bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonstationary Motions in Stationary Vibrating Systems: A Discussion
Authors: Szemplińska-Stupnicka W. 
Published: March 2021

Abstract
The paper presents a discussion on relationships between the concepts of nonstationary, random and chaotic motion. The discussion is based on computer simulation results and the approximate theory of nonlinear oscillations. Two forced oscillators are considered: the dissipative unsymmetric oscillator and the self-excited symmetric system. It is concluded that chaotic component of motion can be interpreted as a sort of nonstationary “free vibration” with randomly modulated amplitude and phase. The proposed approximate model of chaos seems to blur a clear distinction between the traditional concepts of stochastic and deterministic, and between stationary and nonstationary system as well.
Modeling and Optimization of Dissipative Properties of Industrial Articulated Manipulators
Authors: Dakev Nickolay V. 
Published: March 2021

Abstract
A mathematical model describing elastic and dissipative properties of manipulator links and joints is considered. An articulated manipulator is regarded as an open kinematic chain of absolutely rigid arms connected by flexible joints. Free and forced vibrations around goal manipulator configurations are studied. Friction forces are supposed to be applied to the manipulator hinges. They are described by the help of generalized dissipative function. According to this model the possibilities for damping the free and forced vibrations of industrial articulated manipulators are studied. Some problems for defining the optimal friction laws with regard to new energy criteria are solved.
A global energy criterion depending on the total mechanical energy is proposed. It is proved that this functional doesn’t depend on the character of the transient oscillation process. A minimax problem is formulated and a computer oriented method for its solving is developed. Another energy criterion is connected with maximizing the average power dissipated for one period of forced oscillations. A general algorithm for defining the corresponding optimal periodic damp laws is worked out. The results obtained can be directly used for optimal passive and active damping of the vibrations of industrial manipulators by realizing of the corresponding friction laws.
An Isoparametric Four-Node Beam Element for the Analysis of Planar Robot Manipulators
Authors: Smaili Ahmad A. , Sannah Muhammad 
Published: March 2021

Abstract
Accurate determination of the dynamic response of high speed flexible manipulators requires that the dynamic model incorporates the influence of joint compliances, in addition to faithfully representing the physical characteristics of the links. A finite element model is herein presented for this purpose. The model is based on a 4-node isoparametric Timoshenko beam element to model the structural characteristics of the links including the effects of shear deformation and rotary inertia. It also includes the influence of the rigid body motion and the time derivatives of the elastic deformations of the manipulator on the characteristic matrices of the system, and accounts for the inertia of the drive units and payload and the damping of externally applied dampers. Quasistatic analysis, modal analysis, and linear and nonlinear vibrational responses of a 3-R planar manipulator are determined by solving the appropriate equations of equilibrium. The results of the analysis revealed that the compliance of the joints have a considerable influence on the manipulator response which is manifested by considerable increase in endpoint deflections and substantial decrease in fundamental natural frequency. Nonlinear transient response exhibited a behavior that differs drastically from that obtained when rigid joints are assumed.
Exploring Artificial Muscles As Actuators for Artificial Hands
Authors: Meghdari Ali , Jafarian Majid , Mojarrad Mehran , Shahinpoor Mohsen 
Published: March 2021

Abstract
This article presents a brief overview of current research and findings in developing artificial muscles. Furthermore, possibilities of applying such muscles as actuators in prosthetic hands (i.e. The Sharif Artificial Hand) have been proposed and investigated.
Spatial Filtering Characteristics of Distributed Piezoelectric Sensors
Authors: Tzou H. S. , Zhong J. P. 
Published: March 2021

Abstract
Distributed spatial filtering characteristics of distributed piezoelectric sensors are investigated. In general, a sensor output signal is contributed by a membrane strain and a bending strain. Depending on the sensor placement, a distributed sensor can be only sensitive to either membrane or bending modes — membrane or bending sensor. In addition, a piezoelectric sensor can be sensitive to a mode or a group of modes due to signal average of electrode surface, especially anti-symmetrical modes. Accordingly, the sensor layer can be spatially shaped such that its sensitivity can be specified. These filtering characteristics are discussed and examples demonstrated.
Analysis of a Piezoelectric Actuator and Receiver on an Elastic Half-Space Subjected to Harmonic Electric Excitation
Authors: Chang Shuo-Hung , Lin Ching-San 
Published: March 2021

