Vibration

15 pages, 5035 KB

Open AccessArticle

Effectiveness of Dynamic Vibration Absorber on Ground-Borne Vibration Induced by Metro

by Javad Sadeghi, Alireza Toloukian and Sogand Mehravar

Vibration 2025, 8(4), 62; https://doi.org/10.3390/vibration8040062 - 5 Oct 2025

The application of dynamic vibration absorbers (DVAs) is a countermeasure to suppress vibrations induced by railway traffic. A key advantage of the DVA application is that it does not require any changes to the path of vibration propagation or the receiver of vibration. [...] Read more.

The application of dynamic vibration absorbers (DVAs) is a countermeasure to suppress vibrations induced by railway traffic. A key advantage of the DVA application is that it does not require any changes to the path of vibration propagation or the receiver of vibration. A review of the literature reveals the necessity of deriving the optimum properties of DVA to mitigate railway vibrations. To this end, the optimum DVA properties were investigated through the development of a two-dimensional finite element model of the track-tunnel-soil system. The model was validated using the results of a field test. A parametric study was made to obtain the optimum properties of DVA for different soils surrounding the tunnel. The results of the model analysis indicate that the DVA has better vibration reduction for metro tunnels built in soft soils as compared to those surrounded by medium and stiff soils. Also, the results disclose that the DVA reduces vibration radiated on the ground surface when the DVA natural frequency is tuned to a low frequency. Using the results of the parametric study, graphs are suggested to select the optimum properties of the DVA as a function of the soil around the tunnel. Full article

(This article belongs to the Special Issue Railway Dynamics and Ground-Borne Vibrations)

12 pages, 776 KB

Open AccessArticle

Mounted Accelerometer Frequency Response of Adhesive Products and Aluminum Frame Quick Mounts

by Kenton Hummel, Jay Hix and Edna Cárdenas

Vibration 2025, 8(4), 61; https://doi.org/10.3390/vibration8040061 - 3 Oct 2025

Abstract

An accelerometer mounting technique has large implications on the frequency range and accuracy of the measurement, with stiffness and the mass relative to the monitored structure as the primary concerns. The International Organization for Standardization (ISO) gives an extensive list in 5348:2021, detailing [...] Read more.

An accelerometer mounting technique has large implications on the frequency range and accuracy of the measurement, with stiffness and the mass relative to the monitored structure as the primary concerns. The International Organization for Standardization (ISO) gives an extensive list in 5348:2021, detailing mounting methods, and provides recommendations for testing mounts that are not specifically defined. In the nuclear industry on the laboratory scale, there is a need for vibration measurements for predictive maintenance and process monitoring that are nondestructive and capable of working in high-temperature environments. Commercial adhesive products with easy application and removal were tested as nondestructive methods, while quick mounts to a commonly used aluminum frame were tested as nondestructive and have potential applicability in high-temperature environments. The sinusoidal excitation method was used, measuring frequencies from 50 Hz to 10 kHz in one-third octave band intervals, utilizing three accelerometers and comparing the results to those obtained with the stud-mounting method. Using the lowest ±3 dB threshold across each accelerometer, foam dots and poster strips were not successful, and foam tapes were accurate up to 2000 Hz, hose clamps and zip ties up to 800 Hz, and a custom 3D printed mount up to 1000 Hz. Knowing the limitations of each mounting technique allows for accurate measurements within the appropriate range. Full article

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21 pages, 2866 KB

Open AccessArticle

Evaluation of the Adaptive Behavior of a Shell-Type Elastic Element of a Drilling Shock Absorber with Increasing External Load Amplitude

by Andrii Velychkovych, Vasyl Mykhailiuk and Andriy Andrusyak

Vibration 2025, 8(4), 60; https://doi.org/10.3390/vibration8040060 - 2 Oct 2025

Abstract

Vibration loads during deep drilling are one of the main causes of reduced service life of drilling tools and emergency failure of downhole motors. This work investigates the adaptive operation of an original elastic element based on an open cylindrical shell used as [...] Read more.

