Research

23 pages, 7311 KiB

Open AccessArticle

Optimization of Sensor Placement for Modal Testing Using Machine Learning

by Todd Kelmar, Maria Chierichetti and Fatemeh Davoudi Kakhki

Appl. Sci. 2024, 14(7), 3040; https://doi.org/10.3390/app14073040 - 04 Apr 2024

Viewed by 484

Modal testing is a common step in aerostructure design, serving to validate the predicted natural frequencies and mode shapes obtained through computational methods. The strategic placement of sensors during testing is crucial for accurately measuring the intended natural frequencies. However, conventional methodologies for [...] Read more.

Modal testing is a common step in aerostructure design, serving to validate the predicted natural frequencies and mode shapes obtained through computational methods. The strategic placement of sensors during testing is crucial for accurately measuring the intended natural frequencies. However, conventional methodologies for sensor placement are often time-consuming and involve iterative processes. This study explores the potential of machine learning techniques to enhance sensor selection methodologies. Three machine learning-based approaches are introduced and assessed, and their efficiencies are compared with established techniques. The evaluation of these methodologies is conducted using a numerical model of a beam to simulate real-world scenarios. The results offer insights into the efficacy of machine learning in optimizing sensor placement, presenting an innovative perspective on enhancing the efficiency and precision of modal testing procedures in aerostructure design. Full article

(This article belongs to the Special Issue Vibration Problems in Engineering Science)

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21 pages, 2150 KiB

Open AccessArticle

Dynamic Analysis of Non-Uniform Functionally Graded Beams on Inhomogeneous Foundations Subjected to Moving Distributed Loads

by Yixin Huang, Haizhou Liu and Yang Zhao

Appl. Sci. 2023, 13(18), 10309; https://doi.org/10.3390/app131810309 - 14 Sep 2023

Viewed by 617

Abstract

Inhomogeneous materials, variable foundations, non-uniform cross-sections, and non-uniformly distributed loads are common in engineering structures and typically complicate their mechanical analysis considerably. This paper presents an accurate and efficient numerical method for the dynamic analysis of non-uniform functionally graded beams resting on inhomogeneous [...] Read more.

Inhomogeneous materials, variable foundations, non-uniform cross-sections, and non-uniformly distributed loads are common in engineering structures and typically complicate their mechanical analysis considerably. This paper presents an accurate and efficient numerical method for the dynamic analysis of non-uniform functionally graded beams resting on inhomogeneous viscoelastic foundations subjected to non-uniformly distributed moving load and investigates the effects of non-uniformities and inhomogeneities on material, foundation, and load. Based on the Timoshenko beam theory and a Chebyshev spectral method, a consistent discrete dynamic model is derived, which can deal with all axially varying properties. A series of numerical experiments are carried out to validate the convergence and accuracy of the proposed method. The results are compared with those obtained through finite element analysis or in the literature, and excellent agreement is observed. Then, the dynamic response of an axially functionally graded beam resting on an inhomogeneous viscoelastic foundation and subjected to a non-uniformly distributed moving load is investigated. The results show that the material gradient and the inhomogeneous foundation can alter the vibration amplitudes and critical speeds of the beam significantly. Compared with more realistic non-uniformly distributed moving load models, idealized concentrated and uniformly distributed moving load models produce apparent computation errors in vibration amplitudes. Full article

(This article belongs to the Special Issue Vibration Problems in Engineering Science)

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42 pages, 700 KiB

Open AccessArticle

Port-Hamiltonian Formulations of Some Elastodynamics Theories of Isotropic and Linearly Elastic Shells: Naghdi–Reissner’s Moderately Thick Shells

by Miguel Charlotte, Ignacio Fernandez Núnez, Yves Gourinat and Denis Matignon

Appl. Sci. 2023, 13(4), 2608; https://doi.org/10.3390/app13042608 - 17 Feb 2023

Viewed by 1304

Abstract

The port-Hamiltonian system approach is intended to be an innovative and unifying way of modeling multiphysics systems, by expressing all of them as systems of conservation laws. Indeed, the increasing developments in recent years allow finding better control and coupling strategies. This work [...] Read more.

