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Vibration
Number of Followers: 30  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2571-631X
Published by MDPI Homepage  [258 journals]
  • Vibration, Vol. 7, Pages 36-52: Evaluating Contact-Less Sensing and Fault
           Diagnosis Characteristics in Vibrating Thin Cantilever Beams with a
           MetGlas® 2826MB Ribbon

    • Authors: Robert-Gabriel Sultana, Achilleas Davrados, Dimitrios Dimogianopoulos
      First page: 36
      Abstract: The contact-less sensing and fault diagnosis characteristics induced by fixing short Metglas® 2826MB ribbons onto the surface of thin cantilever polymer beams are examined and statistically evaluated in this study. Excitation of the beam’s free end generates magnetic flux from the vibrating ribbon (fixed near the clamp side), which, via a coil suspended above the ribbon surface, is recorded as voltage with an oscilloscope. Cost-efficient design and operation are key objectives of this setup since only conventional equipment (coil, oscilloscope) is used, whereas filtering, amplification and similar circuits are absent. A statistical framework for extending past findings on the relationship between spectral changes in voltage and fault occurrence is introduced. Currently, different levels of beam excitation (within a frequency range) are shown to result in statistically different voltage spectral changes (frequency shifts). The principle is also valid for loads (faults) of different magnitudes and/or locations on the beam for a given excitation. Testing with either various beam excitation frequencies or different loads (magnitude/locations) at a given excitation demonstrates that voltage spectral changes are statistically mapped onto excitation levels or occurrences of distinct faults (loads). Thus, conventional beams may cost-efficiently acquire contact-less sensing and fault diagnosis capabilities using limited hardware/equipment.
      Citation: Vibration
      PubDate: 2024-01-06
      DOI: 10.3390/vibration7010002
      Issue No: Vol. 7, No. 1 (2024)
       
  • Vibration, Vol. 7, Pages 53-63: A Study of Seating Suspension System
           Vibration Isolation Using a Hybrid Method of an Artificial Neural Network
           and Response Surface Modelling

    • Authors: Yuli Zhao, Mohamed Khayet, Xu Wang
      First page: 53
      Abstract: A reliable prediction model can greatly contribute to the research of car seating system vibration control. The novelty of this paper lies in the development of a hybrid method of an artificial neural network (ANN) and response surface methodology (RSM) to predict the peak seat-to-head transmissibility ratio of a seating suspension system and to evaluate its ride comfort for different seat design parameters. Additionally, this method can remove the experimental design of the RSM model. In this paper, four seat design parameters are selected as input parameters and arranged using the central composite design method. The peak transmissibility ratio from seat to head at 4 Hz is chosen as the response target output value. To illustrate this hybrid method, the response target output value of the peak transmissibility ratio is calculated from the frequency response of a five-degrees-of-freedom (5-DOF) lumped-parameter biodynamic seating suspension model. The input design parameters and the response target output values are used to train an ANN to establish the relationship between the seat design parameters and the peak transmissibility ratio. At the same time, the input design parameters and the response target output values predicted by the ANN are used to develop the relationship between the seat design parameters and the peak transmissibility ratio using the response surface method and linear regression models. The hybrid of the ANN and response surface methods makes the planning or design of experiments not essential. The hybrid model of the ANN and response surface method is more accurate and convenient than a linear regression model for the study of seating system vibration isolation.
      Citation: Vibration
      PubDate: 2024-01-08
      DOI: 10.3390/vibration7010003
      Issue No: Vol. 7, No. 1 (2024)
       
  • Vibration, Vol. 7, Pages 64-82: Application of Pebbles for Geotechnical
           Seismic Isolation (GSI): Experimental Parametric Study

    • Authors: Ivan Banović, Jure Radnić, Nikola Grgić, Marko Galić
      First page: 64
      Abstract: Low-income regions do not have the economic strength to use conventional isolators; therefore, low-cost alternatives are needed. The recent series of earthquakes in Turkey has once again demonstrated the destructive power of this natural disaster and highlighted the need for high-quality earthquake-resistant structures. In this context, a comprehensive experimental parametric study on the use of natural stone pebbles (ASL-1) and stone pebbles in combination with a geogrid layer (ASL-2) as suitable materials for a GSI system is conducted and the main results are presented. The seismic behavior of five different models was tested using four different acceleration diagrams with different peak ground accelerations (PGAs). Characteristic displacements, accelerations, and strains were measured. The results and conclusions presented are based on the integration and synthesis of several previously conducted studies.
      Citation: Vibration
      PubDate: 2024-01-16
      DOI: 10.3390/vibration7010004
      Issue No: Vol. 7, No. 1 (2024)
       
  • Vibration, Vol. 7, Pages 83-97: Study on the Mechanism and Suppression of
           Harmonic Vibration of AMB-Rotor System

    • Authors: Qi Chen, Jinlei Li
      First page: 83
      Abstract: The AMB-rotor system is complex and has strong coupling characteristics, which allows multi-harmonic disturbances to enter the system through different ways to produce vibrations with rich spectrum components, which has a great influence on the improvement of micro-vibration accuracy of the rotor system. To further achieve active control of the micro-vibration in the AMB-rotor system, firstly, the mechanism of multi-source disturbance is analyzed according to the working principle of the AMB-rotor system, and the mathematical and physical relationship between the mechanism of disturbance generation and the inducement is deeply studied. Then, the structure of a novel adaptive notch filter, the method of adaptive frequency estimation and analysis of harmonic current suppression in the AMB system are presented. Finally, simulation and experimental research using an MSCMG system demonstrate the feasibility of the proposed method regarding the elimination of harmonic control current.
      Citation: Vibration
      PubDate: 2024-01-18
      DOI: 10.3390/vibration7010005
      Issue No: Vol. 7, No. 1 (2024)
       
  • Vibration, Vol. 7, Pages 98-128: Energy-Preserving/Group-Preserving
           Schemes for Depicting Nonlinear Vibrations of Multi-Coupled Duffing
           Oscillators

    • Authors: Chein-Shan Liu, Chung-Lun Kuo, Chih-Wen Chang
      First page: 98
      Abstract: In the paper, we first develop a novel automatically energy-preserving scheme (AEPS) for the undamped and unforced single and multi-coupled Duffing equations by recasting them to the Lie-type systems of ordinary differential equations. The AEPS can automatically preserve the energy to be a constant value in a long-term free vibration behavior. The analytical solution of a special Duffing–van der Pol equation is compared with that computed by the novel group-preserving scheme (GPS) which has fourth-order accuracy. The main novelty is that we constructed the quadratic forms of the energy equations, the Lie-algebras and Lie-groups for the multi-coupled Duffing oscillator system. Then, we extend the GPS to the damped and forced Duffing equations. The corresponding algorithms are developed, which are effective to depict the long term nonlinear vibration behaviors of the multi-coupled Duffing oscillators with an accuracy of O(h4) for a small time stepsize h.
      Citation: Vibration
      PubDate: 2024-01-18
      DOI: 10.3390/vibration7010006
      Issue No: Vol. 7, No. 1 (2024)
       
  • Vibration, Vol. 7, Pages 129-145: Modelling and Control of Longitudinal
           Vibrations in a Radio Frequency Cavity

    • Authors: Mahsa Keikha, Jalal Taheri Kahnamouei, Mehrdad Moallem
      First page: 129
      Abstract: Radio frequency (RF) cavities hold a crucial role in Electron Linear Accelerators, serving to provide precisely controlled accelerating fields. However, the susceptibility of these cavities to microphonic interference necessitates the development of effective controllers to mitigate vibration due to interference and disturbances. This paper undertakes an investigation into the modeling of RF cavities, treating them as cylindrical beams. To this end, a pseudo-rigid body model is employed to represent the translational vibration of the beam under various boundary conditions. The model is systematically analyzed using ANSYS software (from Ansys, Inc., Canonsburg, PA, USA, 2022). The study further delves into the controllability and observability of the proposed model, laying the foundation for the subsequent design of an observer-based controller geared towards suppressing longitudinal vibrations. The paper presents the design considerations and methodology for the controller. The performance of the proposed controller is evaluated via comprehensive simulations, providing valuable insights into its effectiveness in mitigating microphonic interference and enhancing the stability of RF cavities in Electron Linear Accelerators.
      Citation: Vibration
      PubDate: 2024-01-31
      DOI: 10.3390/vibration7010007
      Issue No: Vol. 7, No. 1 (2024)
       
  • Vibration, Vol. 7, Pages 146-160: Vibrational Analysis of a Splash Cymbal
           by Experimental Measurements and Parametric CAD-FEM Simulations

    • Authors: Spyros Brezas, Evaggelos Kaselouris, Yannis Orphanos, Michael Tatarakis, Makis Bakarezos, Nektarios A. Papadogiannis, Vasilis Dimitriou
      First page: 146
      Abstract: The present study encompasses a thorough analysis of the vibrations in a splash musical cymbal. The analysis is performed using a hybrid methodology that combines experimental measurements with parametric computer-aided design and finite element method simulations. Experimental measurements, including electronic speckle pattern interferometry, and impulse response measurements are conducted. The interferometric measurements are used as a reference for the evaluation of finite element method modal analysis results. The modal damping ratio is calculated via the impulse response measurements and is adopted by the corresponding simulations. Two different approximations are employed for the computer-aided design and finite element method models: one using three-point arcs and the other using lines to describe the non-smooth curvature introduced during manufacturing finishing procedures. The numerical models employing the latter approximation exhibit better agreement with experimental results. The numerical results demonstrate that the cymbal geometrical characteristics, such as the non-smooth curvature and thickness, greatly affect the vibrational behavior of the percussion instrument. These results are of valuable importance for the development of vibroacoustic numerical models that will accurately simulate the sound synthesis of cymbals.
      Citation: Vibration
      PubDate: 2024-02-01
      DOI: 10.3390/vibration7010008
      Issue No: Vol. 7, No. 1 (2024)
       
  • Vibration, Vol. 7, Pages 161-176: A Nonparametric Regularization for
           Spectrum Estimation of Time-Varying Output-Only Measurements

    • Authors: Péter Zoltán Csurcsia, Muhammad Ajmal, Tim De Troyer
      First page: 161
      Abstract: In this work, an advanced 2D nonparametric correlogram method is presented to cope with output-only measurements of linear (slow) time-varying systems. The proposed method is a novel generalization of the kernel function-based regularization techniques that have been developed for estimating linear time-invariant impulse response functions. In the proposed system identification technique, an estimation method is provided that can estimate the time-varying auto- and cross-correlation function and indirectly, the time-varying auto- and cross-correlation power spectrum estimates based on real-life measurements without measuring the perturbation signals. The (slow) time-varying behavior means that the dynamic of the system changes as a function of time. In this work, a tailored regularization cost function is considered to impose assumptions such as smoothness and stability on the 2D auto- and cross-correlation function resulting in robust and uniquely determined estimates. The proposed method is validated on two examples: a simulation to check the numerical correctness of the method, and a flutter test measurement of a scaled airplane model to illustrate the power of the method on a real-life challenging problem.
      Citation: Vibration
      PubDate: 2024-02-07
      DOI: 10.3390/vibration7010009
      Issue No: Vol. 7, No. 1 (2024)
       
  • Vibration, Vol. 7, Pages 1-35: A Testbench for Measuring the Dynamic
           Force-Displacement Characteristics of Shockmounts

