bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of Non-Conservative Coupling Loss Factors Between Rotating Machinery Components
Authors: Cuschieri J. M. , Sun J. C. , Journeau F. 
Published: April 2021

Abstract
An expression for calculating the coupling loss factors between non-conservatively coupled substructures is derived based on the characteristics of the coupled substructures and the interface medium. The expressions consists of point mobility functions evaluated on the substructures near or at the junctions and a joint impedance function which represents the interface characteristics. The point mobility functions can be obtained analytically, for simple structures, or experimentally. The joint impedance is modeled by a dissipative stiffness element. The derived expressions for the coupling loss factors simplify to the well known expressions for conservative coupling when the dissipation term tends to zero. This approach is used to estimate the coupling loss factor between a shaft and a bearing liner with an oil film interface. The estimated results for the coupling loss factors are compared to experimental results obtained from a statistical energy analysis model. The estimated results and the experimental results show good agreement which verifies the approach used for the determination of the non-conservative coupling loss factors.
Effect of Backlash on Vibration Spectrum in Spur Gearboxes Incorporating Sleeve Bearings
Authors: El-Saeidy Fawzi M. A. 
Published: April 2021

Abstract
An Analytical model is presented to simulate effect of tooth backlash on vibration spectrum of spur gearboxes incorporating sleeve bearings. Included in the model are: elasticity of shafts, friction between meshing teeth, interaction between gearbox casing and internals, and time-varying tooth backlash (backlash is a function of operating center distance), mesh stiffness (stiffness is calculated based on the strain energies of the tooth that is treated as a cantilever beam of involute shape) and Hertzian mesh damping. The bearing forces are calculated with consideration of bearing radial clearance and system vibrations. The analysis is applied to a single stage gearbox and equations of motion are numerically integrated to obtain system reponse in time domain. This response is transformed into frequency domain (vibration spectrum) using Fast Fourier Transform (FFT) algorithm and samples of the results are shown for different values of tooth backlash. The results show that backlash has a pronounced effect on gearbox vibration and study provides an analysis procedure for predicting such effects.
Fluid Inertia Forces in Squeeze Film Dampers
Authors: El-Shafei A. , Crandall S. M. 
Published: April 2021

Abstract
Fluid inertia forces in Squeeze Film Dampers (SFDs) are obtained for short and long dampers using an energy approximation based on the assumption that the velocity profiles with inertia are the same as those for an inertialess fluid. It is shown that the inertia forces thus obtained are proportional to the usual radial, centripetal, tangential and Coriolis accelerations of the journal, plus an additional nonlinear acceleration. The inertia coefficients of the dampers are obtained, for both uncavitated and cavitated dampers, and are plotted versus the eccentricity ratio for centered, nearly circular whirl. The inertia forces obtained by the energy approximation are compared to an exact linearized solution for centered, circular whirl, and good agreement is found for both short and long dampers in the Reynolds number range of ordinary SFD application.
The Effectiveness of Porous Squeeze Film Dampers for Suppressing Nonsynchronous Motions
Authors: Zhang Shiping , Yan Litang , Li Qihan , Kawazoe Yoshihiko 
Published: April 2021

Abstract
The rotor time domain orbits and the transmissibility trajectories of a rigid rotor supported on squeeze film damper (SFD) and porous squeeze film damper (PSFD) systems were investigated. Under certain system parameters, The SFD system with a centralising spring exhibits excessive nonsynchronous motions with approximate third harmonic frequencies and opposite whirling motions as well as severe transmitted forces. However, under same system parameters and with a porous permeable film outer race PSFD system could effectively attenuate the nonsynchronous motions with very small transmissibilities. The rigid rotor without a centering spring supported on SFD and PSFD systems were also investigated. The highly nonlinear film force characteristics take the major responsibility for the nonsynchronous motions of uncentralized SFD systems, and typical second and third harmonic orbits of SFD system were predicted. While under the same conditions, perfect synchronous orbits of PSFD system were resulted. PSFD through outer race permeability could provide more reasonable film force characteristics, and thus has the capability of suppressing nonsynchronous motions.
Optimal Design of Centered Squeeze Film Dampers
Authors: Nataraj C. , Ashrafiuon Hashem 
Published: April 2021

