bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unsteady Aerodynamics and Vortex Induced Aeroelastic Instability of a Structural Angle Section
Authors: Modi V. J. , Slater J. E. 
Published: April 2021

Abstract
Wake-body interactions for a two-dimensional structural angle member during stationary and vortex induced oscillatory conditions are studied using a conventional low turbulence wind tunnel. The response of an angle section with combined plunging and torsion indicates that the oscillations occur essentially in one of the two degrees of freedom. The measurements of frequency and phase substantiated this observation. The plunging resonance exhibits the familiar vortex capture phenomenon where the shedding frequency is controlled by the cylinder motion over a finite wind speed range. On the other hand, the torsional vibration shows a vortex control phenomenon where the vortex shedding governs the frequency of oscillation. The vortex induced torsional resonance was found to be severe even at moderate damping levels. The results should prove useful in structural designs such as high voltage transmission towers, antenna masts, bridges, etc. where angle sections are often used as secondary members.
Vibration and Stability of an Elastic Beam Subjected to a Periodic Axial Load With Time-Dependent Displacement Excitation at Both Ends
Authors: Wu Xiao-Feng , Akay Adnan 
Published: April 2021

Abstract
This paper concerns the transverse vibrations and stabilities of an elastic beam simultaneously subjected to a periodic axial load, a distributed transverse load, and time-dependent displacement excitations at both ends. The equation of motion derived from Bernoulli-Euler beam theory is a fourth-order partial differential equation with periodic coefficients. To obtain approximate solutions, the method of assumed-modes is used. The unknown time-dependent function in the assumed-modes method is determined by a generalized inhomogeneous Hill’s equation. The instability regions possessed by this generalized Hill’s equation are obtained by both the perturbation technique up to the second order and the harmonic balance method. The dynamic response and the corresponding spectrum of the transversely oscillating elastic beam are calculated by the weighted-residual method.
On Tool Instability During Machining
Authors: Sahay C. , Dubey R. N. 
Published: April 2021

Abstract
The present paper describes the role of the tool in vibrations of a machining system. The cutting force has been assumed to be constant. The shear deformation of the tool is considered. The quasi-static analysis of the situation yields a maximum allowable uncut chip thickness, which shows how the frictional interaction at the tool face and the ratio of the components of cutting forces alter this value. The relationship also expresses the effect of tool dimensions and work material on the vibration of the tool.
Stability of Perfect Viscoelastic Columns Subjected to Periodic Axial Loading
Authors: Shirahatti Uday S. , Sinha S. C. 
Published: April 2021

Abstract
The stability problem associated with an Euler-Bernoulli beam made of an arbitrary linear viscoelastic material is formulated. The three parameter solid and the Kelvin-Voigt models are analyzed in the presence of constant as well as periodic loads. The application of a finite time stability concept is shown for the constant loading case when the traditional stability criterion fails to make sense. For the case of a periodic loading, the stability diagrams are obtained through an application of Floquet theory. It is found that the addition of periodic loads may significantly alter the stability behavior of a column which is originally subjected to a constant load only.
Stability Analysis of Turbomachinery From the Viewpoint of Seal
Authors: Iwatsubo T. , Sheng B. C. 
Published: April 2021

Abstract
The stability of the typical rotating fluid machineries such as the single-stage and multi-stage pumps which consist of impellers, bearings and noncontacting seals is evaluated from the viewpoint of seals. The individual contribution of the impeller, bearing as well as seal to the stability, and the dynamic interactions of these fluid elements are investigated. In the investigation, some types of bearings, and seals such as annular smooth seals, parallel grooved seals and damper seals are compared to seek the better ones for the rotor stability. The effect of working conditions on the stability is also investigated. The results show that the rotor stability is strongly affected by the characteristics of these fluid elements, and the stability can be improved by changing the unstable fluid element.
Application of the Boundary Element Method to Predict the Acoustic Field in a Two-Dimensional Duct
Authors: Pates Carl S. , Shirahatti Uday S. 
Published: April 2021

Abstract
In the development of the newer supersonic and hypersonic flight vehicles, an increased need for the analysis of acoustic fields and the response of structures to acoustic loads in the presence of high temperature and large mean flow velocities have become necessary. A major concern has been in the area of pressure fields associated with ducts. Such acoustic ducts are frequently used to test the response of various structural elements of flight vehicles. Many new methods have been created and used to approximate the sound fields in ducts. Since the region or boundary of an acoustic problem can extend to infinity, some approximating methods require much time and effort to solve the problem. Many ways have been examined to simplify the acoustic problem and still obtain reasonable results. In the past thirty years, the boundary element method (BEM) has been researched and proven to be an extremely simplified and accurate method for solving acoustic problems. Since BEM only discretizes the boundary, the dimensionality of the problem is reduced by one.
This paper presents a boundary element formulation to predict the pressure field in a two-dimensional acoustic duct. The boundary conditions basically consist of two types: known pressure or known normal derivative of pressure. In order to examine the boundary element method, a 2-D rectangular duct problem will be investigated. The example problem will consist of a duct with rigid walls and a specified pressure distribution at the entrance. Pressure values will be calculated for boundary nodes using the boundary element method. These values will be compared with the available classical solutions.
Enhanced Vibration Control of Ultrasonic Tooling Using Finite Element Analysis
Authors: O’Shea Kevin 
Published: April 2021

