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Accepted Manuscripts

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research-article  
Olumuyiwa David Owoseni, Kehinde/Oluwole Orolu and Ayo Oyediran
J. Vib. Acoust   doi: 10.1115/1.4037703
One of the most important facilities in the oil and gas industry is the pipeline. These pipelines convey HPHT fluids and transit several kilometres travelling through different seafloor soils. The topography of seabed which act as viscoelastic foundation to the pipeline is rough and irregular thereby making the pipelines to be slightly curved. This erratic behaviour of these soils present several problems to the constructor and threatens the lifespan of the pipeline. The average useful lifespan of pipelines is between 25 - 30 years but improper construction and mal-operation have dropped this span drastically, accounting for more than 50% of pipeline failures, hence this work. The nonlinear governing partial differential equations were derived and solved using energy and eigenfunction expansion methods respectively. The resultant ordinary differential equations were truncated after the fourth mode and solved numerically using eight-seventh order Runge-Kutta code in MATLAB. Two types of foundations were investigated. Both with viscous damping but one is with linear spring, while the other is with nonlinear spring. Bifurcation and orbit diagrams with their corresponding phase portraits showing periodic and chaotic motions of the system trajectories are generated and presented. It was discovered that foundation, curvature and tension stiffen the pipe, while pressure and temperature are of softening effect. Nonlinear stiffness makes the pipe to undergo chaotic oscillation which may result in soil trenching or upheaval which is absent in the linear case, meaning that linear foundations enhance the life span of pipelines than the nonlinear ones.
research-article  
Yang Song, Zhigang Liu, Fuchuan Duan, Xiaobing Lu and Hongrui Wang
J. Vib. Acoust   doi: 10.1115/1.4037521
Due to its long-span structure and large flexibility, an electrified railway catenary is very sensitive to environmental wind load, especially the time-varying stochastic wind, which may lead to a strong forced vibration of contact line and deteriorate the current collection quality of the pantograph-catenary system. In this paper, in order to study the wind-induced vibration behaviour of railway catenary, a nonlinear finite element procedure is implemented to construct the model of catenary, which can properly describe the large nonlinear deformation and the non-smooth nonlinearity of dropper. The spatial stochastic wind field is developed considering the fluctuating winds in along-wind, vertical-wind and cross-wind directions. Using the empirical spectrums suggested by Kaimal, Panofsky and Tieleman, the fluctuating wind velocities in three directions are generated considering the temporal and spatial correlations. Based on fluid-induced vibration theory, the model of fluctuating forces acting on catenary are developed considering the spatial characteristics of catenary. The time-domain and frequency-domain analyses are conducted to study the wind-induced vibration behaviour with different angles of wind deflection, different angles of attack as well as different geometries of catenary. The effect of spatial wind load on contact force of pantograph-catenary system is also investigated.
TOPICS: Finite element analysis, Vibration, Railroads, Wind, Stress, Deformation, Fluids, Wind velocity, Deflection, Frequency-domain analysis
research-article  
Atsushi Nishimura, Tsuyoshi Inoue and Yusuke Watanabe
J. Vib. Acoust   doi: 10.1115/1.4037520
Various vibration problems occur in rotating machinery. Specifically, the large amplitude vibration can occur in the vertical pump using a journal bearing. Moreover, in an actual vertical pump, the stator's structure supporting the pump shaft may be relatively flexible. In such a case, rotor's motion such as self-excited vibration is not able to be predicted accurately without considering the fluid force reacting in the relative motion between the rotor and the stator. However, the vibration characteristics in such situations have not been explained theoretically so far. In this paper, the simple and quantitative method for evaluating vibration characteristics of a vertical rotating shaft with journal bearing is investigated. Eigenvalue analysis is demonstrated for the linearized system, and then, the nonlinear steady-state vibration analysis of the self-excited vibration is demonstrated. As a result, the influences of the parameters, such as fluid viscosity, radial clearance, and stiffness and damping of the flexible supporting part, on the vibration characteristics of the system are explained. Moreover, these theoretical results of the self-excited vibration in the vertical rotating shaft with journal bearing are verified experimentally.
