Vibration Analysis Research Articles

Experimental and numerical modal analysis of CFM56-3 Oil tank

To determine the dynamic behavior of components which is performed through the mechanical vibration analysis. The Experimental Modal Analysis (EMA) is the process to determine the modal parameters i.e. of natural frequencies, mode shapes, and damping. The Experimental Modal Analysis (EMA) of the CFM56 oil tank was performed using an impact hammer and a laser vibrometer. Finite Element Modeling (FEM) software, ANSYS APDL 19.2, was used to performed numerical modal analysis of the same oil tank. Thus, the results obtained for natural frequencies and mode shapes is presented in this document. It will contribute to the demonstration of the component functionality and to the validation of the proposed analysis methodology.

Vibration Correlation Technique: Methodology Applied to Buckling of Large-Scale Sandwich Cylindrical Shell

This paper assesses the Vibration Correlation Technique's (VCT) applicability within the context of sandwich cylindrical shells through detailed numerical investigation. The study utilizes a sandwich shell from NASA's Shell Buckling Knockdown Factor project. Finite element models are implemented, incorporating initial mid-surface and thickness imperfections to replicate NASA's buckling test campaign. The numerical results are compared to the experimental data, validating the nonlinear solution with an approximate deviation of 1%. Subsequently, the VCT experimental campaign is numerically conducted through free vibration analyses at different load levels, enabling a comprehensive evaluation of VCT's applicability. The results verified the effectiveness of the VCT, demonstrating a deviation of less than 10% when estimating the buckling load for load levels below 65% of the nonlinear buckling load. Overall, the findings confirm the non-destructive nature of the VCT when employed on such structures, supporting future practical applications.

Prediction maintenance based on vibration analysis and deep learning — A case study of a drying press supported on a Hidden Markov Model

The main objective of this paper is to describe a methodology that was developed to support maintenance decision-making methods based on equipment condition. Condition-Based Maintenance allows to increase equipment availability and maximize investments. This is mainly due to the prevention of unexpected equipment downtime. By avoiding turning on/off industrial equipment, production flows are more efficient, allowing manufacturers to improve the quality of the end-product. The industry aims more and more to correspond satisfying customer expectations. We argue that the methodology developed in this paper adds value to the existing literature, namely because the fact that it is possible to anticipate the state of an equipment without a large amount of support data. In other words, although one could find information gaps regarding the occurrence of failures, it was possible to accurately assess the state of the equipment. This approach is robust, as it can be used in distinct equipment with different sensors, making this methodology generalizable for Condition-Based Maintenance. The paper presents the validation of the preceding through a case study on drying presses in the paper industry. To do so, three states were adopted, namely: “Proper function”; “Alert state”; and “Equipment failure”. The methodology follows a series of steps, going through the collection of values from vibration sensors, imputation of values using Deep Artificial Neural Networks through on-line sensors, until reaching the last stage of classification carried out by the Hidden Markov Model. Through optimized observations from the previous steps, it was possible to define the hidden states through the Viterbi algorithm, which corresponds to the health states of the equipment. Additionally, it was possible to demonstrate that the proposed methodology can accurately characterize the condition states of the equipment based on the data obtained and can be generalized to other types of equipment.

Fault Diagnosis of Wind Turbine Gearbox Based on Modified Hierarchical Fluctuation Dispersion Entropy of Tan-Sigmoid Mapping.