    • Authors: Bernhard Heinemann, Kai Simanowski, Michael Clasen, Jan Dreesen, Delf Sachau
      First page: 1
      Abstract: Shockmounts in naval applications are used to mount technical equipment onto the structure of naval vessels. The insulating effect against mechanical shock is important here, as it can excite the structure in the event of underwater explosions and otherwise cause damage to the equipment. Although knowledge of the dynamic properties of shockmounts is important to naval architects, the dynamic force-displacement characteristics of shockmounts are often tested and measured statically and/or in the harmonic field. Recently, an inertia-based method and a dynamic model for measuring the dynamic force-displacement characteristics of shockmounts was described. This paper presents a full description of a testbench for implementing this method. The testbench incorporates a drop table for excitation. The proposed setup can be configured for measuring the dynamic characteristics of elastomer and wire rope shockmounts, with shock loads in compression, tension, shear and roll directions. The advanced Kelvin–Voigt model for shockmounts is applied, showing that the dynamic force-displacement characteristics measured with this setup are qualified to generate model parameters for further use.
      Citation: Vibration
      PubDate: 2023-12-21
      DOI: 10.3390/vibration7010001
      Issue No: Vol. 7, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 726-742: Modes of Vibration in Basketball Rims
           and Backboards and the Energy Rebound Testing Device

    • Authors: Daniel Winarski, Kip P. Nygren, Tyson Winarski
      First page: 726
      Abstract: Six mode shapes, including bending and torsion, were documented for five different basketball rims and backboards at the United States Military Academy, West Point, New York, NY, USA. The frequency and damping ratio of each mode shape were also determined. The empirical process began with the time-domain excitation and response of each rim-backboard system. The impulse of excitation came from an impact hammer separately applied sequentially to each node. The sinusoidal response was gathered from an accelerometer at a fixed location (node 1). Each time-domain excitation response was then converted to a frequency-domain Bode plot for each node by a Brüel & Kjær 2034 Signal Analyzer, giving transfer functions of output/input versus frequency. Structural Measurements System (SMS) StarStruc software was used to fit mode shapes to the Bode plots. Each of the six mode shapes was fitted to the Bode plots of each node at a specific modal frequency. Each of the six mode shapes was a function of the locations of the nodes, and the Bode plots gathered at each node. The first and second modes were critical for showing that the Energy Rebound Testing Device statistically correlated with the energy transferred to the rim and backboard. A known perturbation mass was selectively attached to the rim to help isolate the dynamic masses and spring rates for the rim and backboard and to ascertain that the kinetic energy transferred to the rim had a 95.67% inverse correlation with rim stiffness.
      Citation: Vibration
      PubDate: 2023-09-22
      DOI: 10.3390/vibration6040045
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 743-761: Vibration Minimisation of Moving
           Flexible Slender Structures Based on Time-Parameterised B-Spline

    • Authors: Marco Riboli, Elisabetta Manconi, Dario Fusai, Marco Silvestri, Alessandra Aimi
      First page: 743
      Abstract: Vibration mitigation of moving flexible structures is a key issue in many applications. Examples include antennas, solar arrays, radar reflectors, and manipulator arms, especially in the aerospace sector. These structures typically consist of inter-connected slender and flexible elements moved by external actuators to reach specific configurations and positions. The movements excite vibrations, which lead to the risk of structural and fatigue failures; once in position, residual vibrations can be further amplified by structure lightness, causing bad performance and malfunctioning of onboard sensors. This paper proposes an effective technique to minimise the vibration of moving flexible structures by calculating the control points of a time-parametrised B-spline representing the shape of the motion law. A testing case of a rotating cantilever beam is considered. Validation using multi-flexible-body simulation software has shown the method’s effectiveness in minimising residual vibrations.
      Citation: Vibration
      PubDate: 2023-09-27
      DOI: 10.3390/vibration6040046
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 762-776: Vibration Response of Manual Wheelchairs
           According to Loads, Propulsion Methods, Speeds, and Ground Floor Types

    • Authors: Ophélie Larivière, Delphine Chadefaux, Christophe Sauret, Patricia Thoreux
      First page: 762
      Abstract: Manual wheelchair (MWC) users are daily exposed to vibration during propulsion. The impact of such exposure on the MWC user’s health has yet to be proven. To date, no agreement has been reached, presumably on the account of the wide variety of experimental parameters that need to be controlled. A possible solution relies on the implementation of a User/MWC model to point out the effect of propelling conditions (MWC loads, propulsion methods, speeds, and ground floor types) on the vibration exposure and eventually on the MWC user’s health. To feed such a model, the evaluation of the MWC vibration response during propulsion is required. Following a necessary MWC experimental modal analysis under laboratory conditions, this study presents the vibration response of an MWC under various propelling conditions. For each investigated condition, the identified set of modal parameters was provided and the effect on the MWC response to vibration at the User/MWC interfaces was highlighted. Results mostly underline that the response to vibration is highly dependent on the propelling conditions. The speed and the ground floor type greatly affect the vibration response: doubling speed and increasing ground surface roughness imply threefold and eightfold vibration levels, respectively. Finally, the main outcome is that an empty MWC or an MWC loaded with a dummy generates vibration outside the range measured for an MWC loaded with a human body, resulting in a lower frequency content and an almost two-fold vibration level increase. The findings of this study will help enhance the understanding of the health risks that wheelchair users encounter as a result of vibrations.
      Citation: Vibration
      PubDate: 2023-09-29
      DOI: 10.3390/vibration6040047
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 777-795: Development of a Novel
           Magneto-Rheological Elastomer-Based Semi-Active Seat Suspension System

    • Authors: Wang, Vatandoost, Sedaghati
      First page: 777
      Abstract: Human operators in the transportation sector are exposed to whole-body vibration (WBV) while driving. Occupational exposure to WBV, predominant at low frequencies (<20 Hz), has been linked to spinal injuries and reduced functioning. This study aims at the design development of a novel semi-active seat suspension system featuring magneto-rheological elastomers (MREs) to mitigate the WBV. The proposed suspension system allows a greater range of strokes, while ensuring the MRE remains within an acceptable level of deformation. Several MRE samples were fabricated and characterized under shear mode. Afterward, a field- and frequency-dependent phenomenological model was developed to predict the viscoelastic properties of MREs as functions of both the excitation frequency and applied magnetic field. The MRE material model was subsequently used to design and optimize an adaptive seat suspension system incorporating a C-shaped MRE-based isolator in parallel and series with passive springs. The proposed adaptive seat suspension system demonstrated a frequency shift of 29% by increasing the applied current from 0 to 2 A. Finally, a 6-DOF lumped parameter model of a seated human subject combined with the proposed semi-active suspension system featuring the MRE isolator has been formulated to investigate the vibration transmissibility from the floor to the subject’s head.
      Citation: Vibration
      PubDate: 2023-09-29
      DOI: 10.3390/vibration6040048
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 796-819: Defect Detection in Carbon
           Fiber-Reinforced Plate by Imaging of Mechanical Nonlinearity-Induced
           Sideband Vibrations

    • Authors: Tommaso Seresini, Sevilia Sunetchiieva, Helge Pfeiffer, Martine Wevers, Christ Glorieux
      First page: 796
      Abstract: Laser Doppler scanning vibrometry is used for imaging spectral vibration components in a carbon fiber-reinforced composite plate that contains a sub-surface delamination defect caused by hammer impact. The images reveal sideband generation at the location of the defect, reflecting mechanical nonlinearity-induced mixing between a high amplitude, low-frequency vibration that modulates the stress–strain behavior near the defect and a low amplitude, high-frequency probe vibration. In this work, a multifrequency probe is used to tackle the problem that the mixing coefficients are, in practice, frequency dependent. Based on the measured sideband amplitudes, a study is presented on the expected feasibility of detecting defects by a full field imaging scheme based on a photorefractive interferometer that is configured as a vibrometer acting as a bandpass filter around a sideband frequency of interest.
      Citation: Vibration
      PubDate: 2023-10-01
      DOI: 10.3390/vibration6040049
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 820-842: Efficient Modal Identification and
           Optimal Sensor Placement via Dynamic DIC Measurement and Feature-Based
           Data Compression

    • Authors: Weizhuo Wang
      First page: 820
      Abstract: Full-field non-contact vibration measurements provide a rich dataset for analysing structural dynamics. However, implementing the identification algorithm directly using high-spatial resolution data can be computationally expensive in modal identification. To address this challenge, performing identification in a shape-preserving but lower-dimensional feature space is more feasible. The full-field mode shapes can then be reconstructed from the identified feature mode shapes. This paper discusses two approaches, namely data-dependent and data-independent, for constructing the feature spaces. The applications of these approaches to modal identification on a curved plate are studied, and their performance is compared. In a case study involving a curved plate, it was found that a spatial data compression ratio as low as 1% could be achieved without compromising the integrity of the shape features essential for a full-field modal. Furthermore, the paper explores the optimal point-wise sensor placement using the feature space. It presents an alternative, data-driven method for optimal sensor placement that eliminates the need for a normal model, which is typically required in conventional approaches. Combining a small number of point-wise sensors with the constructed feature space can accurately reconstruct the full-field response. This approach demonstrates a two-step structural health monitoring (SHM) preparation process: offline full-field identification of the structure and the recommended point-wise sensor placement for online long-term monitoring.
      Citation: Vibration
      PubDate: 2023-10-06
      DOI: 10.3390/vibration6040050
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 843-875: A Review on Vibration-Based Damage
           Detection Methods for Civil Structures

    • Authors: Xutao Sun, Sinniah Ilanko, Yusuke Mochida, Rachael C. Tighe
      First page: 843
      Abstract: Vibration-based damage detection is a range of methods that utilizes the dynamic response of a structure to evaluate its condition and detect damage. It is an important approach for structural health monitoring and has drawn much attention from researchers. While multiple reviews have been published focusing on different aspects of this field, there has not been a study specifically examining the recent development across the range of methods, including natural frequency, mode shape, modal curvature, modal strain energy, and modal flexibility-based damage detection methods. This paper aims to fill this gap by reviewing the recent application of these methods in civil structures, including beams, plates, trusses, frames, and composite structural members. The merits and limitations of each method are discussed, and research opportunities are presented. This broader review also provides an opportunity for critical comparison across this range of methods. While predominantly reviewing experiment-based studies, this review also considers some numerical studies that may motivate further research.
      Citation: Vibration
      PubDate: 2023-10-11
      DOI: 10.3390/vibration6040051
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 876-894: Analysis of the Axial Vibration of
           Non-Uniform and Functionally Graded Rods via an Analytical-Based Numerical
           Approach

    • Authors: Koray Kondakcı, Safa Bozkurt Coşkun
      First page: 876
      Abstract: In this study, an analytical-based numerical approach was proposed for the analysis of the free axial vibration of homogeneous and functionally graded rods with varying cross-sectional areas. The proposed approach is based on analytical approximation techniques, such as the Adomian decomposition method, variational iteration method, and homotopy perturbation method. However, the governing equations of the problems solved in this study were variable coefficient differential equations. These equations provide analytical solutions for strictly limited cases. Analytical approximation methods easily handle problems with uniform material properties and constant cross-sections, whereas with varying cross-sectional areas, the analytical integration process becomes a difficult task for the software. If the rod’s material is functionally graded with varying cross-sectional areas, the analytical integration process becomes a cumbersome task. The proposed approach eliminates all difficulties and requires computation within several seconds. The application of this method is straightforward, and the results obtained in this study are in excellent agreement with the solutions provided in the literature.
      Citation: Vibration
      PubDate: 2023-10-12
      DOI: 10.3390/vibration6040052
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 895-916: Predicting Critical Speed of Railway
           Tracks Using Artificial Intelligence Algorithms

