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Vibration Problems in Engineering Science

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Acoustics and Vibrations".

Deadline for manuscript submissions: closed (20 March 2025) | Viewed by 27950

Special Issue Editor

Prof. Dr. Yves Gourinat

E-Mail Website
Guest Editor
Department of Mechanics, Structures and Materials, ISAE-SUPAERO, l’Institut supérieur de l’aéronautique et de l’espace, 10 Avenue Edouard Belin, 31055 Toulouse, France
Interests: nonlinear dynamics; biophysics; shell structures; modal dynamics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The generalization of the dynamic approach to design, calculation, and certification has radically changed the representation of structures.

Indeed, for the last thirty years, mathematical models have enabled the universal use of operational modal diagnosis and generalized predictive control, making structures more observable and controllable. In fact, the fundamental definition of the structure becomes dynamic. The eigenshape base can be considered the DNA of the system, which has also revolutionized measurement and digitalization techniques. Modal mass and stiffness evolution can even be considered an indicator for performing design. In addition, the presence and integration of lasers in tests, the dynamic analysis of 3D images, and the emergence of new digital post-finite element methods are among new techniques that are now classic. However, it is in the nonlinear extensions of dynamic modes that the prospects for knowledge, performance, and safety of structures are most promising. Nonlinear conservative modes are indeed much better known and provide information on the behavior of the structure at the limits of its domain. The entropic dissipation became a powerful tool for structural diagnosis and control. Fatigue, aging, and damage can now be directly linked to vibration modeling, with possibilities for control and a significant reduction in the number of tests. Finally, structure–fluid vibration interactions, environmental representation, and stochastic vibration models are now fully integrated into certification tools. The stakes are huge, for aerospace structures, civil engineering, and light systems.

This Special Issue of Applied Sciences is of remarkable importance in this period of change in structural mathematics and certification and will bring together first-rate articles at the cutting edge of science in this field. It is also a very topical Special Issue, as it significant developments in the field of structural models and tests are anticipated.

Prof. Dr. Yves Gourinat
Guest Editor

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Keywords

  • operational modal diagnosis
  • generalized predictive control
  • eigenshapes
  • structural dissipation
  • digital structural model
  • optimized measures
  • vibroacoustics
  • shell fluid interaction
  • stochastic dynamic model

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Published Papers (17 papers)