Vibration monitoring and analysis are important methods in wind turbine gearbox fault diagnosis, and determining how to extract fault characteristics from the vibration signal is of primary importance. This paper presents a fault diagnosis approach based on modified hierarchical fluctuation dispersion entropy of tan-sigmoid mapping (MHFDE_TANSIG) and northern goshawk optimization-support vector machine (NGO-SVM) for wind turbine gearboxes. The tan-sigmoid (TANSIG) mapping function replaces the normal cumulative distribution function (NCDF) of the hierarchical fluctuation dispersion entropy (HFDE) method. Additionally, the hierarchical decomposition of the HFDE method is improved, resulting in the proposed MHFDE_TANSIG method. The vibration signals of wind turbine gearboxes are analyzed using the MHFDE_TANSIG method to extract fault features. The constructed fault feature set is used to intelligently recognize and classify the fault type of the gearboxes with the NGO-SVM classifier. The fault diagnosis methods based on MHFDE_TANSIG and NGO-SVM are applied to the experimental data analysis of gearboxes with different operating conditions. The results show that the fault diagnosis model proposed in this paper has the best performance with an average accuracy rate of 97.25%.

Predicting masticatory muscle activity and deviations in mouth opening from non-invasive temporomandibular joint complex functional analyses.

A quantitative approach to predict expected muscle activity and mandibular movement from non-invasive hard tissue assessments remains unexplored. This study investigated the predictive potential of normalised muscle activity during various jaw movements combined with temporomandibular joint (TMJ) vibration analyses to predict expected maximum lateral deviation during mouth opening. Sixty-six participants underwent electrognathography (EGN), surface electromyography (EMG) and joint vibration analyses (JVA). They performed maximum mouth opening, lateral excursion and anterior protrusion as jaw movement activities in a single session. Multiple predictive models were trained from synthetic observations generated from the 66 human observations. Muscle function intensity and activity duration were normalised and a decision support system with branching logic was developed to predict lateral deviation. Performance of the models in predicting temporalis, masseter and digastric muscle activity from hard tissue data was evaluated through root mean squared error (RMSE) and mean absolute error. Temporalis muscle intensity ranged from 0.135 ± 0.056, masseter from 0.111 ± 0.053 and digastric from 0.120 ± 0.051. Muscle activity duration varied with temporalis at 112.23 ± 126.81 ms, masseter at 101.02 ± 121.34 ms and digastric at 168.13 ± 222.82 ms. XGBoost predicted muscle intensity and activity duration and scored an RMSE of 0.03-0.05. Jaw deviations were successfully predicted with a MAE of 0.9 mm. Applying deep learning to EGN, EMG and JVA data can establish a quantifiable relationship between muscles and hard tissue movement within the TMJ complex and can predict jaw deviations.

Free and Forced Vibration Analysis of Composite Beam Composed Laminated Composite Material and Functionally Graded Material

Free and Forced Vibration Analysis of Composite Beam Composed Laminated Composite Material and Functionally Graded Material

A Numerical Analysis of the Non-Uniform Layered Ground Vibration Caused by a Moving Railway Load Using an Efficient Frequency–Wave-Number Method

The ground vibration caused by the operation of high-speed trains has become a key challenge in the development of high-speed railways. In order to study the train-induced ground vibration affected by geotechnical heterogeneity, an efficient frequency–wave-number method coupled with the random variable theory model is proposed to quickly obtain the numerical results without losing accuracy. The track is regarded as a composite Euler–Bernoulli beam resting on the layered ground, and the spatial heterogeneity of the ground soil is considered. The ground dynamic characteristics of an elastic, layered, non-uniform foundation are investigated, and numerical results at three typical train speeds are reported based on the developed Fortran computer programs. The results show that as the soil homogeneity coefficient increases, the peak acceleration continuously decreases in the transonic case, while it gradually increases in the supersonic case, and the ground acceleration spectrum at a far distance obviously decreases; the maximum acceleration occurs at the track edge, and a local rebound in vibration attenuation occurs in the supersonic case.