TOPICS: Rotors, Vibration, Journal bearings, Pumps, Fluids, Machinery, Viscosity, Clearances (Engineering), Damping, Eigenvalues, Stators, Steady state, Stiffness, Vibration analysis
Technical Brief  
Laihao Yang, Xuefeng Chen and Shibin Wang
J. Vib. Acoust   doi: 10.1115/1.4037509
Fast time-varying (FTV) phenomena, such as significant speed changes, fast time-varying stiffness, and vibration signals with fast-oscillated instantaneous frequency (IF), carry critical fault information of high-speed rotating machines. However, the mechanism of FTV phenomenon remains unclear, and conventional methods cannot characterize the FTV features. In this study, the FTV vibration mechanism for rotor-stator contact systems is first revealed, and then a novel fast-modulation-based rub-impact detection method (FRiDM) is significantly developed to extract the FTV features and thus promote the effectiveness of rub-impact diagnosis. The FTV vibration mechanism indicates that the fast-oscillated modulation of the vibration signal is the physical property and the fast oscillation of IF is the mathematical nature. By theoretical and experimental study, it is demonstrated that the FTV features of the rotor-stator contact system are periodic for the periodic motion but aperiodic for the quasiperiodic and chaotic motions. Finally, the validity of the proposed FTV vibration mechanism and FRiDM is verified by the application to the rub-impact diagnosis of a bearing life testing rig and a dual-rotor turbine engine. The study results provide a potential way to nonlinear behavior identification and fault localization of sophisticated rotor systems.
TOPICS: Rotors, Vibration, Fault diagnosis, Stators, Signals, Stiffness, Life testing, Oscillations, Machinery, Bearings, Gas turbines
research-article  
Ali Hossain Alewai Daraji, Jack M. Hale and Jianqiao Ye
J. Vib. Acoust   doi: 10.1115/1.4037510
This paper describes a computationally efficient method to determine optimal locations of sensor/actuator (s/a) pairs for active vibration reduction of a flexible structure. Previous studies have tackled this problem using heuristic optimization techniques achieved with numerous combinations of s/a locations and converging on a suboptimal or optimal solution after multi thousands of generations. This is computationally expensive and directly proportional to the number of sensors, actuators, possible locations on structures and the number of modes required to be supressed (control variables). The current work takes a simplified approach of modeling a structure with sensors at all locations, subjecting it to external excitation force or structure base excitation in various modes of interest and noting the locations of n sensors giving the largest average percentage sensors effectiveness. The percentage sensor effectiveness is measured by dividing all sensor output voltage over the maximum for each mode using time and frequency domain analysis. The methodology was implemented for dynamically symmetric and asymmetric structures under external force and structure base excitations to find the optimal distribution based on time and frequency responses analysis. It was found that the optimized sensor locations agreed well with the published results for a cantilever plate, while with very much reduced computational effort and higher effectiveness. Furthermore, it was found that collocated s/a pairs placed in these locations offered very effective active vibration reduction for the structure considered.
TOPICS: Sensors, Vibration control, Actuators, Flexible structures, Excitation, Vibration, Cantilevers, Frequency response, Frequency-domain analysis, Modeling, Optimization
research-article  
Hui Ren, Wei Fan and Weidong Zhu
J. Vib. Acoust   doi: 10.1115/1.4037513
An accurate and robust geometrically-exact beam formulation (GEBF) is developed to simulate the dynamics of a beam with large deformations and large rotations. The undeformed configuration of the centroid line of the beam can be either straight or curved, and cross-sections of the beam can be either uniform or nonuniform with arbitrary shapes. The beam is described by the position of the centroid line and a local frame of a cross-section, and a rotation vector is used to characterize the rotation of the cross-section. The elastic potential energy of the beam is derived using continuum mechanics with the small-strain assumption and linear constitutive relation, and a factor naturally arises in the elastic potential energy, which can resolve the drawback of the traditional GEBF. Shape functions of the position vector and rotation vector are carefully chosen, and numerical incompatibility due to independent discretization of the position vector and rotation vector is resolved, which can avoid the shear locking problem. Numerical singularity of the rotation vector with its norm equal to zero is eliminated by Taylor polynomials. A rescaling strategy is adopted to resolve the singularity problem with its norm equal to 2m*pi, where m is a nonzero integer. The current formulation can be used to handle linear and nonlinear dynamics of beams under arbitrary concentrated and distributed loads. Several benchmark problems are simulated using the current formulation to validate its accuracy, adaptiveness, and robustness.
