bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computational and Experimental Prediction of Multi-Disk Brakes Performance at the Design Stage
Authors: Chichinadze A. V. , Kokonin S. S. , Braun E. D. , Chebotarev L. V. 
Published: March 2021

Abstract
Friction and wear coefficients can vary a lot in multi-disk aircraft brakes under the condition of loaded friction regimes. That is why heat loading, friction duration and distance and also service life calculation procedures, based on constant friction and wear coefficients, are not always applicable to such devices. Such a calculation can provide sufficiently valid results only if experimental data are available, obtained by testing friction couples in a full-scale brake on a test bench. The results will be reliable if a full-scale brake structure is similar to a new one, which is under design, the same friction couple is used and brakes operation modes do not differ too much. It is also possible to use the results of friction couples specimens braking tests, in case the test procedure is based on friction and wear modelling theory recommendations.
Vibration Testing at High Loads and Frequencies
Authors: Occhiuto Scott F. , Jaquish David A. , Duleba George S. 
Published: March 2021

Abstract
This paper describes the design and conduct of high load, high frequency vibration tests of axially loaded brake rods used on typical aircraft landing gear. The main test objective was to evaluate damping characteristics of brake rods incorporating internal Coulomb damping. Tests were conducted with static and vibration loads combined at frequencies up to 350 Hz. Loads of 30,000 lb. static and ± 20,000 lb. dynamic were achieved. This combination of high static and dynamic loads at frequencies greater than 200 Hz is believed to never have been achieved before. This paper presents engineers and vibration test laboratories with a proven concept for analyzing and testing the damping and stiffness characteristics of brake rods and other load carrying members at high loads and frequencies.
Low and High-Frequency Vibrations of the Acoustic Range in Break Gears and Chassis of Highway and Flying Vehicles
Authors: Lukanin Valentin N. , Lujnov Yury M. , Derbaremdiker Anatoly D. 
Published: March 2021

Abstract
The report will focus on the interaction of friction-induced vibrations in break gears and oscillations in chassis of highway vehicles (HV) and in break and landing gears of flying vehicles (FV) when landing.
Mathematical modelling of the observed dependencies of low and high-frequency vibration in break gear and chassis units, as well as on vehicle body, and in cargo and passenger compartments is associated with solving incorrect tasks of the mentioned vehicles dynamics under non-stationary excitation.
Progress in the Application of Wavelet Theory to Vibration Analysis
Authors: Newland David E. 
Published: March 2021

Abstract
For vibration signal analysis, the objective is usually to extract frequency data from a signal and study how the signal’s frequency content changes with time. Because wavelets are local functions of time, each with a predetermined frequency content, wavelet analysis provides a good means of doing this. As a result, practical wavelet analysis is growing rapidly. There are many different wavelets to use but no accepted procedure for choosing between them. This paper discusses various alternative wavelets for practical calculations and describes two of the key numerical algorithms. Examples of recent applications using these algorithms are reviewed, including vibration monitoring and detection, transient signal analysis and denoising.
A Harmonic Tracking Technique for Recovery of Gear Motion From Non-Stationary Vibration Signals
Authors: Lerch Christopher A. , Lyon Richard H. 
Published: March 2021

Abstract
A method termed harmonic tracking is developed to recover time dependent gear motion from machine casing vibration. The harmonic tracking method uses short-time spectral generation and a subsequent set of algorithms to locate and track gear meshing frequencies as functions of time. The meshing frequencies are then integrated with respect to time to obtain the rotation of individual gears. More specifically, spectral generation is performed using the discrete Fourier transform, and the locating and tracking algorithms involve locating tones in each short-time spectrum and tracking them through successive spectra to recover gear meshing harmonics. The harmonic tracking method is found to be more robust than demodulation-based methods in the presence of measurement noise and signal distortion from the structural transfer function between gears and the casing.
The harmonic tracking method is tested, both through simulation and experiments involving motor-operated valves (MOV’s) as part of the development of a diagnostic system for MOV’s. In all cases, the harmonic tracking method is found to recover gear motion with sufficient accuracy to perform diagnostics.
The harmonic tracking method should be generally applicable to situations in which a non-invasive technique is required for determining the time-dependent angular speeds and displacements of gearbox input, intermediary, and output shafts.
Wavelet Analysis for Assessment of Localized Spectral Variations in Surface Topographic Data
Authors: Badami Vivek G. , Hefner Susan S. , Smith Stuart T. 
Published: March 2021

