bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sensor Electromechanics and Distributed Signal Analysis of Piezo(Electric)-Elastic Spherical Shells Based on the Bending Approximation
Authors: Tzou H. S. , Smithmaitrie P. 
Published: November 2020

Abstract
Spatially distributed modal voltages and sensing signal generations of a distributed piezoelectric sensor layer laminated on spherical shells of revolution are investigated in this study. The generic sensing signal equation is derived based on the direct piezoelectric effect, the Gauss theory, the open-circuit assumption, the Maxwell equation, and also the generic double-curvature thin shell theory. Due to difficulties in analytical solution procedures, assumed mode shape functions based on the bending approximation theory are used in the modal signal expressions and analyses. Spatially distributed electromechanical characteristics resulting from various meridional and circumferential membrane/bending strain components are evaluated and major signal sources are identified. Analytical results suggest that the spatially distributed modal voltages clearly illustrate the distinct modal behavior, similar to mode shapes. The major signal source of a free-edge hemispherical shell is the circumferential bending component. Accordingly, circumferential layout of distributed sensor strips would provide effective monitoring and diagnosis of free hemispheric shells.
Optimal Design of Underwater Shells With Active Stiffeners
Authors: Akl W. , Ruzzene M. , Baz A. 
Published: November 2020

Abstract
The optimal design parameters of fluid-loaded shells, provided with actively controlled stiffeners, are determined using a rational multi-criteria optimization approach. The adopted approach aims at simultaneously minimizing the shell vibration, associated sound radiation, weight of the stiffening rings, the control energy, and the cost of the shell/stiffeners assembly while maximizing the controllability and observability indices.
A finite element model is presented to predict the vibration and noise radiation from cylindrical shells, with active stiffeners, into the surrounding fluid domain. The production cost as well as the life cycle and maintenance costs of the stiffened shells are computed using the Parametric Review of Information for Costing and Evaluation (PRICE) model. A Pareto/min-max multi-criteria optimization approach is then utilized to select the optimal locations and dimensions of the active stiffeners. Numerical examples are presented to compare the vibration and noise radiation characteristics of me optimally designed/controlled stiffened shells with the corresponding characteristics of plain un-stiffened and uncontrolled shells. The obtained results emphasize me importance of the adopted multi-criteria optimization approach in the design of quiet, low weight and low cost underwater shells which are suitable for various critical applications.
Analysis of Pump Induced Radiated Noise From Undersea Vehicles
Authors: Hassan Scott E. , Roberts Raymond W. 
Published: November 2020

Abstract
Positive displacement pumps are one of the many potential noise and vibration sources associated with undersea vehicles. This paper presents an approach to predict the tonals radiated from vane-type pumps mounted in undersea vehicles. The approach is based on using a numerical model of a vane pump coupled to an analytical model of the pump inlet hose and a finite element model of the hull and internal structure associated with the fluid-loaded undersea vehicle. An illustrative example is presented that demonstrates the influence of the various propagation paths and pump parameters on the overall radiated power. The basic approach can be readily extended and implemented as part of a simulation based design process for managing vehicle acoustics and vibration.
The Effect of Hertzian, Bending and Shearing Stiffness on Noise and Vibration
Authors: Abdo Jamil , Farhang Kambiz , Mohsen Mousa 
Published: November 2020

Abstract
Since the apparent stiffness due to contact of one surface on another relates directly to the localized resonant frequencies, it is believed that accurate account of this property will lead to the fundamental understanding of causes of friction-induced vibration and noise. The mathematical model of contact is utilized to develop formulae for normal and tangential contact stiffness. The inclusion of a study in which the various modes of elastic deflections of an asperity are also considered, as well as their effects. The bending, shear and Hertz contact modes of elastic deflection are assumed to simultaneously occur for an asperity. Investigation of the combined effect of bending, shear and Hertzian contributions to the contact stiffness is indicating that the equivalent contact stiffness is best represented, among the three types of stiffness, by that due to Hertzian contact.
Simulating and Detecting a Vibration-Induced Failure in an Air-Handling Assembly
Authors: McGee C. Gavin , Adams Douglas E. 
Published: November 2020

