bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Magnetostrictive Sonar Projector Utilizing a Terfenol Driver
Authors: Dunlap R. A. , Purcell C. J. 
Published: March 2021

Abstract
Defence Research Establishment Atlantic (DREA) is developing a flextensional barrel-stave projector which utilizes a magnetostrictive Terfenol-D driver. Our attention has focussed on three critical aspects of the design of the projector: (1) reduction of eddy currents, (2) incorporation of permanent magnets to bias the Terfenol and (3) a low reluctance magnetic flux return path. Here we describe a projector design which deals with these three aspects. The Terfenol rod is sectioned radially in order to reduce eddy current losses. Co-Sm permanent magnets are used to provide the magnetic bias field to the Terfenol. The magnetic flux return path is comprised of ferrite disks at the ends of the drive rod and a high permeability cylinder constructed of Metglas 2605TCA. The total projector mass is 3.85 kg. In water the resonance occurs at approximately 1.0 kHz and the bandwidth is 310 Hz. At resonance the distortion limited source level was measured to be 197.7 dB re 1μPa@ 1m and the efficiency was 32.3%.
Alternative Concepts for Vibration Test Fixtures Used in Quiet Product Manufacture
Authors: Bowen David L. 
Published: March 2021

Abstract
Test fixtures are widely used in industry for quality control to determine the potential of a product to make excessive noise. Since acceptable parts may be rejected unnecessarily, or noisy parts may be passed if the test is inaccurate, it is desirable to have a reliable test setup, including the test fixture. When the part being tested is a motor and gearbox, and the test measurement is vibration, the vibratory response may vary significantly, depending on exactly how the motor and gear tones line up with the test fixture resonances. This potential for variability has led to vibration test fixtures being designed to be as precise as possible, so that the construction of the test fixture can be repeated from one application to the next. However, such an approach has led to rather stiff and massive designs, with few resonant modes, with the result that the repeatability of the measurements can be affected by rather small variations in motor speed and mounting conditions. A similar situation in acoustics leads to the use of reverberation chambers with rotating diffusers. This paper describes an investigation into the possibility of employing a vibration analog to the reverberant room as a test fixture, in order to make vibration measurements on a production line more reliable. The fixture is a plate, sized to achieve a higher modal density than exists in a typical test fixture. The geometry, edge restraints and interior loads are varied, either through analysis or experiments, to produce a variability of response to be averaged over during the data analysis period. Our conclusion is that the reverberant plate test fixture is able to reduce the variability of vibrational response in comparison to a more standard test fixture.
Structural-Acoustic Design at High Frequency Using the Energy Finite Element Method
Authors: Bernhard Robert J. , Huff John E. 
Published: March 2021

Abstract
Energy flow analysis methods, particularly as implemented using the finite element method, are useful as design techniques for high frequency structural-acoustic applications. In this paper, the derivation of energy flow analysis techniques are summarized. Particular attention is given to the specification of joint models for situations where there is a discontinuity in either geometric properties or material properties. The finite element formulation of this approach is also summarized. A case study is included to illustrate the utility of the method as a design technique.
Reducing the Noise of Pressure Pulp Screen: Theory and Application
Authors: Berry Alain , Oddo Rémy , Panneton Raymond , Nicolas Jean 
Published: March 2021

Abstract
A pressure pulp screen is a machine used in the pulp and paper industry to remove and class cellulose fibres in paper pulp. It involves an inner perforated cylindrical basket which receives the pulp under pressure, an inner rotor with profiled blades used to clear the holes or slits of the basket, and an outer cylindrical shell. The noise radiated by the outer shell is characterized by discrete frequencies in mid- and high frequency (1–4 kHz). A preliminary study has shown that the radiated noise is due to the vibration of the perforated basket under the moving load of the rotor. This vibration is transmitted to the outer shell through various paths which were analyzed and classified. An analytical model of the vibroacoustic behavior of a cylindrical shell under a circumferentially moving load was used to establish various rotating speed regimes with respect to the vibration and sound radiation of the shell. It was shown that a circumferential modulation of the load (corresponding to the effect of holes or slits on the inner basket) leads to theoretical noise spectra similar to measured data. On the practical front, the model was used to identify significant design parameters with respect to the noise of the machine. The paths of energy transmission from the basket to the outer shell were studied and various noise reduction approaches have been investigated.
The Vibroacoustic Behavior of a Rotating Annular Complex Plate With Application to the Design of Circular Saws
Authors: Atalla Noureddine , Côté André , Cournoyer Benoît , Nicolas Jean 
Published: March 2021

