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The application of vibration-based condition monitoring methods to power transformers has shown the potential for detecting mechanical transformer failures. The ageing of winding insulation paper, which is a common problem in long-serving power transformers, affects both the electrical and mechanical strength of the windings. This paper is concerned with the vibration features of winding disks with aged insulation paper. The vibration characteristics of single-layer winding disks wrapped with insulation paper are investigated. By examining the vibration frequency responses of winding disks with different degrees of ageing of insulation paper, the effects of aged paper on the vibration behaviors of winding disks are demonstrated. The experimental results show that changes in the vibration responses of winding disks can be related to the ageing of insulation paper, and thus it is possible to detect this failure mode in a power transformer using a vibration-based method. A qualitative explanation for these changes is presented, using the degradation of the mechanical strength of the insulation paper. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical properties of nano-silica modified insulating paper under the combined action of mechanical vibration and temperature conditions are studied. Unmodified and nano-silica modified cellulose insulating paper with 2 wt% and 4 wt% were prepared, respectively, and a series of mechanical-thermal synergy experiments were carried out. With the same mechanical stress and temperature, and with the same aging duration of 144 h (6d), the tensile strength of modified insulating paper with 4 wt% nano-silica, increased 0.99 kN/m and 0.55 kN/m, respectively, compared with those of the unmodified and the 2 wt% nano-silica modified insulating paper. The experiments indicate that the nano-silica modification can effectively improve the mechanical properties of insulating paper. In this work, the modified mechanism of nano-silica is analyzed from the interface effect of modified polymer and the quantum effect of the modified polymer interface two aspects. It is shown that the interface formed in the modified insulating paper can transfer the mechanical stress acted on the insulating paper and prevent the cracks formed in the aging process of the test sample from further expansion, while the quantum effect discretizes the electron energy level, which can restrict the motion of the molecular chain segment to some extent. The conclusion can be used for reference to improve the performance of insulating paper. [ABSTRACT FROM AUTHOR]

It is assumed that a sheet of paper performs transverse vibrations as a plate having additional stiffness due to static tension in its plane. The first eigenmodes are determined. The setup for experimental investigation of the nodal lines of the standing waves and for the determination of eigenmodes using projection moire is created for the analysis of unsymmetric loading of the paper. The comparison of the theoretical and experimental results of investigations is performed. The obtained results could be used in the process of design of the elements of the printing device. [ABSTRACT FROM AUTHOR]

In this paper, a finite element procedure is used to study the dynamic behaviour of a paper web in a free span between two rollers, including effects of transport velocity and surrounding air. The paper web is modelled as a three-dimensional orthotropic structure. The influence of air is accounted for by utilizing fluid–solid interaction analyses based on acoustic theory. The contribution of transport velocity is included through gyroscopic matrices and forces. The structural response on harmonic excitations has been studied using linear and non-linear models. Results show that air significantly reduces eigenfrequencies of the web. So called “edge-flutter” is nothing but the result of skew tension profile. Excessive web vibration can be eliminated by adjusting the web tension. [Copyright &y& Elsevier]

Paper board with bending stiffness is usually used as the substrates on cigarette package printing industry. The vibration of these paper boards in high speed affects the printing precision. The dynamic characteristics and stability of moving paper board with finite interior elastic point supports and elastic edges restrained are investigated. First, the energy function of the system is established by using the extended Hamilton’s principle; second, the dimensionless equations of motion for the moving paper board are obtained using the element-free Galerkin method. The equations of motion and the eigenvalue equations of the system are established. The relationship between the first three complex frequencies of the system and the moving speed is then obtained by the numerical calculation. The effects of the elastic point supports, the elastically restrained edges, and the dimensionless speed of the motion on the dynamic stability of the paper board are analyzed. The critical speed when the paper board is in a stable state under different conditions is obtained. The results improve the dynamic stability of the paper board in printing process and provide the theoretical basis for the optimization of printing equipment. [ABSTRACT FROM AUTHOR]

This paper presents a simulation method that is used to study subcritical vibrations of a tube roll in a paper machine. This study employs asymmetric 3D beam elements based on the Timoshenko beam theory. An asymmetric beam model accounts for varying stiffness and mass distributions. Additionally, a detailed rolling element bearing model defines the excitations arising from the set of spherical roller bearings at both ends of the rotor. The results obtained from the simulation model are compared against the results from the measurements. The results indicate that the waviness of the bearing rolling surfaces contributes significantly to the subcritical vibrations while the asymmetric properties of the tube roll have only a fractional effect on the studied vibrations. [ABSTRACT FROM AUTHOR]