Abstract
Excessive vibrations usually cause mechanical parts to fail. This paper describes a vibration-induced failure in an air handling assembly. Cyclic impacts between a valve and a set of powdered metal bushings cause the failure. A variety of signal processing techniques are used to analyze experimental response data from the failing part including standard spectral signature approaches (i.e. Fourier, cepstral) in addition to more advanced time-frequency analysis techniques (i.e. wavelet contour maps). The theory and application of each method is reviewed in the context of the specific failure mode under consideration. The paper demonstrates that where friction or impact related vibrations are present, structural dynamic “health” monitoring schemes can be used to track changes in operating response signatures and schedule condition-based maintenance or re-design.
Stability and Bifurcation for the Equispaced, Periodic Motion of a Horizontal Impact Damper
Authors: Luo Albert C. J. 
Published: November 2020

Abstract
Stability and bifurcation conditions for the asymmetric, periodic motion of a horizontal impact damper under a periodic excitation are developed through four mappings for two switch-planes relative to discontinuities. Period-doubling bifurcation for equispaced motion does not occur, but the asymmetric period-1 motions change to the asymmetric, period-2 ones through a period doubling bifurcation. A numerical prediction for equispaced to chaotic motions is completed. The numerical and analytical predictions of the periodic motion are in very good agreement. The asymmetric, periodic motions are also simulated.
Stability Analysis of a Free-Standing Block With Friction on a Moving Foundation
Authors: Sinopoli Anna , Ageno Alessio 
Published: November 2020

Abstract
The problem analyzed here concerns the dynamic response of a bidimensional polygonal rigid body simply supported on a harmonically moving rigid ground. The immediate scientific purpose of the paper is to obtain and analyze the dynamic response by using a variational formulation, recently proposed by one of the authors [1], where the dynamics is described as a differential inclusion. This formulation allows us to determine the instantaneous accelerations of the system by means of a mechanical model with friction and unilateral constraints, which does not reduce the degrees of freedom or impose an “a priori” choice of the mechanism activated during the motion. By treating the friction coefficient as a stability parameter, it has been possible to obtain different kind of responses, ranging from rocking to sliding-rocking, and compare them with those obtained in the literature. Sliding-rocking motions obtained so far have exhibited not only harmonic but also interesting and more complex behaviors with chaotic features.
The search for theoretical and numerical instruments able to identify and classify these more complex motions was first performed in the case of rocking, characterized by a smaller number of degrees of freedom. A technique was then implemented for calculating Lyapunov’s exponents also during the time intervals of the impacts. The introduction and evaluation of these exponents can also permit us to perform the stability analysis with respect to overturning, by limiting the analysis and evaluation to the first impact that the system undergoes by starting at rest: in fact, large values of Lyapunov’s exponents before the first impact are connected with overturning during the motion which follows. This circumstance can make it easier to carry out the stability analysis with respect to overturning, as a function of the amplitude and frequency of the excitation.
Bending Effects in the Frictional Energy Dissipation in Lap Joints
Authors: Heinstein Martin W. , Segalman Daniel J. 
Published: November 2020

Abstract
Frictional energy dissipation in joints is an issue of longstanding interest in the effort to predict damping of built up structures. Even obtaining a qualitative understanding of how energy dissipation depends on applied loads has not yet been accomplished. Goodman[1] postulated that in harmonic loading, the energy dissipation per cycle would go as the cube of the amplitude of loading. Though experiment does support a power-law relationship, the exponent tends to be lower than Goodman predicted. Recent calculations discussed here suggest that the cause of that deviation has to with reshaping of the contact patch over each loading period.
Moving Force Identification for Multi-Span Bridges by Using Acceleration Measurements
Authors: Au F. T. K. , Jiang R. J. , Cheung Y. K. 
Published: November 2020