Abstract
In this paper, a two dimensional wavelet analysis using Daubechies D14 wavelets has been used to decompose an Atomic Force Microscope image of the surface of a two dimensional calibration grid. Operating the microscope in open loop mode results in image distortions due to nonlinearities of the scanning mechanism which are subsequently reduced under closed loop control. Such distortions in the image are not readily apparent even using Fourier transform techniques and may be overlooked in a routine calibration. Through an appropriate choice of sample length so that the periodicity of the grid is coincident with the bandpass cut-off of the wavelet transform, it is shown in this paper that distortions can be clearly identified in individual levels of the wavelet reconstruction.
A Statistical Index for Monitoring Tooth Cracks in a Gearbox
Authors: Ismail Fathy , Martin Hugh R. , Omar Farag 
Published: March 2021

Abstract
This paper is concerned with detecting and monitoring the growth of a tooth root crack in a gearbox. It uses the reciprocal of the Kurtosis of the beta distribution 1/k for each tooth period, as the damage indicator. A general equation to generate the statistical moments strictly in terms of the α and β parameters of the beta function is developed. To monitor the growth of the crack, a new index, called the “Kurtosis Index”, is formulated from 1/k’s of all the teeth. This index correlates well with the size of the crack, and it shows that small cracks can be detected.
Efficient Structural Acoustic Analysis Using Finite and Infinite Elements
Authors: Allik Henno , Dees Robert N. , Moore Stewart W. 
Published: March 2021

Abstract
The analysis of three-dimensional shell structures submerged in an infinite fluid and subjected to arbitrary loadings is a computationally demanding problem regardless of the analytical technique used. Over the past several years, we have developed a combined finite/infinite element method of solving this class of problems that is more efficient than other available techniques, and have implemented it in a comprehensive set of computer programs called SARA.
This paper presents an overview of our work. In the first part of the paper, we describe our method for solving the fluid-structure interaction equations including infinite element theory, and modeling practices that have evolved for solving cylindrical geometries.
The second part of the paper addresses another aspect of computational efficiency that is available for shells of basically axisymmetric geometry, but containing arbitrary, three-dimensional internal structures. The axisymmetric fluid-loaded shell can be solved as a series of uncoupled two-dimensional problems far more economically than as a full three-dimensional problem. Coupling this solution to three-dimensional parts of the problem can result in significant computational savings. The SARA implementation of the method is described along with sample problems, and a comparison to a SARA-3D solution is provided.
Static Design and Dynamic Analysis of Light Weight Machinery Support Structures
Authors: Remington Paul J. , Allik Henno , Martin Nathan 
Published: March 2021

Abstract
Light weight truss-like structures to support shipboard machinery are currently under consideration for a variety of marine applications by the US Navy. The objective of this study was to develop the structural acoustic design principles for minimizing the transmission of vibration through the truss to the hull of a vessel and thereby reduce radiated sound. A design procedure was developed to select truss member sizes to satisfy specified design criteria, e.g., minimum weight, minimum radius of gyration, etc., while ensuring that the structure will support the design loads. The procedure interacts with the ANSYS finite element computer code to perform structural analysis. The resulting truss configurations were then analyzed to determine their dynamic performance using the SARA family of finite element programs that incorporate a continuum beam element to increase computational efficiency. A number of two dimensional and three dimensional truss configurations have been analyzed. Results will be presented illustrating the influence of a variety of design parameters on the force transmissibility between excitation point and truss support points. In addition the strong influence of local drive point admittance on the force transmissibility will be illustrated.
Stochastic Behavior of Complex Submerged Systems
Authors: Ettouney Mohammed M. , Daddazio Raymond P. , Abboud Najib N. 
Published: March 2021