Fruit quality is a crucial factor in affecting shelf-life and purchase choice for customers. Protecting the quality of cantaloupe fruits in the chain from harvest to marketing is a very important process. The objective of this study was to investigate the dynamic characteristics of cantaloupe fruit during excitation, to investigate the effect of vibration strength on the mechanical characteristics of cantaloupe fruit, and to show the effects of this strength on the mechanical damage of cantaloupe. Experiments were performed to measure the dynamic behavior of cantaloupe fruit during transportation and to evaluate the dynamic behavior of the packaging and the damage to the cantaloupes due to transient vibration during transportation. The results show that using the paper pulp tray packing method reduces cantaloupe damage and improves their quality during harvest and post-harvest processes. The range of resonance frequencies is important for the transporting of cantaloupes; a higher starting resonance is an indication of a stiffer cantaloupe bottom, and the paper pulp tray shifts the resonance frequency when compared to volume packing methods. Another interesting observation in this study is that a fruit with a high internal damping capacity is not as injured by exciting vibrations as a fruit with a low damping capacity, even if its natural frequency falls within the range of excitation. [ABSTRACT FROM AUTHOR]

In this paper the deep drawing of cups from fiber-based materials, which is explored for some time now, is further developed through the use of micron-small vibrations in an ultrasonic frequency range within the deep-drawing tools. The design of such tools required preliminary investigations concerning the limitations of use and feasibility of this technology. These include tests for necessary clearances between punch and die, occurring pressure in this clearance, necessary punch forces and the heating of the material under the vibrational influence. According to these experiences a flexible test machine was developed enabling the examination of the deep drawing process with vibrating tools as well as its possibilities and limits. The dependence of punch force and cup quality from the ultrasonic parameters was determined and it was found that the required punch force can be reduced by up to 80% and a significant smoothing of the cup surface as well as an improved stiffness of the 3D-shapes is achieved. [ABSTRACT FROM AUTHOR]

The objective of this paper is to provide the physical bases that allow more accurate diagnosis of the conditions of paper machines for better maintenance. The diagnostic of the mechanical condition of press felts and rolls in the press section of paper machines using the classical vibration analysis is complex, so maintenance of these elements is done in a preventive and not predictive way. In this work a mathematical model that describes the dynamic behavior of the presses in paper machines is developed. Through numerical simulations, the motion equation of the proposed model is solved and compared with measurements done in industrial machines. It is concluded that the proposed model properly describes the vibratory behavior of presses and provides the vibratory symptoms that allow the diagnosis of the problems that they may have. [ABSTRACT FROM AUTHOR]

Rolling element bearing failures in paper mill machines are considered in relation to their critical role in the machine function. The paper discusses these failures according to what becomes damaged and how, and relates them to the vibration spectra and their develop ment over the lives of the bearings. Interpretations of some variations in the vibration signature, i.e. relating vibration amplitude changes and frequency shifts to the deterioration processes involved, are proposed and discussed. The literature was found mainly to confirm this analysis . A new approach to envelope alarming is presented and shown theoretically (logically) to offer later renewal with fewer failures, and therefore lower cost and higher productivity. Deficiencies in data coverage and quality, and the feedback of case study results, are discussed. A model to improve maintenance experience is proposed and discussed. Using vibration to monitor component conditions, the accurate prediction of remaining life requires (a) enough vibration measurements, (b) numerate records of operating conditions, (c) better discrimination bet ween frequencies in the spectrum and (d) correlation of (b) and (c). This is because life prediction depends on the amplitudes of (and) the frequencies generated by the component damage. Much money could be saved because some of the present policies utilize as little as half of the useful life of a bearing. [ABSTRACT FROM AUTHOR]

Parametric vibration and dynamic stability of the printing paper web with variable speed were studied. The speed of the moving paper web was regarded as the sum of the constant mean speed and the sine pulse speed. The dynamical model and the transverse vibration differential equation were established. The period coefficient state equation was obtained by discretizing the space variable of the differential equation with the differential quadrature method and imported state vector. The instability region and the stability region of the paper web were determined by the implicit Runge-Kutta method. The relationships of the instability region versus the tension ratio, length-width ratio and the amplitude of the sine pulse speed were analyzed. The results provide a theoretical basis for optimizing the structure of the printing machine and improving the working stability of the paper web. [ABSTRACT FROM AUTHOR]

Highlights: [•] A dynamic model for longitudinal vibration assisted guillotining of paper is developed. [•] Empirical model of a stack of thin paper material is identified. [•] Novel measurement procedure for determining dynamic behavior for ultrasonic assisted cutting is developed. [•] Simulated cutting forces are in agreement with the experimentally recorded cutting forces. [Copyright &y& Elsevier]