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25 pages, 6836 KiB  
Article
Mechanical Modeling and Dynamic Characteristics of a Three-Directional Vibration Absorber
by Zhangbin Wu, Mao Chen, Qiuyu Li, Canhui Li, Yunzhe Qiu, Zi Ye and Guangming Xue
Appl. Sci. 2025, 15(8), 4420; https://doi.org/10.3390/app15084420 - 17 Apr 2025
Viewed by 189
Abstract
Vibration is a prevalent phenomenon in mechanical systems, often adversely affecting equipment performance and operational stability. To address this issue, this study proposes a novel three-directional vibration absorber, which provides stiffness in three orthogonal directions. The mechanical properties of the isolator are theoretically [...] Read more.
Vibration is a prevalent phenomenon in mechanical systems, often adversely affecting equipment performance and operational stability. To address this issue, this study proposes a novel three-directional vibration absorber, which provides stiffness in three orthogonal directions. The mechanical properties of the isolator are theoretically analyzed, focusing on its load-bearing capacity and working stroke, which are influenced by the initial configuration angle of the spring assembly. The dynamic characteristics of the proposed isolator are evaluated by comparing its peak dynamic displacement and force transmissibility rate with those of a conventional linear vibration isolator. The results indicate that under low excitation amplitudes, the three-directional isolator achieves a lower peak force transmissibility but exhibits a higher dynamic displacement peak compared to the linear isolator. Furthermore, a dynamic model incorporating Coulomb friction damping is developed to assess its impact on the system’s dynamic response. The findings reveal that increasing the equivalent Coulomb friction factor effectively reduces the dynamic response amplitude and force transmission rate below the resonance frequency but exacerbates these parameters beyond the resonance point. Finally, experimental studies were conducted on the isolator prototype. The results show that the static theoretical model can well reflect the static characteristics of the isolator and the dynamic theoretical model can effectively fit the dynamic test curves of the isolator. This research provides a theoretical foundation for the further optimization and practical application of three-directional vibration isolators. Full article
(This article belongs to the Special Issue Vibration Problems in Engineering Science)
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29 pages, 43807 KiB  
Article
Insights on the Influence of the Central-Cut Width of the Box Assembly with Removable Component on Its Dynamical Responses
by Christopher Padilla, Antonio Flores, Jonah Madrid, Ezekiel Granillo and Abdessattar Abdelkefi
Appl. Sci. 2025, 15(3), 1671; https://doi.org/10.3390/app15031671 - 6 Feb 2025
Viewed by 643
Abstract
This investigation focuses on the dynamical effects caused by varying the central-cut width within the Box Assembly with Removable Component (BARC) system. The central-cut widths included in this study are a 0.5″ cut, a 0.25″ cut, a thin 0.1″ cut, and a structure [...] Read more.
This investigation focuses on the dynamical effects caused by varying the central-cut width within the Box Assembly with Removable Component (BARC) system. The central-cut widths included in this study are a 0.5″ cut, a 0.25″ cut, a thin 0.1″ cut, and a structure that did not have a cut at all. Finite element analysis was conducted to determine the mode shapes and natural frequencies of each of the BARC structures. Structural dynamics experiments were run to examine the effects of the central-cut width on the dynamical responses and nonlinear characteristics of the BARC system. Free vibration testing with an impact hammer was carried out to excite the system and extract the dominant frequencies and directions of the significant responses. A pseudorandom vibration test that allows for the qualitative determination of any nonlinear behavior within the system was performed. This type of behavior can include nonlinear softening, nonlinear hardening, and the most common, nonlinear damping due to the presence of several bolted-joint connections and the possible activation of geometric and inertia nonlinearities. To quantitatively investigate the impacts of the central-cut width on the dynamics of the system, swept sinusoidal testing was conducted. It is determined that almost all systems with central cuts demonstrate the presence of nonlinear softening, but at times, nonlinear hardening trends are seen, particularly in the 0.1″ cut and no-cut systems when testing harmonically. Each of the central-cut systems displays nonlinear damping, with the amount of damping generally increasing as the central cut decreases in size. The effect of the central cut of the BARC system on the mode-switching ability of the system is negligible; however, mode switching takes place when comparing the central-cut configurations to the no-cut one. These results show the significance of accurately measuring the central-cut width and how geometric uncertainty may change the dynamical responses and nonlinear properties of the system. Full article
(This article belongs to the Special Issue Vibration Problems in Engineering Science)
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26 pages, 7006 KiB  
Article