Abstract
Acoustic performance is an important issue in naval applications. The structural dynamics of internal systems strongly effects the acoustic performance of the entire structure. Due to the complexity of the internal structures, it is difficult to construct numerical models of sufficient fidelity to represent the essential physics of the system. Hence the complexity of internal systems essentially introduces uncertainty into the total structure. This paper develops a stochastic computational technique which can account for the uncertainties of the problem using physically based definitions of the governing statistical properties of the uncertain systems.
External Acoustic Mode Analysis
Authors: O’Regan Stephen D. 
Published: March 2021

Abstract
This paper presents first an acoustic mode theory for continuous surfaces. The necessary step of basis function normalization is made and is then introduced into the discrete theory to make the two theories consistent. Significant reductions in degrees-of-freedom are illustrated using an example of a cylinder with endcaps as the source surface. The analysis shows that the acoustic modes and radiation efficiencies vary with frequency and, notably, field geometry. A procedure is then described for developing acoustic modal filters to construct a cost function for active sound control.
Wave Component Analysis of Fluid-Loaded, Finite Cylindrical Shell Response
Authors: Grosh Karl , Pinsky Peter M. 
Published: March 2021

Abstract
In this paper, the surface displacement response of a finite fluid-loaded shell and the resulting far field acoustic pressure are studied. A high resolution signal processing algorithm is applied to the surface displacement to estimate the constituent wave numbers and corresponding amplitudes for these wave components. This parameter estimation technique identifies the fluid-loaded cylinder’s complex dispersion relations from finite shell data; the dispersion relations consist of subsonic, leaky, evanescent and oscillatory-decaying wave-number loci. The identified results are compared to the analytic dispersion relations. The far field pressure radiated due to each wave-number component is computed allowing for the determination of important contributors to the far field response. For the frequencies studied, the subsonic wave dominates the far field response due to the finite length of the shell and large amplitude of this component. The supersonic components have the next largest contribution to the far field pressure.
Identifying Critical Elastic Scales in Structural-Acoustic Models
Authors: Shepard W. Steve , Cunefare Kenneth A. , Ginsberg Jerry H. 
Published: March 2021

Abstract
The level of detail required for accurate structural acoustic modeling of fluid loaded structures remains an issue of significant debate. Analytical solutions are rarely available, and discrete numerical solutions are typically too complex for ready extraction of physical understanding. In addition, numerical techniques introduce their own explicit scales, through the minimum mesh dimension. However, the wavenumber based formulation of the surface variational principle describes the surface pressure and displacement as a comparatively small set of interacting waves. Coupling the SVP with distributed methods of representing structural attachment features provides a means to introduce, control and investigate features of differing scales. We present here a technique for assessing the critical resolution scales for a fluid loaded two-dimensional plate. For feature attachments, we consider a line-mass elastically suspended by a line-spring from the wetted plate. We then use a spatial expansion for the elastic attachment to the wetted plate. The excitation applied to the plate is taken as a concentrated harmonic force. With the excitation held fixed, the influence of the scale of the feature spatial representation on the radiated power is assessed.
Wideband Spatial Filters for the Active Control of the Radiation of Elastic Shells in an Acoustic Fluid
Authors: Borgiotti Giorgio V. , Jones Kenneth E. 
Published: March 2021