Vibration loads during deep drilling are one of the main causes of reduced service life of drilling tools and emergency failure of downhole motors. This work investigates the adaptive operation of an original elastic element based on an open cylindrical shell used as part of a drilling shock absorber. The vibration protection device contains an adjustable radial clearance between the load-bearing shell and the rigid housing, which provides the effect of structural nonlinearity. This allows effective combination of two operating modes of the drilling shock absorber: normal mode, when the clearance does not close and the elastic element operates with increased compliance; and emergency mode, when the clearance closes and gradual load redistribution and increase in device stiffness occur. A nonconservative problem concerning the contact interaction of an elastic filler with a coaxially installed shaft and an open shell is formulated, and as the load increases, contact between the shell and the housing, installed with a radial clearance, is taken into account. Numerical finite element modeling is performed considering dry friction in contact pairs. The distributions of radial displacements, contact stresses, and equivalent stresses are examined, and deformation diagrams are presented for two loading modes. The influence of different cycle asymmetry coefficients on the formation of hysteresis loops and energy dissipation is analyzed. It is shown that with increasing load, clearance closure begins from local sectors and gradually covers almost the entire outer surface of the shell. This results in deconcentration of contact pressure between the shell and housing and reduction of peak concentrations of equivalent stresses in the open shell. The results confirm the effectiveness of the adaptive approach to designing shell shock absorbers capable of reliably withstanding emergency overloads, which is important for deep drilling where the exact range of external impacts is difficult to predict. Full article

(This article belongs to the Special Issue Vibration Damping)

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13 pages, 3175 KB

Open AccessArticle

Enhancement of Inner Race Fault Features in Servo Motor Bearings via Servo Motor Encoder Signals

by Yubo Lyu, Yu Guo, Jiangbo Li and Haipeng Wang

Vibration 2025, 8(4), 59; https://doi.org/10.3390/vibration8040059 - 1 Oct 2025

Abstract

This study proposes a novel framework to enhance inner race fault features in servo motor bearings by acquiring rotary encoder-derived instantaneous angular speed (IAS) signals, which are obtained from a servo motor encoder without requiring additional external sensors. However, such signals are often [...] Read more.

This study proposes a novel framework to enhance inner race fault features in servo motor bearings by acquiring rotary encoder-derived instantaneous angular speed (IAS) signals, which are obtained from a servo motor encoder without requiring additional external sensors. However, such signals are often obscured by strong periodic interferences from motor pole-pair and shaft rotation order components. To address this issue, three key improvements are introduced within the cyclic blind deconvolution (CYCBD) framework: (1) a comb-notch filtering strategy based on rotation domain synchronous averaging (RDA) to suppress dominant periodic interferences; (2) an adaptive fault order estimation method using the autocorrelation of the squared envelope spectrum (SES) for robust localization of the true fault modulation order; and (3) an improved envelope harmonic product (IEHP), based on the geometric mean of harmonics, which optimizes the deconvolution filter length. These combined enhancements enable the proposed improved CYCBD (ICYCBD) method to accurately extract weak fault-induced cyclic impulses under complex interference conditions. Experimental validation on a test rig demonstrates the effectiveness of the approach in enhancing and extracting the fault-related features associated with the inner race defect. Full article

(This article belongs to the Special Issue Vibration in 2025)

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23 pages, 3652 KB

Open AccessArticle

Vibration Control of a Two-Link Manipulator Using a Reduced Model

by Amir Mohamad Kamalirad and Reza Fotouhi

Vibration 2025, 8(4), 58; https://doi.org/10.3390/vibration8040058 - 1 Oct 2025

Abstract

This research aims to actively suppress vibrations at the end-effector of a flexible manipulator. When configured in a locked state, the system behaves as a two-link manipulator subjected to disturbances on the first link. To analyze its behavior, Finite Element Analysis (FEA) is [...] Read more.