TOPICS: Dynamics (Mechanics), Rotation, Deformation, Potential energy, Stress, Continuum mechanics, Cross section (Physics), Shear (Mechanics), Dynamic analysis, Polynomials, Robustness, Shapes, Nonlinear dynamics
research-article  
Jaroslav Zapomel and Petr Ferfecki
J. Vib. Acoust   doi: 10.1115/1.4037512
Adding damping devices to the rotor supports is a frequently used technological solution for reducing vibrations of rotating machines. To achieve their optimum performance, their damping effect must be adaptable to the current operating speed. This is offered by magnetorheological squeeze film dampers. The magnetorheological oils are liquids sensitive to magnetic induction and belong to the class of fluids with a yielding shear stress. Their response to the change of a magnetic field is not instantaneous, but it is a process called the delayed yielding. The developed mathematical model of the magnetorheological squeeze film damper is based on the assumptions of the classical theory of lubrication. The lubricant is represented by a bilinear material, the yielding shear stress of which depends on magnetic induction. The delayed yielding process is described by a convolution integral with an exponential kernel. The developed mathematical model of the damper was implemented in the computational procedures for transient analysis of rotors working at variable operating speed. The carried-out simulations showed that the delayed yielding effect could have a significant influence on performance of magnetorheological damping devices. The development of a novel mathematical model of a magnetorheological squeeze film damper, the representation of the magnetorheological oil by bilinear material, taking the delayed yielding phenomenon into consideration, increased numerical stability of the computational procedures for transient analysis of flexible rotors, and extension of knowledge on behavior of rotor systems damped by magnetorheological squeeze film dampers are the principal contributions of this article.
TOPICS: Oscillations, Rotors, Dampers, Damping, Transient analysis, Magnetic induction, Shear stress, Engineering simulation, Vibration, Numerical stability, Oils, Petroleum, Lubrication, Fluids, Machinery, Magnetic fields, Lubricants, Simulation
research-article  
Ronald N. Miles and Jian Zhou
J. Vib. Acoust   doi: 10.1115/1.4037511
An analysis is presented of the motion of a thin fiber, supported on each end, due to a sound wave that propagates in the direction perpendicular to its long axis. Predicted and measured results indicate that when fibers or hairs having a diameter measurably less than one micron are subjected to acoustic excitation, their motion can be a very reasonable approximation to that of the acoustic particle motion at frequencies spanning the audible range. When their diameter is reduced to the sub-micron range, the results presented here suggest that forces associated with mechanical behavior, such as bending stiffness, material density, and axial loads, can be dominated by fluid forces associated with fluid viscosity. Resonant behavior due to reflections from the supports tends to be heavily damped so that the details of the boundary conditions do not play a significant role in determining the overall system response. Thin fibers are thus constrained to simply move with the surrounding viscous fluid. The results presented here suggest that if the diameter or radius is chosen to be sufficiently small, incorporating a suitable transduction scheme to convert its mechanical motion into an electronic signal could lead to a sound sensor that very closely depicts the acoustic particle motion over a wide range of frequencies.