Abstract
Analytical solutions are formulated for the displacement, stress, and electric potential in piezoelectric actuator and receiver on an elastic half-space. The surface wave is taken into account when the piezoelectric actuator is subjected to the harmonic electric excitation. The derived analytical formulas are used to compute the output potential of piezoelectric receiver. Experiment measurements are performed and compared with numerical results in good agreement. The influence of excitation frequency, material property and dimension of the piezoelectric material is presented.
An Introduction to Smart Fractal Structures and Mechanisms
Authors: Shahinpoor Mohsen 
Published: March 2021

Abstract
Fractal structures are unique in the sense that they are highly expandible or collapsible and yet they are capable of preserving their basic structural geometry in a dynamic fashion. This dynamic geometric invariance opens up a new territory in fractal solids, i.e., fractal structures, mechanisms and robot manipulators. Some of these structure are in the form of highly deployable mechanisms and possibly redundant, multi-axis, multi-arm, multi-finger robot manipulators whose kinematic structure is fractal. Thus, simple fractal structures, such as triadic cantor set, and fractal functions, such as the Weirstraus-Mandelbrot functions, govern the structural branching of such robots and essentially define their kinematic structure. These deployable fractal structures, mechanisms and robot manipulators are shown to be capable of generating unique, and yet unparalleled properties such as computer-controlled microsensing even down to molecular level (micromachining) and computer-controlled dynamics such as the creation of hypervelocity fractons with speeds in the range of hundreds of kilometers per second. A number of structures and mechanisms and their unique properties are presented in this paper and a simple kinematic model is presented and briefly discussed.
Eigenvalue Veering, Perturbed Bifurcation Theory and Modal Analysis of Mistuned Linear Systems
Authors: Happawana G. S. , Bajaj A. K. , Nwokah O. D. I. 
Published: March 2021

Abstract
Eigenloci crossing or veering in structural systems dependent on parameters, and having two nearly identical eigenvalues, is the subject of this paper. Utilizing some basic ideas from the perturbed bifurcation theory, a criterion for identifying eigenloci crossing or veering is presented along with a method for studying the modal properties of mistuned structural systems. Two classical continuous systems: a clamped rectangular membrane and a rotating guided circular string, have been chosen as illustrations. The analysis is performed by applying the singular perturbations technique for asymptotic expansions. These expansions are used to detect correctly, whether the eigenloci will cross over or veer away from a particular “singular” point under the influence of small parameter variations from nominal values. This is useful in the correct identification of the vibration behavior of mechanical systems subject to structural parameter variations, since it is known that only the eigenloci veering leads to modal bifurcations.
Theoretical and Experimental Analysis of the Forced Response of Sagged Cable/Mass Suspensions
Authors: Cheng S.-P. , Perkins N. C. 
Published: March 2021

Abstract
This study examines the forced response of a sagged elastic cable supporting an array of discrete masses. Such systems arise, for instance, in ocean engineering applications employing cable hydrophone arrays. The excitation considered is harmonic and normal to the cable and may, for instance, approximate prescribed environmental loading. An asymptotic model is presented that describes the linear forced response of a cable/mass suspension having small equilibrium curvature. Closed-form expressions for the Green’s function to an associated boundary-value problem are obtained using a transfer matrix formulation. The derived Green’s function is utilized to construct integral representations for steady-state response under boundary and/or domain excitation. Solutions obtained for a variety of domain loading distributions demonstrate the utility and efficiency of this solution strategy. The theoretical response predictions are verified through experimental measurements of the natural frequency spectrum and frequency response of laboratory cable/mass suspensions.
Moving Contact and Coupling in Belt Strand Vibration
Authors: Yue M. G. 
Published: March 2021