Abstract
The use of finite element analysis (FEA) in high frequency (20–40 kHz), high power ultrasonics to date has been limited. Of paramount importance to the performance of ultrasonic tooling (horns) is the accurate identification of pertinent modeshapes and frequencies. Ideally, the ultrasonic horn will vibrate in a purely axial mode with a uniform amplitude of vibration. However, spurious resonances can couple with this fundamental resonance and alter the axial vibration. This effect becomes more pronounced for ultrasonic tools with larger cross-sections.
The current study examines a 4.5″ × 6″ cross-section titanium horn which is designed to resonate axially at 20 kHz. Modeshapes and frequencies from 17–23 kHz are examined experimentally and using finite element analysis. The effect of design variables — slot length, slot width, and number of slots — on modeshapes and frequency spacing is shown. An optimum configuration based on the finite element results is prescribed. The computed results are compared with actual prototype data. Excellent correlation between analytical and experimental data is found.
Boundary Element Method Used in Random Response Calculation of the Plate-Beam Structure
Authors: Zhu J. M. , Huang L. 
Published: April 2021

Abstract
The furnace walls of the large boilers in power plants are combined structures consisting of orthotopic plate and equally spaced beams, which are usually submitted to random vibration under the excitation of the pressure fluctuation induced by combustion in the furnace. In this paper, a numerical method based on BEM to compute the random response of the structure is offered. The agreement between the computing results and the measured data in a practical example verifies the effectiveness of the method.
Coupled Axial-Lateral Dynamic Analysis Using 3-D Riccati-Finite Element Method
Authors: Subbiah Rajagopal 
Published: April 2021

Abstract
An improved algorithmic procedure is discussed to obtain the dynamical characteristics of rotating systems applicable to both 2-D and 3-D models. The beam structure has been modeled in 3 dimension representing five degrees of freedom at each node (three translations and two rotations) using the Riccatifinite element method and solved by an iterative technique. This method provides another convenient way of solving a variety of rotating structural problems using personal computers.
The Method of Modal Parameters to Determine the Boundary Condition of Finite Element Model
Authors: Shiyu Chen , Fengquan Wang 
Published: April 2021

Abstract
In this paper, a method used to determine the boundary condition of Finite Element Model with structure modal parameters is presented. On deriving the method, the theory of Finite Element Model for dynamic calculating is used. Combined with the modal parameters got from experiment, a FEM-Modal Parameter equation to determine the boundary condition is put forward. For solving the equation, three methods are given. The first is the accurate method. The second is the full mode computation method by means of generlized inverse matrix. The third is the interpolation method of frequency. An applied example is given and the results of calculation fully verify the effectiveness of the method offered.
A Nonlinear Analysis of the Whirling Motions of Slender Beams Under Various Resonant Excitations
Authors: Shyu In-Ming K. , Mook Dean T. , Plaut Raymond H. 
Published: April 2021

Abstract
The response of a slender, elastic, cantilevered beam to a simple harmonic excitation is investigated. The nonlinear equations governing the motion of the beam are essentially those derived earlier by Crespo da Silva and Glynn (1978). In the current study, the governing equations are extended to include static deflection. These equations not only include nonlinear curvature, nonlinear inertia, inextensionality and static deflection, but also include torsional displacement. In all cases, the torsional displacement is written in terms of lateral displacements and eliminated from the governing equations. Previous derivations of equations of motion contain only the linear and cubic terms without consideration of the static displacement produced by the weight of the beam. As a result of this static deflection, there are quadratic terms in the governing equations, which introduce the possibility of superharmonic and subharmonic resonances of order two.
The partial-differential equations of motion are converted into a system of coupled ordinary-differential equations in time by the application of Galerkin’s procedure. Approximate solutions of the temporal equations are determined by the method of multiple scales. The analysis reveals that only the in-plane modes directly excited by a primary or secondary resonance and the out-of-plane modes excited by an internal resonance are involved in the first approximation of the response. The amplitudes of the other modes decay. Under some circumstances, there is no steady-state (constant amplitude, constant phase) response. Instead, the amplitude and phase are slowly modulated. Under some circumstances, the modulations are harmonic and produce discrete side bands around the fundamental frequency. For other circumstances, the modulations are chaotic.
Both stable and unstable whirling motions are found in every resonance when the principal moments of inertia of the cross-section are approximately equal. The longer the beam is, the more prominent the whirling motion becomes. The accuracy of some of the approximate solutions is verified by numerical integration. The analysis reveals some interesting possibilities: For example, in a subharmonic resonance of order two, it is possible for the out of plane motion to have a frequency that is exactly one half that of the in-plane motion, which has a frequency equal to that of the excitation. It is also possible for the frequency of the in-plane motion to be equal to that of the out-of-plane motion, which is the one half frequency of the excitation.
Characterization of a Nonlinear Mechanical System by Experimental Attractors
Authors: Kesaraju R. , Noah S. T. 
Published: April 2021

