In this paper, the dynamic behavior of a rotor system with electromechanically coupled boundary condition under periodic axial load is studied, where the boundary condition is derived from a ring-shaped piezoelectric damper which is developed for vibration control of rotor system. This damper is based on the piezoelectric shunt damping technique, which can produce much or little damping performance

Locally resonant piezoelectric metamaterials offer outstanding vibration attenuation properties with the versatility in updating local resonances using either analog or digital electric circuits. The typically narrow bandgap observed in this sort of metamaterial can be enlarged through perturbations (or disorder) on the target frequencies of the resonant attachments, which also induce localization

Metaporous layers composed of finite-length porous layers with rigid inclusions embedded have recently received much attention given their ability to greatly enhance sound absorption. Compared with homogeneous porous layers, the insertion of rigid inclusions into porous layers can lead to a significant enhancement in the sound-absorbing performance. It is because the resulting inhomogeneity in metaporous

Semi-passive vibration control with the Synchronized Switching Damping on Inductor (SSDI) technique has attracted significant attention in recent years. However, the damping performance of the SSDI technique will be decreased by the lag in detection of switching time. In order to detect switching time without lag, the paper proposes a self-powered semi-passive vibration damping system based on self-sensing

Precise and target-oriented control of acoustic/elastic wave bandgaps in phononic crystals or acoustic metamaterials according to particular requirements is of both theoretical and practical importance. A very challenging and also interesting task is to tune the widths and the overall positions of the bandgaps of interest independently and arbitrarily. This work presents a simple and smart acoustic

The resonances of forced dynamical systems occur when either the amplitude of the frequency response undergoes a local maximum (amplitude resonance) or phase lag quadrature takes places (phase resonance). This study focuses on the phase resonance of nonlinear mechanical systems subjected to single-point, single-harmonic excitation. In this context, the main contribution of this paper is to develop

This paper proposes a novel technique that aims at detecting the effect of damage on structural frequency signals as “bad” outliers. To this end, a procedure is developed based on the Variational Mode Decomposition (VMD), Minimum Covariance Determinant (MCD), and Recurrent Neural Network (RNN) with Bi-directional Long-Short Term Memory (BiLSTM) cells. VMD is first used in a pre-processing stage to

Trailing-edge serrations are used as means to reduce aerofoil broadband self-noise in various industrial applications. However, a reliable prediction of the reduced noise level has not been established to date. In this paper, the authors suggest that Amiet’s theory can be used to accurately predict the sound radiated from serrated trailing edges. A plausible explanation as to how the classical theory

A control method for multi-shaker half sine shock on random mixed vibration test is presented. The key parts of the multi-shaker shock on random vibration control are the generation of desired multi-input drive signals, separation of measured multi-output response signals and control of separated response signals. In this work, the classic half sine shock signal is recalled first and then a compensated

The propagation of sound waves in a horizontally stratified environment, a classic problem in ocean acoustics, has traditionally been calculated using normal modes. Most programs based on the normal mode model are discretized using the finite difference method (FDM). In this paper, a Legendre collocation method (LCM) based on domain decomposition is proposed to solve this problem. A set of collocation

High-speed, light-weight and high-load gearing is widely used in the transmission systems of modern aero-engines. Some dynamic phenomena, such as the traveling wave resonance, can be more easily encountered. It generally occurs quite suddenly and causes catastrophic accidents. This study presents an experimental investigation of the signal characteristics of the gear fatigue fracture process caused

Landing gears are an important noise source of aircraft during approach and landing, which makes the research on their aerodynamic noise reduction a topical problem. This paper experimentally studies the method of noise reduction developed by the authors, which consists in using truncated-cylinder elements for landing gears instead of circular-cylinder parts (e.g. struts, links, actuators, etc). The

This paper investigates the mechanisms that can be used to enhance the absorption performance of poro-elastic materials in the viscous regime. It is shown that by adding small inclusions in a poro-elastic foam layer, a mass–spring effect can be introduced. If the poro-elastic material has relatively high viscous losses in the frequency range of interest, the mass–spring effect can enhance the sound

Coulomb sliders are used widely in order to model frictional interfaces. In many applications, the nonlinear Frequency Response Functions (FRFs) of these systems is desired, but it is extremely computationally expensive to use time-domain integration methods to compute the steady-state response. The nonlinear force and stiffness of these devices depends on the position of sliders, and the implicit