Abstract
This paper reports some initial findings in the attempt to develop a robust method to identify more than one moving force on multi-span non-uniform continuous bridges. To keep the number of unknowns in the moving force identification problem to a minimum, the modified beam vibration functions are chosen as the assumed modes of a multi-span bridge. These modified beam vibration functions satisfy the zero deflection conditions at all the intermediate supports as well as the boundary conditions at the two ends of the bridge. The least squares method is used to solve the inverse problem to get the closest approximation to the moving forces. The pseudo-inverse to obtain the solution to the inverse problem is obtained by singular value decomposition. Only acceleration measurements are used for the moving force identification. The results show that this method is applicable and robust.
Analysis of Varying Natural Frequencies and Damping Ratios of a Sample Parallel Manipulator Throughout its Workspace Using Linearized Equations of Motion
Authors: Kozak Kris , Ebert-Uphoff Imme , Singhose William 
Published: November 2020

Abstract
This article investigates the dynamic properties of robotic manipulators of parallel architecture. In particular, the dependency of the dynamic equations on the manipulator’s configuration within the workspace is analyzed. The proposed approach is to linearize the dynamic equations locally throughout the workspace and to plot the corresponding natural frequencies and damping ratios. While the results are only applicable for small velocities of the manipulator, they present a first step towards the classification of the nonlinear dynamics of parallel manipulators.
The method is applied to a sample manipulator with two degrees-of-freedom. The corresponding numerical results demonstrate the extreme variation of its natural frequencies and damping ratios throughout the workspace.
A Structural Health Monitoring System for Laminated Composites
Authors: Díaz Valdés Sergio H. , Soutis Costas 
Published: November 2020

Abstract
This investigation examines the application of low frequency Lamb waves for the detection of delaminations in thick composite laminates. Surface mounted piezoelectric devices were excited with a tone burst of few cycles generating a stress wave that propagates along the structure. Experiments were carried out on composite beam specimens where wave propagation distances over 2 m were achieved and artificially induced delaminations as small as 1 cm2 were successfully identified. The resonance spectrum method, which is based on the study of spectra obtained by forced mechanical resonance of samples using sine-sweep excitation, was used for measuring the A0 Lamb mode phase velocity. Finite element analyses of wave generation and propagation in wide laminated plates are also presented. The feasibility of employing piezoelectric devices for the development of smart structures, where a small and lightweight transducer system design is required, has been demonstrated.
Vibration Testing and Control of Inflatable Structures Using Smart Materials
Authors: Park Gyuhae , Kim Myung-Hyun , Mandin Matthias , Inman Daniel J. 
Published: November 2020

Abstract
An experimental investigation of vibration testing and control of an inflated thin-film torus is presented. Lightweight inflatable structures are a viable alternative in aerospace structure design. These structures, however, pose special problems in testing and in controlling vibrations due to their extremely lightweight, flexible, and high-damping properties.
In this study, we show that smart materials, which can be fully integrated into an inflatable space system, could be used as sensors/actuators in order to find modal parameters and to reduce vibrations. The results indicate the potential smart materials for use in the dynamics and control of inflated structures.
Evaluation of a Distributed Sensor for Structural Health Monitoring
Authors: Sundaresan M. J. , Ghoshal A. , Martin W. N. , Schulz M. J. 
Published: November 2020

Abstract
A distributed in-situ sensor that can simplify structural health monitoring is investigated in this paper. The distributed sensor can detect damage within the coverage area of the sensor by measuring acoustic emissions, but it cannot exactly locate the damage source due to the continuous nature of the sensor. A simulation and experiment showed that acoustic emissions occurring at any location on a composite panel can be detected by a single channel distributed sensor. In contrast, nine individual piezoceramic patch sensors would be needed to detect the acoustic emission.
Spatially Distributed Signals of Nonlinear Paraboloidal Shells With Distributed Neurons
Authors: Tzou H. S. , Ding J. H. 
Published: November 2020