Abstract
This paper discusses the vibroacoustic behavior of an annular rotating complex plate with application to the design of circular saws. The effects of rotation and constrained viscoelastic damping are investigated both theoretically and experimentally. On the theoretical front, a model based on the variational approach has been developed. Special attention has been devoted to 1) the effects of rotation on both the vibration and the noise radiated by the annular plate and 2) the optimization of viscoelastic constrained damping. On the experimental front, several set ups have been devised to validate the theoretical models and to test some noise reduction avenues. Examples showing predictions from the theoretical models will be presented together with comparisons to experimental data. Finally, application of the above results to the design of a quieter circular saw will be discussed.
Quieting Plate Modes With Optimally Sized Point Masses: A Volume Velocity Approach
Authors: Wodtke Hans-Walter , Koopmann Gary H. 
Published: March 2021

Abstract
The radiated sound power of the second symmetric mode of a clamped square plate is minimized by attaching optimally sized point masses to the plate. The plate is driven by a point force at its center and the positions of the masses are prescribed. The structural vibration problem is solved using a simple Rayleigh-Ritz approach. Solving the acoustic radiation problem is simplified by making a low-ka-assumption, i.e., the point masses are determined so as to minimize the surface volume velocity of the plate. The predicted results are verified experimentally by means of sound intensity measurements. It is shown that a structural resonance can be deleted from the acoustic response by exploiting volume velocity cancellation. The effects involved are illustrated in detail.
Optimum Design of Vibration Absorbers Using Genetic Algorithm
Authors: Chen Ting-Yu , Lan Jun-Jei 
Published: March 2021

Abstract
The genetic algorithm (GA) is used to design vibration absorbers. The problem is formulated as mixed continuous and discrete variable problem. The continuous design variables include the mass, the spring constant and the damping coefficient of the vibration absorbers. The discrete variables are the installing locations of the absorbers. GA fits in this problem very well. Two examples are given. The near optimum solutions show that when the number of constrained frequency responses is less than or equal to the number of vibration absorbers, the optimum locations of the absorbers are exactly the nodes where the frequency response constraints are imposed. On the other hand, if the number of constrained frequency responses is greater than the number of absorbers, the optimum locations for the absorbers tend to be at the nodes that keep near equal distances to those constrained nodes.
Dynamic Behavior of the Band/Wheel Mechanical System of Industrial Band Saws
Authors: Chung Y. Y. , Sung C. K. 
Published: March 2021

Abstract
This paper presents an analytical and experimental investigation on the dynamic behavior of the band/wheel mechanical system of an industrial metal-cutting band saws. In practice, as a result of the existence of the wheel tilt angle, a pair of roller bearings in which one of them is movable must be employed to twist the saw band perpendicular to the workpiece. Therefore, the saw band is modelled as a finite moving beam span that composes of three consecutive segments, in which the middle segment, that is, the cutting span, and the neighboring two segments may be assumed to be a straight and a twisted beams, respectively. The deformation of the band must satisfy the continuity condition at the connections between segments.
The equations of motion governing the dynamic behavior of the beam span in axial, torsional and transverse directions are derived using mixed variational principle. The axial motion of the beam span couples linearly with its torsional motion. The dynamic responses and the natural frequencies of the beam are computed when parameters vary, such as the transport velocity of the saw band, band tension, wheel tilt angle, and the length of the cutting span. Finally, an experimental study is performed on an industrial band saw for the verification of the mathematical model and the predictive capability proposed in this investigation. Favorable comparisons between the analytical and experimental results are obtained.
Broadband Dynamic Modification Using Feedforward Control
Authors: Alberts Thomas E. , Pota Hemanshu R. 
Published: March 2021