Synthesis of reduced graphene oxide and Nickel oxide/reduced graphene oxide composite materials for supercapacitor applications and their computational investigations

This study outlines the synthesis of reduced graphene oxide (rGO) and Nickel oxide/reduced graphene oxide (NiO/rGO) composite materials without the use of binders. The synthesis method involved microwave-assisted reduction using ascorbic acid (AA) and varying weight ratios of potassium hydroxide (KOH) to convert graphene oxide (GO) to rGO. The research investigates how adjusting the weight ratios of GO and KOH influences the electrical conductivity (EC) properties of the synthesized materials, particularly exploring the impact of KOH addition on the porosity growth in the rGO layers during fabrication. Various analytical techniques, including optical, vibrational, morphological, bonding, and network analysis, were employed to characterize the synthesized materials. The materials were evaluated as potential supercapacitor electrodes using electrochemical techniques such as cyclic voltammetry and A.C. impedance analysis, including Nyquist and Bode plots. The specific capacitance (CS) of rGO and NiO/rGO was determined to be 1400 Fg−1 at a scan rate of 0.005 Vs−1. The synthesis process avoided the use of hazardous reagents. Additionally, density functional theory (DFT) based computational analysis was conducted to support the experimental findings. The study documents the influence of incorporating NiO onto the surface of GO and rGO on the energy gap (Egap) and investigates the density of state (DOS) to understand the effect of MO-rGO interaction. Furthermore, frontier molecular orbital (FMO) contours were examined to analyze excitation qualities, and electron potential was visualized and mapped onto the electron density surface to gain insights into charge dispersion within the structures.

Effect of the porous structure on the hygrothermal vibration analysis of functional graded nanoplates using nonlocal high-order continuum plate model

AbstractThis study delves into the thermomechanical vibration behavior of functionally graded porous nanoplates under extreme thermal temperature and humidity conditions. The equation of motion of the nanoplate was derived using advanced theories in elasticity and deformation. The nanoplate consists of metal (SUS304) on the bottom surface and ceramic (Ni3S4) on the top surface, with the material distribution changing according to the power law across the plate thickness. The nanoplate was modeled with uniform and symmetric distributions of porosity reaching as high as 60%. Upon incorporating the thermal and moisture loads from the humid surroundings into the equations of motion derived from Hamilton's principle, the equations were solved using Navier's method and simplified to the eigenvalue equation. Analyzed within a broad framework are the thermomechanical vibration behavior of the nanoplate, temperature impact, humidity influence, porosity and its distribution, material grading parameter effects, and nonlocal integral elasticity effects. Observations indicate that variations in thermal temperature, humidity, and nonlocal parameters can lower the thermomechanical vibration frequency of the nanoplate, whereas porosity has the opposite effect. The effects mentioned are influenced by factors, such as the porosity ratio, porosity distribution, material ratios, and the size of the nonlocal parameter in the plate. The primary objective of this work is to uncover the nonlinear frequency response of nanoplates with high porosity in conditions characterized by high temperature and humidity.

Nonlinear vibration and stability analysis of a dual-disk rotor-bearing system under multiple frequency excitations

Nonlinear vibration and stability analysis of a dual-disk rotor-bearing system under multiple frequency excitations

Free and Forced Vibration Analysis of Carbon/Glass Hybrid Composite Laminated Plates Under Arbitrary Boundary Conditions

AbstractThis paper presents the theoretical investigations on the free and forced vibration behaviours of carbon/glass hybrid composite laminated plates with arbitrary boundary conditions. The unknown allowable displacement functions of the physical middle surface are expressed in terms of standard cosine Fourier series and sinusoidal auxiliary functions to ensure the continuity of the displacement functions and their derivatives at the structural boundaries. Arbitrary boundary conditions are achieved through the introduction of an artificial spring technique. The first shear deformation theory and Lagrange equations are utilized to derive the energy expression, and the eigenvalue equations associated with free and forced vibration are obtained by Rayleigh-Ritz variational operations. Subsequently, these equations are then solved to determine the natural frequency, mode of vibration, and the steady-state displacement response under forced excitation. The new results are compared with those from references and finite element methods to verify the convergence, accuracy and efficiency of the analytical method. The effects of hybrid ratios, stacking sequences, lamination schemes, fibre orientation, boundary conditions and excitation force on the free and forced vibration behaviours of the carbon/glass hybrid composite laminated plates are analyzed in detail.