Abstract
A two degree-of-freedom model, consisting of a rigid rotor supported on rigid bearings which are in turn supported on squeeze film dampers, is considered. Isotropic centering springs are assumed resulting in a steady synchronous centered circular response for the rotor. The resulting nonlinear system is modeled in nondimensional form. The transmissibility ratio of the system as well as the power dissipated are minimized for various values of unbalance and at several speeds, with the squeeze film bearing parameter as the primary design variable. Expressions are derived for linear variational stability of the circular orbit, and are imposed as constraints in the optimization process. The dependence of the optimal configuration on speed and unbalance is discussed.
Experimental Investigation on the Dynamic Pressure and Force Response of a Partially Sealed Squeeze Film Damper
Authors: Meng G. , Andres L. A. San , Vance J. M. 
Published: April 2021

Abstract
The influence of rotational speed, oil temperature and supply pressure on the squeeze film pressure and fluid forces is investigated experimentally for a partially sealed squeeze film damper (SFD) test rig executing circular centered orbits. Experimental Tesults show that the sealed damper produces higher damping forces than an open end SFD, though it is more prone to produce oil cavitation. As a result, the peak-to-peak pressures and the tangential force (damping force) decrease with increasing rotational speed; while, the radial force (stiffhening force) becomes negative due to the large extent of the cavitation zone. The tangential force decreases and the radial force increases with increasing lubricant temperature. The squeeze film pressure and film force increase as the supply pressure rises. The film cavitation onset is determined by the level of supply pressure and rotational speed.
Controllable Squeeze Film Damper: An Application of Electro-Rheological Fluid
Authors: Morishita Shin , Mitsui Jun’ichi 
Published: April 2021

Abstract
A notable characteristic of Electro-Rheological (ER) fluid is the variation of its apparent viscosity with the application of an electric field. The application of this characteristic to the performance of squeeze film damper of a flexible rotor is investigated in this paper. It is shown experimentally that by controlling the supporting damping capacity continuously, rotor vibration can be reduced remarkably in a wide range of rotating speed. Moreover, the study indicates experimentally that there exists an optimum supporting damping for every vibration mode.
Vibrations of Foundations Interacting With Subsoil Experimental Studies and BE Calculations
Authors: Gaul L. 
Published: April 2021

Abstract
Calculation of the dynamic response of sensitive structures like foundations for vibrating machinery requires to take the interaction with subsoil into account. Structures and soil are discretized by boundary elements and coupled by a substructure technique. Viscoelastic constitutive equations contain fractional time derivatives.
Surface waves generated by machine foundations and diffracted by embedded structures and soil inhomogeneities are analyzed by conventional and optoelectronic experimental techniques and calculated by the boundary element method (BEM).
Self-Operating On-Off Type Semi-Active Damper and its Performance Test
Authors: Kim Hyeong-keun , Sung Nak Hoon , Park Youn-sik 
Published: April 2021

Abstract
The semi-active damper idea is not new. Many previous researchers showed that a semi-active damper and an on-off type semi-active damper can each bring about almost die equivalent suspension performance as that of an active suspension system. In this work, a self-operating on-off type semi-active damper idea is devised. The advantage of the self-operating on-off type semi-active damper over the conventional semi-active damper or on-off type semi-active damper is its mechanical simplicity. The self-operating semi-active damper does not need any sensors and logic circuits for on-off control motion and brings about an identical suspension performance. In order to prove the practical applicability of the damper, two prototype dampers are designed, built and tested. As a result, the tested prototype damper shows very good agreement not only with the peak damping forces, but also with the timely self-operating on-off valve motion.
Semiactive Control of Vibrations in Automobiles
Authors: Lieh Junghsen , Haque Imtiaz 
Published: April 2021