    • Authors: Ana Ramos, Alexandre Castanheira-Pinto, Aires Colaço, Jesús Fernández-Ruiz, Pedro Alves Costa
      First page: 895
      Abstract: Motivated by concerns regarding safety and maintenance, the operational speed of a railway line must remain significantly below the critical speed associated with the track–ground system. Given the large number of track sections within a railway corridor that potentially need to be analyzed, the development of efficient predictive tools is of the utmost importance. Based on that, the problem can be analyzed in a few seconds instead of taking several hours of computational effort, as required by a numerical analysis. In this context, and for the first time, machine learning algorithms, namely artificial neural networks and support vector machine techniques, are applied to this particular issue. For its derivation, a reliable and robust dataset was developed by means of advanced numerical methodologies that were previously experimentally validated. The database is available as supplemental data and may be used by other researchers. Regarding the prediction process, the performance of both models was very satisfactory. From the results achieved, it is possible to conclude that the prediction tool is a novel and reliable approach for an almost instantaneous prediction of critical speed in a high number of track sections.
      Citation: Vibration
      PubDate: 2023-10-12
      DOI: 10.3390/vibration6040053
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 917-931: Vibration and Aerodynamic Analysis and
           Optimization Design of a Test Centrifuge

    • Authors: Chunyan Deng, Lidong He, Zhifu Tan, Xingyun Jia
      First page: 917
      Abstract: Taking a type of test centrifuge as the research object, the finite element model of the test centrifuge was established, the vibration characteristics and aerodynamic performance of the test centrifuge were analyzed, and a structural optimization design of the test centrifuge was carried out. In this paper, the load was applied according to the actual working condition of a type of test centrifuge. The vibration of the mounting seat of the test centrifuge was analyzed, and the structure of the mounting seat was improved. After improvement, the vibration of the mounting seat was 77.38% lower than that of the original mounting seat. Then, the aerodynamic analysis of the test centrifuge was carried out. The analysis results show that the test centrifuge moved more smoothly under the whole-package shell and the fairing, the resistance decreased, and the shaft load decreased. Finally, the fairing of the test centrifuge was optimized. The analysis shows that an increase in the width of the fairing can reduce the resistance coefficient, which is helpful to the stability of the test centrifuge during operation and reduces the unbalanced response of the system caused by air resistance.
      Citation: Vibration
      PubDate: 2023-10-15
      DOI: 10.3390/vibration6040054
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 932-944: Effects of a Single Session of Whole
           Body Vibration Compared to Multiple Sessions—An Updated Review and
           Meta-Analysis

    • Authors: Andrea Dincher
      First page: 932
      Abstract: Parkinson’s disease is an incurable neurological disease. Only the symptoms can be treated with medication or exercise therapy. The present analysis is intended to show how whole-body vibration training affects the symptoms of Parkinson’s disease, distinguishing between acute and long-term effects. Methods: online databases (EMBASE, PubMed, PEDro) were searched for reviews, meta-analyses and new studies since the previous most recent review/meta-analysis. Studies with at least a medium methodological quality (PEDro score at least 5 points) were selected. Results were presented as forest plots that indicated standardized mean differences with 95% confidence interval. Results: Sixteen studies were found with a PEDro-score of at least 5 points. Of these, three studies were excluded from the qualitative analysis because the necessary data, such as standard deviation or control group results, were missing. The effect sizes are very mixed. In some parameters there is no effect, in others a very strong effect. The effects in the comparison between single and multiple treatments are similar. Discussion: The different effects may be partly due to the different vibration frequencies or sentence durations, as well as to different valid test procedures. Conclusions: Since the study situation still does not show clear results, further studies must follow that compare different frequencies, sentence durations and vibration types with each other, so that training recommendations can be given on this basis.
      Citation: Vibration
      PubDate: 2023-10-18
      DOI: 10.3390/vibration6040055
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 945-959: FEM Investigation of the Air Resonance
           in a Cretan Lyra

    • Authors: Nikolaos M. Papadakis, Nikolaos Nikolidakis, Georgios E. Stavroulakis
      First page: 945
      Abstract: Cretan lyra is a stringed instrument very popular on the island of Crete, Greece, and an important part of its musical tradition. For stringed musical instruments, the air mode resonance plays a vital part in their sound, especially in the low frequency range. For this study, the air mode resonance of a Cretan lyra is investigated with the use of finite element method (FEM). Two different FEM acoustic models were utilized: First, a pressure acoustics model with the Cretan lyra body treated as rigid was used to provide an approximate result. Secondly, an acoustic–structure interaction model was applied for a more accurate representation. In addition, acoustic measurements were performed to identify the air mode resonance frequency. The results of this study reveal that the acoustic–structure interaction model has a 3.7% difference regarding the actual measurements of the resonance frequency. In contrast, the pressure acoustics solution is approximately 13.8% too high compared with the actual measurements. Taken together, the findings of this study support the idea that utilizing the FEM acoustic–structure interaction models could possibly predict the vibroacoustic behavior of musical instruments more accurately, which in turn can enable the determination of key aspects that can be used to control the instrument’s tone and sound quality.
      Citation: Vibration
      PubDate: 2023-10-18
      DOI: 10.3390/vibration6040056
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 960-973: Experimental and Theoretical
           Reproducibility Research on the Earthquake Resistance of Cylindrical Steel
           Tanks

    • Authors: Nurlan Zhangabay, Marco Bonopera, Akmaral Utelbayeva, Timur Tursunkululy, Murat Rakhimov
      First page: 960
      Abstract: This article analyzes the convergence of the obtained values as a result of the authors’ earlier experimental and theoretical studies. On the basis of the correlations, it was found that the analyses of a traditional cylindrical steel tank without a steel wire strand wrapping and with a filling level of zero by a liquid showed a difference in natural vibration frequencies of 8.4%, while with half and maximal filling by a liquid showed differences equal to 3.2% and 6.2%, respectively. Vice versa, analyses of a cylindrical steel tank with a steel wire strand winding pitch of a = 3d and with a filling level of zero by a liquid showed a difference in natural vibration frequencies of 8.1%, while with half and maximum filling by a liquid and with the same steel wire strand winding pitch showed differences of 10.1% and 5.9%, respectively. Conversely, analyses of a cylindrical steel tank with a steel wire strand winding pitch of a = d and in absence of filling level amounted to a difference of 5.5%, while with half and maximum filling and with the same steel wire strand winding pitch of a = d, differences of 1.6% and 1.4% were, respectively, achieved. Based on the aforementioned results, the general difference between experimental and theoretical vibration frequencies showed up to 10%, which is a satisfactory result of convergence. The obtained findings of this research can be used by engineers and technical workers in the industries of various fields, research institutes and professional companies in designing new earthquake-resistant steel tanks and strengthening existing ones. Conclusions were then mentioned at the end of the article.
      Citation: Vibration
      PubDate: 2023-11-04
      DOI: 10.3390/vibration6040057
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 975-1003: Optimal Placement and Active Control
           Methods for Integrating Smart Material in Dynamic Suppression Structures

    • Authors: Amalia Moutsopoulou, Georgios E. Stavroulakis, Markos Petousis, Anastasios Pouliezos, Nectarios Vidakis
      First page: 975
      Abstract: To simulate a lightweight structure with integrated actuators and sensors, two-dimensional finite elements are utilized. The study looks at the optimal location and active vibration control for a piezoelectric smart flexible structure. Intelligent applications are commonly used in engineering applications. In computational mechanics, selecting the ideal position for actuators to suppress oscillations is crucial. The structure oscillates due to dynamic disturbance, and active control is used to try to reduce the oscillation. Utilizing an LQR and Hinfinity controller, optimization is carried out to determine the best controller weights, which will dampen the oscillation. Challenging issues arise in the design of control techniques for piezoelectric smart structures. Piezoelectric materials have been investigated for use in distributed parameter systems (for example airplane wings, intelligent bridges, etc.) to provide active control efficiently and affordably. Still, no full suppression of the oscillation with this approach has been achieved so far. The controller’s order is then decreased using optimization techniques. Piezoelectric actuators are positioned optimally according to an enhanced optimization method. The outcomes demonstrate that the actuator optimization strategies used in the piezoelectric smart single flexible manipulator system have increased observability in addition to good vibration suppression results.
      Citation: Vibration
      PubDate: 2023-11-08
      DOI: 10.3390/vibration6040058
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 1004-1029: A Few-Shot Learning Based Fault
           Diagnosis Model Using Sensors Data from Industrial Machineries

    • Authors: Farhan Md. Siraj, Syed Tasnimul Karim Ayon, Jia Uddin
      First page: 1004
      Abstract: Efficient maintenance in the face of complex and interconnected industrial equipment is crucial for corporate competitiveness. Traditional reactive approaches often prove inadequate, necessitating a shift towards proactive strategies. This study addresses the challenges of data scarcity and timely defect identification by providing practical guidance for selecting optimal solutions for various equipment malfunction scenarios. Utilizing three datasets—Machine Sound to Machine Condition Monitoring and Intelligent Information (MIMII), Case Western Reserve University (CWRU), and Machinery Failure Prevention Technology (MFPT)—the study employs the Short-Time Fourier Transform (STFT) as a preprocessing method to enhance feature extraction. To determine the best preprocessing technique, Gammatone Transformation, and raw data are also considered. The research optimizes performance and training efficiency by adjusting hyperparameters, minimizing overfitting, and using the KERAS Early Halting API within resource constraints. To address data scarcity, which is one of the major obstacles to detecting faults in the industrial environment, Few-shot learning (FSL) is employed. Various architectures, including ConvNeXt Base, Large MobileNetV3, ResNet-18, and ResNet-50, are incorporated within a prototypical network-based few-shot learning model. MobileNet’s lower parameter count, high accuracy, efficiency, and portability make it the ideal choice for this application. By combining few-shot learning, MobileNet architecture, and STFT preprocessing, this study proposes a practical and data-efficient fault diagnosis method. The model demonstrates adaptability across datasets, offering valuable insights for enhancing industrial fault detection and preventive maintenance procedures.
      Citation: Vibration
      PubDate: 2023-11-14
      DOI: 10.3390/vibration6040059
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 1030-1047: Theoretical and Non-Dimensional
           Investigations into Vibration Control Using Viscoelastic and Endochronic
           Elements

    • Authors: Thomas Kletschkowski
      First page: 1030
      Abstract: Theoretical and non-dimensional investigations have been performed to study the vibration control potential of approaches that are not only based on viscoelastic but also on endochronic elements. The latter are known from the endochronic theory of plasticity and provide the possibility of establishing rate-independent schemes for vibration control. The main question that has to be answered is: Can rate-independent damping be efficiently used to reduce mechanical vibrations' To answer this question, non-dimensional models for dynamical systems are derived and analyzed numerically in the time domain as well as in the frequency domain. The results are used to compare the performance of an optimally tuned endochronic absorber to the performance of an optimally tuned dynamic absorber with viscoelastic damping. Based on a novel closed-form representation for non-linear systems with endochronic elements, it has been possible to prove that the rate-independent control of vibration results in an overall control profit that is close to the control profit obtained by the application of well-established approaches. It has also been found that the new concept is advantageous if anti-resonances have to be considered in broadband vibration control. Based on these novel findings, a practical realization in the context of active vibration control is proposed in which the rate-independent control law is implemented with an appropriate signal processing hardware.
      Citation: Vibration
      PubDate: 2023-11-30
      DOI: 10.3390/vibration6040060
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 1048-1059: Study on Lateral Vibration of Tail
           Coach for High-Speed Train under Unsteady Aerodynamic Loads

    • Authors: Tian Li, Yifan Li, Lai Wei, Jiye Zhang
      First page: 1048
      Abstract: As the speed of high-speed trains increases, the vehicle’s lateral stability steadily deteriorates. There have been observations of abnormal vibrations in the tail car, particularly on certain sections of the railway line. This study built a high-speed train aerodynamic simulation model for a three-car consist, and a multibody dynamics simulation model for an eight-car consist based on numerical simulations of train aerodynamics and multibody dynamics. It investigated both steady and unsteady aerodynamic loads, flow field characteristics, and the dynamic performance of vehicles under varied aerodynamic loads at 400 km/h. The results indicate that the aerodynamic loads generated during high-speed train operation exhibit highly unsteady characteristics. Steady aerodynamic loads have a relatively minor impact on the vehicle’s dynamic performance, whereas unsteady loads exert a more significant influence. Under unsteady aerodynamic forces, the tail car experiences severe lateral vibrations. The lateral stability index, displacement, velocity, and acceleration of the tail car under unsteady conditions were measured at 2.26, 7.54 mm, and 0.53 m/s2, respectively. These values represent increases of over 17.71%, 148.84%, and 111.24%, respectively, compared to the steady loads. Large oscillation amplitudes result in more significant lateral displacements and accelerations of the vehicle. This phenomenon is a crucial factor contributing to the “tail swing” effect observed in high-speed trains. This study emphasizes the importance of considering unsteady aerodynamic effects in assessing the lateral stability of high-speed trains and highlights the significance of mitigating the adverse impacts of such dynamic responses, particularly in the tail car.
      Citation: Vibration
      PubDate: 2023-12-08
      DOI: 10.3390/vibration6040061
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 1060-1074: Study on Fluid–Structure
           Interaction of a Camber Morphing Wing