Predicting Lightweight Powders with Useful Sound Absorption Characteristics from Their Specifications
by Shuichi Sakamoto, Keisuke Jindai, Koki Ikeda, Yuya Kawakami and Hiroaki Soeta
Appl. Sci. 2024, 14(21), 9765; https://doi.org/10.3390/app14219765 - 25 Oct 2024
Viewed by 814
Abstract
Powders that absorb sound by longitudinal vibration have either a gentle or sharp sound absorption curve at the first absorption peak frequency. Experiments were performed to investigate the conditions under which longitudinal vibration occurs in powders of various grain sizes and bulk densities. [...] Read more.
Powders that absorb sound by longitudinal vibration have either a gentle or sharp sound absorption curve at the first absorption peak frequency. Experiments were performed to investigate the conditions under which longitudinal vibration occurs in powders of various grain sizes and bulk densities. The sound absorption characteristics of the powders were then classified according to their specifications, and the sound absorption coefficients predicted by derived empirical equations were compared with the measured sound absorption coefficients. A threshold value for the areal density per grain layer was identified where lightweight powders at 0.0006 g/cm2 or less demonstrated useful sound absorption characteristics via longitudinal vibration. Powders with smooth (i.e., useful) and sharp (i.e., not useful) sound absorption curves could be further identified by the half-width value at 0.0974 < log f2 − log f1 < 0.119 decade. The bulk density can also be used to identify powders with useful sound absorption characteristics at 0.0868 < ρ < 0.124 g/cm3. A regression analysis was performed to obtain empirical equations expressing the relationship between the areal density per grain layer and first sound absorption peak frequency normalized by the layer thickness. Full article
(This article belongs to the Special Issue Vibration Problems in Engineering Science)
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18 pages, 12740 KiB  
Article
Design of a Spin Test System for Burst Phenomen Considering Nonlinear Rotordynamic Effects
by Mert Uğur and Osman Kopmaz
Appl. Sci. 2024, 14(20), 9399; https://doi.org/10.3390/app14209399 - 15 Oct 2024
Viewed by 996
Abstract
This study presents the development and evaluation of a spin test rig for high-speed rotating components. The innovation of this study is using a discrete model to determine dynamic positioning during the preliminary design phase based on vibration characteristics. The primary aim is [...] Read more.
This study presents the development and evaluation of a spin test rig for high-speed rotating components. The innovation of this study is using a discrete model to determine dynamic positioning during the preliminary design phase based on vibration characteristics. The primary aim is to manage vibrations and alternating stress effects from rotor dynamics to prevent issues such as crack propagation or bursts before achieving desired speeds. MATLAB 2023b Simulink-based tool was developed, which played a role in providing the design of bearing support regions and stiffness values. The system underwent rigorous validation through structural, modal, and harmonic finite element analyses. Testing showed a maximum deviation of 4.2% for 10 kg specimen and 4.85% for 4 kg specimen between Simulink predictions and actual data, due to factors such as contact and bearing damping. For the 10 kg specimen, the maximum equivalent stress was 314.92 MPa with an alternating stress of 64.87 MPa at 0.5% damping ratio, representing 37.27% of the yield limit. For the 4 kg specimen, the maximum equivalent stress was 513 MPa with alternating stress below 40 MPa at 3% damping ratio, corresponding to 54.32% of the yield limit. This research enhances the reliability and performance of high-speed rotating machinery. Full article
(This article belongs to the Special Issue Vibration Problems in Engineering Science)
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19 pages, 5658 KiB  
Article
Experimentally Aided Operational Virtual Prototyping to Predict Best Clamping Conditions for Face Milling of Large-Size Structures
by Krzysztof J. Kaliński, Marek A. Galewski, Michał R. Mazur and Natalia Stawicka-Morawska
Appl. Sci. 2024, 14(16), 7346; https://doi.org/10.3390/app14167346 - 20 Aug 2024
Cited by 1 | Viewed by 1134
Abstract
Vibrations occurring during milling operations are one of the main issues disturbing the pursuit of better efficiency of milling operations and product quality. Even in the case of a stable cutting process, vibration reduction is still an important goal. One of the possible [...] Read more.
Vibrations occurring during milling operations are one of the main issues disturbing the pursuit of better efficiency of milling operations and product quality. Even in the case of a stable cutting process, vibration reduction is still an important goal. One of the possible solutions to obtain it is selection of the favorable conditions for clamping the workpiece to the machine table. In this paper, a method for predicting and selecting the clamping condition of a large-size workpiece for the reduction in vibrations during milling is presented. A modal test of the workpiece is performed first for a selected set of tightening screw settings. Next, one milling pass is performed to obtain reference data which are then used to tune the hybrid computational model. In the subsequent step, milling simulations are performed for a set of tightening variants, and the best one is selected, providing the lowest vibrations, assessed as the root mean square (RMS) of vibration displacements. In this paper, the description of the clamping selection procedure, key elements of the simulation model, and simulation and experimental results obtained for the milling of the test workpiece performed for a set of different clamping conditions are provided. The proposed method accurately predicts not only the best but also the worst clamping conditions. Full article