This research aims to actively suppress vibrations at the end-effector of a flexible manipulator. When configured in a locked state, the system behaves as a two-link manipulator subjected to disturbances on the first link. To analyze its behavior, Finite Element Analysis (FEA) is employed to extract the natural frequencies (eigenvalues) and corresponding mode shapes (eigenvectors) of a two-link, two-joint flexible manipulator (2L2JM). The obtained eigenvectors are transformed into uncoupled state-space equations using balanced realization and the Match-DC-Gain model reduction algorithm. An H-infinity controller is then designed and applied to both the full-order and reduced-order models of the manipulator. The objective of this study is to validate an analytical framework through FEA, demonstrating its applicability to complex manipulators with multiple joints and flexible links. Given that the full state-space representation typically results in high-dimensional matrices, model reduction enables effective vibration control with a minimal number of states. The derivation of the 2L2JM state space, its model reduction, and a subsequent control strategy have not been previously addressed in this manner. Simulation results showcasing vibration suppression of a cantilever beam are presented and benchmarked against two alternative modeling approaches. Full article

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23 pages, 11214 KB

Open AccessArticle

Influence of Random Parametric Errors on Nonlinear Dynamic Behaviors of a Laminated Composite Cantilever Beam

by Lin Sun, Xudong Li and Xiaopei Liu

Vibration 2025, 8(4), 57; https://doi.org/10.3390/vibration8040057 - 29 Sep 2025

Abstract

For the first time, the influence of random parametric errors (RPEs) on the nonlinear dynamic behaviors of a laminated composite cantilever beam (LCCB) is studied. A nonlinear dynamic model for the LCCB is first established based on Hamilton’s principle. In a numerical simulation, [...] Read more.

For the first time, the influence of random parametric errors (RPEs) on the nonlinear dynamic behaviors of a laminated composite cantilever beam (LCCB) is studied. A nonlinear dynamic model for the LCCB is first established based on Hamilton’s principle. In a numerical simulation, four different cases are presented to analyze the dynamic behavior of the studied LCCB. This study reveals that varying RPE levels cause significant changes in the dynamic response of the LCCB. The results indicate that RPE not only induces a transition from a periodic to a chaotic behavior but may also alter the maximum amplitude of chaotic vibrations, providing a critical theoretical basis for incorporating uncertainty factors in engineering design. Full article

34 pages, 16346 KB

Open AccessReview

A Review on Vibration Sensor: Key Parameters, Fundamental Principles, and Recent Progress on Industrial Monitoring Applications

by Limin Ma, Zhangpeng Li, Shengrong Yang and Jinqing Wang

Vibration 2025, 8(4), 56; https://doi.org/10.3390/vibration8040056 - 25 Sep 2025

Abstract

This paper presents a systematic review of vibration sensors and their application in industrial-monitoring systems, aiming to provide a comprehensive reference for both academic research and practical applications in this field. Through the classification of measured parameters and sensing principles, this work endeavors [...] Read more.

This paper presents a systematic review of vibration sensors and their application in industrial-monitoring systems, aiming to provide a comprehensive reference for both academic research and practical applications in this field. Through the classification of measured parameters and sensing principles, this work endeavors to establish a structured understanding of vibration sensor’s working mechanism and deliver an in-depth analysis of their recent research achievements. By integrating practical cases from typical domains, this manuscript comprehensively demonstrates the practical value and application potential of vibration sensors in equipment-monitoring systems, illustrating how these sensors are utilized to detect mechanical failures and enhance the performance and safety of industrial systems, such as wind turbine, tunnel boring machine, and aerospace engine. Looking forward, with the rapid advancement of the Internet of Things (IoT) and artificial intelligence (AI) technologies, vibration sensors are anticipated to evolve towards multifunctionalization, miniaturization and intelligentization, thereby forming a comprehensive monitoring network that improves overall efficiency and reliability of the mechanical systems. Full article

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21 pages, 20900 KB

Open AccessArticle

Balancing Accuracy and Efficiency in Wire-Rope Isolator Modeling: A Simplified Beam-Element Framework

by Claudia Marin-Artieda

Vibration 2025, 8(3), 55; https://doi.org/10.3390/vibration8030055 - 22 Sep 2025

Abstract

Wire-rope isolators (WRIs) are widely used in vibration and seismic protection due to their multidirectional flexibility and amplitude-dependent hysteretic damping. However, their complex nonlinear behavior, especially under inclined and combined-mode loading, poses challenges for predictive modeling. This study presents a simplified finite-element modeling [...] Read more.