TOPICS: Fibers, Nanoscale phenomena, Fluids, Acoustics, Particulate matter, Viscosity, Approximation, Boundary-value problems, Signals, Stiffness, Excitation, Sound waves, Reflection, Stress, Mechanical behavior, Sensors, Density, Resonance
research-article  
Baizhan Xia, Liping Li, Jian Liu and Dejie Yu
J. Vib. Acoust   doi: 10.1115/1.4037514
Inspired by fractal photonic/phononic crystals, the self-similar fractal technique is applied to the design of the Mie-resonant metamaterial. By replacing the straight channel of the coiling up space with a smaller coiling up space, a class of topological architectures of the Mie-resonant metamaterial with fractal coiling up space is developed. The significant effect of the fractal-inspired hierarchy on the band structure of the Mie-resonant metamaterial with the fractal coiling up space is systematically investigated. Furthermore, the sound wave propagation in the Mie-resonant metamaterial with the fractal coiling up space is comprehensively highlighted. Our results show that the Mie-resonant metamaterial with the higher order fractal coiling up space exhibits deep subwavelength bandgaps, in which the sound propagation will be well blocked. Furthermore, the Mie-resonant metamaterial with the fractal coiling up space shows a good robustness against the irregular arrangement. Thus, this work provides insights into the role of the fractal hierarchy in regulating the dynamic behavior of the Mie-resonant metamaterial and provides opportunities for the design of the robust filtering device in a subwavelength scale.
TOPICS: Fractals, Phononic crystals, Metamaterials, Resonance, Design, Architecture, Energy gap, Filtration, Sound waves, Robustness
research-article  
Xiaole Luan, Yong Wang, Xiao-ling Jin and Z. L. Huang
J. Vib. Acoust   doi: 10.1115/1.4037508
Inspired by the phenomenon of localized response intensification in wideband random vibration, a novel procedure is proposed to determine the optimal locations of piezoelectric patch attaching on wideband random point-driven beam for vibration energy harvesting application. The optimization objective is to maximize the mean output voltage, and the optimal locations lie on the vicinities of the excited point and its symmetric point. The optimal locations keep invariable regardless of typical symmetric boundary conditions (such as the clamped, simply-supported, free and torsional spring supports), the lower and upper cut-off frequencies of the band-limited white noise and the external damping, provided that the excited point is not too close to boundaries and the bandwidth of excitation covers enough modes of primary structure. The robustness of optimal locations is illustrated from an electromechanical coupling model and is qualitatively verified through experimental testing on a random-excited Aluminum beam with piezoelectric patches attached on its surface.
TOPICS: Energy harvesting, Robustness, Springs, White noise, Excitation, Aluminum, Damping, Optimization, Random vibration, Testing, Vibration, Boundary-value problems
research-article  
Shancheng Cao and Huajiang Ouyang
J. Vib. Acoust   doi: 10.1115/1.4037469
Structural characteristic deflection shapes (CDS's) such as mode shapes which contain spatial knowledge of structures are highly sensitive for damage detection and localisation. Nevertheless, CDS's are vulnerable to measurement noise, which degrades the accuracy of damage identification. In order to enhance CDS-based damage identification, contributions are made in three aspects. First, a robust CDS estimation approach is proposed based on common principal component analysis, which estimates the CDS's as the common diagonaliser of a set of covariance matrices by joint approximation diagonalisation. Secondly, an adaptive gapped smoothing method is proposed and validated to be more accurate than the traditional gapped smoothing method. Thirdly, a new damage identification index capable of localising damage and indicating relative damage severity is defined without requiring information of healthy structures. Finally, numerical and experimental examples of beams and a frame with cracks are studied to demonstrate the advantages of the proposed damage identification method in terms of noise robustness and accuracy.
TOPICS: Deflection, Shapes, Smoothing methods, Damage, Noise (Sound), Fracture (Materials), Approximation, Principal component analysis, Robustness, Mode shapes
research-article  
Lijun Zhang, Jun Wu and Dejian Meng
J. Vib. Acoust   doi: 10.1115/1.4037468
In this paper, a flexible pin-on-disc system is used to simulate how squeal noise can be generated in frictional contact. As the research object, the modelling process and transient simulation method of the flexible pin-on-disc system is introduced. By means of numerical simulation, the time-varying frictional squeal reappears by introducing rotation-generating periodic frictional coefficient. Afterwards, the features of time-varying squeal is studied including time-domain features, frequency-domain features, transient deformation features of the disc and the pin on the occurrence of squeal as well as energy features. Finally, the conception and mathematical expression of modal contribution factor is defined, the transient modal contribution factor features of every mode are studied to make clear the function of every mode. The relationship between mode contribution factors and the vibration is revealed. It reveals that modal contribution factors between squeal and not are quite different from each other; On no occurrence of squeal, the modal contribution factors of sine and cosine modes of the disc fluctuate in the way similar to harmonic wave, the phase difference between the contribution factors of sine and cosine mode with the same nodal circle and the same nodal diameter is 90?; During squeal, the coupling mode may play the most important role but not all the time. At any time, the low-frequency modes play the leading role.