Abstract
Belt vibration behavior is analyzed, by considering moving contact between belt and pulley and the coupling between longitudinal and transverse motions. For typical belt drive parameters there is a very weak coupling on lateral vibration from longitudinal vibration but a moderate coupling the other way around. This coupling in combination with the moving contact increases the fundamental transverse natural frequency difference compared to the simply supported case.
Thermal/Mechanical Effect of Rotor-to-Stator Rubs in Rotating Machinery
Authors: Muszynska Agnes 
Published: March 2021

Abstract
The thermal effects of rotor-to-stator rubbing resulting in rotor bowing, and subsequent changes in rotor vibrational responses are discussed in this paper. The rotor thermal bow is modeled following relationships quoted in rotordynamic literature. The rotor model takes into account its first lateral mode in which the rubbing spot differs from the modal mass location. It is shown that the rotor responds to the rub thermal effect in a “spiraling/oscillating” mode which represents a form of rotor self-exciting vibrations. A simplified model explains physical phenomena occurring in the rubbing rotor system. An example of the field data illustrates the rotor dynamic behavior.
A Theoretical and Experimental Investigation of a Gas Operated Bearing Damper for Turbomachinery: Part II — Experimental Results and Comparison With Theory
Authors: Sundararajan Padmanabhan , Vance John M. 
Published: March 2021

Abstract
This is the second of two papers describing results of a research project directed at developing a gas operated vibration damper for high temperature turbomachinery applications. This part presents the experimental measurements made on three variations of the gas damper hardware and compares them with the theoretical predictions presented in Part I. It is found that the isentropic theoretical model predicts the damper characteristics quite well. A maximum damping of 13.2 Ib-s/in was measured for a single actuator at a natural frequency of 100 hz using the present design and the results suggest that significantly higher damping levels are possible with design modifications.
A Waved Journal Bearing Concept-Evaluating Steady-State and Dynamic Performance With a Potential Active Control Alternative
Authors: Dimofte Florin 
Published: March 2021

Abstract
Analysis of the waved journal bearing concept featuring a waved inner bearing diameter for use with a compressible lubricant (gas) is presented. The performance of generic waved bearings having either three or four waves is predicted for air lubricated bearings. Steady-state performance is discussed in terms of bearing load capacity, while the dynamic performance is discussed in terms of fluid film stability and dynamic coefficients.
It was found that the bearing wave amplitude has an important influence on both steady-state and dynamic performance of the waved journal bearing. For a fixed eccentricity ratio, the bearing steady-state load capacity and direct dynamic stiffness coefficient increase as the wave amplitude increases. Also, the waved bearing becomes more stable as the wave amplitude increases. In addition, increasing the number of waves (e.g., four waves instead of three waves) reduces the waved bearing’s sensitivity to the direction of the applied load relative to the wave. However, the range in which the bearing performance can be varied decreases as the number of waves increases. Therefore, both the number and the amplitude of the waves must be properly selected to optimize the waved bearing design for a specific application. Another possibility is to use the waved bearing to actively control the rotor-bearing system dynamic coefficients via actively controlling the wave amplitude.
Effect of Straight Through Labyrinth Seals on Rotordynamics
Authors: Vance John M. , Zierer J. J. , Conway E. M. 
Published: March 2021