Abstract
Response cycles (periodic orbits) provide a detailed invariant characterization for low dimensional deterministic dynamical systems (Gunaratne and Procaccia, 1987). One can extract all the periodic orbits of order n, for n not too large, directly from the chaotic attractor and calculate their stabilities (Lyapunov exponents), Lathrop and Kostelich, 1989. This information is crucial for asserting whether two experimental attractors are the same or that a theoretical model faithfully reproduces an experimental attractor. Moreover, the periodic orbits can provide a useful characterization of the structure and dynamics of the attractor as parameters vary. This could prove to be a useful tool in failure prediction or parameter identification.
Chaotic Response of an Impulsively Loaded Two Degree of Freedom Beam Model
Authors: Symonds P. S. , Lee J.-Y. 
Published: April 2021

Abstract
The paper shows some recent results for a two-degree of freedom beam model, with lumped parameters of elastic and plastic behavior, as a tool for interpreting anomalous response behaviors of structural elements (beams and plates) subjected to transverse impulsive loading [1]. Such behaviors may occur when the structure has fully fixed edges and the transverse loading leads to extensional permanent strains. The 2DoF model predicts behaviors like those from numerical solutions of discretized beams and plates, but facilitates more extensive calculations. A single DoF model also provides important insights [2, 3], but the 2DoF model [4, 5] reveals the complexity, including chaos, not shown by a SDoF model.
Structural Damage Configurations Subject to Modal Oscillations
Authors: Lu Yaw-Min , Ju Frederick D. 
Published: April 2021

Abstract
The present investigation aims to develop a general probabilistic approach for the prediction of potential damage configurations of structure under modal oscillations. The multiple-crack distribution of the as-predicted damage configurations were characterized by the associated probability measure in terms of crack patterns, crack locations and crack depths. It is postulated that the structure is damaged at a prevailing modal response and the cracking process is sequential. The first passage probability of critical structural parameter exceeding the characteristic material allowable was evaluated to predict the mean time to failure, crack initiation, and crack propagation. In conjunction with the multiple-crack interactive stress relief effects, the probabilistic distributions of damage configuration were established for some representative modal shapes. The analysis results indicate that the damage configurations are highly affected by the modal shape wherein modal stress peak regions provide the most probable locations for cracking. Multiple-crack configuration is more likely to occur at higher mode of vibration. A single crack pattern is dominant at lower mode of vibration.
Modal Analysis of Mini-Small Object: Dental Drill
Authors: Zhang P. Q. , Huang T. C. , Wang Q. M. , Tang X. L. 
Published: April 2021

Abstract
In this paper, we analyze theoretically the use of correlation statistical properties in the random speckle field, in the non-contact recording of free response information of vibrating object, and in terms of time domain signals collected simultaneously at the multiple points, and we conduct system identification techniques in the frequency and time domains to identify the dynamic parameters. The vibration of the bending arm of the dental drill is measured and analyzed. The lower-order natural frequencies and mode shapes are obtained.
Multiple Excitation Sine Testing: An Integrated Approach
Authors: Van der Auweraer H. , Otte D. , Leuridan J. , Bakkers W. 
Published: April 2021

Abstract
Current modal test techniques based on multiple sinusoidal excitation are reviewed. Multiple input stepped sine testing is a phase separation technique. It consists of two steps: the estimation of Frequency Response Functions, followed by modal parameter estimation.
Multiple exiter normal mode testing is a phase resonance technique, where the structure is actually forced to vibrate as a pure normal mode.
The current paper aims to review and investigate the forcing requirements for both approaches from a global point of view, and to present a new, unifying approach combining several of the advantages of both.
Complex Modal Testing Methods for Rotating Machinery
Authors: Lee Chong-Won , Joh Young-Don 
Published: April 2021

Abstract
Various modal testing methods are proposed for the effective use of complex modal testing for rotating machinery, focusing on excitations and measurements. The proposed methods are developed, based on the input/output relationships for complex signals, for the direct or indirect assessment of frequency response and coherence functions between complex inputs and outputs. The proposed testing methods and the classical modal testing method are compared in consideration of required number of frequency response functions (FRFs) and testing efforts.
Parametric Identification of a Vibratory System With a Clearance
Authors: Alexander Richard M. , Noah Sherif T. , Franck Charles G. 
Published: April 2021