TOPICS: Disks, Transient analysis, Transients (Dynamics), Noise (Sound), Modeling, Vibration, Rotation, Deformation, Computer simulation, Simulation, Waves
research-article  
Yansong He, Chong Liu, Zhongming Xu, Zhifei Zhang and Shu Li
J. Vib. Acoust   doi: 10.1115/1.4037471
Inverse Patch Transfer Functions (iPTF) method has been developed to reconstruct the sound field of irregularly shaped sources in a noisy environment. The iPTF method, which uses classic regularization methods to solve the ill-posed problems generally, would incur some sidelobes ghosting in the process of identifying sparse sources. In view of the fact that the algorithm in Wideband Holography (WBH) can promote sparsity of results, a technique combining iPTF method with WBH algorithm is proposed to identify sparsely distributed sources in the present work. In the proposed technique, double layer pressure measurements are used to replace the measurements of the pressure and normal velocity which uses costly p-u probes. A gradient descent algorithm and a filtering process are applied to solve the minimization problem of identifying the normal velocities of target sources, which can suppress ghosting sources rapidly by an iterative process. In simulations, the field reconstruction results of two anti-phase square piston sources show good sparsity and accuracy by employing the technique, nearly without ghosting sources. At different distances and frequencies of the two sources, the technique still performs well. Experimental validations at 200Hz and 400Hz are carried out in the end. The present results in experiments are also coincident with those in simulations.
TOPICS: Holography, Transfer functions, Algorithms, Engineering simulation, Simulation, Pressure, Filtration, Pressure measurement, Pistons, Probes
research-article  
Sanchez Gomez Gomez, Andrei V. Metrikine, Biagio Carboni and Walter Lacarbonara
J. Vib. Acoust   doi: 10.1115/1.4037470
In this paper identification of energy dissipation in the joints of a lab-scale structure is accomplished. The identification is carried out by means of an energy flow analysis and experimental data. The devised procedure enables to formulate damping matrices based on identified local damping coefficients. The identified damping coefficients are latter used in a five-degree-of-freedom system for validation. The results obtained with the proposed method are in good agreement with the experimental data, especially in the low frequency range.
TOPICS: Flow (Dynamics), Joints, Energy dissipation, Damping
research-article  
David Griese, Joshua D. Summers and Lonny Thompson
J. Vib. Acoust   doi: 10.1115/1.4029043
This work defines a finite element model to study the sound transmission properties of aluminium honeycomb sandwich panels. Honeycomb cellular metamaterial structures offer many distinct advantages over homogenous materials because their effective material properties depend on both their constituent material properties and their geometric cell configuration. From this, a wide range of targeted effective material properties can be achieved thus supporting forward design by tailoring the honeycomb cellular materials for specific applications. One area that has not been fully explored is the set of acoustic properties of honeycomb materials and how these can offer increased acoustic design flexibility. Understanding these relations, the designer can effectively tune designs to perform better in specific acoustic applications. One such example is the insulation of target sound frequencies to prevent sound transmission through a panel. This work explores how certain geometric and effective structural properties of in-plane honeycomb cores in sandwich panels affect the sound pressure transmission loss properties of the panel. The two acoustic responses of interest in this work are the general level of sound transmission loss of the panel and the location of the resonance frequencies that exhibit high levels of sound transmission, or low sound pressure transmission loss. Constant mass honeycomb core models are studied with internal cell angles ranging from -45° to +45°. It is shown in this work that models with lower core internal cell angles, under constant mass constraints, have more resonances in the 1-1000 Hz range, but exhibit a higher sound pressure transmission loss between resonant frequencies.
TOPICS: Sound, Honeycomb structures, Geometry, Acoustics, Materials properties, Sound pressure, Resonance, Design, Finite element model, Insulation, Metamaterials, Aluminum, Mechanical properties, Acoustical properties

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