Wire-rope isolators (WRIs) are widely used in vibration and seismic protection due to their multidirectional flexibility and amplitude-dependent hysteretic damping. However, their complex nonlinear behavior, especially under inclined and combined-mode loading, poses challenges for predictive modeling. This study presents a simplified finite-element modeling framework using constant-property Timoshenko beam elements with tuned Rayleigh damping to simulate WRI behavior across various configurations. Benchmark validation against analytical ring deformation confirmed the model’s ability to capture geometric nonlinearities. The framework was extended to five WRI types, with effective cross-sectional properties calibrated against vendor-supplied quasi-static data. Dynamic simulations under sinusoidal excitation demonstrated strong agreement with experimental force-displacement loops in pure modes and showed moderate accuracy (within 29%) in inclined configurations. System-level validation using a rocking-control platform with four inclined WRIs showed that the model reliably predicts global stiffness and energy dissipation under base accelerations. While the model does not capture localized nonlinearities such as pinched hysteresis due to interstrand friction, it offers a computationally efficient tool for engineering design. The proposed method enables rapid evaluation of WRI performance in complex scenarios, supporting broader integration into performance-based seismic mitigation strategies. Full article

(This article belongs to the Special Issue Nonlinear Vibration of Mechanical Systems)

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32 pages, 5256 KB

Open AccessArticle

The Effect of Wave Signature on the Voltage Output of an Oscillating Water Column

by Marcel Ilie

Vibration 2025, 8(3), 54; https://doi.org/10.3390/vibration8030054 - 22 Sep 2025

Abstract

The reduction in carbon footprint and scarcity of energy resources have increased the demand for renewable and sustainable energy resources, and thus, significant efforts have been concentrated on harnessing renewable and sustainable energy resources. The oscillating water column (OWC) wave energy converter has [...] Read more.

The reduction in carbon footprint and scarcity of energy resources have increased the demand for renewable and sustainable energy resources, and thus, significant efforts have been concentrated on harnessing renewable and sustainable energy resources. The oscillating water column (OWC) wave energy converter has proven to be the most promising approach for harnessing wave energy. The OWC offers the benefits of a long operating time span and low maintenance, as air serves as the driving fluid. The hydrodynamic efficiency of OWC depends on the wave motion and its interaction with the OWC structure. Therefore, the present research concerns the impact of the incident wave signature on the OWC’s efficiency voltage output, and it is carried out experimentally using a laboratory-scale wave tank. Four different waves, of different amplitudes and frequencies, and their impact on the OWC voltage output are experimentally investigated. This study shows that the four waves exhibit different characteristics, such as crests and troughs of different slopes and amplitudes. However, although the wave crests exhibit relatively similar amplitudes, the wave troughs exhibit significantly different characteristics. This study also reveals that the OWC voltage output exhibits a nonlinear behavior due to the nonlinear nature of the incident waves and compressible air inside the OWC chamber. The maximum voltage output is obtained for a maximum air compressibility factor. However, lower voltage outputs are obtained for both compression and decompression of the air inside the OWC chamber. Full article

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24 pages, 39815 KB

Open AccessArticle

Damage Identification in Beams via Contourlet Transform of Shearography Modal Data

by Ali Mohammad Mohammadi, Atefeh Soleymani, Hashem Jahangir, Mohsen Khatibinia, José Viriato Araújo dos Santos and Hernâni Miguel Lopes

Vibration 2025, 8(3), 53; https://doi.org/10.3390/vibration8030053 - 21 Sep 2025

Abstract

This paper presents a novel method for damage identification in aluminum beams using the contourlet transform. Four aluminum beams were used in the study: one was undamaged, while the other three had different damage scenarios. The damage included middle and side slots with [...] Read more.