The model for the analysis of vibrations of paper in a printing device is presented. It is assumed that paper performs transverse vibrations as a membrane having stiffness due to static tension in its plane. The first eigenmodes are determined. It is shown that the eigenfrequencies of transverse vibrations of the analyzed paper can be controlled by the static tension in the plane of the paper. The model for the analysis of stability of paper in a printing device is presented. It is assumed that paper moves with constant velocity in a given direction. The analysis is performed using a plate-bending element with the contribution of the forces of inertia from the convective accelerations. This results in the eigenproblem determining the critical velocities and stability eigenmodes. The stand was made for obtaining the experimental investigations. Using it the nodal lines of the standing waves were determined and using projection moiré the eigenmodes were determined. The obtained results are used in the process of design of the elements of the printing device. [ABSTRACT FROM AUTHOR]

Proposes and implements a method for active compensation for vibrations, without contact, to eliminate the vibrations of a moving paper band in a printing press. Description of the printing test bench; Theoretical vibration frequencies of the natural modes of a paper band; Identification results for the first natural mode of vibration.

Torsional oscillations bound the velocity loop bandwidth (BW) of industrial drives and servo systems, deteriorating the transient response to commands and disturbances. This is especially harmful in multidrive systems like paper machines that need to run synchronized. This paper presents two methods to dynamically compensate the torsional oscillations produced by the compliant components between the motor and the load: either a notch filter or an acceleration feedback based on the rigid-body Luenberger observer. The evaluation includes the effect of reducer backlash, whereby both time and frequency domain responses are used to compare the benefits of each technique in a typical paper machine section. Results show that both methods, if properly tuned, are effective techniques to reduce torsional oscillations and are robust to parameter variations. [ABSTRACT FROM AUTHOR]

The vibration analysis of large and complex structures such as ships is difficult, because a vibrating ship hull (or its components) exhibits quite different vibration characteristics. Technological developments offer new concepts, definitions and comprehensive studies in the ship vibration field. The aim of this paper (bibliography) is to list references to papers, conferences, and proceedings dealing with ship vibrations that were published between January 2000 and April 2003. It contains 64 bibliographic references. The following types of ship vibrations are included: sea conditions, structural analysis, machine components, ship propulsive system, ship machines and special studies. Moreover, basic and brief information (reference, publication type, simulation models, utilizing methods and/or models, examined subject and/or problem) about grouped references has been given in the tables. So, this review paper not only lists references to papers at the millennium, but also helps researchers in their studies on ship vibration to find the necessary references quickly and practically. [ABSTRACT FROM AUTHOR]

A surface acoustic wave-based sample delivery and ionization method that requires minimal to no sample pretreatment and that can operate under ambient conditions is described. This miniaturized technology enables real-time, rapid, and high-through put analysis of trace compounds in complex mixtures, especially high ionic strength and viscous samples that can be challenging for conventional ionization techniques such as electrospray ionization. This technique takes advantage of high order surface acoustic wave (SAW) vibrations that both manipulate small volumes of liquid mixtures containing trace analyte compounds and seamlessly transfers analytes from the liquid sample into gas phase ions for mass spectrometry (MS) analysis. Drugs in human whole blood and plasma and heavy metals in tap water have been successfully detected at nanomolar concentrations by coupling a SAW atomization and ionization device with an inexpensive, paper-based sample delivery system and mass spectrometer. The miniaturized SAW ionization unit requires only a modest operating power of 3 to 4 W and, therefore, provides a viable and efficient ionization platform for the realtime analysis of a wide range of compound. [ABSTRACT FROM AUTHOR]

In this paper, a damage detection method based on an efficient algebraic algorithm of element modal strain energy sensitivity is proposed for detecting damage location and severity. The method adopts a closed form of element modal strain energy sensitivity. The element damage equations have been systematically established and a solution technique incorporated with the singular value decomposition-based regularization algorithm is used to ensure the correct solutions. A number of assumed damage scenarios for numerically simulated beams and two-dimensional frame structure have been used to demonstrate the applicability of proposed method. The noise effect is also presented. It is demonstrated that the proposed method is efficient in a one-step (non-iterative) procedure. [ABSTRACT FROM AUTHOR]

The following response to the discussion of the above mentioned paper is divided into two parts: (1) a response to the issue of our comparison of the ‘apparent period of specimen oscillation’, t, and the natural vibration period of a cracked specimen,T, and (2) a verification of the applicability of our model to ‘short time-to-fracture’ tests, which Rokach has questioned, due to a lack of knowledge of Hopkinson bar techniques. [ABSTRACT FROM AUTHOR]