Abstract
This paper presents a general proof of a result due to Fuller and Burdisso, that asserts that system eigenvalues can be modified using feedforward control. The original result applies to the case of steady-state harmonic excitation. This paper extends that work to allow for broadband excitation. The results apply to any flexible structure representable using modal expansion, and are applicable to systems with non-minimum phase zeros. A design procedure is presented to allow arbitrary assignment of the controlled system’s poles, using a fixed feedforward compensator.
Application of Method of Moments to Acoustic Scattering From Fluid Filled Cylinders Using Three Different Formulations
Authors: Sun S. P. , Raju P. K. , Rao S. M. 
Published: March 2021

Abstract
In this work, we present three different formulations Viz. The pressure field integral equation formulation (PFIE), the velocity field integral equation formulation (VFIE), and the combined field integral equation formulation (CEDE) for solving acoustic scattering problems associated with two dimensional fluid-filled bodies of arbitrary cross section. In particular using the boundary conditions on the surface of the body, two equivalent problems, each valid for the outside and inside regions of the scatterer, are derived. By properly selecting the associated equations for these equivalent problems, the three different formulations are derived. The PFIE, VFIE, and CFIE are then solved by approximating the cylindrical cross section by linear segments and employing the method of moments. Further, it is shown that the moment matrices generated by the PFIE and VFIE are ill-conditioned at resonant frequencies of the cylinder, whereas the CFIE generates a well-conditioned matrix at all frequencies. The solution techniques presented in this work are simple, efficient and applicable to truly arbitrary geometries. Numerical results are presented for certain canonical shapes and compared with other available data.
Space-Time hp-Version Finite Elements Applied to Wave Propagation With Moving Loads
Authors: Zhao Bo , Peters David A. 
Published: March 2021

Abstract
The space-time finite element method has emerged as a promising alternative numerical analysis technique for structural dynamics. This paper concentrates on hp-version triangular elements based on a variational statement of elasto-dynamics formed on Hamilton’s law of varying action. As such, forces and momenta are weak; and element boundaries may cut across space and time. This forms a natural framework for problems with both moving load and wave propagation. This paper presents applications of the method to such problems with numerical results and conclusions regarding proper mesh geometry.
Nonlinear Transient Response and its Sensitivity Using Finite Elements in Time
Authors: Kapania Rakesh K. , Park Sungho 
Published: March 2021

Abstract
The bilinear formulation proposed earlier by Peters and Izadpanah to develop finite elements in time to solve undamped linear systems, is extended (and found to be readily amenable) to develop time finite elements to obtain transient responses of both linear and nonlinear, and damped and undamped systems. The formulation is used in the h-, p- and hp-versions. The resulting linear and nonlinear algebraic equations are differentiated to obtain the sensitivity of the transient response with respect to various design parameters. The present developments were tested on a series of linear and nonlinear examples and were found to yield, when compared with results obtained using other methods, excellent results for both the transient response and its sensitivity to system parameters. Mostly, the results were obtained using the Legendre polynomials as basis functions, though, in some cases other orthogonal polynomials namely, the Hermite, the Chebyshev, and integrated Legendre polynomials were also employed (but to no great advantage). A key advantage of the time finite element method, and the one often overlooked in its past applications, is the ease in which the sensitivity of the transient response with respect to various system parameters can be obtained.
Second-Order Systems With Singular Mass Matrix and an Extension of Guyan Reduction
Authors: Bhat Sanjay P. , Bernstein Dennis S. 
Published: March 2021