This paper presents a novel method for damage identification in aluminum beams using the contourlet transform. Four aluminum beams were used in the study: one was undamaged, while the other three had different damage scenarios. The damage included middle and side slots with depth-to-thickness ratios of 7% and 28%. Damage is identified using the proposed index of contourlet transform of the modal rotations and modal curvatures of the beams for the free-free condition. The beam’s first three modal rotations are directly measured with digital shearography, and the corresponding modal curvatures are obtained through their numerical differentiation. The results indicated that to detect the exact locations and identify damage severities using the proposed damage indices, instead of modal rotations, the modal curvatures should be introduced as the input. Moreover, they revealed that the proposed damage indices need modal data of the undamaged state as a baseline to identify smaller damage. In addition, comparing the proposed contourlet-based damage indices with previously suggested wavelet-based damage detection methods revealed that, although the wavelet-based damage index is more sensitive to damage severity, it also exhibits higher noise levels in undamaged locations. The Tukey windowing process was introduced to address the boundary effect problem. Full article

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28 pages, 10288 KB

Open AccessArticle

Prediction of Local Vibration Analysis for Ship Stiffened Panel Structure Using Artificial Neural Network Algorithm

by Mahardika Rizki Pynasti and Chang-Yong Song

Vibration 2025, 8(3), 52; https://doi.org/10.3390/vibration8030052 - 13 Sep 2025

Abstract

Ship stiffened panels, typically flat plates reinforced with various types of stiffeners, form a substantial part of a ship’s structure and are susceptible to resonance, especially in areas such as the after peak structure, engine room, and accommodation compartments. These vibrations are primarily [...] Read more.

Ship stiffened panels, typically flat plates reinforced with various types of stiffeners, form a substantial part of a ship’s structure and are susceptible to resonance, especially in areas such as the after peak structure, engine room, and accommodation compartments. These vibrations are primarily excited by main engine and propeller forces. Conventional methods such as finite element analysis (FEA) and plate theory are widely used to estimate vibration frequencies, but they are time-consuming and computationally intensive when applied to numerous stiffened panels. This study proposes a machine learning approach using an artificial neural network (ANN) algorithm to efficiently predict the vibration frequencies of ship stiffened panels. A crude oil tanker is chosen as the case study, and FEA is conducted to generate the vibration frequency and mass data for panels across critical regions. The input layer features for the ANN include panel area, thickness, number and area of stiffeners, fluid density, number of fluid contact sides, and overall structural stiffness. The ANN model predicts two outputs: the fundamental vibration frequency and the mass of the panel structure. To evaluate the model performance, hyperparameters such as the number of hidden neurons are optimized. The results indicate that the ANN achieves accurate predictions while significantly reducing the time and resources required compared with conventional methods. This approach offers a promising tool for accelerating the local vibration analysis process in ship structural design. Full article

(This article belongs to the Special Issue Machine Learning Applications to Vibration Problems)

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17 pages, 9781 KB

Open AccessArticle

Research on the Tensile-Bending Dynamic Response of the Half-Through Arch Bridge Short Suspender Considering Vehicle-Bridge Coupling Vibration

by Lianhua Wang, Guowen Yao and Xuanbo He

Vibration 2025, 8(3), 51; https://doi.org/10.3390/vibration8030051 - 4 Sep 2025

Abstract

The half-through arch bridge short suspender is more prone to damage due to its high linear stiffness and special force characteristics. To analyze the vehicle-induced vibration characteristics of the short suspender during service, a half-through arch bridge finite element model and a three-axis [...] Read more.

The half-through arch bridge short suspender is more prone to damage due to its high linear stiffness and special force characteristics. To analyze the vehicle-induced vibration characteristics of the short suspender during service, a half-through arch bridge finite element model and a three-axis vehicle model were established to realize the coupled vibration of the suspender axle under bridge deck unevenness excitation. The suspender was simulated using LINK element and BEAM element and separated along its axial and radial directions, and its tension-bending response characteristics was studied. The study found that the short suspender’s amplitude and frequency are higher than those of the long suspender as vehicle critical duration increases. Influenced by the tensile bending effect, the vibration, cross-section equivalent force amplitude, and impact coefficient at the anchorage end are larger than those at the center, and the lower anchorage end’s cross-section peak stress is biased towards the direction of the side column. The internal force of the short suspender is consistent with the deformation trend; its internal force coincides with the deformation trend; and its axial alternating load is generated by the axial relative deformation between the arch rib and the bridge deck, while the bending alternating load originates from the rotational deformation of the short suspender. Full article