Transfer matrix modeling for asymmetrically-nonuniform curved beams by beam-discrete strategies

Nonuniform and curved beams can be found in extensive engineering scenarios, ranging from big-scale structures of buildings, bridges to small mechanical systems of aerofoils, blades, micromachines, robotics and sensors. However, variable curvature and transverse asymmetry often lead to a complicated dynamic modeling. In this paper, two beam-discrete strategies are comparatively presented for the free vibration analysis of transversely asymmetric and curved beams and even their combinations. The proposed methodology involves discretizing a general nonuniform and curved beams into a sequence of constant beam segments with non-coaxial nodes or inclination angles, which enables a modular transfer matrix modeling process and hence offers a new way to divide the complex modeling into easier steps. A unified transfer matrix is derived for constant beam elements with non-coaxial nodes and inclination angles accounting for the shear deformation, rotary inertia and axial load in any combinations. The proposed beam-discrete strategies with a unified transfer matrix provide a new perspective in contrast to previous investigations. The advantages of easy programming and small degrees of freedom in the traditional transfer matrix method is extended to transversely asymmetric nonuniform and curved beams. Comparative validation with several engineering beams confirms these advantages.

Vibration analysis of a partially submerged structure using the DIC technique

The continuous expansion of offshore wind turbine sites has been garnering increasing attention, particularly in countries where available land is limited. Nevertheless, efficiently allocating resources for the maintenance and repair of offshore wind turbines presents a formidable challenge. This challenge is compounded by the complex and often unpredictable weather conditions, as well as various business-related issues specific to the offshore environment. To tackle these challenges, one effective solution is to implement vibration analysis through the use of digital image correlation (DIC) methods. This approach has a well-established theoretic background dating back to approximately 2008 and has demonstrated its effectiveness in the realm of structural health monitoring for large structures like bridges and towers. Relevant information on the upper structure of the wind turbines has been obtained using numerical models in our previous work. Changes in the structural feature frequencies of wind turbines are the primary focus in vibration analysis. However, changes in feature frequencies can occur for various reasons, and relying solely on frequency shifts can make it challenging to pinpoint the precise areas of damage within wind turbine structures, especially without the benefit of long-term observations. In this study, the DIC method is employed on scaled cylindrical models to gain insights into the frequency variations stemming from the erosion of non-cohesive soils beneath offshore wind turbine foundations. Changes in modal curvature within the upper structure of the wind turbine will also be analyzed. This additional investigation will enable a clear differentiation between defects in the upper structure and frequency shifts resulting from erosion or problems with the underwater foundation.

Synthesis, spectroscopic characterizations, TD/DFT calculations, colorimetric metal ions, and molecular docking studies of a novel 3-acetylpyridine 2-hyrdoxyphenyl thiosemicarbazone

A novel thiosemicarbazone scaffold, namely 3-acetylpyridine-2-hydroxyphenyl thiosemicarbazone (3APHT), which contains π-conjugated heterocyclic and phenyl rings, was successfully synthesized and characterized experimentally and theoretically. Through TD/DFT calculations, it was found that the new compound has 14 signals in 13CNMR spectroscopy, 96 types of vibrations for vibration analysis, and n-π* and π-π* electronic transitions that lead to an 87.12 % HOMO-LUMO excitation. The vibrations follow 3N-6 degrees of freedom for a non-linear compound. Based on the global reactivity parameter and other results, it has been shown that 3APHT has potential applications in metal ion detection and as an inhibitor for the overexpressed receptor of breast cancer caused by copper ions pollution. The novel APHT was optimized as a colorimetric metal ions recognition using UV–Vis analysis. Suitable conditions for 3APHT to act as a colorimetric metal ion recognition was detected in DMSO/water (8:2 v/v, pH 7). The change of test strips from colorless to yellowish revealed the presence of Cu2+ ions in the water. The selectivity toward the Cu2+ ion did not interfere with other metal ions. The potential of 3APHT to inhibit the upregulation of apoptotic genes caused by copper ions in BCL-2 family proteins—the main cause of breast cancer—was determined using an in-silico approach. The results showed strong binding of 3APHT with BCL-2, BCL-W, MCL-1, and ER-α through hydrogen bonds and electrostatic interactions at -6.35, -6.31, -8.05, and -7.05 kcal/mol, respectively. The physicochemical through ADME analysis showed that the compound has a structure that presents good absorption properties, therefore permeability across the cell membrane, and good theoretical oral bioavailability.