(This article belongs to the Special Issue Vibration Problems in Engineering Science)
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15 pages, 1956 KiB  
Article
Design and Implementation of a MIMO Integral Resonant Control for Active Vibration Control of Pedestrian Structures
by Emiliano Pereira, Xidong Wang, Iván M. Díaz and Sumeet S. Aphale
Appl. Sci. 2024, 14(15), 6784; https://doi.org/10.3390/app14156784 - 3 Aug 2024
Viewed by 960
Abstract
In contemporary construction, the prevalence of vibration serviceability issues in lightweight and slender structures has become increasingly common, owing to advancements in building materials and construction methods. While these structures often meet the criteria for ultimate limit states, they can still elicit complaints [...] Read more.
In contemporary construction, the prevalence of vibration serviceability issues in lightweight and slender structures has become increasingly common, owing to advancements in building materials and construction methods. While these structures often meet the criteria for ultimate limit states, they can still elicit complaints due to excessive vibrations induced by human activity. To address this challenge, the integral resonant control (IRC) technique has emerged as a favored approach for actively damping vibrations in various systems. This study introduces a fresh perspective by proposing the implementation of a multi-input multi-output (MIMO) IRC scheme for active vibration control (AVC) specifically tailored for pedestrian structures utilizing inertial mass actuators. This application of MIMO IRC for AVC represents a novel advancement in the field, offering a new solution to address vibration issues in lightweight and slender structures. Building upon a common framework and design methodology outlined in previous research, this work presents a novel application of MIMO IRC for AVC. The designed controller undergoes rigorous testing and is implemented on a laboratory floor structure to validate its efficacy. The outcomes of this study demonstrate the effectiveness of the proposed MIMO IRC scheme in actively damping vibrations, thereby enhancing the serviceability and comfort levels of lightweight and slender structures subjected to human-induced excitations. Full article
(This article belongs to the Special Issue Vibration Problems in Engineering Science)
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22 pages, 8448 KiB  
Article
Free Vibration Analysis of Curvilinearly Tapered Axially Functionally Graded Material Beams
by Vyacheslav N. Burlayenko, Reijo Kouhia and Svetlana D. Dimitrova
Appl. Sci. 2024, 14(15), 6446; https://doi.org/10.3390/app14156446 - 24 Jul 2024
Cited by 4 | Viewed by 1064
Abstract
The study focuses on the free vibration analysis of beams made of axially functionally graded materials (AFGM) with curvilinear variable cross-sections along their length. The beams encompass various shapes, including concave and convex conic sections, with axial material properties varying according to polynomial [...] Read more.
The study focuses on the free vibration analysis of beams made of axially functionally graded materials (AFGM) with curvilinear variable cross-sections along their length. The beams encompass various shapes, including concave and convex conic sections, with axial material properties varying according to polynomial and exponential laws. The equations of motion are derived using Hamilton’s principle within the framework of Timoshenko beam theory. These governing equations, subjected to various boundary conditions, are solved using the differential transform method (DTM). The proposed solution technique is validated by comparing computed natural frequencies with the existing literature and results obtained using three-dimensional finite element analysis in ABAQUS. The incorporation of material gradients into the beam finite element models was achieved using the user-defined material subroutine (UMAT). Additionally, a comprehensive study is conducted to examine the influence of various factors on the natural frequencies of functionally graded beams. These factors include parameters of material laws, types of variable beam shapes, slenderness ratio, and specific boundary conditions. This study provides a thorough understanding of the modal dynamics of the considered beams, offering valuable insights into the behavior of FGM structures. Full article
(This article belongs to the Special Issue Vibration Problems in Engineering Science)
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21 pages, 15472 KiB  
Article
Research on Bifurcated Origami Hydraulic Dampers for Real Road Vibration Loads
by Jingchao Guan, Baoluo Zheng, Yalan Li, Wei Zhao and Xilu Zhao
Appl. Sci. 2024, 14(14), 6374; https://doi.org/10.3390/app14146374 - 22 Jul 2024
Viewed by 1028
Abstract