Under the conditions of a mechanical fault in a motor, mechanical vibration of a specific frequency can be generated. The electrical contact points directly connected to the motor can vibrate at the same frequency. The electrical contact points with poor contact can easily produce a series arc fault under vibration conditions, which affects the reliability of the power supply. In order to detect the series arc fault under different vibration conditions, the arc fault generator is connected between the back end of the frequency converter and the motor. An arc fault experiment under different vibration conditions was carried out and the fault phase current and arc voltage signals were collected. In this paper, the noise-assisted multivariate empirical mode decomposition and the correlation coefficient between each intrinsic mode function are used to select the fault feature signals. Then, the reconstructed signal is input into the series arc fault model combining a multi-scale convolutional neural network and a bidirectional long short-term memory network for training. The research results show that the series arc fault detection method proposed in this paper can effectively detect the series arc fault and can preliminarily identify the type of motor fault causing the mechanical vibration of the motor; the model has good noise immunity and generalization. [ABSTRACT FROM AUTHOR]

Magnetorheological elastomer (MRE) cored sandwich beams with steel skins offer potentially advantageous features when used in the context of structural dynamics. Modelling of the dynamic behaviour is undertaken in this investigation by adopting a higher order sandwich beam theory. Frequency responses from the theoretical modelling are compared with experimental results on MRE cored sandwich beams. The experimental responses are generated from a specially designed test rig to study dynamic behaviour, damping effects, localised magnetic field effects and energy dissipation with varying topology. A numerically based parametric study is conducted to find the optimum geometry for skins and core material to enhance damping performance. Under the same magnetic field strength, sandwich beams with thinner skins and thicker MRE core dissapate more vibration energy. Correlation between the experimental results and numerical studies has been found to be reasonably good. [ABSTRACT FROM AUTHOR]

The article presents a study on conductive polyaniline-coated electroactive paper actuators. It discusses details of the experimentation to design electroactive paper actuators (EAPap) with conductive polymers, including their synthesis, characterization and actuation behaviors. It explores the significance of the research on applications in medical imaging, artificial muscles and organs and smart materials for vibration and noise control.

Abstract: This study concentrated upon refining an in-situ FTIR method to study accelerated ageing of paper under controlled conditions. The standardisation method applying the CH band at 2900cm-1 allowed comparison of different samples from various experiments. To distinguish the features present in the spectra in the carbonyl region coming from carbonyl vibrations not disturbed by water vibrations, bound water present in paper was desorbed and the spectra were recorded at an elevated temperature. An oxidation index of paper defined as a ratio of integrals of bands at 1730cm-1 to that at 1620cm-1 has proved amenable to follow the degradation of cellulose aged under various conditions. The boundary conditions of experiments selected by us were able to discriminate between hydrolysis of glycosidic bonds and oxidation of carbon atoms in a glycopyranose anomer. Following the changes of the spectrum in the carbonyl range proceeding with oxidation time various intermediates of the cellulose partial oxidation were distinguished starting from the least oxidized monocarbonyl groups, through diketones to aldehydes and carboxyls. Assuming a parallel–consecutive mechanism of the cellulose oxidation the spectra were resolved by fitting with multiple Gaussian–Lorentzian functions. [Copyright &y& Elsevier]

Electro-active paper (EAPap) is a cellulose-based smart material that has shown promising results in a variety of smart applications (e.g., vibration sensor, piezo-speaker, bending actuator) with the merits of being flexible, lightweight, fracture tolerant, biodegradable, naturally abundant, cheap, biocompatible, and with the ability to form hybrid nanocomposites. This paper presents a review of the characterization and application of EAPap as a flexible mechanical vibration/strain sensor, bending actuator, and vibration energy harvester. The working mechanism of EAPap is explained along with the various parameters and factors that influence the sensing, actuation, and energy harvesting capabilities of EAPap. Although the piezoelectricity of EAPap is comparable to that of commercially available polyvinylidene fluoride (PVDF), EAPap has the preferable merits in terms of natural abundance and ample capacity of chemical modification. The article would provide guidelines for the characterization and application of EAPap in mechanical sensing, actuation, and vibration energy scavenging, along with the possible limitations and future research prospects. [ABSTRACT FROM AUTHOR]