Abstract
A seven-DOF vehicle model comprising a full car body and four wheel-axle assemblies is used to investigate the influence of active and semiactive suspensions on ride performance. The active control of car body roll, pitch and bounce is based on an optimal control strategy assuming the tire deflection measurements are not available. The frequency analysis shows a significant attenuation in car body modes but a potential increase in wheel motions. Dissipative dampers with solenoid valves are used as the semiactive control mechanism. Simulation results in the time domain indicate that suboptimal values exist in the damping “on” state and an on-off damping control scheme can effectively reduce the car body motions and suspension travels.
Integral and State Variable Feedback Controllers for Improved Performance in Automotive Vehicles
Authors: ElMadany Mohamed M. 
Published: April 2021

Abstract
An analytical investigation of a half-car model using an integral plus state variable feedback controller for tracking and regulation is performed. The potential benefits of incorporating, actively or semi-actively, such controller to remedy the inherent problems associated with conventional passive suspensions and active suspensions based on state variable feedback controllers are examined. Both random and deterministic roadway inputs as well as deterministic body force and moment disturbances are used. The results demonstrate that an optimal suspension using an integral plus state variable feedback controller retains both excellent ride and attitude control characteristics.
Application of Generalized Polynomial Expansion Method to Nonlinear Rotor Bearing Systems
Authors: Hwang Jon Li , Shiau Ting Nung 
Published: April 2021

Abstract
The Generalized Polynomial Expansion Method (GPEM) is utilized to model a large-order flexible-rotor system with nonlinear supports. With the application of GPEM, a set of nonlinear ordinary differential equations are obtained. A hybrid method which combines the merits of the Harmonic Balance Method (HBM) and the Trigonometric Collocation Method (TCM) is used to solve for the nonlinear response of the system. This hybrid method together with reduction techniques can efficiently solve for the motion of the system. The overall algorithm presented provides a very efficient technique for investigating the periodic response of large-order nonlinear rotor systems. Two examples are used to illustrate the merits of the method. One is the simple Jeffcott rotor which is used to check the accuracy of the present numerical algorithms. The other is a flexible shaft with multiple disks, supported by multiple bearings. It is used to show the advantages of the linkage between GPEM and the presented hybrid numerical algorithm. Some of the support bearings are modeled as a squeeze-film damper associated with a center spring. The center spring is considered to be linear and the squeeze-film damper is nonlinear. The nonlinear hydrodynamic forces are obtained using short-bearing theory.
Based on the example results, the conclusions can be summarized as follows:
(l) For a nonlinear flexible-rotor system, the number of equations needed for the system described by the Generalized Polynomial Expansion Method are always smaller than the number required by the finite element method before applying the condensation technique. This is also true for the linear case which has been discussed by Shiau and Hwang (1989, 1990).
(2) A technique of component mode synthesis has been developed based on the modeling approach of the Generalized Polynomial Expansion Method. It is applied to decouple the nonlinear independent and dependent modal coordinates. With this technique, the number of non-zero elements in the generalized modal-forces vector is equal to the number of nonlinear, dependent modal coordinates. The results indicate that the use of GPEM together with component mode synthesis not only retains its merits in solving a linear rotor-dynamic problem, but also provides attainable solutions for the nonlinear rotor-dynamic problem.
(3) The hybrid numerical algorithm developed in the present study combines both the advantages of the harmonic-balance method and the collocation method. The use of this hybrid method with condensation technique can significantly save computing time. Furthermore, it can be used to predict the periodic response, including the sub-harmonic response and the super-harmonic response, of a nonlinear system.
(4) The time required for the initial formulation processing with this method may be a little more than that required by the finite-element approach. However, it is very small compared to the overall time savings that are accrued.
Nonobstructive Particle Damping (NOPD) Performance Under Compaction Forces
Authors: Panossian H. V. 
Published: April 2021