    • Authors: Yuanjing Wang, Pengxuan Lei, Binbin Lv, Yuchen Li, Hongtao Guo
      First page: 1060
      Abstract: The influence of trailing edge deformation on the aerodynamic characteristics of camber morphing wings is an important topic in the aviation field. In this paper, a new memory alloy actuator is proposed to realize trailing edge deformation, and computational fluid dynamics (CFD) and wind tunnel experiments are used to study the influence of trailing edge deformation on the aerodynamic characteristics of the camber morphing wings. The experiments was carried out in a transonic wind tunnel with Mach numbers ranging from 0.4 to 0.8 and angles of attack ranging from 0° to 6°. The external flow fields and aerodynamic force coefficients with and without deformation were calculated using the CFD method. A loose coupled method based on data exchange was used to achieve a fluid–structure interaction (FSI) analysis. The research results indicate that when the trailing edge is deflected downwards, the phenomenon of shock wave forward movement reduces the negative pressure area on the upper wing surface, increases the pressure on the lower wing surface, and ultimately increases the total lift. This work provides a new approach for the implementation of trailing edge deformation and a powerful data reference for the design of camber morphing wings.
      Citation: Vibration
      PubDate: 2023-12-12
      DOI: 10.3390/vibration6040062
      Issue No: Vol. 6, No. 4 (2023)
       
  • Vibration, Vol. 6, Pages 466-476: Ultrasonic Signal Time-Expansion Using
           DAC Frequency Modulation

    • Authors: Massimiliano Rossi, Marco Frasca
      First page: 466
      Abstract: Ultrasonic signals can be conveniently recorded using modern high-speed analog-to-digital converters and analyzed through digital signal processing algorithms. Sometimes, in some applications, such as in bioacoustics, it is necessary to convert digital data to analog signals with a special transformation that allows compressing and translating the spectrum toward audible frequencies. The process is called time expansion and can be conveniently achieved by slowing down the frequency clock of a digital-to-analog converter. This paper analyzes in detail the spectral characteristics of a time-expanded signal.
      Citation: Vibration
      PubDate: 2023-06-27
      DOI: 10.3390/vibration6030029
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 477-493: Numerical Approach to Optimize the
           Dynamic Behaviour of Structures Considering Structural Durability

    • Authors: William Kaal, Jörg Baumgartner, Maximilian Budnik, Christoph Tamm
      First page: 477
      Abstract: In the design of lightweight structures, both the dynamics and durability must be taken into account. In this paper, a methodology for the combined optimization of structural dynamics, lightweight design, and lifetime with discrete vibration engineering measures is developed and discussed using a demonstration structure. A two-sided welded bending beam is excited at the centre and optimal parameters for tuned mass dampers (TMD) are searched, satisfying the requirements for the dynamic behaviour, the overall mass, and the lifetime of the weldings. It is shown that the combination of a reduced order model with the implementation of the structural stress approach at critical welds enables an efficient evaluation of certain design concepts in the time domain. Using this approach, multi-criterial optimization methods are used to identify the best set of parameters of the TMD to reduce the structural vibrations and enhance the durability.
      Citation: Vibration
      PubDate: 2023-06-29
      DOI: 10.3390/vibration6030030
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 494-511: State-of-the-Art Review on the Seismic
           Performance Assessment of On-Ground Steel Cylindrical Tanks

    • Authors: Mehran S. Razzaghi
      First page: 494
      Abstract: Steel cylindrical tanks are vital structures for storing various types of liquid in industrial plants or as a component in a water distributing system. As they sometimes are used to store toxic, flammable, and explosive material, their inapt performance during an earthquake may lead to catastrophic consequences. Therefore, practicing engineers, researchers, and industry owners are concerned about their structural safety. Meanwhile, the seismic performance of liquid storage tanks is rather complex. Thus, this subject has garnered many researchers’ interest in the past decades. This paper aims to briefly review the most significant studies on the seismic performance of on-ground steel cylindrical tanks. It focuses on analytical approaches and does not include experimental and on-site ones. Finally, the new horizons for the seismic performance assessment of such structures are presented herein.
      Citation: Vibration
      PubDate: 2023-06-29
      DOI: 10.3390/vibration6030031
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 512-535: Influence of the Suspension Model in the
           Simulation of the Vertical Vibration Behavior of the Railway Vehicle Car
           Body

    • Authors: Mădălina Dumitriu, Ioana Izabela Apostol, Dragoș Ionuț Stănică
      First page: 512
      Abstract: The evaluation of the vibration behavior of railway vehicle car bodies based on the results of numerical simulations requires the adoption of an appropriate theoretical model of the suspension which considers the important factors that influence the vibration level of the car body. In this paper, the influence of the secondary suspension model on the vertical vibration behavior of the railway vehicle car body is investigated, based on the results of numerical simulations on the frequency response functions of the acceleration, the power spectral density of the acceleration and the root mean square of the acceleration of the car body. Numerical simulation applications are developed based on a rigid-flexible coupled vehicle model with seven degrees of freedom, corresponding to car body vibration modes: bounce, pitch, and first vertical bending mode, and bogie vibration modes: bounce and pitch. Four different models of secondary suspension are integrated into the vehicle model, namely a reference model and four analysis models. Analysis models include systems through which the pitch vibration of the bogies is transmitted to the car body, influencing its vibration behavior and, respectively, a system that takes the relative angular displacement between the car body and the bogie and a system that models the transmission system of the longitudinal forces between the bogie and the car body are analyzed. The effects of these two systems on the vibration behavior of the railway vehicle car body are analyzed both for each system separately and together. In the conclusions of the paper, the influence of the secondary suspension model on the vibration level at the resonance frequencies of the vertical bending of the car body and the pitch of the bogie is pointed out. It also highlights the important contribution of the transmission system of the longitudinal forces between the bogie and the car body in transmitting pitch vibrations of the bogies to the car body, with effects on the vibration level of the car body at high speeds.
      Citation: Vibration
      PubDate: 2023-07-04
      DOI: 10.3390/vibration6030032
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 536-555: Annoyance Caused by Simultaneous Noise
           and Vibration in Commercial Vehicles: Multimodal Interaction and the
           Effects of Sinusoidal Components in Recorded Seat Vibrations

    • Authors: Maria Mareen Maravich, Robert Rosenkranz, M. Ercan Altinsoy
      First page: 536
      Abstract: Noise and whole-body vibrations (WBV) inside commercial vehicles can lead to annoyance and reduced comfort. As a result, negative effects on the driver can occur even below the legal exposure limits. In order to understand the annoyance perception and the interaction between noise and WBV, two perception experiments were conducted. For both experiments, recorded signals inside different commercial vehicles were used. Sound pressure and acceleration levels varied. In addition, the frequency content of the recorded vertical seat vibrations was reproduced in different modified variants. The varied parameters (sound pressure level, acceleration level and vibration frequency) were investigated within a three-factorial experimental design. It was found that noise and vibration levels, as well as the vibration spectrum, had a significant effect on total annoyance. Furthermore, an interaction between noise and vibration levels in both experiments could be observed. The results show that for the highest noise level, changing vibration exposure influences annoyance ratings less than the lowest noise level. The results also show that despite the same Wk-weighted RMS level of the WBV according to ISO 2631-1, vibration spectra with sinusoidal components or narrowband vibrations below <10 Hz were significantly perceived as more annoying during a ride in a vehicle.
      Citation: Vibration
      PubDate: 2023-07-13
      DOI: 10.3390/vibration6030033
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 556-565: Evaluation of Multi-Compartment Particle
           Dampers for the Attenuation of Dynamic Vibrations

    • Authors: Angeliki Papalou
      First page: 556
      Abstract: An experimental study was performed examining the effectiveness of a multi-compartment damper in attenuating the response of structures under random and earthquake excitations. The damper consisted of four compartments of unequal size; it was mounted on a small one-story steel structure. The same number of steel spherical particles were placed inside each compartment, resulting in filling area ratios (the total area of the squares around the projected particles divided by the area of the compartment) from 40% to 70%. The damper was effective in reducing the response displacement and acceleration of the structure considerably. The use of different filling area ratios enabled the damper to be effective for a wide range of excitation levels.
      Citation: Vibration
      PubDate: 2023-07-14
      DOI: 10.3390/vibration6030034
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 566-583: Effects of Internal Boundary Layers and
           Sensitivity on Frequency Response of Shells of Revolution

    • Authors: Harri Hakula
      First page: 566
      Abstract: New applications introduced capsule designs with features that have not been fully analysed in the literature. In this study, thin shells of revolution are used to model drug delivery capsules both with closed and open designs including perforations. The effects of internal boundary layers and sensitivity on frequency response are discussed in the special case with symmetric concentrated load. The simulations are carried out using high-order finite element method and the frequency response is computed with a very accurate low-rank approximation. Due to the propagation of the singularities induced by the concentrated loads, the most energetic responses do not necessarily include a pinch-through at the point of action. In sensitive configurations, the presence of regions with elliptic curvature leads to strong oscillations at lower frequencies. The amplitudes of these oscillations decay as the frequencies increase. For efficient and reliable analysis of such structures, it is necessary to understand the intricate interplay of loading types and geometry, including the effects of the chosen shell models.
      Citation: Vibration
      PubDate: 2023-07-18
      DOI: 10.3390/vibration6030035
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 584-598: The Application of Micro-Vibratory
           Phenomena of a Shape-Memory Alloy Wire to a Novel Vibrator

    • Authors: Takashi Chujo, Hideyuki Sawada
      First page: 584
      Abstract: The widespread use of smartphones and smart wearable devices has created a great demand for vibrators with complex vibration patterns driven by simple circuits. In our previous studies, we observed that a filiform shape-memory alloy (SMA) wire will shrink and then return to its initial length, perfectly synchronizing with a given pulse current. Here, we developed a novel vibrator whose structure allows the micro-vibrations of an SMA wire to be amplified up to a recognizable level without directly touching the wire. The vibrator has the advantage of independently controlling its magnitude and frequency together with a simple driving circuit since it is directly driven by a frequency-modulated pulse current with a controlled duty ratio. We measured the power consumption and the acceleration generated by the vibrator. The results showed that the vibrator consumed only 4–77 milliwatts of power with a quick vibration response within 5 milliseconds, and the acceleration increased significantly in a duty ratio range of around 1%. Furthermore, user evaluations demonstrated that differences in the magnitude and frequency of the generated vibrations were sufficiently recognized when the vibrator was driven by different duty ratios and frequencies, and the vibrator provided various tactile and haptic sensations to users.
      Citation: Vibration
      PubDate: 2023-07-26
      DOI: 10.3390/vibration6030036
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 599-609: Residual Shift of Vibrotactile
           Perception Thresholds Following Repeated Hand-Arm Vibration Exposure:
           Screening Parameter for Early Signs of Neurosensory Disorders