Abstract
Effective health monitoring and distributed control of advanced structures depends on accurate measurements of dynamic responses of elastic structures. Conventional sensors used for structural measurement are usually add-on “discrete” devices. Lightweight distributed thin-film piezoelectric neurons fully integrated (laminated or embedded) with structural components can serve as in-situ sensors monitoring structure’s dynamic state and health status. This study is to investigate modal voltages and detailed signal contributions of linear or nonlinear paraboloidal shells of revolution laminated with piezoelectric neurons. Signal generation of distributed neuron sensors laminated on paraboloidal shells is defined first, based on the open-voltage assumption and Maxwell’s principle. The neuron signal of a linear paraboloidal shell is composed of a linear membrane component and a linear bending component; the signal of a nonlinear paraboloidal shell governed by the von Karman geometric nonlinearity is composed of nonlinear and linear membrane components and a linear bending component. Signal components and distributed modal voltages of linear and nonlinear paraboloidal shells with various curvatures and thickness are investigated.
Analysis of Belt-Drive Mechanics Using a Creep-Rate Dependent Friction Law
Authors: Leamy Michael J. , Wasfy Tamer M. 
Published: November 2020

Abstract
An analysis of the frictional mechanics of a steadily rotating belt-drive is carried out using a physically-appropriate creep-rate dependent friction law. Unlike in belt-drive mechanics analyzed using a Coulomb friction law, the current analysis predicts no adhesion zones in the belt-pulley contact region, although all response quantities (including the belt creep) approach those of the Coulomb law for a steep enough creep-rate law. Depending on the slope of the profile, one or two sliding zones exist on each pulley, which together, span the belt-pulley contact region. Closed-form expressions are obtained for the tension distribution, the sliding-zone are magnitudes, and the frictional and normal forces exerted on the belt. A sample two-pulley belt-drive is analyzed further to determine its pulley angular velocity ratio and belt-span tensions. Results from this analysis are compared to a dynamic finite element solution of the same belt-drive. Excellent agreement in predicted results is found. Due to the presence of arbitrarily large system rotations and a numerically-friendly friction law, the analytical solution presented herein is recommended as a convenient comparison test case for validating friction-enabled dynamic finite element schemes.
Nonlinearly Coupled in-Plane and Transverse Vibrations of a Spinning Disk
Authors: Baddour Natalie , Zu Jean W. 
Published: November 2020

Abstract
Previous nonlinear spinning disk models neglected the in-plane inertia of the disk since this permits the use of a stress function. This paper aims to consider the effect of including the in-plane inertia of the disk on the resulting nonlinear dynamics. The inclusion of the in-plane inertia results in coupling between the in-plane and transverse vibrations of the spinning disk. The full nonlinear equations are simplified to a simpler nonlinear two degrees-of-freedom model via the method of Galerkin. This 2 DOF model is analyzed with a canonical perturbation approach and with numerical simulations. Through the use of these analytical and numerical tools, it becomes apparent that the inclusion of in-plane inertia gives rise to new phenomena in the dynamics of the system that are not predicted if the in-plane inertia is ignored.
An Investigation of Torsional Wave Control in a Multiple Stepped Turbogenerator Shaft System
Authors: Hao Zhiyong , Ye Min , Fu Luhua 
Published: November 2020

Abstract
In the paper, a new analysis method is presented for calculating the torsional wave in a multi-stepped shaft system according to the elastic wave theory, and it is used to simulate the torsional vibration of a turbo-generator shaft system (TSS). Based on the continuous mass model, an active control strategy for minimizing the total energy of torsional vibration in a TSS is deduced against the excitation due to short circuits in the generator or ground faults in the electric network. The responses of torsional vibration and their control process are simulated under the different operate condition. It is shown that active control can not only achieve good vibration attenuation and a fast response to the faults, but also adapt the change of exciting load and work effectively in all of the operating range of the machine.
An Experimental Study of Torsional Vibration Absorbers
Authors: Haddow Alan G. , Shaw Steven W. 
Published: November 2020