The port-Hamiltonian system approach is intended to be an innovative and unifying way of modeling multiphysics systems, by expressing all of them as systems of conservation laws. Indeed, the increasing developments in recent years allow finding better control and coupling strategies. This work aimed to apply such an approach to Naghdi–Reissner’s five-kinematic-field shell model in linear elasticity, while including often-neglected higher-order intrinsic geometric coupling effects, therefore preparing the theoretical background required for the coupling (or interconnection) with an acoustic fluid model and the different types of interactions that can arise among them. The model derived thusly can be used for controller design in a wide variety of applications such as inflatable space structures, launcher tank vibration damping, payload vibration protection using smart materials, and many other related applications. Full article

(This article belongs to the Special Issue Vibration Problems in Engineering Science)

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14 pages, 3706 KiB

Open AccessArticle

Analytical and Experimental Investigation of the Rotary Inertia Effects of Unequal End Masses on Transverse Vibration of Beams

by Habibullah Bilge and Ömer Kadir Morgül

Appl. Sci. 2023, 13(4), 2518; https://doi.org/10.3390/app13042518 - 15 Feb 2023

Viewed by 1331

Abstract

In this study, the transverse vibration of free–free slender beams with two unequal end masses attached were studied. The effects of the rotary inertia of the end masses on the free vibration of the beam were investigated. An exact frequency equation and the [...] Read more.

In this study, the transverse vibration of free–free slender beams with two unequal end masses attached were studied. The effects of the rotary inertia of the end masses on the free vibration of the beam were investigated. An exact frequency equation and the boundary conditions were obtained by using the Euler–Bernoulli beam theory and Hamilton’s principle. Natural frequencies and mode shapes of the beams in transverse vibrations were calculated for various combinations of physical and geometrical parameters, such as mass ratios, the distances between the attachment point and the center of the masses, etc. The effects of an increase in the rotational inertia of the end masses and different mass ratios on the natural frequencies and mode shapes of the beam are presented. It is shown that the increase in the rotational inertia of the end masses had a greater effect at low frequencies of the beam. In addition, experimental tests were performed to validate the obtained analytical results. A good agreement was obtained between the analytical and experimental results. The main scope of this study was to reveal the effects of the rotary inertia of the end masses on the dynamic behavior of the beam. Thus, the aim is to contribute to the understanding of the properties of the end mass and the effect of rotary inertia on the dynamics of end-mass-attached structures. Furthermore, the results obtained from this research are helpful for designing end-mass-attached structures, such as micromechanical sensors, energy harvesters, and Stockbridge-type dynamic absorbers. Full article

(This article belongs to the Special Issue Vibration Problems in Engineering Science)

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18 pages, 3602 KiB

Open AccessArticle

Enhanced Rolling Bearing Fault Diagnosis Combining Novel Fluctuation Entropy Guided-VMD with Neighborhood Statistical Model

by Xing Yuan, Hui Liu and Huijie Zhang

Appl. Sci. 2023, 13(1), 192; https://doi.org/10.3390/app13010192 - 23 Dec 2022

Cited by 1 | Viewed by 1207

Abstract

Variational Mode Decomposition (VMD) provides a robust and feasible scheme for the analysis of mechanical non-stationary signals based on the variational principle, but this method still has no adaptability, which greatly limits the application of this method in bearing fault diagnosis. To solve [...] Read more.

Variational Mode Decomposition (VMD) provides a robust and feasible scheme for the analysis of mechanical non-stationary signals based on the variational principle, but this method still has no adaptability, which greatly limits the application of this method in bearing fault diagnosis. To solve this problem effectively, this paper proposes a novel fluctuation entropy (FE) guided-VMD method based on the essential characteristics of fault impulse signals. The FE reported in this paper not only considers the order of amplitude values but also considers the variation of amplitude, and hence it can comprehensively characterize the transient and fluctuation characteristics of rolling bearing fault impulse signal. On the basis of establishing FE, the FE-based fitness functions are then conducted, after which the mode number and balance parameter can be adaptively determined. Meanwhile, an adaptive neighborhood statistical model is developed to further reduce the noise of the mode component containing fault information so as to highlight the periodic impulse component more significantly and improve the diagnostic accuracy. Simulation and case analysis show that this research is effective and quite accurate in fault mode separation and fault feature enhancement. Compared with the traditional VMD method and the current common diagnosis methods, the proposed method has obvious advantages in the comprehensive utilization of fault impulse information and enhanced diagnosis. Full article

(This article belongs to the Special Issue Vibration Problems in Engineering Science)

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17 pages, 3055 KiB

Open AccessArticle

Inverse Determination of Acoustic Properties of Acoustic Ventilation Cloth (Woven and Non-Woven) by Particle Swarm Optimization and Estimation of Its Effect on the Frequency Response of the Microspeaker

by Yu-Cheng Liu, Suryappa Jayappa Pawar and Jin-Huang Huang

Appl. Sci. 2022, 12(17), 8588; https://doi.org/10.3390/app12178588 - 27 Aug 2022

Viewed by 1432

Abstract

In this work, microspeaker frequency response was determined based on measurement and simulation. The vents after the rear chamber of the microspeaker were covered with ventilation cloths. Two types of ventilation cloths (acoustic cloths) are commonly used in electroacoustic products, non-woven and woven. [...] Read more.