    • Authors: Nobuyuki Shibata
      First page: 599
      Abstract: Background: The purpose of this study was to validate the applicability of a new screening parameter of VPTW defined as the difference between the ascending and descending thresholds of vibrotactile perception to evaluation of the increasing risk of the neurological components of hand-arm vibration syndrome (HAVS) for repeated exposure to hand-arm vibration (HAV). Methods: Thirty subjects—10 old exposed (G1), 10 old non-exposed (G2), and 10 young non-exposed subjects (G3)—were required to carry out three 3 min grip tasks with exposure to two intensities of HAV at 10 min intervals. Vibration perception measurements, each of which lasted 90 s, were performed at 5 min intervals at the right index finger. Results: VPTWs calculated from pairs of the vibrotactile ascending and descending thresholds at the fingertips were not significantly affected by repeated HAV exposure. Moreover, the VPTWs measured for non-exposed subjects were almost invariant regardless of the subjects’ age or the time elapsed after repeated exposure to HAV. Residual TTSs at 125 Hz gradually recovered in all subject groups under both HAV exposure conditions. The residual TTSs of non-exposed subject groups significantly increased as the number of iterations of HAV exposure increased. Conclusions: VPTWs measured after exposure to repeated HAV are invariant and independent of the individual neurosensory characteristics of the fingertips, which supports the hypothesis that VPTWs can be used as a screening parameter to detect potential patients only with neurosensory components observed as early signs of HAVS.
      Citation: Vibration
      PubDate: 2023-08-01
      DOI: 10.3390/vibration6030037
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 610-624: Uncertainty Propagation and Global
           Sensitivity Analysis of a Surface Acoustic Wave Gas Sensor Using Finite
           Elements and Sparse Polynomial Chaos Expansions

    • Authors: Mohamed Hamdaoui
      First page: 610
      Abstract: The aim of this work is to perform an uncertainty propagation and global sensitivity analysis of a surface acoustic wave (SAW) gas sensor using finite elements and sparse polynomial chaos. The SAW gas sensor is modeled using finite elements (FEM) under COMSOL, and the sensitivity to DCM of its Sezawa mode is considered to be the quantity of interest. The importance of several geometrical (width and PIB thickness), material (PIB Young’s modulus and density), and ambient (pressure, temperature, and concentration) parameters on the sensor’s sensitivity is figured out by means of Sobol’ indices using sparse polynomial chaos expansions. It is shown that when the variability of the input parameters is low (inferior to 5%), the only impacting parameter is the cell width. However, when the variability of the input parameters reaches medium levels (around 10%), all the input parameters except the ambient temperature are impacting the sensor’s sensitivity. It is also reported that in the medium variability case, the sensor’s sensitivity experiences high variations that can lead to a degradation of its performances.
      Citation: Vibration
      PubDate: 2023-08-01
      DOI: 10.3390/vibration6030038
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 625-644: Vibration Measurements by Self-Mixing
           Interferometry: An Overview of Configurations and Benchmark Performances

    • Authors: Silvano Donati
      First page: 625
      Abstract: Self-mixing interferometry (SMI) is suitable to sense and measure vibrations of amplitudes ranging from picometers to millimeters at frequencies from sub-Hz to MHz’sz. As an optical probe, SMI has the advantage of being non-invasive with the ability to measure without any treatment of the target surface and operate from a substantial standoff distance from the target. As an additional advantage, the SMI configuration is much simpler than that of conventional interferometers as it does not require any optical part external to the laser source. After a short introduction to the basics of SMI, we review the development of configurations of SMI instruments for vibration measurements, based on both analog and digital processing, with record performance to cover the range of vibration amplitudes from 0.1 nm to 1 mm, frequencies up to MHz, and stand-off distances up to 100 m. These performances set a benchmark that is unequaled by other approaches reported so far in the literature. The configurations we describe are (i) a simple MEMS-response testing instrument based on fringe counting, (ii) a half-fringe locking vibrometer for mechanical mode analysis and transfer function measurements, with a wide linear response on six decades of amplitude, (iii) a vibrometer with analog switching cancellation for μm-to-mm amplitude of vibrations, and (iv) a long standoff distance vibrometer for testing large structures at distances up to 100 m and with nm sensitivity. Lastly, as the vibrometer will almost invariably operate on untreated, diffusing surfaces, we provide an evaluation of phase-induced speckle pattern errors affecting the SMI measurement.
      Citation: Vibration
      PubDate: 2023-08-02
      DOI: 10.3390/vibration6030039
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 645-658: Focal Muscle Vibration (fMV) for
           Post-Stroke Motor Recovery: Multisite Neuroplasticity Induction, Timing of
           Intervention, Clinical Approaches, and Prospects from a Narrative Review

    • Authors: Alessandro Viganò, Claudia Celletti, Giada Giuliani, Tommaso B. Jannini, Francesco Marenco, Ilaria Maestrini, Rosaceleste Zumpano, Edoardo Vicenzini, Marta Altieri, Filippo Camerota, Vittorio Di Piero, Massimiliano Toscano
      First page: 645
      Abstract: Despite newly available therapies for acute stroke and innovative prevention strategies, stroke remains the third leading cause of disability-adjusted life-years (DALYs) lost worldwide, mostly because more than half of stroke survivors aged 65 and over exhibit an incomplete functional recovery of the paretic limb. Given that a repeated sensory input is one of the most effective modulators of cortical motor and somatosensory structures, focal muscle vibration (fMV) is gaining growing interest as a safe, well-tolerated, and non-invasive brain stimulation technique to promote motor recovery after stroke with a long-lasting and clinically relevant improvement in strength, step symmetry, gait, and kinematics parameters. In this narrative review, we first summarize the structural (neural plasticity) and functional changes (network relearning) triggered by the stroke lesion and carried out at a brain and spinal cord level in an attempt to recover from the loss of function. Then, we will focus on the fMV’s plasticity-based mechanisms reporting evidence of a possible concurrently acting multisite plasticity induced by fMV. Finally, to understand what the most effective fMV rehabilitation protocol could be, we will report the most recent evidence regarding the different clinical approaches and timing of the fMV treatment, the related open issues, and prospects.
      Citation: Vibration
      PubDate: 2023-08-08
      DOI: 10.3390/vibration6030040
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 659-679: Investigation on the Rotordynamic
           Characteristics of Turbopumps with Angular Contact Ball Bearings

    • Authors: Yue Su, Kaifu Xu, Yongqiang Gao, Lu Jin
      First page: 659
      Abstract: The support stiffness of the turbopump rotor system with angular contact ball bearing varies with the rotational speed, which leads to the inaccurate prediction of the dynamics of the turbopump rotor system. The model of the rotor bearing system was constructed based on the theoretical model of angular contact ball bearing stiffness, and the dynamics characteristics of the turbopump system were calculated. To verify the accuracy of the stiffness and the dynamics model, a test system of the turbopump rotor with angular contact ball bearings was designed. Since the bearing stiffness cannot be measured directly, a stiffness identification model was introduced, and an unbalanced response test was conducted to verify the dynamics model. It was found that the turbopump bearing stiffness increased dynamically with speed and reduced the unbalance response of the rotor. The results show that the angular contact ball bearing stiffness model and the dynamics model of the rotor support system are accurate and provide support for the dynamics design of the turbopump rotor system with angular contact ball bearings.
      Citation: Vibration
      PubDate: 2023-08-28
      DOI: 10.3390/vibration6030041
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 680-694: Using Wearable Accelerometers to Develop
           a Vertical Ground Reaction Force Prediction Model during Running: A
           Sensitivity Study

    • Authors: Thomas Provot, Samaneh Choupani, Maxime Bourgain, Laura Valdes-Tamayo, Delphine Chadefaux
      First page: 680
      Abstract: The estimation of vertical ground reaction forces (VGRFs) during running is necessary to understand running mechanisms. For this purpose, the use of force platforms is fundamental. However, to extend the study of VGRFs to real conditions, wearable accelerometers are a promising alternative to force platforms, whose use is often limited to the laboratory environment. The objective of this study was to develop a VGRF model using wearable accelerometers and a stepwise regression algorithm. Several models were developed and validated using the VGRFs and acceleration signals collected during 100 stances performed by one participant. The validated models were tested on eight participants. In a sensitivity study, the strongest correlations were observed at cut-off frequencies of ≤25 Hz and in models developed with 30 to 90 stances. After the validation phase, the 10 best models had, on average, low relative differences (≤10%) in the estimation of discrete VGRF parameters, i.e., the passive peak (εpp=6.26%), active peak (εap=2.22%), and loading rate (εlr=2.17%). The results indicate that the development of personalized models is more suitable for achieving the best estimates. The proposed methodology opens many perspectives for monitoring VGRFs under real conditions using a limited number of wearable sensors.
      Citation: Vibration
      PubDate: 2023-09-12
      DOI: 10.3390/vibration6030042
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 695-712: Vibrational Effects on the Acoustic
           Performance of Multi-Layered Micro-Perforated Metamaterials

    • Authors: Cédric Maury, Teresa Bravo
      First page: 695
      Abstract: Broadband noise reduction over the low–mid frequency range in the building and transportation sectors requires compact lightweight sound absorbers of a typical subwavelength size. The use of multi-layered, closely spaced (micro-)perforated membranes or panels, if suitably optimized, contributes to these objectives. However, their elasticity or modal behaviors often impede the final acoustical performance of the partition. The objective of this study is to obtain insights into the vibrational effects induced by elastic limp membranes or panel volumetric modes on the optimized sound absorption properties of acoustic fishnets and functionally graded partitions (FGP). The cost-efficient global optimization of the partitions’ frequency-averaged dissipation is achieved using the simulated annealing optimization method, while vibrational effects are included through an impedance translation method. A critical coupling analysis reveals how the membranes or panel vibrations redistribute the locations of the Hole-Cavity resonances, as well as their cross-coupling with the panels’ first volumetric mode. It is found that elastic limp micro-perforated membranes broaden the pass-band of acoustic fishnets, while smoothing out the dissipation ripples over the FGP optimization bandwidth. Moreover, the resonance frequency of the first panels mode sets an upper limit to the broadband optimization of FGPs, up to which a high dissipation, high absorption, and low transmission can be achieved.
      Citation: Vibration
      PubDate: 2023-09-17
      DOI: 10.3390/vibration6030043
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 713-725: Quadruped Rotary Galloping Gait Pattern
           within a Constant Radius Bend Using Accelerometry

    • Authors: David Eager, Imam Hossain, Callan Brook
      First page: 713
      Abstract: This paper provides an initial investigation of quadruped rotary galloping gait patterns using data from racing greyhounds as they navigate their way around a constant radius bend. This study reviewed actual race data collected over a five month period from 2986 racing greyhounds. Using numerical dynamics modelling and value range analysis important factors were identified and analysed. By cleaning and synthesising simple X and Y data and also processing data for accuracy greyhound motion path dynamics results were produced for analysis. The results show that the galloping path greyhounds took going into the bend was different from the path coming out of the bend. It also shows that more than 50% of the greyhounds naturally optimised their path for a longer transition while minimising jerk when entering and exiting the bend. This research verified that individual greyhounds naturally chose different path transition lengths for accommodating their dynamic conditions. Finally, it was found that the greyhound galloping path dynamics state is less intense during the second half of the bend.
      Citation: Vibration
      PubDate: 2023-09-20
      DOI: 10.3390/vibration6030044
      Issue No: Vol. 6, No. 3 (2023)
       
  • Vibration, Vol. 6, Pages 319-342: Radio Frequency Cavity’s
           Analytical Model and Control Design