This paper presents a novel waste-heat-powered, wireless, and battery-less Industrial Internet of Things (IIoT) device designed for predictive maintenance in Industry 4.0 environments. With a focus on real-time quality data, this device addresses the limitations of current battery-operated IIoT devices, such as energy consumption, transmission range, data rate, and constant quality of service. It is specifically developed for heat-intensive industries (e.g., iron and steel, cement, petrochemical, etc.), where self-heating nodes, low-power processing platforms, and industrial sensors align with the stringent requirements of industrial monitoring. The presented IIoT device uses thermoelectric generators based on the Seebeck effect to harness waste heat from any hot surface, such as pipes or chimneys, ensuring continuous power without the need for batteries. The energy that is recovered can be used to power devices using mid-range wireless protocols like Bluetooth 5.0, minimizing the need for extensive in-house wireless infrastructure and incorporating light-edge computing. Consequently, up to 98% of cloud computation efforts and associated greenhouse gas emissions are reduced as data is processed within the IoT device. From the environmental perspective, the deployment of such self-powered IIoT devices contributes to reducing the carbon footprint in energy-demanding industries, aiding their digitalization transition towards the industry 5.0 paradigm. This paper presents the results of the most challenging energy harvesting technologies based on an all-silicon micro thermoelectric generator with planar architecture. The effectiveness and self-powering ability of the selected model, coupled with an ultra-low-power processing platform and Bluetooth 5 connectivity, are validated in an equivalent industrial environment to monitor vibrations in an electric machine. This approach aligns with the EU's strategic objective of achieving net zero manufacturing capacity for renewable energy technologies, enhancing its position as a global leader in renewable energy technology (RET). [ABSTRACT FROM AUTHOR]

A mechanical vibration fault diagnosis is a key means of ensuring the safe and stable operation of transformers. To achieve an accurate diagnosis of transformer vibration faults, this paper proposes a novel fault diagnosis method based on time-shift multiscale increment entropy (TSMIE) combined with CatBoost. Firstly, inspired by the concept of a time shift, TSMIE was proposed. TSMIE effectively solves the problem of the information loss caused by the coarse-graining process of traditional multiscale entropy. Secondly, the TSMIE of transformer vibration signals under different operating conditions was extracted as fault features. Finally, the features were sent into the CatBoost model for pattern recognition. Compared with different models, the simulation and experimental results showed that the proposed model had a higher diagnostic accuracy and stability, and this provides a new tool for transformer vibration fault diagnoses. [ABSTRACT FROM AUTHOR]

Phononic crystals based on lattice structures provide important wave dispersion characteristics as band structures, showing excellent compatibility with additive manufacturing. Although the lattice structures have shown the potential for vibration suppression, a design guideline to control the frequency range of the bandgap has not been well established. This paper studies the dispersion characteristics of plane wave propagation in lattice-based mechanical metamaterials to realize effective vibration suppression for potential aerospace applications. Triangular and hexagonal periodic lattice structures are mainly studied in this paper. The influence of different geometric parameters on the bandgap characteristics is investigated. A finite element approach with Floquet–Bloch's principles is implemented to effectively evaluate the dispersion characteristics of waves in lattice structures, which is validated numerically and experimentally with a 3D-printed lattice plate. Based on numerical studies with the developed analysis framework, the influences of the geometric parameters of lattice plate structures on dispersion characteristics can mainly be categorized into three patterns: change in specific branches related to in-plane or out-of-plane vibrations, upward/downward shift in frequency range, and drastic change in dispersion characteristics. The results obtained from the study provide insight into the design of band structures to realize vibration suppression at specific frequencies for engineering applications. [ABSTRACT FROM AUTHOR]

Wind turbine blades are the main component of wind turbines to capture effective wind energy, and require good quality and reliable performance. Therefore, the manufacturing cost of wind turbine blades is much higher than that of other components of wind turbines. The blade is a slender elastomer prone to vibration. The wind turbine vibration always arises in the blade instability. At the same time, the blade is also a typical aerodynamic component. In the process of rotation, it will not only produce mechanical vibration but also bear aerodynamic force. In this paper, the mechanical properties and modal numerical simulation analysis of composite blades with different hybrid ratios of carbon fiber and glass fiber are analyzed, it is found that with the increase of carbon fiber content, the mechanical properties of the blade gradually increase, and the torsional vibration resistance of the blade become stronger. Therefore, the wind turbine blades of hybrid fiber composites have a longer service life, which can reduce material wastage and help protect the environment. [ABSTRACT FROM AUTHOR]

Honeycomb paperboard has been widely used in transportation and packaging of electronic instruments and furniture owing to the advantages of light weight, good compression resistance, environmental friendliness, and easy degradation. As a common cushioning material in transportation, it is worth studying the damping characteristic and vibration reduction mechanism of honeycomb paperboard. Based on the basic principles of vibration mechanics, the damping of honeycomb paperboard was proposed. Then the influences of cell length, paperboard thickness, grammage of core paper, and the honeycomb structures with face sheet or without face sheet on the damping characteristic of honeycomb paperboard were analyzed. Finally, the vibration reduction mechanism of packaging system with honeycomb paperboard and block was discussed briefly. The results show that the damping value of honeycomb paperboard decreases with the increase of cell length and paperboard thickness. The honeycomb paperboard with large grammage of core paper has high damping value, and yet paper honeycomb core structure without face sheet has poor damping capacity. What's more, the vibration reduction capacity of packaging system is influenced by the deformation and damping characteristic of honeycomb paperboard, among which material damping and structural damping contribute more, honeycomb deformation and air damping contribute less. The weight of block does not affect the damping characteristic of honeycomb paperboard, but affects the vibration reduction capacity of the whole system. [ABSTRACT FROM AUTHOR]

