pol oscillator. This approach follows Andersen and Geer’s (1982) solution for the limit cycle of an isolated van der Pol oscillator. The coupling strength corresponding to the periodic solution of the variational equation defines an additional stability transition curve which has only been observed previously in the relaxation limit. We show that this transition curve, which provides a consistent connection between the sinusoidal and relaxation limits, is O(ε2) and could not have been delected in O(ε) analyses. We determine the analytical expression for this stability transition curve to O(ε31) and show very favorable agreement with numerical results we obtained using an Adams-Gear method.
Nonlinear Interaction of a Parametrically-Excited Coupled Column-Pendulum Oscillator
Authors: Mustafa G. , Ertas A. 
Published: March 2021

Abstract
A new vibration absorbing device is introduced for large flexible structures. The bifurcation diagrams obtained for the averaged system, indicate that the system loses stability via two distinct routes. One leading to a saddle-node bifurcation, normally associated with the jump phenomena. The second instability is due to the Hopf bifurcation, that results in amplitude modulated motion of the oscillator. A parameter range has been identified where these bifurcations coalesce. This phenomenon is a strong indicator of existence of homoclinic orbits. In addition to the regular solution branches, that bifurcate from the zero solution, the system also possesses isolated solutions (the so-called “isolas”) that form isolated loops bounded away from zero. As the forcing amplitude is varied, the isolas appear, disappear or coalesce with the regular solution branches. The response curves indicate that the column amplitude shows saturation. The pendulum acts as a vibration absorber over a range of frequency where the column response is saturated. However, there is also a frequency range over which a reverse flow of energy occurs, where the pendulum shows reduced amplitude at the cost of large amplitudes of the column.
Free and Forced Response of an Axially Moving String Transporting a Damped Linear Oscillator
Authors: Zhu W. D. , Mote C. D. 
Published: March 2021

Abstract
The transverse response of a cable transport system, which is modelled as an ideal, constant tension string travelling at constant speed between two supports with a damped linear oscillator attached to it, is predicted for arbitrary initial conditions, external forces and boundary excitations. The exact formulation of the coupled system reduces to a single integral equation of Volterra type governing the interaction force between the string and the payload oscillator. The time history of the interaction force is discontinuous for non-vanishing damping of the oscillator. These discontinuities occur at the instants when transverse waves propagating along the string interact with the oscillator. The discontinuities are treated using the theory of distributions. Numerical algorithms for computing the integrals involving generalized functions and for solution of the delay-integral-differential equation are developed. Response analysis shows a discontinuous velocity history of the payload attachment point. Special conditions leading to absence of the discontinuities above are given.
Kinematics and Dynamics of a Parallel Manipulator With Woven Joints
Authors: Pang Hyunsok 
Published: March 2021

Abstract
Presented is an analysis of the kinematics and the inverse dynamics of a proposed three DOF parallel manipulator resembling the Stewart platform in a general form. In the kinematic analysis, the inverse kinematics, velocity and acceleration analyses are performed, respectively, using vector analysis and general homogeneous transformations. An algorithm to solve the inverse dynamics of the proposed parallel manipulator is then presented using a Lagrangin technique. In this case, it is found that one should introduce and subsequently eliminate Lagrange multipliers in order to arrive at the governing equations. Numerical examples are finally carried out to examine the validity of the approach and the accuracy of the numerical technique employed. The trajectory of motion of the manipulator is also performed using a cubic spline.
Distributed Observing and Active Control of a Cantilever Plate
Authors: Tseng C. I. , Tzou H. S. 
Published: March 2021

Abstract
Structural identification and vibration control of flexible systems have drawn much attention in recent years. This article presents an analytical study on a distributed piezoelectric sensor and a distributed actuator coupled with a flexible plate. The integrated piezoelectric sensor/actuator can monitor the oscillation as well as actively control the structural vibration by the direct/converse piezoelectric effects, respectively. Based on Love assumptions, theories on distributed sensing and active vibration control of a plate using piezoelectric materials are derived. By employing the finite element technique, the integrated structure is further discretized. Applications to the dynamic measurement is demonstrated and the dynamic performance of a cantilever plate is also evaluated.
Distributed Transfer Function Synthesis of Complex Flexible Systems
Authors: Yang Bingen 
Published: March 2021

Abstract
This paper presents a new analytical and numerical method for modeling and synthesis of complex flexible systems (CFS) that are multiple continua combined with lumped parameter systems. In the analysis, the CFS is first divided into a number of subsystems; the distributed transfer functions of each subsystem are determined in exact and closed form by a state space technique. The CFS is then assembled by imposing displacement compatibility and force balance at the nodes where the subsystems are interconnected. With the distributed transfer functions and the transfer functions of the constraints and lumped parameter systems, exact, closed-form formulation is obtained for various dynamics and vibration problems. The method does not require a knowledge of system eigensolutions, and is valid for non-self-adjoint systems with inhomogeneous boundary conditions. In addition, the proposed method is convenient in computer coding, and suitable for computerized symbolic manipulation.
On the Identification of Localized Losses of Stiffness in Structures
Authors: Pabst Ulrich , Hagedorn Peter 
Published: March 2021