Abstract
This paper presents results from tests completed on a rotor system fitted with pendulum-type torsional vibration absorbers. A review of the associated theoretical background is also given and the experimental and theoretical results are compared and contrasted. An overview of the test apparatus is provided and its unique features are discussed. To the best knowledge of the authors, this is the first time that a systematic study of the dynamic behavior of torsional vibration absorbers has been undertaken in a controlled environment.
Phase Shift Near Natural Frequencies of Non Linear Rods
Authors: Georgiou Ioannis T. 
Published: November 2020

Abstract
We study the transient and steady state dynamics of a special class of motions of forced planar rods with exact geometric nonlinearity. The attractors of these motions are separated by a finite jump at a critical forcing frequency in an attractor diagram of the undistorted configuration generated by a quasi-static frequency sweep at fixed forcing amplitude. As the frequency of the forcing passes through this critical or jump frequency, the motion (trajectory) of the undistorted configuration changes basin of attraction. For forcing frequency slightly greater than the jump frequency, the response trajectories of the undistorted configuration pass near an unstable periodic attractor and undergo continuous phase shift while approaching a stable attractor. For forcing frequency slightly smaller than the jump frequency, the response trajectories of the undistorted configuration pass near the same unstable attractor and undergo no net phase angle when landing on the stable attractor that attracts them. The phase-shifting property reveals that the frequncy at which the jump occurs is indeed a natural frequncy of the nonlinear rod.
Global Behavior of a Nonlinear Quasiperiodic Mathieu Equation
Authors: Zounes Randolph S. , Rand Richard H. 
Published: November 2020

Abstract
We investigate the interaction of subharmonic resonances in the nonlinear quasiperiodic Mathieu equation,(1)x..+[δ+ϵ(cos⁡ω1t+cos⁡ω2t)]x+αx3=0. We assume that ϵ ≪ 1 and that the coefficient of the nonlinear term, α, is positive but not necessarily small.
We utilize Lie transform perturbation theory with elliptic functions — rather than the usual trigonometric functions — to study subharmonic resonances associated with orbits in 2m : 1 resonance with a respective driver. In particular, we derive analytic expressions that place conditions on (δ, ϵ, ω1, ω2) at which subharmonic resonance bands in a Poincaré section of action space begin to overlap. These results are used in combination with Chirikov’s overlap criterion to obtain an overview of the O(ϵ) global behavior of equation (1) as a function of δ and ω2 with ω1, α, and ϵ fixed.
Signatures of Acoustic Emission Signals Generated During High Speed Cutting
Authors: Sitz Andre , Schwarz Udo , Kurths J. , Maus Doris , Wiese Michael , Warnecke G. 
Published: November 2020

Abstract
Acoustic emission signals generated during high speed cutting of steel are investigated. The data are represented in time-folded form. Several methods from linear and nonlinear data analysis based on time- and frequency-domain are applied to the data and reveal signatures of the observed acoustic emission signal. These investigations are first steps for modeling the cutting process by means of differential equations.
Linear and Nonlinear Dynamical Coupling of a Class of Electro-Mechanical Systems
Authors: Vidoli Stefano , Vestroni Fabrizio 
Published: November 2020

Abstract
The linear and nonlinear dynamics of an electro-mechanical system, characterized by a gyroscopic internal coupling, are analyzed. Since the technical importance of this system lies in the possibility of damping and controlling structural vibrations, the interest is focused on the energy exchanges between the mechanical and electric components. In order to maximize these energy transformations, the optimal values of the system parameters and their modifications in the nonlinear case are investigated.