Cylindrical hydraulic dampers are commonly utilized to mitigate vibrations in machinery and structural applications. These devices generally feature a single linear stroke and are often linked to rotary joints to handle complex loading conditions. However, their installation in confined spaces, such as vehicle [...] Read more.
Cylindrical hydraulic dampers are commonly utilized to mitigate vibrations in machinery and structural applications. These devices generally feature a single linear stroke and are often linked to rotary joints to handle complex loading conditions. However, their installation in confined spaces, such as vehicle suspensions, poses considerable difficulties. In this research, we introduce an innovative bifurcated origami hydraulic damper with nonlinear damping capabilities. Initially, we formulated the collapsible conditional equations essential for the design of the bifurcated origami hydraulic dampers. We then examined the fluid dynamics within the damper and its flow channels, determining that the damping force is proportional to the square of the velocity. Furthermore, we developed motion equations based on the derived damping force and suggested vibration analysis methods using the Runge–Kutta approach. For the mass-spring vibration system, we created an experimental setup with the bifurcated origami hydraulic damper and performed vibration tests using noise signals recorded from a vehicle traveling on a gravel road, thus validating its damping performance and efficacy. Additional tests, which varied the orifice size at the end of the origami structure, as well as the type and temperature of the internal fluid, showed that the orifice size had a more pronounced effect on damping efficiency than the fluid type and temperature. This confirmed the vibration-damping effectiveness of the bifurcated origami hydraulic damper. Full article
(This article belongs to the Special Issue Vibration Problems in Engineering Science)
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14 pages, 2460 KiB  
Article
Acceleration of Service Life Testing by Using Weibull Distribution on Fiber Optical Connectors
by Jesús M. Barraza-Contreras, Manuel R. Piña-Monarrez, María M. Hernández-Ramos, Osvaldo Monclova-Quintana and Secundino Ramos-Lozano
Appl. Sci. 2024, 14(14), 6198; https://doi.org/10.3390/app14146198 - 17 Jul 2024
Cited by 1 | Viewed by 1250
Abstract
The service life assessment of previous fatigue stress has a fundamental role in estimating the reliability of products like fiber optical connectors, and should replicate use in severe environments in telecommunications systems. However, the vibration prediction models used in the literature present limitations [...] Read more.
The service life assessment of previous fatigue stress has a fundamental role in estimating the reliability of products like fiber optical connectors, and should replicate use in severe environments in telecommunications systems. However, the vibration prediction models used in the literature present limitations in vibration life prediction. In this paper, we propose using the insertion loss fatigue life and including it in the Weibull distribution to determine the Weibull parameters ƞ and β to evaluate fiber optic connector reliability R(t) under environmental and mechanical testing stress. We analyzed the failure data of a standard telecommunication fiber optical connector under a program of service life stress testing against that of a fiber optical connector under only mechanical vibration stress testing. The fiber connectors were monitored during the vibration testing to review the transient change of the optical signal. Their results showed that the reliability of the fiber connectors submitted to the service life program was Rt=0.694, while that of the fiber connectors submitted to mechanical vibration only was Rt=0.970. In addition, the analysis showed that the service life testing consumed 70.2% of the product’s lifetime. We present in Numerical Validation the steps to determine the acceleration factors of the vibration test developed. Full article
(This article belongs to the Special Issue Vibration Problems in Engineering Science)
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23 pages, 7311 KiB  
Article
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 - 4 Apr 2024
Cited by 1 | Viewed by 2466
Abstract
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  
Article
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
Cited by 4 | Viewed by 1436
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  
Article
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 2093
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  
Article
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
Cited by 1 | Viewed by 2172
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  
Article
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 3 | Viewed by 1801
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  
Article
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
Cited by 1 | Viewed by 2112
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  
Article
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 1571
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  
Article
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 12 | Viewed by 4101
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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