Abstract
Presented herein are nonobstructive particle damping (NOPD) performance characteristics under forced compaction conditions. NOPD is a new passive vibration damping technique that consists of making small diameter holes (or cavities) at appropriate locations inside the main load-paths of a vibrating structure and filling these holes to appropriate levels with such particles that yield the maximum damping effect. Metallic or nonmetallic particles in powder, spherical, or liquid form (or even mixtures) with different densities, viscosities, and adhesive and cohesive characteristics can be utilized.
In an effort to simulate centrifugal forces on particles placed inside blades of high rotational speed turbomachines, a special test article was made and different particles were tested under various compaction forces and vibration amplitudes. The effectiveness of NOPD was measured and compared with no compaction and no-particle conditions.
Determination of Instability Boundaries for a Highly Flexible Prismatic-Jointed Robot Performing Repetitive Maneuvers
Authors: Buffinton Keith W. 
Published: April 2021

Abstract
Presented in this work are the equations of motion governing the behavior of a simple, highly flexible, prismatic-jointed robotic manipulator performing repetitive maneuvers. The robot is modeled as a uniform cantilever beam that is subject to harmonic axial motions over a single bilateral support. To conveniently and accurately predict motions that lead to unstable behavior, three methods are investigated for determining the boundaries of unstable regions in the parameter space defined by the amplitude and frequency of axial motion. The first method is based on a straightforward application of Floquet theory; the second makes use of the results of a perturbation analysis; and the third employs Bolotin’s infinite determinate method. Results indicate that both perturbation techniques and Bolotin’s method yield acceptably accurate results for only very small amplitudes of axial motion and that a direct application of Floquet theory, while computational expensive, is the most reliable way to ensure that all instability boundaries are correctly represented. These results are particularly relevant to the study of prismatic-jointed robotic devices that experience amplitudes of periodic motion that are a significant percentage of the length of the axially moving member.
Aerodynamics of Moving Belts, Tapes, and Webs
Authors: Chang Y. B. , Fox S. J. , Lilley D. G. , Moretti P. M. 
Published: April 2021

Abstract
The mass of the air surrounding a moving belt leads to a number of forces normal to the belt: hydrodynamically induced inertia, Coriolis force, and centrifugal force. These forces act in concert with those generated by the belt’s own inertia to govern out-of-plane dynamics. Their effect is to reduce stability and limit the safe running speed. These detrimental consequences can be reduced through management of the air flow around the belt. An analysis of the governing partial differential equations is presented; experiments on the aerodynamic interaction terms are reported; and a numerical simulation method for belt dynamics is outlined.
On the Stability of Chain Drive Systems Under Periodic Sprocket Oscillations
Authors: Wang K. W. 
Published: April 2021

Abstract
Experimental observations have shown that periodic torsional oscillations of engine camshafts induced by powertrain loads can cause significant tension variation in the timing chain and magnifies the chain transverse vibrations and noise level. This result indicates that the sprocket dynamic characteristics and the chain vibration behavior are closely coupled. The chain drive models to-date are not able to address these phenomena. This paper presents a nonlinear model of an integrated chain drive system which couples the sprocket motion with the transverse and longitudinal vibration of the axially-moving chain spans. With this model, the effects of the sprocket shaft periodic loads upon the total system are investigated. It is concluded that the sprocket oscillations will cause chain longitudinal vibrations. This could destabilize the system and induce the chains to undergo large transverse vibration. Both the subharmonic and summation types of parametric resonance are found and the instability regions are derived. The effects of various system parameters, such as the sprocket inertia, the chain speed, and the speed dependent excitation frequencies upon the instability regions have been studied. The significance of the gyroscopic terms on the prediction of the stability boundary has been shown. This paper presents an approach that provides new insight to the research of chain drive dynamics.
Dynamic Deflection of Paper Emerging From a Channel
Authors: Stolte James , Benson Richard C. 
Published: April 2021