    • Authors: Mahsa Keikha, Jalal Taheri Kahnamouei, Mehrdad Moallem
      First page: 319
      Abstract: Reduction or suppression of microphonic interference in radio frequency (RF) cavities, such as those used in Electron Linear Accelerators, is necessary to precisely control accelerating fields. In this paper, we investigate modeling the cavity as a cylindrical shell and present its free vibration analysis along with an appropriate control scheme to suppress vibrations. To this end, we first obtain an analytical mechanical dynamic model of a nine-cell cavity using a modified Fourier-Ritz method that provides a unified solution for cylindrical shell systems with general boundary conditions. The model is then verified using the ANSYS software in terms of a comparison of eigenfrequencies which prove to be identical to the proposed model. We also present an active observer-based vibration control scheme to suppress the dominant mechanical modes of the cavity. The control system performance is investigated using simulations.
      Citation: Vibration
      PubDate: 2023-03-25
      DOI: 10.3390/vibration6020020
      Issue No: Vol. 6, No. 2 (2023)
       
  • Vibration, Vol. 6, Pages 343-358: Effect of Whole-Body Vibration Exposure
           in Vehicles on Static Standing Balance after Riding

    • Authors: Junya Tatsuno, Setsuo Maeda
      First page: 343
      Abstract: This study aims to investigate the effects of whole-body vibration (WBV) exposure on the disturbance of standing balance function assuming that the cause of slip, trip and fall accidents in the land transportation industry is related to WBV exposure when traveling in vehicles. In the experiment, ten participants underwent 60 min of virtual driving in a driving simulator (DS) for WBV exposure. In addition, standing balance measurements were conducted before exposure, immediately after exposure, 2 min after exposure and 4 min after exposure. Four conditions were considered by combining two magnitudes of WBV exposure and the driver and passenger conditions. This study focused on two indexes of standing balance, namely, total length and enveloped area and the rate of change relative to the value before the vibration exposure was calculated. The rate of change remained almost constant at 1.0 in the control condition without vibration exposure, whereas that under vibration exposure conditions varied. Interestingly, the rate of change at 2 min after exposure remained high in the driver condition, but it decreased to almost 1.0 in the passenger condition. Since no difference appeared in the vibration acceleration measured at the seating surface between the driver and passenger conditions, it was believed that the difference between the driving and passenger conditions was related to fatigue caused by the accelerator-pedal operation. As a result of considering the percentage of the standing balance that returned to 1.0 after 4 min in most conditions, this study proposed that a rest period of several minutes be allowed from the experiment in which the participants were exposed to vibration at 0.5m/s2 rms for 60 min at the DS. Further basic experiments will be conducted to introduce another WBV exposure assessment, including loss of standing balance as a health indicator, to ISO 2631-1.
      Citation: Vibration
      PubDate: 2023-04-01
      DOI: 10.3390/vibration6020021
      Issue No: Vol. 6, No. 2 (2023)
       
  • Vibration, Vol. 6, Pages 359-374: Semi-Analytical Finite-Element Analysis
           

    • Authors: Davide Raffaele, Emiliano Rustighi, Timothy Waters
      First page: 359
      Abstract: The Semi-Analytical Finite-Element (SAFE) method represents one of the most established numerical approaches for predicting the propagation of elastic waves in one-dimensional structures of arbitrary cross-sections. Its implementation in the commercial finite-element software COMSOL Multiphysics has been proposed in recent years; however, it is limited to only the free wave propagation for computing dispersion curves. To overcome this limitation, this paper proposes an extension of this approach that combines COMSOL and its Livelink for Matlab tool. This enables the extraction from COMSOL of the assembled mass and stiffness SAFE matrices to solve problems of both free and forced wave propagation in the Matlab environment. The resulting customised software takes advantage of both the potential of commercial FE software and the power of Matlab without worrying about compatibility issues. A model of a simply supported plate strip and that of a more complex geometry are implemented to validate, respectively, the SAFE matrix extraction procedure and the implemented forced response formulation. The results agree well with corresponding analytical and numerical results validating the proposed implementation of the SAFE method.
      Citation: Vibration
      PubDate: 2023-04-03
      DOI: 10.3390/vibration6020022
      Issue No: Vol. 6, No. 2 (2023)
       
  • Vibration, Vol. 6, Pages 375-397: Influence of Coupling Forces and Body
           Posture on Rotational Hand–Arm Impedance in yh Direction

    • Authors: Tassilo Schröder, Andreas Lindenmann, Sven Matthiesen
      First page: 375
      Abstract: This manuscript investigates the rotational mechanical impedance of the human hand–arm system with vibration excitation along the gripping axis of the hand under the influence of body posture, gripping force, and push force. Knowledge about rotational mechanical impedance is required for deriving models of hand–arm biodynamics. These models are used in power tools validation to predict further vibrational human–machine interactions. In the current state of research, such models exist for translational but not rotational vibration excitation. Consequently, this study investigates the properties of the hand–arm system with rotational vibration excitation. In this study, the rotational impedance of the hand–arm systems of 13 adults was measured with various gripping and push forces applied in different body postures. The test setup of this study consisted of a shaker that applied rotational vibrations at certain frequencies to the subjects’ hand–arm systems via a cylindrical handle. The results of this study indicate a spring-damper dynamic in the hand–arm system. Gripping force strongly influences the magnitude of rotational impedance across the frequency spectrum. For push force and posture, no corresponding influence could be determined. The results suggest that the friction contact between a hand and handle might have a damping effect.
      Citation: Vibration
      PubDate: 2023-04-12
      DOI: 10.3390/vibration6020023
      Issue No: Vol. 6, No. 2 (2023)
       
  • Vibration, Vol. 6, Pages 399-406: Acute Effects of Whole-Body Vibration on
           Quadriceps Isometric Muscular Endurance in Middle-Aged Adults: A Pilot
           Study

    • Authors: Francesca Greco, Federico Quinzi, Katia Folino, Marco Spadafora, Loretta Francesca Cosco, Maria Grazia Tarsitano, Gian Pietro Emerenziani
      First page: 399
      Abstract: This study analysed the acute effects of whole-body vibration (WBV) on quadriceps isometric muscular endurance. Fifteen healthy middle-aged males performed an endurance isometric strength test after three different warm-up conditions: static half squat plus WBV (HSV), static half squat without WBV (HS), and control condition (CC). The endurance isometric strength test consisted of 10 maximal isometric contractions held for 4 s and interspersed by 2 s of rest between each repetition. Rate of Perceived Exertion (RPE) was assessed after warm-up (RPE1) and at the end of the testing session (RPE2). During each testing session, participant’s heart rate (HR) was continuously recorded. For each trial, the mean force across the 10 repetitions and fatigue index were evaluated. Mean force was significantly higher (p < 0.01) in CC than in the other two conditions. Both RPE1 and RPE2 were significantly lower (p < 0.01) in CC than HSV and HS condition. Warm-up HR and the mean testing session HR were significantly lower in CC than the other two conditions (p < 0.01). No significant differences were observed in fatigue index between conditions (p > 0.05) or in HR during the endurance protocol. Performing half-squat with or without vibration stimuli does not increase isometric muscular endurance and does not influence fatigue index.
      Citation: Vibration
      PubDate: 2023-04-22
      DOI: 10.3390/vibration6020024
      Issue No: Vol. 6, No. 2 (2023)
       
  • Vibration, Vol. 6, Pages 407-420: Basic Study on Mechanical Vibration
           Suppression System Using 2-Degree-of-Freedom Vibration Analysis

    • Authors: Keigo Ikeda, Kota Kamimori, Ikkei Kobayashi, Jumpei Kuroda, Daigo Uchino, Kazuki Ogawa, Ayato Endo, Taro Kato, Xiaojun Liu, Mohamad Heerwan Bin Peeie, Hideaki Kato, Takayoshi Narita
      First page: 407
      Abstract: Mechanical vibrations adversely affect mechanical components, and in the worst case, lead to serious accidents by breaking themselves. To suppress vibrations, various studies have been conducted on vibration isolation, suppression, and resistance. In addition, technologies to actively suppress vibration have been rapidly developed in recent years, and it has been reported that vibrations can be suppressed with higher performance. However, these studies have been conducted mostly for low-order systems, and few studies have employed control models that consider the complex vibration characteristics of multi-degree-of-freedom (DOF) systems. This study is a basic study that establishes a control model for complex control systems, and the vibration characteristics of a 2-DOF system are calculated using the vibration analysis of a multi-DOF system. Furthermore, the vibration suppression performance of the 2-DOF system is investigated by performing vibration experiments.
      Citation: Vibration
      PubDate: 2023-05-01
      DOI: 10.3390/vibration6020025
      Issue No: Vol. 6, No. 2 (2023)
       
  • Vibration, Vol. 6, Pages 421-433: Vibration Distribution Measurement of
           Car Door and Engine Head Using OPPA Vibration Distribution Analyzer

    • Authors: Mona Yadi, Yoshiharu Morimoto, Yasuhiro Takaya
      First page: 421
      Abstract: In order to address the issue of vibration, it is crucial to accurately measure the vibration distribution. The authors previously developed the one-pitch phase analysis (OPPA) method, which allows for rapidly capturing the three-dimensional shape of a flat object. By integrating this method into a system, an OPPA vibration distribution measurement system was created, utilizing a line light source consisting of LEDs or optical fibers and also a high-speed camera to measure the vibrations of three-dimensional objects without physical contact. To further extend the application of the OPPA method to larger objects, such as cars, in this paper, a new system is introduced using a commercially available projector using a liquid crystal display (LCD) instead of a liner light source and a glass grating. This new system, which employs an ultra-short throw projector, is highly sensitive in displacement measurements and provides a wide-area analysis. These kinds of projectors produce noises at the frequency of the cooling fan and the refresh rate of the LCD. However, in this study, these noise sources were also examined. The capabilities of the new system are demonstrated through its application to the measurement of vibrations in a car door and an engine head. The measurement system and examples of its application are presented.
      Citation: Vibration
      PubDate: 2023-05-03
      DOI: 10.3390/vibration6020026
      Issue No: Vol. 6, No. 2 (2023)
       
  • Vibration, Vol. 6, Pages 434-448: Assessing the Welfare of Technicians
           during Transits to Offshore Wind Farms

    • Authors: Tobenna D. Uzuegbunam, Rodney Forster, Terry Williams
      First page: 434
      Abstract: Available decision-support tools rarely account for the welfare of technicians in maintenance scheduling for offshore wind farms. This creates uncertainties, especially since current operational limits might make a wind farm accessible but the vibrations from transits might be unacceptable to technicians. We explore technician exposure to vibration in transit based on the levels of discomfort and the likelihood of seasickness occurring on crew transfer vessels (CTVs). Vessel motion monitoring systems deployed on CTVs operating in the North Sea and sea-state data are used in a machine learning (ML) process to model the welfare of technicians based on operational limits applied to modelled proxy variables including composite weighted RMS acceleration (aWRMS) and motion sickness incidence (MSI). The model results revealed poor to moderate performance in predicting the proxies based on selected model evaluation criteria, raising the possibility of more data and relevant variables being needed to improve model performance. Therefore, this research presents a framework for an ML approach towards accounting for the wellbeing of technicians in sailing decisions once the highlighted limitations can be addressed.
      Citation: Vibration
      PubDate: 2023-05-28
      DOI: 10.3390/vibration6020027
      Issue No: Vol. 6, No. 2 (2023)
       
  • Vibration, Vol. 6, Pages 449-465: Vibration Therapy for Cancer-Related
           Bone Diseases

    • Authors: Xin Song, Amel Sassi, Kimberly Seaman, Chun-Yu Lin, Lidan You
      First page: 449
      Abstract: Patients undergoing cancer treatments and/or suffering from metastatic bone lesions experience various skeletal-related events (SREs), substantially reducing functional independence and quality of life. Therefore, researchers are working towards developing new interventions by harnessing the bone’s innate anabolic response to mechanical stimulations. Whole body vibration (WBV) has recently gained interest due to its nature of being safe, effective, and easy to perform. In this review, we will summarize the most cutting-edge vibration studies of cancer models and bone-cancer cell interactions. We will also discuss various parameters, including age, vibration settings, and differences between bone sites, which may affect vibration efficacy. Studies have shown that WBV improves bone mineral density (BMD) and bone volume in patients and mice with cancer. WBV also reduces tumor burden and normalizes bone vasculature in mice. At the cellular level, vibration promotes interactions between bone cells and cancer cells, which reduce osteoclastogenesis and inhibit cancer metastatic potential. Hence, WBV could potentially serve as a new intervention or adjuvant treatment to attenuate cancer progression while preserving bone health.
      Citation: Vibration
      PubDate: 2023-06-08
      DOI: 10.3390/vibration6020028
      Issue No: Vol. 6, No. 2 (2023)
       