Abstract
Experimental measurements have been made to evaluate the rotordynamic performance of straight-through labyrinth seals under conditions that are realistic for many turbomachines. Both teeth-on-rotor and teeth-on-stator gas seals were tested, each with twelve blades, 173 mm (6.8″) blade diameter, and 102 mm (4″) total length. The nominal blade tip clearance was 0.5 mm (20 mils). The teeth-on-stator seal was tested with the blade tip clearances diverging (in the direction of the flow), uniform, and converging. The teeth-on-rotor seal was tested with uniform clearances. The inlet air pressure to the seals was varied from 1.7 bar to 14.6 bar (25 psi to 200 psig) with the last blade exhausting to the atmosphere. Coastdown tests of all the seals were performed on a rotordynamic test rig to show their effect on synchronous response to imbalance when passing through a 3700 rpm critical speed. For the teeth-on-rotor seal, rap tests at 4500 rpm were also conducted to measure the effective damping coefficient for subsynchronous vibration.
The synchronous response to imbalance was generally increased by all the seals at inlet pressures up to about 11.2 bar (150 psig). The worst case was for the teeth-on-rotor seal at about 2.7 bar (35–45 psi) inlet pressure where the rotor whirl amplitude was increased from .1 mm (3.75 mils, peak to peak) to over .13 mm (5 mils). In most cases the rotor whirl amplitude was slightly decreased at inlet pressures above 13 bar (176 psig).
The teeth-on-rotor seal provided a small amount of damping to attenuate the 61 Hz subsynchronous vibration with the rotor running at 4500 rpm. A computer model which includes both the rotor and housing dynamics was developed to evaluate the possible range of values of the rotordynamic seal coefficients. Simulations show that the effective subsynchronous damping coefficient of the teeth-on-rotor seal ranges from 175 N-s/m at 5.1 bar inlet pressure (1 lb-s/in at 75 psi) to 876 N-s/m at 10.2 bar (5 lb-s/in at 150 psi). This corresponds to a range of 0.3% to 1.4% of critical damping added by the seal for subsynchronous vibration, even though the seal increased the synchronous response at the critical speed. It is shown that the orbit conditions for the synchronous and subsynchronous tests were radically different, as they likely will be in most turbomachines.
The Effect of Inlet Grooves and Swirl on the Dynamics of Long Annular Seals in Centrifugal Pumps
Authors: Ismail Mohamed , Brown R. David , France David 
Published: March 2021

Abstract
This paper describes additional results from a continuing research program which aims to identify the dynamics of long annular seals in centrifugal pumps. A seal test rig designed to experimentally identify dynamic coefficients using a least-squares technique based on the singular value decomposition method. The analysis is carried out in the time domain using a multifrequency forcing function. The experimental method relies on the forced excitation of a flexibly supported stator by two hydraulic shakers. A rigid rotor supported in rolling element bearings runs through the stator. The only physical connection between shaft and stator is a pair of annular gaps filled with pressurised water discharged axially. The experimental coefficients obtained from the tests are compared with theoretical values.
An Eigenvalue Inclusion Principle for Simple, Rotationally Periodic Structures
Authors: Shen I. Y. 
Published: March 2021

Abstract
This paper describes an eigenvalue inclusion principle for a simple, rotationally periodic structure P whose i-th substructure Si is connected to a neighboring substructure Si+1 through a single-degree-of-freedom interface constraint Ii+1. The state vector vi+1 at the interface Ii+1, consisting of the displacement and the force at the interface, is represented in terms of the state vector vi at the interface Ii through transfer functions of the substructure Si. The periodicity of the structure P then requires that a linear combination of the transfer functions of Si be zero. As a consequence, a simple periodic structure P with period N will have exactly N eigenvalues lying between two consecutive eigenvalues of the substructure Si. Finally, this eigenvalue inclusion property is illustrated on a periodic structure with known exact eigensolutions.
Digital Measurement Method on Rotating Shaft Torsional Vibration
Authors: Fu Haizhong , Yan Puqiang 
Published: March 2021

Abstract
For many large scale rotating machines, torsional vibration is one of key factors affecting operation safety. Torsional vibration measurement of the rotating shaft is a difficult task in monitoring the machine operation. The non-contact measuring approach is considered to be a practical method for the torsional vibration measurement. However, because the measurement usually depends on the accuracy of on-shaft gears, it is neither easy to conduct nor can reach a high precision. A new digital measurement method is presented in this paper to overcome the difficulty. The principle of the new method is described Experimental measurements indicate that the measurement is easy to execute and its accuracy is higher than 0.01 degree.
Rotating, Axially Loaded Timoshenko Shaft: Modeling and Stability
Authors: Karch Gerald , Wauer Jörg 
Published: March 2021