Abstract
An analytical and experimental investigation of a vibratory system with a clearance was conducted. A finite element model and an equivalent single degree of freedom closed-form solution were used to determine the dynamic parameters and response of an experimental structure interacting with a gap. The closed-form solution is obtained by taking advantage of the piecewise linearity of the system. Results from these solution methods are in agreement with experimental data. The results also suggest that the closed-form solution approximates the response of the experimental structure with accuracy greater than that of the finite element model.
The closed-form solution was also used to determine the gap size of the structure. The parameter identification procedure utilized in this study appears to be simple to use and can be readily extended to other types of piecewise-linear multidegree of freedom systems.
Modeling and Dynamic Analysis of a Slider-Crank Mechanism With Flexible Coupler and Joint
Authors: Lieh Junghsen , Haque Imtiaz 
Published: April 2021

Abstract
Modeling and dynamic analysis of a slider-crank mechanism with flexible joint and coupler is presented. The equations of motion of the mechanism model are formulated using a virtual work multibody formalism and cast in terms of a minimum set of generalized coordinates through a Jacobian matrix expansion. Numerical results show the influence of time-varying coefficients on the mechanism dynamic behavior due to a repeated task. The results illustrate that the joint motion and coupler deformation are highly coupled. The joint response is dominated by double frequency of input, however, the coupler deformation is influenced by the same frequency as that of excitation. Increase in joint stiffness tends to decrease the variations in coupler deformation.
Modal Control by Modal Force Technique
Authors: Tsai C. D. , Ju M. S. , Tsuei Y. G. 
Published: April 2021

Abstract
Modal control of structure requires the estimation of the modal states variables for feedback. One approach that does not require modal states variables estimation is the direct feedback control. Recent developments in modal control for direct feedback are mainly time domain methods. In this paper, an efficient method based on frequency domain approach named Modal Force Technique is developed. The method not only allows one to modify the global dynamic behavior of the synthesized structure but also can be utilized for modal control problem if the acceleration, velocity and displacement feedbacks are used.
Approximate Linear Theories for the Dynamics of Slack Cables Supporting a Discrete Mass
Authors: Cheng S.-P. , Perkins N. C. 
Published: April 2021

Abstract
A continuum model is presented that describes the three-dimensional response of an elastic cable that supports a single attached mass. Two asymptotic forms of this model are analyzed for the free, linear response of slack suspensions having small equilibrium curvature (sag) and level supports. The first model, which is valid for relatively small attached masses, assumes that the cable stretches quasi-statically and results in uniform dynamic cable tension. The quasi-static stretching assumption is partially relaxed in the second model which accounts for spatially varying dynamic tension in an approximate manner. The eigen-solutions associated with free response are compared for the two models. Results indicate that the “small mass model” provides excellent approximations to the natural frequency spectrum and vibration mode shapes for most cables and modes of technical interest. A simple criterion is presented which governs the range of validity of the small mass model.
Modeling and Dynamic Behaviors of a Rotor Suspended in Electromagnetic Bearings
Authors: Xu Jiankang , Xie Youbai , Mao Junhong 
Published: April 2021

Abstract
A closed loop system composed of a rotor in electromagnetic bearings and a PID (proportion-integration-differentiation) controller is developed. With the active electromagnetic forces the rotor 50 millimeters in diameter can be fully suspended in two radial electromagnetic bearings and can be driven from zero up to 3000 rpm. This closed loop system is modeled and its dynamic behaviors are analized by digital simulation. The influence of controller parameters on motion of the rotor and the relation between controller parameters and dynamic stiffness of the electromagnetic bearings are presented.
On the Optimal Correction of Structural Dynamic Models
Authors: Mottershead John E. 
Published: April 2021

Abstract
It is well known that a discrete analytical model cannot accurately represent the dynamics of a continuous physical system over the frequency range of the model. Methods have been presented with the intention of improving analytical models (finite element models in particular) by the use of either (a) measured modal data or (b) measured frequency responses. In this paper we consider in particular the selection of weighting terms and the physical significance of the estimates. In both cases the discussion is illustrated by means of example problems.
An Analysis of Sensitivity of Multidimensional Electromechanical System
Authors: Jasińska-Choromańska Danuta 
Published: April 2021

Abstract
Subject of this paper in connected with problems reffering to analysis of parametrical sensitivity of mathematical model of static properties of complex multidimensional mechanical and electromechanical systems. A full definition of an analysis requires analysis of sensitivity’s invariants and preliminary selection of tolerances of the model. This paper presents application of the above method in order to a mathematical model of an inductive transducer for the measurement of displacements.