In this work, microspeaker frequency response was determined based on measurement and simulation. The vents after the rear chamber of the microspeaker were covered with ventilation cloths. Two types of ventilation cloths (acoustic cloths) are commonly used in electroacoustic products, non-woven and woven. Non-woven cloths (5 nos.) consist of irregular meshes and woven cloths (5 nos.) consist of regular meshes. The equivalent circuit model of the microspeaker was formulated by considering five types each of non-woven and woven ventilation cloths. The acoustic properties of the ventilation cloths were estimated from the measured frequency response of the microspeaker and by subsequent use of particle swarm optimization algorithm. Estimated value of the acoustic impedances of the ventilation cloths were used in an equivalent circuit model of the microspeaker for the simulated frequency responses and subsequently compared with the anechoic chamber measurements. Based on the results, the equivalent circuit adequately simulated the measured frequency response of the microspeaker and the estimations of the acoustic impedances of the ventilation cloths were in good agreement with the measured frequency responses of the microspeaker. Full article

(This article belongs to the Special Issue Vibration Problems in Engineering Science)

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23 pages, 3228 KiB

Open AccessArticle

Boundaries of Oscillatory Motion in Structures with Nonviscous Dampers

by Mario Lázaro and Luis M. García-Raffi

Appl. Sci. 2022, 12(5), 2478; https://doi.org/10.3390/app12052478 - 27 Feb 2022

Cited by 2 | Viewed by 1028

Abstract

In this paper, a new methodology for the determination of the boundaries between oscillatory and non-oscillatory motion for nonviscously damped nonproportional systems is proposed. It is assumed that the damping forces are expressed as convolution integrals of the velocities via hereditary exponential kernels. [...] Read more.

In this paper, a new methodology for the determination of the boundaries between oscillatory and non-oscillatory motion for nonviscously damped nonproportional systems is proposed. It is assumed that the damping forces are expressed as convolution integrals of the velocities via hereditary exponential kernels. Oscillatory motion is directly related to the complex nature of eigensolutions in a frequency domain and, in turn, on the value of the damping parameters. New theoretical results are derived on critical eigenmodes for viscoelastic systems with multiple degrees of freedom, with no restrictions on the number of hereditary kernels. Furthermore, these outcomes enable the construction of a numerical approach to draw the critical curves as solutions of certain parameter-dependent eigenvalue problems. The method is illustrated and validated through two numerical examples, covering discrete and continuous systems. Full article

(This article belongs to the Special Issue Vibration Problems in Engineering Science)

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17 pages, 4912 KiB

Open AccessArticle

Vibration Reduction in Ballasted Track Using Ballast Mat: Numerical and Experimental Evaluation by Wheelset Drop Test

by Bowen Hou, Di Wang, Bingbing Wang, Xingyu Chen and João Pombo

Appl. Sci. 2022, 12(4), 1844; https://doi.org/10.3390/app12041844 - 10 Feb 2022

Cited by 7 | Viewed by 3196

Abstract

Ballast mats are considered as an effective solution for reducing vehicle-induced vibrations. However, the research on the vibration characteristics of each part of the ballasted track with a ballast mat is limited. In this study, the ballast mat vibration reduction effects are evaluated [...] Read more.

Ballast mats are considered as an effective solution for reducing vehicle-induced vibrations. However, the research on the vibration characteristics of each part of the ballasted track with a ballast mat is limited. In this study, the ballast mat vibration reduction effects are evaluated by numerical and experimental analysis using wheelset drop tests. A three-dimensional model consisting of a wheel, track and the contact between them is built using a rigid–flexible coupling method. The accuracy of the numerical model is verified by comparison with the finite element model in terms of the track receptance and phase angle. Comparisons show that the proposed model is in good agreement with the finite element model, which allows validating the flexible-body model. Moreover, the track dynamic performance in the presence and absence of the ballast mat is studied with the wheelset drop tests in both time and frequency domains. The results from the wheelset drop excitation tests show that the use of the ballast mat decreases the mid- and high-frequency track vibration by 13–17 dB but increases the low-frequency track vibration by 5–15 dB. Full article

(This article belongs to the Special Issue Vibration Problems in Engineering Science)

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