Abstract
It is known that by linearly filtering the outputs of a dense set of accelerometers, sensing the motion of the boundary of an acoustically radiating object, a relatively small set of quantities is obtained, from which the far field (FF) can be identified. Key properties of the spatial filters are: a) the filters are purely combinatorial (i.e. non-dispersive) and, b) the filtering functions are algorithmically identified from the geometry of the radiator boundary and the highest frequency of the disturbance exciting the system. Abating the acoustic radiation does not require to stop the boundary vibration motion, being sufficient instead to actively modify the boundary normal velocity with the objective of nulling, or practically, substantially reducing the outputs of the radiation filters. The shell here considered has rotational symmetry and the disturbance, modeled as a ring force excited by either a single tone or by a broadband process, is also assumed to be axisymmetric. The radiation filter outputs constitute the signals fed back to the multivariate controller that drives a set of uniform ring force actuators. The number of actuators is the minimum possible (or close to it) for the given boundary geometry and the highest frequency of the disturbance. The controller includes a compensating network subtracting electronically the effect of the actuators from the outputs of the sensors. With this scheme the system becomes essentially feedforward, and therefore is inherently stable. The controller and the compensating network are causally implemented via finite impulse response (FIR) matrix filters. The identification of the FIR matrix coefficients of the controller is obtained by minimizing the average residual power which is radiated when the controller is acting. A highly efficient optimization algorithm is established. Several numerical examples for different disturbance configurations show the effectiveness of the approach here presented for radiating noise cancellation. The simulation was performed by using the well known NASHUA computer model for a shell in water.
Acoustics of Layered Poroelastic Obstacles in Poroelastic Hosts
Authors: Lim Raymond 
Published: March 2021

Abstract
A transition matrix for the field scattered by a 3-dimensional, multilayered, poroelastic obstacle embedded in an unbounded poroelastic host is derived. The result is analogous to Peterson and Ström’s (1975) solution for fluid obstacles and Boström’s (1980) extension for elastic obstacles. An exact solution of the vector Biot equations is obtained, obeying all boundary conditions prescribed on all boundaries of the layered obstacle. By numerically implementing the solution for general poroelastic media, scattering with hosts and obstacles made of nonporous materials is also included in this formulation by choosing material parameters in a limiting sense. By incorporating this solution into a recently reported transition-matrix formulation of scattering in a plane-stratified, poroelastic environment, it becomes possible to study the acoustics of obstacles such as shells buried in ocean sediments. Examples are presented to study the acoustics of spheres with porous outer layers and buried spherical shells.
Relation of the Sound Insulating and Reflecting Properties With Noise Dampening Effect of the Construction With Coatings
Authors: Kouzmitchev Michail N. 
Published: March 2021

Abstract
Calculated evaluation of the relation of the sound insulating and reflecting properties taking into account noise damping effect of an external coating put on construction elements in water is presented by the example of a measurement made using “Underwater Measuring Tubes” installation. The expressions permitting to determine first frequency range and the frequency of largest negative effect in dependence on the parameters of a construction and coating and their materials are obtained.
Numerical Investigation of the Problem of a Plane Acoustic Wave Scattering by a Triaxial Ellipsoid
Authors: Abramov Aleksander A. , Konyukhova Nadezhda B. , Levitina Tatyana V. 
Published: March 2021

Abstract
The problem of scalar scattering by a triaxial ellipsoid is considered. A triaxial ellipsoid is the unique essentially three-dimensional object for which the scattering problem may be solved ‘exactly’ via separation of variables. The solution is expressed in terms of ellipsoidal coordinates associated with a given ellipsoid. The expansions in ellipsoidal wave functions are given for a point source field, a plane wave, and diffraction characteristics of a scattering ellipsoid. These expansions were first obtained by Fedoryuk. The resultant formulas have permitted, in particular, numerical investigation of plane acoustic wave scattering by both ideally soft and ideally rigid triaxial ellipsoids. Far field amplitudes have been calculated and plotted for various parameter values. Separation of the variables allows effective parallel implementation.
Materials Issues in Underwater Transducer Systems
Authors: Cross L. Eric 
Published: March 2021