Abstract
The set of consistent initial conditions for a second-order system with singular mass matrix is obtained. In general, such a system can be decomposed (i.e., partitioned) into three coupled subsystems of which the first is algebraic, the second is a regular system of first-order differential equations, and the third is a regular system of second-order differential equations. Under specialized conditions, these subsystems are decoupled. This result provides an extension of Guyan reduction to include viscous damping.
Coupled Bending-Torsion Vibration of Geared Rotors
Authors: Rao J. S. , Chang J. R. , Shiau T. N. 
Published: March 2021

Abstract
A general finite element model is presented for determining the coupled bending-torsion natural frequencies and mode shapes of geared rotors. Uncoupled bending and torsion frequencies are obtained for examples available in literature and the present program is verified against these. The effect of the gear box is considered to determine the coupled frequencies. Parameters studied include the pressure angle, gear mesh stiffness, and bearing properties. The gear pressure angle is shown to have no effect on the natural frequencies of rotors supported on isotropic bearing supports. Several case studies with bending-torsion coupling are considered and the results obtained are compared with those available in literature. The results of a general rotor system with 8lodes are also presented.
Studies of the Rotor Dynamics of Gas Centrifuges for Fine Particulate Separation
Authors: Al-Ajlouni Musa , Syred Nick 
Published: March 2021

Abstract
A range of techniques have been used to evaluate the performance of an existing design of gas centrifuge for separating sub-micron particles from gas streams. The rotor dynamics of the system are complex, very dependant on the bearing type, design, and layout. The first harmonic typically occurs at low speeds of about 15,000 rpm and can be of sufficient a high amplitude to require special bearing systems.
This paper analyses the performance of an existing unit with a number of tools, including a computer aided package called ROMAX II that carries out a dynamic vibrational analysis of the self acting foil and annular air thrust bearing system. Results are compared with experiment. It is shown that the first harmonic vibrational mode is well predicted. Changes in performance occurring from detail design alterations made to the thrust bearings are also shown to be sensibly predicted.
Finally extrapolations are made to units of 1 metre in length and performance predictions made. It is clearly shown that by an appropriate choice of bearing system the first natural frequency can be raised to well above that required for sensible centrifuge operation.
Finite Element Analysis of an Automotive Turbocharger Turbine Wheel
Authors: Subramani D. A. , Ramamurti V. , Sridhara K. 
Published: March 2021

Abstract
This paper describes the finite element analysis carried out on a typical automotive turbocharger turbine wheel using the concept of cyclic symmetry. The results of this analysis are compared with those obtained using a relatively simple analysis carried out by treating the blade and the hub separately.
Dynamic Modelling and Response Characteristics of a Magnetic Bearing Rotor System With Auxiliary Bearings
Authors: Free April M. , Flowers George T. , Trent Victor S. 
Published: March 2021

Abstract
Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotordynamic model which describes the dynamic behavior of a flexible rotor system with magnetic bearings including auxiliary bearings. The model is based upon an experimental test facility. Some simulation studies are presented to illustrate the behavior of the model. In particular, the effects of introducing sideloading from the magnetic bearing when one coil fails is studied. These results are presented and discussed.
Theory Versus Experiment for the Effects of Pressure Ratio on the Performance of an Orifice-Compensated Hybrid Bearing
Authors: Mosher Phillip , Childs Dara W. 
Published: March 2021

Abstract
This research investigates the effect of varying the concentric recess pressure ratio of hybrid (combination hydrostatic and hydrodynamic) bearings to be used in highspeed, high-pressure applications. Bearing flowrate, load capacity, torque, rotordynamic coefficients, and whirl frequency ratio are examined to determine the concentric, recess-pressure ratio which yields optimum bearing load capacity and dynamic stiffness. An analytical model, using two-dimensional bulk-flow Navier-Stokes equations and anchored by experimental test results, is used to examine bearing performance over a wide range of concentric recess pressure ratios. Typically, a concentric recess pressure ratio of 0.50 is used to obtain maximum bearing load capacity. This analysis reveals that theoretical optimum bearing performance occurs for a pressure ratio near 0.40, while experimental results indicate the optimum value to be somewhat higher than 0.45. This research demonstrates the ability to analytically investigate hybrid bearings and shows the need for more hybrid-bearing experimental data.
The Effects of Converging and Diverging Axial Taper on the Rotordynamic Coefficients of Liquid Annular Pressure Seals: Theory Versus Experiment
Authors: Lindsey W. Todd , Childs Dara W. 
Published: March 2021