  • Vibration, Vol. 6, Pages 29-44: Unsteady Aerodynamic Lift Force on a
           Pitching Wing: Experimental Measurement and Data Processing

    • Authors: Péter Zoltán Csurcsia, Muhammad Faheem Siddiqui, Mark Charles Runacres, Tim De Troyer
      First page: 29
      Abstract: This work discusses the experimental challenges and processing of unsteady experiments for a pitching wing in the low-speed wind tunnel of the Vrije Universiteit Brussel. The setup used for unsteady experiments consisted of two independent devices: (a) a position control device to steer the pitch angle of the wing, and (b) a pressure measurement device to measure the aerodynamic loads. The position control setup can pitch the wing for a range of frequencies, amplitude, and offset levels. In this work, a NACA-0018 wing profile was used with an aspect ratio of 1.8. The position control and the pressure measurement setups operate independently of each other, necessitating advanced signal processing techniques to synchronize the pitch angle and the lift force. Furthermore, there is a (not well-documented) issue with the (sampling) clock frequency of the pressure measurement setup, which was resolved using a fully automated spectral analysis technique. The wing was pitched using a simple harmonic sine excitation signal at eight different offset levels (between 6° and 21°) for a fixed amplitude variation (std) of 6°. At each offset level, the wing was pitched at five different frequencies between 0.1 Hz and 2 Hz (that correspond to reduced frequencies k ranging from 0.006 to 0.125). All the experiments were conducted at a fixed chord-based Reynolds number of 2.85 × 105. The choice of operating parameters invokes the linear and nonlinear behavior of the wing. The linear unsteady measurements agreed with the analytical results. The unsteady pressure measurements at higher offset levels revealed the nonlinear aerodynamic phenomenon of dynamic stall. This confirms that a nonlinear and dynamic model is required to capture the salient characteristics of the lift force on a pitching wing.
      Citation: Vibration
      PubDate: 2023-01-04
      DOI: 10.3390/vibration6010003
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 45-56: Motion Sickness during Roll Motion: VR HMD
           View versus Monitor View

    • Authors: Yahya Sumayli, Ying Ye
      First page: 45
      Abstract: The purpose of this study was to investigate the effect of two views on motion sickness caused by low-frequency roll motion in the laboratory. Fifteen healthy male subjects participated in the study and were exposed to 30 min of 0.25 Hz roll oscillation at an angle of rotation (±5°). Subjects sat on a rigid seat with one of two visual scenes each session: (i) viewing 360° videos through virtual reality (VR) head-mounted display (HMD) device and (ii) reading articles on a monitor in a closed cabin. Ratings of motion sickness were obtained at 1 min intervals. The mean illness ratings of subjects for all visual conditions increased over the 30 min exposure to motion. There was significantly less sickness in the HMD condition than in the monitor condition. The findings suggest a beneficial effect of the HMD view on the severity of sickness. However, the HMD view had no effect on the sickness experienced by those vulnerable to sickness caused by exposure to motion or use of VR. It was concluded that the visual activity had a significant influence on motion sickness induced by 0.25 Hz roll oscillation with an angle of rotation (±5°), and the applications of VR could be implemented to further reduce motion sickness.
      Citation: Vibration
      PubDate: 2023-01-06
      DOI: 10.3390/vibration6010004
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 57-64: Asymptotic Formulation for the Rayleigh
           Wave on a Nonlocally Elastic Half-Space

    • Authors: Danila A. Prikazchikov
      First page: 57
      Abstract: This paper deals with the Rayleigh wave, propagating on a nonlocally elastic, linearly isotropic half-space, excited by a prescribed surface loading. The consideration develops the methodology of hyperbolic–elliptic models for Rayleigh and Rayleigh-type waves, and relies on the effective boundary conditions formulated recently, accounting for the crucial contributions of the nonlocal boundary layer. A slow-time perturbation scheme is established, leading to the reduced model for the Rayleigh wave field, comprised of a singularly perturbed hyperbolic equation for the longitudinal wave potential on the surface, acting as a boundary condition for the elliptic equation governing the decay over the interior. An equivalent alternative formulation involving a pseudo-differential operator acting on the loading terms, with parametric dependence on the depth coordinate, is also presented.
      Citation: Vibration
      PubDate: 2023-01-07
      DOI: 10.3390/vibration6010005
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 65-81: Investigations into Nonlinear Effects of
           Normal Pressures on Dynamic Cyclic Responses of Novel 3D-Printed TPMS
           Bridge Bearings

    • Authors: Pasakorn Sengsri, Sakdirat Kaewunruen
      First page: 65
      Abstract: Bridge bearings are one of the most important components in bridge systems. Typical bearings are extensively used in small- to medium-span highway bridges since they are economical and offer a good performance at service-level conditions. On the other hand, common bridge bearings possess a low performance-to-weight ratio under combined compression and shear loading conditions (low crashworthiness and specific energy absorption), due to their heavy weight, high costs, and the non-recyclability of steel and elastomer materials. With the help of a relatively higher ratio of a 3D-printed triply periodic minimal surface (TPMS) structure, this method can potentially be used for bridge bearing applications. However, the cyclic responses of this TPMS structure used in bearings have never been completely investigated. This study is the world’s first to investigate the effects of normal pressure on the cyclic responses of novel 3D-printed TPMS bridge bearings. A numerical TPMS unit cell model considering the effects of normal pressure on cyclic responses of a novel TPMS bridge bearing is developed and validated with experimental data. The numerical results reveal new insights related to the nonlinear effects of normal pressure on the cyclic behaviours of 3D-printed TPMS bearings. Higher normal pressures result in a higher degree of nonlinearity in the dynamic cyclic responses of the 3D-printed TPMS bearings.
      Citation: Vibration
      PubDate: 2023-01-11
      DOI: 10.3390/vibration6010006
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 82-101: Free Vibration Characteristics of
           Multi-Material Lattice Structures

    • Authors: Kadir Gunaydin, Ahmet Yavuz, Aykut Tamer
      First page: 82
      Abstract: This paper presents a modal analysis of honeycomb and re-entrant lattice structures to understand the change in natural frequencies when multi-material configuration is implemented. For this purpose, parallel nylon ligaments within re-entrant and honeycomb lattice structures are replaced with chopped and continuous carbon fibre to constitute multi-material lattice configurations. For each set, the first five natural frequencies were compared using detailed finite element models. For each configuration, three different boundary conditions were considered, which are free–free and clamping at the two sides that are parallel and perpendicular to the vertical parts of the structure. The comparison of the natural frequencies was based on mode-shape matching using modal assurance criteria to identify the correct modes of different configurations. The results showed that the natural frequency of the multi-material configurations increases from 4% to 18% depending on the configuration and material.
      Citation: Vibration
      PubDate: 2023-01-16
      DOI: 10.3390/vibration6010007
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 102-112: Effectiveness of the Seesaw System as a
           Means of Seismic Upgrading in Older, Non-Ductile Reinforced Concrete
           Buildings

    • Authors: Panagiota S. Katsimpini, George A. Papagiannopoulos
      First page: 102
      Abstract: This work investigates and discusses the effectiveness of the seesaw system when installed in an older, non-ductile reinforced concrete (RC) building for seismic upgrading purposes. In particular, two different configurations of the seesaw system are assumed in a two-storey 3D RC framed building which was designed according to older seismic provisions and, thus, is susceptible to flexural and shear failures. To check if there is any merit in employing the seesaw system in this RC building, non-linear time-history (NLTH) analyses are conducting using 11 seismic motions. Peak values for inter-story drift ratios (IDR), residual inter-story drift ratios (RIDR) and floor accelerations (FA) are computed, and the sequence and cause (i.e., due to surpass of flexural or shear strength) of plastic hinge formations are monitored. Leaving aside any issues related to fabrication and cost, interpretation of the results obtained by the aforementioned seismic response indices for the RC building under study leads to the conclusion that the seesaw system can be a retrofitting scheme for the seismic upgrading of older, non-ductile RC framed buildings.
      Citation: Vibration
      PubDate: 2023-01-21
      DOI: 10.3390/vibration6010008
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 113-146: On the Critical Velocity of Moving Force
           and Instability of Moving Mass in Layered Railway Track Models by
           Semianalytical Approaches

    • Authors: Zuzana Dimitrovová
      First page: 113
      Abstract: This article presents a comparison between layered models of a railway track. All analyses are based on semianalytical approaches to show how powerful they can be. Results are presented in dimensionless form, making them applicable to a wide range of possible real-world scenarios. The main results and conclusions are obtained using repeated exact calculations of the equivalent flexibility of supporting structure related to each model by contour integration. New terms and a fundamentally different approach with respect to other published works underline the scientific contribution to this field. Semianalytical methods demonstrate that the intended results can be obtained easily and accurately. However, this benefit cannot be extended to a large number of models due to the simplifications that must be introduced in order to apply such methods. It turns out that even though the one-layer model is the furthest away from reality, it is easy to handle analytically because it has a regular and predictable behavior. The three-layer model, on the other hand, has many unpredictable properties that will be detailed in this article.
      Citation: Vibration
      PubDate: 2023-01-26
      DOI: 10.3390/vibration6010009
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 147-148: Acknowledgment to the Reviewers of
           Vibration in 2022

    • Authors: Vibration Editorial Office Vibration Editorial Office
      First page: 147
      Abstract: High-quality academic publishing is built on rigorous peer review [...]
      Citation: Vibration
      PubDate: 2023-01-28
      DOI: 10.3390/vibration6010010
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 149-164: Vibration Transmission across
           Seismically Damaged Beam-to-Column Junctions of Reinforced Concrete Using
           Statistical Energy Analysis

    • Authors: Marios Filippoupolitis, Carl Hopkins
      First page: 149
      Abstract: To detect human survivors trapped in buildings after earthquakes by using structure-borne sound it is necessary to have knowledge of vibration transmission in collapsed and fragmented reinforced-concrete buildings. In this paper, statistical energy analysis (SEA) is considered for modelling vibration transmission in seismically damaged, reinforced concrete, beam-to-column junctions where the connection between the beam and the column is made only via the steel reinforcement. An ensemble of 30 randomly damaged beam-to-column junctions was generated using a Monte Carlo simulation with FEM. Experimental SEA (ESEA) is then considered with two or three subsystems to determine the coupling loss factors (CLFs) between the beam and the column with either bending modes or the combination of all mode types. It is shown that bending modes dominate the dynamic response and that the uncertainty of predicting the CLFs using FEM with ESEA is sufficiently low that it should be feasible to estimate the coupling even when the exact angle between the beam and the column is unknown. In addition, the use of two rather than three subsystems for the junction significantly decreases the number of negative coupling loss factors with ESEA. An initial analysis of the results in this paper was presented at the 50th International Congress and Exposition on Noise Control Engineering.
      Citation: Vibration
      PubDate: 2023-02-02
      DOI: 10.3390/vibration6010011
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 165-194: Gender and Anthropometric Effects on
           Seat-to-Head Transmissibility Responses to Vertical Whole-Body Vibration
           of Humans Seated on an Elastic Seat