This paper aims at presenting the guidelines to follow in order to set up an identification procedure which is able to determine the axial force, the flexural rigidity and the rotational end stiffnesses of slender and tensioned structural elements, based on measurements of their natural frequencies and mode shapes. First of all, when such an element is slightly affected by bending stiffness effects

In the area of gearbox fault diagnosis, to obtain sufficient and effective vibration information, traditional studies are usually conducted from the perspective of optimizing the layout of measuring points. This paper focuses on a gearbox fault diagnosis method based on bearing dynamic force identification. Gearbox bearing dynamic forces under the operating condition are modeled as excitation sources

Response of vehicle suspension system has traditionally been studied under the assumption of stationary road excitation. However, road excitation becomes a non-stationary random input in the time domain when the vehicle travels at a varying speed. In this paper, we investigate the non-stationary response of vehicle suspension under random road excitation. Despite its importance and relevant applications

This paper leverages recent progress on orthonormal splines for solving uncertainty quantification (UQ) problems from linear structural dynamics. The resulting methods, premised on spline chaos expansion (SCE) and spline dimensional decomposition (SDD), both construe Fourier-like expansion of a dynamic system response of interest with respect to measure-consistent orthonormalized basis splines in input

This paper develops an averaging technique based on the combination of the eigenfunction expansion method and the collaboration method to investigate the multiple scattering effect of the SH wave propagation in a porous medium. The semi-analytical averaging technique is conducted using Monto Carlo method to understand the macroscopic dispersion and attenuation phenomena of the stress wave propagation

This paper presents a new Moving Internal Node Element (MINE) method for the dynamic analysis of bridges/beam structure under a moving load/vehicle. By introducing a moving internal node within the standard beam element, the resulting MINE method eliminates the need for interpolation for the dynamic responses at the contact point between the moving load/vehicle and the beam structure. The governing

Considering the flexibility of gear foundations and rotational effects, a geared rotor dynamic model for thin-rimmed helical gears is established. The deformable shafts and gear foundations are modelled by Timoshenko beam elements and Mindlin-Reissner shell elements, respectively. The beam element and the shell element are connected using the ‘interfacial coupling element’. Then the modal superposition

A vibro-acoustic model of a structurally excited cylindrical shell of infinite length submerged in a heavy fluid at a finite distance from a free surface is presented. Expressions for the shell displacement, the acoustic pressure in the interior cavity of the shell and the acoustic pressure at all field locations in the exterior domain are analytically derived. The formulation for the exterior acoustic

In noise and vibration engineering, a structure’s passive dynamic properties are often quantified by frequency response functions (FRFs). This paper focuses on acquiring FRFs from experimental tests, considering both, translational (x, y, z) and rotational (e.g. moments around these axes) terms. In practical applications, test structures may not allow FRFs to be measured directly due to the impracticality

Periodic slab tracks, as a type of non-ballasted track, are widely used in the high-speed railway and urban subway. Efficient and accurate dynamics modelling of the periodic slab track is a crucial issue for solving the vehicle-track dynamic interaction. In this paper, a time-frequency hybrid Green's function method (GFM) is first developed to model the dynamics of the periodic slab track, in light

The present work is a lucubration and verification of the previous research through theory and experiment. Because of the physical model of the published paper is oversimplified, the revised model is proposed in present research. And the small parameter averaging method and Routh-Hurwitz criterion are adopted to investigate the stability criterion and synchronization condition. Numerical analyses are

This study investigates the dynamic responses of a two-degree-of-freedom (2DOF) nonlinear bistable electromagnetic energy harvester under filtered band-limited stochastic excitation. The mathematical model of the 2DOF bistable energy harvester is derived, and its fidelity is experimentally verified. A comprehensive numerical investigation is conducted under filtered band-limited stochastic excitation

There has been a common assumption that neglects the in-plane inertia or rotary inertia of a cylindrical shell to yield analytical and numerical solutions of the vibration characteristics. This assumption can largely simplify some derivation processes and result in a unified governing equation, nevertheless, precondition and justification of this assumption have not been examined yet. Presented herein