Abstract
Experimental results are compared to predictions for turbulent flow, short (D = 76.2mm, L/D = .17), smooth annular seals with converging and diverging axial taper. Results are presented for four geometries: two convergent, two divergent, and a constant-clearance. Measurements were taken at seal pressure differentials and shaft rotation rates ranging from 1.34 to 3.54 MPa and 10,200 to 24,600 rpm, respectively.
Measurements parameters include leakage, direct stiffness, cross-coupled stiffness, and direct damping coefficients. Results show that direct stiffness generally increases with converging axial taper and decreases with diverging axial taper. Direct damping and cross-coupled stiffness were shown to decrease with increasing convergent or divergent taper. Measured damping values increase with increased running speed and decreasing average clearance. Theoretical predictions for rotordynamic coefficients are in good overall agreement with measured results. The theory consistently underpredicts leakage by ranges of 10 ∼ 30%. The accuracy of predictions for leakage and rotordynamic coefficients was not influenced by running speed.
Dynamical Behaviors of Hybrid Squeeze Film Damper for Rotor System Vibration Control
Authors: Changsheng Zhu 
Published: March 2021

Abstract
The behaviors of oil film stiffness and damping coefficients of the deep multi-recessed hybrid squeeze film damper (HSFD) with the orifices compensated are first analysed in this paper. The control ability of the HSFD on the rotor system vibrations is studied theoretically and experimentally with a rigid rotor system supported on the HSFD, and compared with that of the conventional squeeze film damper (SFD). Investigation shows that the HSFD not only can significantly improve the high nonlinearity of the SFD, but also can effectively control the rotor vibrational amplitudes, especially for larger rotor unbalance levels and radial clearance ratios, as compared with the SFD.
Vibration Analysis of Bladed Disc Assemblies
Authors: Minas C. , Kodiyalam S. 
Published: March 2021

Abstract
The dynamic behavior of a bladed disc assembly was determined by developing a finite element model (FEM). The object of this work is to develop an understanding of the dynamic behavior of the system with respect to the various boundary conditions. The analysis included variation of the boundary conditions at the blade-disc interface, between adjacent blades, and the shroud. It was clearly shown that only certain mode patterns are affected with respect to a particular boundary condition, leaving the remaining modes unchanged. The quantitative effect of the various boundary conditions was calculated by finite element analysis of a cyclic symmetric model. A methodology is also presented where the associated modes of the higher harmonics natural frequencies of the assembly, are identified in a systematic and automated way without being plotted and viewed. This methodology which uses the cross-orthogonality equations, is valuable to systems with a large number of nodal diameters, where the complete set of the associated mode shapes can be analyzed in an efficient and systematic way. The technique is illustrated through an example, where a complete analytical Campbell diagram for the lower order modes is developed.
Study on the Unbalanced Effect of Rotary Systems
Authors: Huang Yuan Mao , Wang Chin-Ming 
Published: March 2021

Abstract
The transient dynamic analysis of rotary systems is very important because the maximum displacements of components due to the unbalanced effect may occur during the transient state. This study develops a numerical method by combining the methodologies of the finite element method, the transfer matrix method, the time marching numerical integration method and the Houbolt numerical method. The effects of rotary inertia, gyroscopic phenomenon, shear deformation and internal damping on the dynamic behaviors of a rotor-bearing system are analyzed. The transient displacements of components in the system are calculated and show good agreement with the available data.