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16 pages, 4975 KB

Open AccessArticle

Optimization of Energy Harvesting Performance and Local Resonance Instability Phenomenon Suppression in Piezoelectric Cantilever Beams with Arrayed Grooves

by Yan Zhang, Qi Li, Haodong Sun, Kaiming Sun, Yuanjing Mou and Jie Wan

Vibration 2025, 8(3), 50; https://doi.org/10.3390/vibration8030050 - 3 Sep 2025

Abstract

This study addresses the performance optimization of piezoelectric cantilever beam energy harvesters by proposing a design method based on surface arrayed groove modulation. Through systematic investigation of the effects of single grooves (upper surface, lower surface, and double-sided grooves) and arrayed grooves on [...] Read more.

This study addresses the performance optimization of piezoelectric cantilever beam energy harvesters by proposing a design method based on surface arrayed groove modulation. Through systematic investigation of the effects of single grooves (upper surface, lower surface, and double-sided grooves) and arrayed grooves on the power generation performance of piezoelectric cantilever beams, the coupling mechanism of stiffness modulation, Local resonance instability phenomenon, and energy conversion in groove design is revealed. The results show that while single grooves can improve the output voltage by altering the neutral axis position, groove widths exceeding 20 mm induce Local resonance instability phenomenon, leading to energy dissipation. In contrast, arrayed grooves effectively suppress Local resonance instability phenomenon by uniformly distributing the grooves, significantly enhancing energy conversion efficiency. The optimized arrayed groove configuration (groove width: 4 mm, depth: 1 mm, number: 7) achieves a peak voltage of 549.525 mV, representing a 17.3% improvement over the ungrooved structure, without inducing narrow-bandwidth effects. Additionally, this design exhibits excellent process compatibility and can be fabricated using conventional machining methods, reducing costs by 30–45% compared to additive manufacturing. This study provides important optimization directions and technical references for the design of piezoelectric cantilever beam energy harvesters. Full article

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24 pages, 10517 KB

Open AccessArticle

Spectral-Clustering-Guided Fourier Decomposition Method and Bearing Fault Feature Extraction

by Wenxu Zhang, Chaoyong Ma, Gehao Feng, Yanping Zhu, Kun Zhang and Yonggang Xu

Vibration 2025, 8(3), 49; https://doi.org/10.3390/vibration8030049 - 1 Sep 2025

Abstract

The Fourier decomposition technique has notable advantages in filtering vibration acceleration signals and enhances the feasibility of frequency-domain mode decomposition. To improve the accuracy of mode extraction, this paper proposed a novel Fourier decomposition technique based on spectral clustering. The methodology comprises three [...] Read more.

The Fourier decomposition technique has notable advantages in filtering vibration acceleration signals and enhances the feasibility of frequency-domain mode decomposition. To improve the accuracy of mode extraction, this paper proposed a novel Fourier decomposition technique based on spectral clustering. The methodology comprises three key steps. First, spectral clustering is performed using feature vectors derived from the spectrum envelope, specifically the frequency and amplitude of its maximum value, along with the average amplitude of local spectral peaks. Subsequently, the spectrum is adaptively segmented based on clustering feedback to determine spectral segmentation boundaries. Followed by this, a filter bank is constructed via Fourier decomposition for signal reconstruction. Finally, a harmonic correlation index is computed for all decomposed components to identify fault-sensitive modes exhibiting the highest diagnostic relevance. These selected modes are subsequently subjected to demodulation for fault diagnosis. The effectiveness of the proposed method is validated through both simulated signals and experimental datasets, demonstrating its improved ability to capture critical fault information. Full article

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20 pages, 3671 KB

Open AccessArticle

Trajectory Control of Flexible Manipulators Using Forward and Inverse Models with Neural Networks

by Minoru Sasaki, Mizuki Takeda, Joseph Muguro and Waweru Njeri

Vibration 2025, 8(3), 48; https://doi.org/10.3390/vibration8030048 - 26 Aug 2025

Abstract

This study explores trajectory control in flexible manipulators using neural-network-based forward and inverse modeling. Unlike traditional approaches that enhance precision by increasing structural rigidity—often at the cost of added weight and energy consumption—this work focuses on lightweight flexible manipulators, which are more suitable [...] Read more.