Abstract
In damage detection it is common to use measured modal data and a mathematical model in connection with system identification. The part of the system undergoing the largest stiffness decrease is defined to contain damage. This approach is very sensitive to measurement errors. The measurement errors are much larger for mode shape functions than for the eigen-frequencies. The errors in the mode shapes are often of the same order of magnitude as the variations due to damage leading to poor results in damage detection. Thus, the use of the mode shape functions themselves instead of their small damage induced variations would dearly be preferable. In this paper we examine the relation between the changes in the eigenfrequencies, the local stiffness losses and the mode shape functions of the undamaged system. This relation is then utilized in a damage detection procedure.
Vibration Localization in Band/Wheel Systems: Theory and Experiment
Authors: Al-jawi A. A. N. , Ulsoy A. G. , Pierre Christophe 
Published: March 2021

Abstract
An investigation of the localization phenomenon in band/wheel systems is presented. The effects of tension disorder, interspan coupling, and translation speed on the confinement of the natural modes of free vibration are investigated both theoretically and experimentally. Two models of the band/wheel system dynamics are discussed; a simple model proposed by the authors [1] and a more complete model originally proposed by Wang and Mote [9]. The results obtained using the simple interspan coupling model reveal phenomena (i.e., eigenvalue crossings and veerings and associated mode localization) that are qualitatively similar to those featured by the more complex model of interspan coupling, thereby confirming the usefulness of the simple coupling model. The analytical predictions of the two models are validated by an experiment. A very good agreement between the experimental results and the theoretical ones for the simple model is observed. While both the experimental observations and the theoretical predictions show that a beating phenomenon takes place for ordered stationary and axially moving beams, beating is destroyed (indicating the occurrence of localization) when any small tension disorder is introduced especially for small interspan coupling (i.e., when localization is strongest).
Input Sensitive Dynamic Resistor of a Rotating System
Authors: Lee B. K. 
Published: March 2021

Abstract
This paper presents the dynamic response and analysis of a dynamic resistor in a rotating system which is sensitive to the vibration of the rotating system. The sensitivity of the dynamic resistor is adjusted in order to stabilize the rotating system when acted upon by various excitation input functions. The equations of motion of the dynamic resistor and the rotating system, derived by the use of the energy method, result in coupled nonlinear differential equations, and the response of the dynamic resistor is highly correlated to the vibration of the rotating system.
In this paper, the derivation of equations of motion of the dynamic resistor and the rotating system and their dynamic responses are analyzed in order to determine the optimal design parameters that provide stability for the rotating system when it is excited by external input forcing functions. The dynamic response is obtained both by experimental data and computer simulation. The experimental data indicate that the sensitivity of the dynamic resistor is related to the vibrating response of the rotating system and the rotational system parameters including the natural frequency.
The dynamic response obtained by computer simulation is compared with the experimental data. The computer simulation results are to be used to determine the optimal values of the parameters of the dynamic resistor with respect to the rotating system.
The uniqueness of this system is that the dynamic resistor is completely isolated from other inputs except the rotational vibration of the rotating system. The conclusions include recommendations and areas for future research.
Non-Linear Vibrations and Asymmetry in Coupled Tandem Hot Rolling Mills
Authors: Jafari A. A. , Tieu A. K. , Basu A. 
Published: March 2021

Abstract
This paper discusses the computer simulation of the interactions between the torsional vibration mode and linear vibration mode of a vertical edging mill and a horizontal roughing mill which are coupled by a hot steel slab. The influence of the mass, rigidity and damping of the slab in both elastic and plastic regions have been considered. This non-linear simulation also takes into account backlash on the drive shaft and asymmetrical rolling condition in horizontal mill.
Vibration of a Rotating Stepped Beam by the Distributed Transfer Function Method
Authors: Kuang W. , Tan C. A. 
Published: March 2021

Abstract
In this paper, the distributed transfer function formulation is used to investigate the dynamic characteristics of a rotating stepped beam. The Rayleigh beam model with general boundary conditions is considered. Exact closed-form solutions are obtained for the free and forced responses. Results for the natural frequencies and mode shapes of the stepped beam are presented. For the purpose of illustration, three sets of boundary conditions are considered: simply-simply supported, clamped-clamped, and clamped-simply supported. Effects of system parameters such as the length ratio and diameter ratio of the beam on the free and forced responses are examined and discussed. It is shown that for different combinations of boundary conditions, the pair of natural frequencies for the forward and backward precession modes are associated with different mode shapes except for the simply-simply supported beam. Moreover, the difference between the forward and backward mode shapes increases with the rotation speed of the beam.
High Speed Rotating Shafts Design Algorithm
Authors: Wong Po Kee 
Published: March 2021