Application of a simple two-point measurement strategy with emphasizing low-frequency signals to the force monitoring of cables

When dealing with vibration tests of tensioned suspenders and cables, signals containing relatively high frequency components in comparing to the fundamental frequency are normally required in order to carry out reliable diagnoses for force estimations. Meanwhile, the necessity of obtaining a precise and broadband spectrum of the vibration signals would inevitably need to acquire relatively detailed time responses. One typical difficulty, which arises when incorporating vibration analyses into monitoring tasks, is the inefficiency caused by the post- processing for the huge amounts of time data. In this work, a set of simple yet effective formulas associated with two-point measurements will be briefly addressed. The proposed formulas are derived based on the continuous formulations of the string model, and the corresponding applications to the tension estimations of slender members will be demonstrated using numerical and experimental data related to stayed cables of various restrained scenarios and linked-suspenders as well. The purposes of this work are twofold; firstly to introduce the potential usefulness of the proposed measurement strategy to form effective schemes for the tension assessments; secondly to evolve an efficient incorporation of wireless measuring techniques without the need of processing cumbersome time data which are the common consequences the analysts would encounter in the analysis tasks. Finally, this work aims to highlight practical ideas in guiding the use of the proposed techniques in the monitoring of cables/suspenders in field.

Enhancing vibration energy dissipation and self-powered sensing in high-rise buildings using origami-inspired triboelectric nanogenerators and buckling-restrained braces

This study introduces a novel Buckling-Restrained Brace (BRB) design, incorporating Origami-inspired structures (OS) with triboelectric nanogenerators (TENGs), creating an intelligent BRB system for both vibration damping during seismic events and self-powered sensing. Rooted in the Miura-tube pattern, we conducted an extensive array of mechanical tests, encompassing varying contact shapes, external resistances, and excitation frequencies. Addressing the challenge of motion synchronicity in the OS base, we introduce an enhanced Miura-tube OS-TENG, featuring reinforced stiffness in the origami structure's creases and panels. Our experiments revealed that the signal strength of these refined devices proportionally escalates with the number of integrated tribo-pairs. Further vibrational analysis of a two-story frame equipped with this enhanced Miura-tube OS-TENG underscored its potential as a sophisticated intelligent BRB. Experiments demonstrated a significant 31.21 % reduction in structural acceleration and a strong correlation between the device's voltage output and the building's dynamic response, with a 90.40 % regression fit. Within the examined range of excitation frequencies 3–15 Hz, the average accuracy of predicting structural acceleration using intelligent BRBs is 92.90 %. This work not only meets the essential demand for vibration mitigation through the innovative use of intelligent OS-TENG BRB systems but also significantly advances the integration of TENG-based self-powered sensors in structural health monitoring frameworks.

Modeling and vibration analysis of an aero-engine dual-rotor-support-casing system with inter-shaft rub-impact

In order to reveal the nonlinear dynamics of dual-rotor-support-casing system, a numerical procedure is proposed using the finite element method and the component mode synthesis method. Especially, the casing system is subdivided into the casings, struts and housings, which are modeled by shell elements, beam elements and rigid regions with mass elements, respectively. Furthermore, the inter-shaft rub-impact, which may occur in the aero-engine because of imbalance and other faulty, is considered in the dynamic model as a nonlinear excitation. The modal analysis verified the validity of the dual-rotor-support-casing system model. The motion equations are established using the reduced-order model and solved by Newmark-β method with Newton-Raphson iteration. The results show that larger rubbing stiffness will cause the rubbing to enter a self-excited vibration state, and the rotational speed ratio will change the speed region where the self-excited vibration occurs. Finally, the experiment is performed based on a real dual-rotor aeroengine under inter-shaft rub-impact and the results are consistent with the theoretical results, which proves the effectiveness of dual-rotor-support-casing system dynamic model.