This study explores trajectory control in flexible manipulators using neural-network-based forward and inverse modeling. Unlike traditional approaches that enhance precision by increasing structural rigidity—often at the cost of added weight and energy consumption—this work focuses on lightweight flexible manipulators, which are more suitable for aerospace and other weight-sensitive applications but introduce control complexities due to elastic deformations. To address these challenges, neural-network-based models are proposed for a two-link, three-degree-of-freedom (3-DOF) flexible manipulator. Simulation and experimental results show that incorporating system delay compensation into the training data significantly improves tracking accuracy. Nonetheless, difficulties remain in achieving smooth trajectory generation. The findings highlight the potential of neural networks in adaptive control and point to future opportunities for refining input–output modeling to better align theoretical developments with practical implementation. Full article

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25 pages, 12038 KB

Open AccessArticle

Numerical Analysis of the Dispersive Behaviour of Buried Elastic Periodic Structures

by Alexandre Castanheira-Pinto, Luís Godinho, Pedro Alves Costa and Aires Colaço

Vibration 2025, 8(3), 47; https://doi.org/10.3390/vibration8030047 - 14 Aug 2025

Abstract

Train-induced vibrations negatively impact residents in nearby buildings and are increasingly recognized as a public health concern. To address this issue, both effective mitigation measures and simplified design procedures are essential. This study investigates the mitigation pattern induced by an array of stiff [...] Read more.

Train-induced vibrations negatively impact residents in nearby buildings and are increasingly recognized as a public health concern. To address this issue, both effective mitigation measures and simplified design procedures are essential. This study investigates the mitigation pattern induced by an array of stiff inclusions employing a modal dispersive analysis. However, applying this type of analysis to a half-space medium presents challenges. To overcome this limitation, a wave-scattering methodology is proposed. This approach enables the computation of the mitigation pattern in a specific direction and at a particular location. It also highlights the conditioning energy content, thereby identifying the key frequency target for attenuation. Full article

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15 pages, 1286 KB

Open AccessArticle

Weibull Reliability Based on Random Vibration Performance for Fiber Optic Connectors

by Jesús M. Barraza-Contreras, Manuel R. Piña-Monárrez, María M. Hernández-Ramos and Secundino Ramos-Lozano

Vibration 2025, 8(3), 46; https://doi.org/10.3390/vibration8030046 - 12 Aug 2025

Abstract

Communication via optical fiber is increasingly being used in harsh applications where environmental vibration is present. This study involves a Weibull reliability analysis focused on the performance of fiber optic connectors when they are subjected to mechanical random vibration stress to simulate real-world [...] Read more.

Communication via optical fiber is increasingly being used in harsh applications where environmental vibration is present. This study involves a Weibull reliability analysis focused on the performance of fiber optic connectors when they are subjected to mechanical random vibration stress to simulate real-world operating conditions, and the insertion loss (IL) degradation is measurable. By analyzing the testing times and stress levels, the Weibull shape (

β

) and scale (

η

) parameters are estimated directly from the maximal and minimal principal IL stresses (

σ_{1}

,

σ_{2}

), enabling the prediction of the connector’s reliability with efficiency. The sample size n is derived from the desired reliability (R(t)), and the GR-326 mechanical vibration test (2.306 Grms for six hours) is performed on optical SC angled physical contact (PC) polish fiber endface connectors that are monitored during testing to evaluate the IL transient change in the optical transmission. The method is verified by an experiment performed with

σ_{1} = 0.3960

and

σ_{2} = 0.1910

where the IL measurements are captured with an Agilent N7745A source-detector optical equipment, and the Weibull statistical results provide a connector’s reliability R(t) = 0.8474, with a characteristic value of