Abstract
For studying the stability of a rotating shaft subject to axial load, the derivation of correct stability equations is the essential preliminary problem. Here, the model of a uniform non-circular Timoshenko shaft under a compressive end load of constant magnitude is dealt with. Starting point is the nonlinear boundary value problem for coupled extensional-bending-torsional oscillations where a finite strain beam theory in a floating reference frame following the rigid body rotation is applied. First, the equation set describing the stationary shaft configuration is deduced. Next, the variational equations for small superimposed perturbations are derived. The only interesting stability problem for usual properties of the shaft cross section is constituted by a linear boundary value problem describing the bending vibrations. The corresponding characteristic equation is evaluated finally to find the critical buckling load also for the case of an oval shaft not considered before.
Stability and Stability Degree of a Cracked Flexible Rotor Supported on Journal Bearings
Authors: Guang Meng , Gasch Robert 
Published: March 2021

Abstract
This paper investigates the stability and the stability degree of a flexible cracked rotor supported on different kinds of journal bearings. It is found that no matter what kind of bearings is used, the unstable zones caused by rotor crack locate always within the speed ratio 2N(1-△Kξ4)&lt;Ω&lt;2N when gravity parameter Wg &gt; 1.0; and locate always within the speed ratio 2ΩαN(1-△Kξ4)&lt;Ω&lt;2ΩαN when Wg &lt; 0.1, where ΔKξ is the crack stiffness ratio, N = 1, 2, 3, 4, 5 … and Ωα=(1+2α2α)1/2. When 0.1 &lt; Wg &lt; 1.0, there is a region, where no unstable zones caused by rotor crack exist.
Outside the crack ridge zones, the rotor crack has almost no influence on system’s stability and stability degree; while within the crack ridge zones, the stability and stability degree depend both on the crack and system’s parameters. In some cases, the system may still be stable even the crack is very large. For small gravity parameter (Wg &lt; 0.1), the mass ratio α has large influence on the position of unstable region, but its influence on the stability degree is small. The influence of fixed Sommerfeld number So on the crack stability degree is small although So has large influence on the stability degree of uncracked rotor.
Dynamic Analysis of Flexible Rotors Subjected to Torque and Force
Authors: Yun Jong-Seop , Lee Chong-Won 
Published: March 2021

Abstract
The effect of the applied direction and magnitude of loads on the stability and natural frequency of flexible rotors is analyzed, when the rotors are subject to nonconservative torque and force. The stability criterion derived from the energy and variational principle is discussed and a general Galerkin’s method which utilizes admissible functions is employed for numerical analysis. Illustrative examples are treated to demonstrate the analytical developments.
On the Generation of Bending Vibration in a Drill Rod
Authors: Kaski Juha 
Published: March 2021

Abstract
In this paper, it is studied how much of the piston blow energy will be transformed to the bending energy of drill rod in a percussive rock drilling process. The mathematical model is based on one-dimensional wave theory and Euler-Bernoulli beam theory. The axial and the transverse motions of drill rod are assumed to be coupled at the boundary only. The rod is considered as semi-infinite in length, and the rod/rock contact condition is modelled with an eccentric linear spring element.
Two kind of problems will be considered. First, the one in which the piston eccentrically impacts on the rod end, thus causing bending vibration; and second, the one in which the purely axial incident pulse arrives at the eccentrically spring-supported rod end, reflects back and generates bending vibration. Using Laplace-transformation techniques, the closed form solution for these problems is discovered. The results show that the disturbances at the rod/rock boundary cause stronger bending effect than those at the piston/rod boundary.
Modeling of Coupled Bending and Torsion in Elastic Structures
Authors: Banks H. T. , Smith C. A. 
Published: March 2021

Abstract
In this presentation we will report on joint efforts with D.J. Inman and his colleagues at MSL, SUNY at Buffalo, to develop viable models for the analysis and control of elastic structures exhibiting coupled torsional and flexural vibrations. A model for coupled torsion and bending is developed which incorporates Kelvin Voigt damping and warping. Approximation techniques are introduced and preliminary numerical results are discussed. Experimental data is presented and used to test our computational results.