    • Authors: Yumeng Yao, Krishna N. Dewangan, Subhash Rakheja
      First page: 165
      Abstract: This study investigated the effects of gender and ten different anthropometric parameters on the vertical vibration transmission from seat to the head of the body seated on an elastic seat. The seat-to-head transmissibility (STHT) responses in the vertical and fore-aft directions of 58 participants (31 males and 27 females) were measured under three levels of vertical vibration (root mean square acceleration: 0.25, 0.50, and 0.75 m/s2) in the 0.50–20 Hz range, when sitting on a viscoelastic seat with and without a vertical back support, and with hands on a steering wheel. Apart from the important effects of elastic coupling between the body and seat, the results show distinctly different vertical and fore-aft STHT responses from the two genders. Moreover, the gender effect was strongly coupled with back support and excitation conditions. The primary resonance frequencies of male subjects were higher than those of female subjects, while the peak vertical STHT magnitudes were comparable. Owing to the strong coupled effects of gender and anthropometric dimensions, the study is designed to reduce the coupling by considering datasets for subjects with comparable chosen dimensions. Among the various anthropometric dimensions considered, the body mass and fat mass revealed strong influences on the primary resonance frequency, which was similar for male and female subjects with comparable body mass index and body fat mass. The vertical STHT magnitude of the two genders with the same lean body mass was also nearly identical. The peak fore-aft STHT magnitudes of the male subjects were notably higher than those of the female subjects with comparable anthropometric dimensions with the exception of the body mass.
      Citation: Vibration
      PubDate: 2023-02-08
      DOI: 10.3390/vibration6010012
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 195-217: Influence of Coexistence of Pitting and
           Cracking Faults on a Two-Stage Spur Gear System

    • Authors: Kemajou Herbert Yakeu Happi, Bernard Xavier Tchomeni Kouejou, Alfayo Anyika Alugongo
      First page: 195
      Abstract: This work considers forced vibrations in a rotating structure consisting of a two-stage spur gear system with coexisting defects, specifically pitting and cracking. Numerical simulations and experimental analysis in various scenarios of the system in operation were conducted using the RPM–Frequency mapping technique. To identify fault characteristics, the analysis performed assumed the gear system had been misadjusted by a combination of pitting and cracking on the gear teeth. The correlation of the system-forced responses under regular and chaotic vibrations revealed that the system is far more sensitive to the crack than to the pitting when there are fluctuating harmonic peaks present at high vibration levels.
      Citation: Vibration
      PubDate: 2023-02-08
      DOI: 10.3390/vibration6010013
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 218-238: Deep Transfer Learning Models for
           Industrial Fault Diagnosis Using Vibration and Acoustic Sensors Data: A
           Review

    • Authors: Md Roman Bhuiyan, Jia Uddin
      First page: 218
      Abstract: In order to evaluate final quality, nondestructive testing techniques for finding bearing flaws have grown in favor. The precision of image processing-based vision-based technology has greatly improved for defect identification, inspection, and classification. Deep Transfer Learning (DTL), a kind of machine learning, combines the superiority of Transfer Learning (TL) for knowledge transfer with the benefits of Deep Learning (DL) for feature representation. As a result, the discipline of Intelligent Fault Diagnosis has extensively developed and researched DTL approaches. They can improve the robustness, reliability, and usefulness of DL-based fault diagnosis techniques (IFD). IFD has been the subject of several thorough and excellent studies, although most of them have appraised important research from an algorithmic standpoint, neglecting real-world applications. DTL-based IFD strategies have also not yet undergone a full evaluation. It is necessary and imperative to go through the relevant DTL-based IFD publications in light of this. Readers will be able to grasp the most cutting-edge concepts and develop practical solutions to any IFD challenges they may encounter by doing this. The theory behind DTL is briefly discussed before describing how transfer learning algorithms may be included into deep learning models. This research study looks at a number of vision-based methods for defect detection and identification utilizing vibration acoustic sensor data. The goal of this review is to assess where vision inspection system research is right now. In this respect, image processing as well as deep learning, machine learning, transfer learning, few-shot learning, and light-weight approach and its selection were explored. This review addresses the creation of defect classifiers and vision-based fault detection systems.
      Citation: Vibration
      PubDate: 2023-02-17
      DOI: 10.3390/vibration6010014
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 239-254: Study of an Optimized Mechanical
           Oscillator for the Forced Vibration of the Soil Cutting Blade

    • Authors: Dario Friso
      First page: 239
      Abstract: In the nursery sector, the transport and planting of trees must occur with the roots wrapped in a ball of the original earth. The cutting of the original soil can be carried out with a semicircular vibrating blade moved by an oscillator mounted on a self-propelled machine. The oscillator produces an excitation torque supplied to the blade together with the soil cutting torque. The advantage of the vibrating blade is a reduction in the cutting torque of up to 70%. However, to correctly design the oscillator, we need to investigate the link between the maximum displacement of the blade, the maximum oscillation velocity, the cutting velocity, the dry friction, the excitation torque, the elastic torque, the cutting torque, the required power, the required energy, and the excitation frequency. The maximum displacement and velocity ratio need to have the right values to minimize the cutting torque and to avoid the springs reaching the end of stroke; otherwise, vibrations are transmitted to the machine and to the operator. Therefore, starting from the forced oscillation differential equation and using an approximate solution method developed by Den Hartog, along with some experimental data, a mathematical model was constructed to optimize the oscillator design. After construction, it was coupled to blades of various diameters (0.6, 0.9, and 1.2 m) to undergo experimental tests. The soil cutting tests highlighted the achievement of the above objectives and, at the same time, confirmed the validity of the Den Hartog equations used to calculate the phase lag and the maximum displacement, resulting in an average error of 4.4% and a maximum error of 6.4%.
      Citation: Vibration
      PubDate: 2023-02-21
      DOI: 10.3390/vibration6010015
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 255-268: Usability and Vibration Analysis of a
           Low-Profile Automatic Powered Wheelchair to Motor Vehicle Docking System

    • Authors: Chang Dae Lee, Brandon J. Daveler, Jorge L. Candiotti, Rosemarie Cooper, Sivashankar Sivakanthan, Nikitha Deepak, Garrett G. Grindle, Rory A. Cooper
      First page: 255
      Abstract: The QLX is a low-profile automatic powered wheelchair docking system (WDS) prototype developed to improve the securement and discomfort of wheelchair users when riding in vehicles. The study evaluates the whole-body vibration effects between the proposed QLX and another WDS (4-point tiedown system) following ISO 2631-1 standards and a systematic usability evaluation. Whole-body vibration analysis was evaluated in wheelchairs using both WDS to dock in a vehicle while riding on real-world surfaces. Also, participants rated the usability of each WDS while driving a wheelchair and while riding in a vehicle in driving tasks. Both WDSs showed similar vibration results within the vibration health-risk margins; but shock values below health-risk margins. Fifteen powered wheelchair users reported low task load demand to operate both WDS; but better performance to dock in vehicles with the QLX (p = 0.03). Also, the QLX showed better usability (p < 0.01), less discomfort (p’s < 0.05), and greater security compared to the 4-point tiedown while riding in a vehicle (p’s < 0.05). Study findings indicate that both WDS maintain low shock exposure for wheelchair users while riding vehicles, but a better performance overall to operate the QLX compared to the 4-point tiedown system; hence enhancing user’s autonomy to dock in vehicles independently.
      Citation: Vibration
      PubDate: 2023-02-24
      DOI: 10.3390/vibration6010016
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 269-285: Free and Forced Vibration Behaviors of
           Magnetodielectric Effect in Magnetorheological Elastomers

    • Authors: Jafari, Sedaghati
      First page: 269
      Abstract: This paper is concerned with the free and forced vibration responses of a magneto/electroactive dielectric elastomer, emphasizing the chaotic phenomena. The dielectric elastomers under external magnetic and electrical excitations undergo large elastic deformation. The magnetodielectric elastomer is modeled based on the Gent–Gent strain energy function to incorporate the influence of the second invariant and the strain stiffening. The viscoelasticity of the active polymer is also considered in the form of Rayleigh’s dissipation function. The equation of motion is governed with the aid of the Lagrangian equation in terms of a physical quantity, namely, the stretch of the elastomer. An energy-based approach is utilized to re-evaluate the static and DC voltage instabilities of the resonator. Time-stretch response (time history behavior), phase plane diagram, Poincaré map, and fast Fourier transform are numerically obtained and presented to explore the chaotic oscillation behavior of the active polymer actuators. The results reveal that the magnetic field may tune the stability and instability regions of the active polymeric membrane. It has also been shown that the applied magnetic field may lead to chaotic vibration responses when a sinusoidal voltage is applied simultaneously to the system. The results presented in this paper can be effectively used to design magnetic and electrical soft robotic actuators and elastomer membranes under electrical and magnetic stimulants.
      Citation: Vibration
      PubDate: 2023-03-03
      DOI: 10.3390/vibration6010017
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 286-302: Adaptive Notch Filter in a Two-Link
           Flexible Manipulator for the Compensation of Vibration and Gravity-Induced
           Distortion

    • Authors: Minoru Sasaki, Joseph Muguro, Waweru Njeri, Arockia Selvakumar Arockia Doss
      First page: 286
      Abstract: This paper presents a 2-link, 2-DOF flexible manipulator control using an inverse feedforward controller and an adaptive notch filter with a direct strain feedback controller. In the flexible manipulator, transient and residue vibrations inhibit the full potential of the manipulator. Vibrations caused by abrupt changes in the direction of the links are referred to as transient vibrations, whereas residual vibrations occur when the arm takes too long to settle after engaging in the intended task. The feedforward adaptive notch filter will reduce transient vibration caused by the manipulator arm beginning and halting suddenly, while the strain feedback will assure the quick decay of leftover vibrations. Maple, Maplesim, and MATLAB tools were used to model the manipulator and create the inverse controller and adaptive notch filter. The experiments took place in the dSPACE control desk environment. The experimental results of the spectral power of strain resulting from the two strategies are compared. From the results, the adaptive notch filter control had over an 80% improvement in the reduction in resonant frequencies that contribute to vibration. The results confirmed the feasibility of the approach, characterized by very minimal transient vibrations and a quick settling of the end effector.
      Citation: Vibration
      PubDate: 2023-03-10
      DOI: 10.3390/vibration6010018
      Issue No: Vol. 6, No. 1 (2023)
       
  • Vibration, Vol. 6, Pages 303-318: Prescribed Performance Control-Based
           Semi-Active Vibration Controller for Seat Suspension Equipped with an
           Electromagnetic Damper

    • Authors: Junjie Zhao, Pengfei Liu, Dingxin Leng, Haoyu Zhan, Guangrui Luan, Donghong Ning, Jianqiang Yu
      First page: 303
      Abstract: Seat suspension plays a vital role in improving riding comfort and protecting drivers’ health. This paper develops semi-active seat suspension that equips a controllable electromagnetic damper (EMD) and proposes a prescribed performance control-based semi-active vibration controller with experimental validation. The semi-active EMD mainly consists of a permanent magnet synchronous motor, a ball screw, a three-phase rectifier, and a controllable external resistor, which can vary its damping from 90 to 800 N·s/m by tuning the controllable external resistor in real-time. The EMD is applied to seat suspension, and a semi-active controller is proposed for the EMD seat suspension. In order to control the seat suspension vibration, a prescribed performance method is applied to obtain a desired control force and then a force-tracking strategy is designed to make the EMD track the desired control force. Finally, the semi-active seat suspension with the proposed controller is tested in experiments with different vibration conditions. The semi-active seat suspension performs excellently for the bump, sine wave and random vibration. The root mean square (RMS) acceleration, the frequency-weighted RMS acceleration and the acceleration’s fourth power vibration dose value were reduced by 17.5%, 39.9%, and 25.4%, respectively, in the random vibration, compared with a passive system.
      Citation: Vibration
      PubDate: 2023-03-11
      DOI: 10.3390/vibration6010019
      Issue No: Vol. 6, No. 1 (2023)
       
 
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The European Physical Journal H     Hybrid Journal   (Followers: 2)
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