Abstract
This paper reveals an invention for the first time to the public about the fundamental concepts for the design of high speed rotating shafts based on the wave spectrum analysis of the vibrational modes of elastic circular rods and shells that was completed in 1967, even though the Pochhammer-Chree-Love solution of the transversal (n = 1) vibration of a solid elastic rod was originated by Pochhammer in 1876.
Development of an On-Line PC-Based Diagnostic Expert System
Authors: Pawtowski E. C. , Kirk R. G. , Cochran J. S. 
Published: March 2021

Abstract
A PC-based hardware and software system has been designed to continuously monitor large numbers of rotating machinery, evaluate each machine’s condition through a series of user-definable standards, and alert operators to potential problems. This system employs multiple program modules written in three different programming languages that multitask under the Windows operating system. These modules interact without the use of dynamic data links. It has developed as an offshoot of the WOT on-line expert system project. Preliminary versions have been tested under operating plant conditions.
Internal Rotor Friction Induced Instability in High-Speed Rotating Machinery
Authors: Walton James F. , Martin Michael R. 
Published: March 2021

Abstract
Results of a program to investigate internal rotor friction destabilizing effects are presented. Internal-friction-producing joints were shown to excite the rotor system first natural frequency, when operating either below or above the first critical speed. The analytical models used to predict the subsynchronous instability were also confirmed. The axial spline joint demonstrated the most severe subsynchronous instability. The interference fit joint also caused subsynchronous vibrations at the first natural frequency but these were bounded and generally smaller than the synchronous vibrations. Comparison of data from the two test joints showed that supersynchronous vibration amplitudes at the first natural frequency were generally larger for the interference fit joint than for the axial spline joint. The effects of changes in imbalance levels and side loads were not distinguishable during testing because amplitude-limiting bumpers were required to restrict orbits.
Active Vibration Control of the Axially Moving String by Wave Cancellation
Authors: Chung C. H. , Tan C. A. 
Published: March 2021

Abstract
Active vibration control of an axially moving string by wave cancellation is presented. The control problem is formulated in the frequency domain. An exact, closed-form expression for the transfer function of the closed-loop system, consisting of the flexible structure, a feedback control law and the dynamics of the sensing and actuation devices, is derived. It is shown that all vibration modes can be stabilized and that the controlled system has no resonance. Moreover, the designed controller is applicable to the control of the string transverse vibration under various kinds of loading and constraint conditions. Results for the response of the controlled string under different excitations are presented and discussed along with the wave propagation and cancellation characteristics.
Modeling and Control of a Nonlinear Beam
Authors: Banks H. T. , King Belinda B. 
Published: March 2021

Abstract
In this paper we develop a mathematical model for a nonlinear analog of the Euler-Bernoulli beam which possesses linear damping and nonlinear stiffness properties. This nonlinear model is used as a basis for approximation and linearization. Feedback design for the linear problem is applied to compute gains which are then used in the nonlinear system.
Segmented Two-Dimensional Modal-Filtering Sensors
Authors: Sumali Hartono , Cudney Harley 
Published: March 2021

Abstract
This paper discusses the development of a method to create modal coordinate sensors on two-dimensional structures. The sensor, which is made of a piezoelectric layer, is divided into an array of segments. The total output of the sensor is the weighted sum of the outputs of the segments. The purpose of this segmentation is to bypass the requirement for a continuous spatial variation of polarization, which is necessary in creating an ideal two-dimensional modal sensor but infeasible in practice and unworkable for most boundary conditions.
Analytical simulation on a simply-supported plate shows that the performance of a modal sensor created by configuring a segmented sensor approaches that of an ideal modal sensor. Modal filtering effects increase with the decrease in the segment size.
A Slewing Motor-Beam System With Coulomb Friction Including Experimental Results
Authors: Crassidis Agamemnon L. , Mayne Roger W. 
Published: March 2021

Abstract
This paper considers the effect of Coulomb friction on the behavior of a slewing motor-beam system. A model of the system is described which includes a finite element representation for the beam, dynamic interaction between the motor and the beam, and a representation for Coulomb friction. The model is used in the study of closed-loop transient response of the slewing system. Simulation results are compared against laboratory behavior. The model reasonably predicts slewing behavior. It simulates steady state error in the control of slewing angle and can represent the case of shaft lock-up which leaves the beam oscillating freely. The system gear ratio is adjusted to produce different levels of motor-beam dynamic interaction. Control performance is similar to that expected from studies of the linear slewing system. For a gear ratio that yields little motor-beam interaction, beam vibration is difficult to suppress. A gear ratio that heavily loads the motor and has too much interaction shows considerable actuation effort for a given level of transient response speed.