The article presents discussion on analysis of the dynamic responses for a pre-cracked three-point bend specimen. Theoretical part presents a very simple model of the impact specimen. As it was shown in the discussion, accuracy of this model and its applicability for the short time to fracture tests is questionable. An example that demonstrates a weak accuracy of the model is also presented. Most controversial section of the discussion is comparison between the vibration period of the cracked specimen and the apparent period of specimen oscillation.

The object of research is a vibrating plate with interchangeable working bodies developed by the authors. Vibrating plates are an integral part of small mechanization equipment and are mainly intended for layer-by-layer compaction of various materials, such as sand, gravel, bituminous mixtures, etc. Vibration compaction methods are widely used in the construction of road surfaces and other infrastructure facilities. Self-propelled vibrating slabs are also used effectively in other construction processes such as compaction, trench reinforcement, land work and laying paving slabs. They ensure effective compaction of materials due to vibration. This paper is aimed at determining the optimal equipment for compaction of materials during the construction of small objects. Analyzing the characteristics of the machines that most affect the quality of compaction, it is also necessary to evaluate their influence in specific conditions. Studies show that for each type of material, a special working body should be selected, taking into account the specific conditions and requirements for compaction, to ensure optimal quality of work. The authors seek to consider the selection of vibrating plates and their working bodies that best meet the requirements and needs of compaction of various materials on limited construction sites. The analysis of different types of working bodies for different surfaces helps to improve the compaction process and provides optimal conditions for different types of building materials, taking into account their unique properties. The paper examines the influence of the working body on the processed environment, in particular, analyzes the ability of various factors to influence the quality of material compaction. Special attention is paid to the influence of the geometry and size of the contact area on the sealing efficiency of each material type. Overall, this analysis can significantly improve material compaction strategies in the construction industry, contributing to improved construction quality. [ABSTRACT FROM AUTHOR]

The main porpose of this paper is to perform and present at transient process analysis on the influence of different specific speeds (nq) of the three-model pump-turbines that may implemented at the hydropower pump storage plant (HPSP) Bajina Basta, Serbia. The intention is to analyze the operation regimes along the S-shaped characteristic curve, which creates difficulties in calculations during the load-rejection process. These problems are manifested by an unusual increase in water pressure, followed by an increase in machine vibrations, thus threatening the stability of machine operation. The subject of this research is the four-quadrant (4Q) characteristic curves, presented in the form of Suter curves (the head and momentum parameters (Wh and Wm), in dependence of angle (θ)) for different wicket gate openings, of the three pump-turbine models with different specific speeds (nq = 27, nq = 38 and nq = 50). These 4Q characteristics are used as input data for numerical code developed to calculate the simultaneous load rejection of both pump-turbines. The numerical code is based on the method of characteristics and applied to the test case at HPSP. This is especially relevant when dealing with characteristic S-shaped curves that may lead to serious instability in operation during the transient process. The calculation results show changes in the pressure, speed of rotation and discharge of the machine operation regimes, but the important findings are reflected in further application of the results to determine the parametric flow and speed (Q11 and n11) trajectories of the operating points, where the unstable behavior of a pump-turbine operating in turbine mode is presented and periodically the trajectories also pass through the reverse pump zone. [ABSTRACT FROM AUTHOR]