Circular cylindrical transducers have a wide range of applications in ultrasound generation. Introducing axial or circumferential stepped-thickness variations affects the performance of these transducers. This paper investigates the effect of circumferential stepped-thickness variations on the vibration and acoustic characteristics of a circular cylindrical piezoelectric shell. FEM software ANSYS is

Multiple propellers are usually used in unmanned aerial vehicles. This work studies the aerodynamic and acoustic properties of dual propellers in close vicinity. Aerodynamic and acoustic tests of the side-by-side propellers were conducted in an anechoic chamber, and the flow recirculation effect was considered in the analysis to reduce uncertainties in the results. We mainly focused on the influence

Wave based method is an efficient numerical technique that can be used to solve the structural dynamic problems, especially the vibration of plates. The approach expands the dynamic field variables to a weighted sum of wave functions, and the contribution factors are determined by minimizing the errors on the boundary conditions. While the governing equation is satisfied a priori, the boundary conditions

In this investigation, a pneumatic suspension model with orifice damping is developed and used to evaluate the performance of the air suspension in comparison with the coil-spring suspension in railroad and highway transportation systems. In railcars, air springs are used as a secondary suspension to isolate the car from vibrations caused by track irregularities, while in highway trucks, air springs

This paper aims to investigate the rub-impact fault of a gas turbine using the proper orthogonal decomposition (POD) and the smooth orthogonal decomposition (SOD). It is an attempt to combine POD and SOD for pattern recognition. First, simulated data are generated to investigate the sensitivity of POD and SOD to pattern changes. After that, field data from a gas turbine are presented. We consider two

This paper aims at investigating how to suppress combustion instability using perforated liners under nonlinear flame response. A theoretical model is thus presented to describe the interaction between the unsteady heat release, acoustics, and fluid fields, which takes both perforated liner and flame nonlinearity into account. To establish an eigenvalue problem to evaluate combustion instability, appropriate

The axial friction force (AFF) of automotive drive-shaft systems is an important nonlinear dynamic characteristic, which will directly cause the vibration and noise of vehicles. During the operation of drive-shaft systems, the AFF has great uncertainty. Taking a drive-shaft system as the research object, a hybrid random and interval uncertainties (HRIU) model of the AFF is proposed to study the AFF

Non-smooth dry friction between the contact surfaces of rotor/stator rubbing systems can induce self-excited dry friction backward whirl, which may exhibit various discontinuity-induced sliding bifurcations corresponding to stick-slip whirling oscillations with different local dynamical characteristics around the switching manifold. The analytical method proposed in this paper aims to predict the self-excited

The objective of this study is to extend the concept of analogous piezoelectric networks to vibration mitigation of multiple nonlinear resonances. First, the undamped linear part of the electrical network is designed so as to possess similar modal characteristics as those of the underlying linear mechanical structure. Then, nonlinear electrical components possessing the same mathematical form as that

Inverse analysis of vibratory system is an important subject in fault identification, model updating, and robust design and control. It is challenging subject because 1) the problem is oftentimes underdetermined while the measurements are limited and/or incomplete; 2) many combinations of parameters may yield results that are similar with respect to actual response measurements; and 3) uncertainties

The wall pressure fluctuations induced by turbulent boundary layers on a flat plate model were measured with an L-shaped array of Kulite miniature pressure sensors. By installing a NACA airfoil above the plate with an adjustable angle of attack, different adverse pressure gradients were produced on the plate. The streamwise and spanwise coherence and coherence lengths of the wall pressure fluctuations

A semi-analytical model for a naval shock problem is proposed in this paper and applied to calculate the dynamic response of a submarine hull with on-board equipment to a pressure wave triggered by an underwater explosion. Although the proposed model corresponds to a simplification of actual configurations, it allows to derive meaningful data which are representative of naval shock environment and

A guided tendon concept in the context of rotating helicopter blades is put forward to modify the dynamics in order to enable the rotorcraft to work in a wider range of working conditions; however, some blade modes are insensitive to the axial force. In this paper, the damping augmentation of a rotating Timoshenko beam axially loaded by a tendon via placing spring-damper elements is studied in the

A virtual vibration absorber (VVA) is a control algorithm that mimics the dynamics of a tuned mass damper, which can compensate for a harmonic disturbance of a specific frequency. A VVA may also be devised to compel the system to track a sinusoidal signal asymptotically. A novel sensorless contact-force detector is proposed for a four-bar-linkage manipulator utilizing two sets of VVA. One VVA acts