Crystal Clear: Metal-Organic Frameworks Pioneering the Path to Future Drug Detox.

The growing number of acute drug abuse overdoses demands the development of innovative detoxification strategies for emergency purposes. In this study, an innovative approach for the application of porous Zr-based metal-organic frameworks for the treatment of acute overdoses of popular drugs of abuse including amphetamine, methamphetamine, cocaine, and MDMA is presented. A comprehensive approach determining the efficacy and the kinetics of drug removal, considering dosage, adsorption time, and adsorption mechanisms, was tested and corroborated with density functional theory (DFT) modeling. The experimental results showed high removal efficiency reaching up to 90% in the case of the application of the NU-1000 metal-organic framework. The difference Raman spectroscopy method presented in this study corroborated with DFT-based vibrational analysis allows the detection of drug adsorbed in the MOF framework even with as low a concentration as 5 mg/g. Additionally, the drug adsorption mechanisms were modeled with DFT, showing the π-π stacking in a vast majority of considered cases. The performance and influence on the living organisms were evaluated throughout the in vitro and in vivo experiments, indicating that Zr-based MOFs could serve as efficient, organic, safe drug adsorbents.

Vibrational Self-Consistent Field (VSCF) and Post-VSCF Method Calculations Combined with the Reference Interaction Site Model Self-Consistent Field Method Coupled with the Constrained Spatial Electron Density Distribution: Applications to NaHCOO in Aqueous Phase.

Investigating vibrational behavior in solution is crucial for understanding molecular dynamics within a solvent environment. Notably, the analysis of Raman spectra for molecules in solution is important owing to its ability to unveil intricate solute-solvent interactions. Previous studies have effectively employed frequency calculations utilizing the reference interaction site model self-consistent field method in conjunction with constrained spatial electron density distribution (RISM-SCF-cSED) to understand molecular vibrations in solution, primarily focusing on fundamental vibrational modes. However, the oversight of overtones and combination tones in these studies prompted us to combine the vibrational self-consistent field (VSCF) and vibrational second-order Mo̷ller-Plesset perturbation (VMP2) methods with RISM-SCF-cSED to address these aspects theoretically. Illustrating the efficacy of this integrated approach, we computed the Raman spectra of sodium formate (NaHCOO) in water, revealing the necessity of accounting for molecular anharmonicity in solution vibrational analysis. Our findings underscore the potency of VSCF and VMP2 in conjunction with RISM-SCF-cSED as a robust theoretical framework for such calculations.

Impact of Cyclic Error on Absolute Distance Measurement Based on Optical Frequency Combs.

Absolute distance measurements based on optical frequency combs (OFCs) have greatly promoted advances in both science and technology, owing to the high precision, large non-ambiguity range (NAR), and a high update rate. However, cyclic error, which is extremely difficult to eliminate, reduces the linearity of measurement results. In this study, we quantitatively investigated the impact of cyclic error on absolute distance measurement using OFCs based on two types of interferometry: synthetic wavelength interferometry and single-wavelength interferometry. The numerical calculations indicate that selecting a suitable reference path length can minimize the impact of cyclic error when combining the two types of interferometry. Recommendations for selecting an appropriate synthetic wavelength to address the tradeoff between achieving a large NAR and minimizing the risk of failure when combining the two methods are provided. The results of this study are applicable not only in absolute distance measurements but also in other applications based on OFCs, such as surface profile, vibration analysis, etc.