Nowadays researchers are investing in electrical machines fault diagnosis area. The users and manufacturers are strong for containing diagnostic features for reliability and scalability improvement. The regular monitoring enables machine faults early detection and hence helpful for automation by providing process control. The fault detection performance and machinelearning algorithms classification are highly dependent on features involved. The aim of this paper is to solve the network mechanical vibration problem and for that a research on mechanical vibration fault diagnosis is proposed. The first is to use the vibration signal receiving device to record the vibration signal of the target device. In the process of receiving the signal, the measurement point is related to the accuracy of the received signal, so it is necessary to prepare the measurement point. Secondly, the principle of fault detection based on vibration detection is introduced. The main purpose of this method is to identify the fault characteristics, simulate the fault with MATLAB, and obtain the error time-frequency diagram behavior. The feature vector dimension obtained by the idling confirmation example is the same as that of the rotor, which is 14, including 8 relative wavelet packet intensity entropy feature indexes and higher values, minimum value, peak-to-peak value, mean value, mean square error and variance. Finally, the deficiencies of the detected vibration faults are identified and similar improvements are proposed. Improvements only reduce signal vibration, disrupting feature isolation and identifying patterns. The observed percentage accuracy for classification of faults through proposed approach is 98.2%. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to propose a two-stage vibration isolation system for large airborne equipment to isolate aircraft vibration load. Design/methodology/approach: First, the vibration isolation law of the discrete model of large airborne equipment under different damping ratios, stiffness ratios and mass ratios is analyzed, which guides the establishment of a three-dimensional solid model of large airborne equipment. Subsequently, the vibration isolation transfer efficiency is analyzed based on the three-dimensional model of the airborne equipment, and the angular and linear vibration responses of the two-stage vibration isolation system under different frequencies are studied. Findings: Finally, studies have shown that the steady-state angular vibration at the non-resonant frequency changes little. In contrast, the maximum angular vibration at the resonance peak reaches 0.0033 rad, at least 20 times the response at the non-resonant frequency. The linear vibration at the resonant frequency is at least 2.14 times the response at the non-resonant frequency. Obviously, the amplification factor of linear vibration is less than that of angular vibration, and angular vibration has the most significant effect on the internal vibration of airborne equipment. Originality/value: The two-stage vibration isolation equipment designed in this paper has a positive guiding significance for the vibration isolation design of large airborne equipment. [ABSTRACT FROM AUTHOR]

During drilling into the soil, the rotating mechanical structure will be affected by soil particles and external disturbances, affecting the health of the rotating mechanical structure. Therefore, real-time monitoring of the operational status of rotating mechanical structures is of great significance. This paper proposes a working state recognition method based on Mel-spectrum and transfer learning, which uses the mechanical vibration signal's time domain and frequency domain information to identify the mechanical structure's working state. Firstly, we cut the signal at window length, and then the Mel-spectrum of the truncated signal is obtained through the Fourier transform and Mel-scale filter bank. Finally, we adopted the method of transfer learning. The pre-trained model VGG16 is adjusted to extract and classify the features of the Mel-spectrum. Experimental results show that the framework maintains an accuracy of more than 90% for vibration signals under minor window conditions, which verifies the real-time reliability of the method. [ABSTRACT FROM AUTHOR]

Featured Application: The roller bearing and the through shaft bearing are the rotating and load-bearing components of the annealing kiln roller system, which operate at different locations and under different working conditions. Their health status is significant for maintaining the stable operation of the glass production line. In order to improve the efficiency of bearing condition monitoring, this paper proposes a variable-scale attention mechanism guided time-frequency feature fusion transfer learning method, which is used for bearing fault diagnoses at different installation locations in the annealing kiln roller system. It effectively achieves the intelligent diagnosis of roller bearing and through shaft bearing faults in the annealing kiln roller system. Effective real-time health condition monitoring of the roller table and through shaft bearings in the annealing kiln roller system of glass production lines is crucial for maintaining their operational safety and stability for the quality and production efficiency of glass products. However, the collected vibration signal of the roller bearing system is affected by the low rotating frequency and strong mechanical background noise, which shows the width impact interval and non-stationary multi-component characteristics. Moreover, the distribution characteristics of monitoring data and probability of fault occurrence of the roller bearing and through shaft bearing improve the difficulty of the fault diagnosis and condition monitoring of the annealing kiln roller system, as well as the reliance on professional experience and prior knowledge. Therefore, this paper proposes a variable-scale attention mechanism guided time-frequency feature fusion transfer learning method for a bearing fault diagnosis at different installation positions in an annealing kiln roller system. Firstly, the instinct time decomposition method and the Gini–Kurtosis composed index are used to decompose and reconstruct the signal for noise reduction, wavelet transform with the Morlet basic function is used to extract the time-frequency features, and histogram equalization is introduced to reform the time-frequency map for the blur and implicit time-frequency features. Secondly, a variable-scale attention mechanism guided time-frequency feature fusion framework is established to extract multiscale time-dependency features from the time-frequency representation for the distinguished fault diagnosis of roller table bearings. Then, for through shaft bearings, the vibration signal of the roller table bearing is used as the source domain and the signal of the through shaft bearing is used as the target domain, based on the feature fusion framework and the multi-kernel maximum mean differences metric function, and the transfer diagnosis method is proposed to reduce the distribution differences and extract the across-domain invariant feature to diagnose the through shaft bearing fault speed under different working conditions, using a small sample. Finally, the effectiveness of the proposed method is verified based on the vibration signal from the experimental platform and the roller bearing system of the glass production line. Results show that the proposed method can effectively diagnose roller table and through shaft bearings' fault information in the annealing kiln roller system. [ABSTRACT FROM AUTHOR]