We present the first full analytical solution to the mode-shape equation of the gravity-loaded Rayleigh–Timoshenko beam, thus describing in closed form the vibration modes of beam–columns, bending cables, and stiff marine risers under self-weight. The modes are given in terms of a family of complex “Hankel–Airy” functions, along with their asymptotic expansions, orthogonality relations and series representations

Particle damping has become a favorable passive damping technique for lightweight structures, however, its complex dimensioning process hinder its wide use in technical applications. In this paper, a multilevel design tool chain is presented to enable a systematic design and dimensioning process of particle dampers. Thereby various numerical models and experimental tests are combined. This starts with

Entropy (temperature) fluctuations produced by turbulent flames generate noise when they are accelerated by the flow. This so-called entropy noise is an important contributor to core noise in modern aeroengines and several semi-analytical models exist in the literature for its prediction. All these models assume the flow to be inviscid. In the present paper, contribution of viscosity on entropy noise

In this paper, the acoustic field with the presence of poro-elastic materials is simulated by the eXtended Finite Element Method (X-FEM). Problems involving interfaces between different media are our main focus. The proposed method allows interfaces to be embedded in the finite elements, easing significantly the discretization, especially when the geometry of the interface is complex. The gradient

In this paper, a novel transient balancing technology for identifying the unbalance parameters of the rotor system is proposed. Through basic coordinate transformation and multi modal analysis of the dynamical equations of rotor system, the calculation method for transient excitation forces is proposed. The transient excitation forces are calculated by the transient responses and modal parameters at

Vibration attenuation and control is a typical topic in mechanical, civil and aeronautical engineering. In recent years, there has been extensive research on smart materials and among all of them, the piezoelectrics seem to be the most attractive for passive and active vibration damping applications. Furthermore if multiple modes are concurrently excited, as in case of turbomachinery blades, active

This paper proposes harnessing bulging or sloshing modes to design locally resonant liquid-solid metamaterials that can be applied to vibration isolation engineering. The longitudinal dynamic effective mass of the proposed bulging or sloshing cell is analyzed through the assumed mode method and the finite element simulation. The meta-structure consisting of a sequence of unit cells is studied as well

Two vibration control devices using the tuned inerter enhanced TMD are introduced to suppress the vibration of Euler–Bernoulli beam-model in this paper. The two tuned inerter enhanced TMD systems are improved on the basis of the classical TMD system by replacing its damper element with the newly developed tuned viscous mass damper (TVMD) and tuned inerter damper (TID), respectively. The equations of

In most output-only-based modal identification methods, the excitation and the measurement error are assumed to be white Gaussian noise. One of the obstacles appears once the excitation has periodic nature and measurements are contaminated by colored noise. In this paper, a time-domain filtering technique is introduced for harmonic excitation/noise elimination in operational modal analysis. The procedure

A geometrically nonlinear forced vibration analysis of circular cylindrical sandwich shells with open/closed cellular core using higher-order thickness and shear deformation theory is presented. The proposed sandwich shell comprises two thin face-sheets perfectly bonded to a functionally graded porous core. The face-sheets are made of carbon nanotubes (CNTs) reinforced composites. Three different types

In this paper, a Floquet Model Order Reduction (MOR) method is proposed for the modelling of finite periodic structures subjected to harmonic or transient loads. This Floquet MOR generates frequency-independent projection matrices of the full-scale structure using a Floquet expansion of the local state-vectors computed on a single unit-cell with the Forced Wave Finite Element framework. This two-step

Structural repairs alter the physical properties of a structure, changing its responses, both in terms of its normal condition and of its different damage states. This difference in responses manifests itself as a shift between the pre- and post-repair data distributions, which can be problematic for conventional data-driven approaches to structural health monitoring (SHM), and limits their effectiveness

This study proposes an efficient method for the evaluation of vibrations and buckling in thin-walled beams with complex geometries subjected to progressive compressive loads. A comprehensive study is conducted in order to investigate the effects of compressive loads on the natural frequencies of the thin-walled beams. Namely, a numerical simulation of the Vibration Correlation Technique is provided