Abstract
In poled piezoelectric ceramic lead zirconate:lead titanate (PZT) compositions, the non zero components of the piezoelectric tensor are d33, d31 = d32, d15 = d24 (Bornstein, 1981). When the positive directions of the three axis in the ceramic is taken as the poling direction and a tensile stress is considered positive, d33 is a positive coefficient and d31 is negative (Jaffe, Cook, Jaffe, 1971). For the very high coupling compositions with zirconia titania ratio close to that of the morphotropic phase boundary between tetragonal an rhombohedral ferroelectric phases (Zr/Ti = 53/48) in the PZT phase diagram there is an unfortunate effect that d33 ∼ 2d31 (Setter and Cola, 1993). Thus in attempting to use monolithic PZT as a hydrostatic pressure wave sensor dh = h33 + 2d31 is unusually small. For all PZTs, the dielectric permittivity ε33 is large (Herbert, 1982) so that the hydrostatic voltage coefficient gh = dh/ε33 is now very small. For many hydrophone applications the product dhgh is often taken as a figure of merit and so monolithic PZT in spite of its very high individual coefficients is useless as a hydrostatic sensor.
Piezoelectric Composite Panels for Underwater Acoustic Control
Authors: Gentilman Richard L. , Bowen Leslie J. , Corsaro Robert D. , Houston Brian H. 
Published: March 2021

Abstract
Large area 1–3 composite piezoelectric transducer panels have been produced by Materials Systems Inc. (MSI). These SonoPanels™ measure 250 × 250 mm and have excellent response as underwater actuators as well as sensors. Piezocomposite panel manufacturing has been facilitated by an injection molding technology for fabricating net-shape lead zirconate titanate (PZT) ceramic preforms.
An array of fifteen 250 × 250 mm 1–3 composite actuator panels, integrated with surface mounted pressure and velocity sensors, has been attached to a steel backing structure. The array has been evaluated for underwater active surface control applications at the Naval Research Laboratory. Sensor-actuator coupling was investigated, with good agreement between calculated and measured performance.
Simultaneous Harmonic and Transient Suppression for Nonlinear Transducers
Authors: Piquette Jean C. , Forsythe S. E. 
Published: March 2021

Abstract
The Navy is constantly developing new materials for use as the active element(s) in high-performance underwater projectors. One such class of materials is the electrostrictive ceramics such as lead magnesium niobate/lead titanate (PMN/PT). These materials are characterized by high strain per unit electric field, high permittivity (ε = 12000), and a low Curie temperature. These ceramics must be used in their unpoled state in contrast to other classes of ceramic, such as lead zirconate titanate (PZT) ceramics that are usually poled before use.
For PMN/PT, the strain as a function of electric field is an almost perfect square-law, s = kE2, over a large range of voltages, neglecting higher-order effects such as hysteresis and saturation. This response suggests that a transducer made of PMN/PT should be driven by superimposing an ac signal upon a large bias voltage. The bias voltage is needed to achieve a large effective strain/volt (d33) in response to the ac signal. If the ac signal amplitude is greater than a few percent of the bias voltage, significant distortion appears in the output due to the material’s nonlinear response (Fig. 1). Further, when this material is incorporated into an electromechanical transducer the transducer’s transient response is a complex combination of the material’s nonlinearity and the poles and zeros of the mechanical system. If the output displacement of the transducer is to be a large fraction of the maximum possible displacement, a method must be found to overcome the effects of nonlinearity and transient response.
The goal of this work is to generate an output signal that is a near-perfect replica of a desired signal (e.g., a sinusoid that is turned on at t = 0) by driving the transducer with an “inverse” signal derived from a nonlinear model of the transducer. The nonlinear model used for a PMN/PT transducer is the Hunt electrostatic model, modified to include both polarization in the PMN material and the effects of radiation loading on the transducer. The model is presented in the form of coupled ordinary (but nonlinear) differential equations. Parameters for the model are estimated by fitting the model to actual data obtained by driving a PMN stack. Results for the parameters and for the goodness-of-fit of the model are presented. The model and its associated parameters for the stack are then effectively inverted by calculating the drive voltage required to produce a given sinusoidal displacement at the face of the transducer. Finally, the transducer is driven by the calculated drive and the resulting waveform is compared with the desired sinusoidal output. Measures of harmonic distortion reduction for a given output amplitude are presented.