η

= 0.2750 dB and

β

= 3. Finally, the connector’s reliability is as worthy of attention as the telecommunication sign conditions. Full article

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33 pages, 1196 KB

Open AccessArticle

Theoretical Formulations of Integral-Type Frequency–Amplitude Relationships for Second-Order Nonlinear Oscillators

by Chein-Shan Liu, Chia-Cheng Tsai and Chih-Wen Chang

Vibration 2025, 8(3), 45; https://doi.org/10.3390/vibration8030045 - 11 Aug 2025

Cited by 1

Abstract

The development of simple and yet accurate formulations of frequency–amplitude relationships for non-conservative nonlinear oscillators is an important issue. The present paper is concerned with integral-type frequency–amplitude formulas in the dimensionless time domain and time domain to accurately determine vibrational frequencies of nonlinear [...] Read more.

The development of simple and yet accurate formulations of frequency–amplitude relationships for non-conservative nonlinear oscillators is an important issue. The present paper is concerned with integral-type frequency–amplitude formulas in the dimensionless time domain and time domain to accurately determine vibrational frequencies of nonlinear oscillators. The novel formulation is a balance of kinetic energy and the work during motion of the nonlinear oscillator within one period; its generalized formulation permits a weight function to appear in the integral formula. The exact values of frequencies can be obtained when exact solutions are inserted into the formulas. In general, the exact solution is not available; hence, low-order periodic functions as trial solutions are inserted into the formulas to obtain approximate values of true frequencies. For conservative nonlinear oscillators, a powerful technique is developed in terms of a weighted integral formula in the spatial domain, which is directly derived from the governing ordinary differential equation (ODE) multiplied by a weight function, and integrating the resulting equation after inserting a general trial ODE to acquire accurate frequency. The free parameter is involved in the frequency–amplitude formula, whose optimal value is achieved by minimizing the absolute error to fulfill the periodicity conditions. Several examples involving two typical non-conservative nonlinear oscillators are explored to display the effectiveness and accuracy of the proposed integral-type formulations. Full article

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27 pages, 4883 KB

Open AccessArticle

Stochastic Vibration of Damaged Cable System Under Random Loads

by Yihao Wang, Wei Li and Drazan Kozak

Vibration 2025, 8(3), 44; https://doi.org/10.3390/vibration8030044 - 4 Aug 2025

Abstract

This study proposes an integrated framework that combines nonlinear stochastic vibration analysis with reliability assessment to address the safety issues of cable systems under damage conditions. First of all, a mathematical model of the damaged cable is established by introducing damage parameters, and [...] Read more.

This study proposes an integrated framework that combines nonlinear stochastic vibration analysis with reliability assessment to address the safety issues of cable systems under damage conditions. First of all, a mathematical model of the damaged cable is established by introducing damage parameters, and its static configuration is determined. Using the Pearl River Huangpu Bridge as a case study, the accuracy of the analytical solution for the cable’s sag displacement is validated through the finite difference method (FDM). Furthermore, a quantitative relationship between the damage parameters and structural response under stochastic excitation is developed, and the nonlinear stochastic dynamic equations governing the in-plane and out-of-plane motions of the damaged cable are derived. Subsequently, a Gaussian Radial Basis Function Neural Network (GRBFNN) method is employed to solve for the steady-state probability density function of the system response, enabling a detailed analysis of how various damage parameters affect structural behavior. Finally, the First-Order and Second-Order Reliability Method (FORM/SORM) are used to compute the reliability index and failure probability, which are further validated using Monte Carlo simulation (MCS). Results show that the severity parameter η shows the highest sensitivity in influencing the failure probability among the damage parameters. For the system of the Pearl River Huangpu bridge, an increase in the damage extent δ from 0.1 to 0.4 can reduce the reliability-based service life of by approximately 40% under fixed values of the damage severity and location, and failure risk is highest when the damage is located at the midspan of the cable. This study provides a theoretical framework from the point of stochastic vibration for evaluating the response and associated reliability of mechanical systems; the results can be applied in practice with guidance for the engineering design and avoid potential damages of suspended cables. Full article

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