Abstract
For many machines handling lightweight, flexible sheets, it is necessary for the sheet to transit an open space. Examples include magnetic tape drives, xerographic copiers, and sewing machines. The nonlinear theory of the elastica has often been used to model nonlinear, static deflections. Dynamic modeling is more difficult, and far less studied. Recently, however, L. Mansfield and J.G. Simmonds (1987) have considered the dynamic deflection of a sheet emerging from a horizontal channel at constant velocity and subjected to gravity loading. In this paper, we consider a generalization of that problem to include arbitrary exit angles, and an accelerating “feed” rate. Gravity loading is retained. The resulting nonlinear equations of motion are tractable and are solved numerically.
Dynamic Response of an Axially Moving Beam Coupled to Hydrodynamic Bearings
Authors: Tan C. A. , Yang B. , Mote C. D. 
Published: April 2021

Abstract
The vibration response of a distributed axially moving beam, controlled through distributed hydrodynamic bearing forces, is analyzed by the transfer function method. In the axially moving beam, all modes are affected by the distributed bearing coupling. The bearing force is described in terms of impedance functions. An approximate closed-form transfer function for the coupled beam-bearing system is derived. The transfer function is applicable to all linear, one-dimensional, coupled systems, and it is exact for localized, linear constraint forces. The derivation requires knowledge of the transfer function of the axially moving beam which is not available in the literature. A method for determining the beam transfer function is also presented. The frequency response of the coupled system is illustrated for several beam and bearing design parameters.
On the Stability and Nonlinear Dynamics of a Horizontally Base-Excited Shaker/Mould Structure With Unsymmetric End Stiffnesses
Authors: Cheng John K. H. , Wang K. W. 
Published: April 2021

Abstract
This paper presents a dynamic analysis of a horizontally base -excited shaker/ mould structure with unsymmetric gripper stiffnesses. The study explains the large rotational and transverse vibrations of the mould at specific operating frequencies observed in the experiments. The governing equations consist of a time-dependent coefficient which indicates the existence of parametric excitation effects. It is concluded that differences between the gripper stiffnesses are responsible for this phenomenon and could destabilize the system. The value of the time-varying parameter is related to the horizontal vibration amplitude of the mould and hence is a function of the system parameters and excitation frequency. The mould’s rotational motion is directly parametrically excited while its transverse vibration is excited indirectly through coupling with the rotational motion. A thorough analysis of this class of mechanical systems has not been performed in the past. In this research, studies are conducted to identify the contributions of various system parameters, such as gripper stiffness, damping, mould inertia, and excitation amplitude to the system dynamic characteristics. The results provide new insight and guidelines toward optimizing such mechanical systems.
On the Impact Intensity of Vibrating Axially Moving Roller Chains
Authors: Wang K. W. , Liu S. P. , Hayek S. I. , Chen F. H. K. 
Published: April 2021

Abstract
Experimental observation has shown that the most significant noise source in roller chain drives is from the impacts between the chain and the sprocket during their meshing process. Despite its importance, studies have not been made to thoroughly analyze the chain/sprocket impact dynamics and their interaction with the vibrating, axially moving chain structure. This paper presents a novel analysis which integrates the local meshing phenomena with the global system. An axially moving chain interacting with local impacts has been modelled and the momentum balance method is employed to derive the impulse function. Convergence of the impulse function is examined and a study is carried out to quantify the intensity of subsequent impacts. It is found that the impact intensity is significantly affected by the vibration characteristics and response of the moving chain, and vice versa. The classical quasi-static approach will create errors in predicting the impulse magnitude and system response. This fundamental investigation provides new insight to roller chain dynamics, which is an essential step toward the design of quiet chain drives.