Quantitative analysis of human gait is critical for the early discovery, progressive tracking, and rehabilitation of neurological and musculoskeletal disorders, such as Parkinson's disease, stroke, and cerebral palsy. Gait analysis typically involves estimating gait characteristics, such as spatiotemporal gait parameters and gait health indicators (e.g., step time, length, symmetry, and balance). Traditional methods of gait analysis involve the use of cameras, wearables, and force plates but are limited in operational requirements when applied in daily life, such as direct line-of-sight, carrying devices, and dense deployment. This paper introduces a novel approach for gait analysis by passively sensing floor vibrations generated by human footsteps using vibration sensors mounted on the floor surface. Our approach is low-cost, non-intrusive, and perceived as privacy-friendly, making it suitable for continuous gait health monitoring in daily life. Our algorithm estimates various gait parameters that are used as standard metrics in medical practices, including temporal parameters (step time, stride time, stance time, swing time, double-support time, and single-support time), spatial parameters (step length, width, angle, and stride length), and extracts gait health indicators (cadence/walking speed, left–right symmetry, gait balance, and initial contact types). The main challenge we addressed in this paper is the effect of different floor types on the resultant vibrations. We develop floor-adaptive algorithms to extract features that are generalizable to various practical settings, including homes, hospitals, and eldercare facilities. We evaluate our approach through real-world walking experiments with 20 adults with 12,231 labeled gait cycles across concrete and wooden floors. Our results show 90.5% (RMSE 0.08s), 71.3% (RMSE 0.38m), and 92.3% (RMSPE 7.7%) accuracy in estimating temporal, spatial parameters, and gait health indicators, respectively. [ABSTRACT FROM AUTHOR]

With the rapid development of metro construction, shield machines inevitably have to traverse a variety of complex geological conditions, leading to the frequent occurrence of geological disasters, equipment failures, building vibration and other problems. Vibration, as an important feature of the shield tunneling process, has received more and more attention in recent years. This paper summarizes the relevant research progress of vibration monitoring during shield construction from 2015 to 2023. It analyzes the shield vibration generation mechanism, monitoring methods and application areas. Firstly, the shield vibration type is divided into mechanical vibration triggered by internal excitation and forced vibration triggered by external excitation, and the principles of vibration generated by shield main bearing, gearbox and disc cutter are discussed. Then, the commonly used vibration monitoring methods are outlined according to the installation location of the sensors (inside and outside of the shield). Finally, the applications of vibration signals in the diagnosis of shield faults, the identification of geologic conditions, and the evaluation of the current status of the interference with the buildings are summarized. This paper discusses the development trend of vibration monitoring during shield tunneling based on the current research situation and the current technology level, which provides valuable insights to enhance the safety and intelligence of shield construction. [ABSTRACT FROM AUTHOR]

Deep learning has the characteristics of high efficiency, high accuracy and low knowledge dependence, and has become a hot method in the research field of rotating machinery fault diagnosis. The time–frequency transform can show both the time and frequency characteristics of the vibration signal, so the time–frequency image is often used as the input of deep learning networks. At present, there are many time–frequency transform methods, and how to choose one is a problem worth discussing. This paper proposed a time–frequency image quality evaluation method based on improved local interpretable model-agnostic explanations (LIME). With the input of deep learning networks as the application background, this method evaluates the time–frequency image quality of rotating machinery vibration signals from two aspects: the accuracy of the diagnosis results and the consistency of the interpretation results with prior knowledge. The feasibility of the proposed evaluation method is verified by experiments on the measured data set, and engineers' trust in the deep learning model is improved. [ABSTRACT FROM AUTHOR]

There is limited research focused on achieving optimal torque control performance of Switched Reluctance Generators (SRGs). The majority of existing studies tend to favor voltage or power control strategies. However, a significant drawback of SRGs is their susceptibility to high torque ripple. In power generation systems, torque ripple implicates fluctuations in the generated power of the generator. Moreover, high torque ripple can lead to mechanical vibrations and noise in the powertrain, impacting the overall system performance. In this paper, a Torque Sharing Function (TSF) with Indirect Instantaneous Torque Control (IITC) for SRG applied to Wind Energy Conversion Systems (WECS) is proposed to minimize torque ripple. The proposed method adjusts the shared reference torque function between the phases based on instantaneous torque, rather than the existing TSF methods formulated with a mathematical expression. Additionally, this paper introduces an innovative speed control scheme for SRG drive using a Fuzzy Super-Twisting Sliding Mode Command (FSTSMC) method. Notably robust against parameter uncertainties and payload disturbances, the proposed scheme ensures finite-time convergence even in the presence of external disturbances, while effectively reducing chattering. To assess the effectiveness of the proposed methods, comprehensive comparisons are made with traditional control techniques, including Proportional–Integral (PI), Integral Sliding Mode Control (ISMC), and Super-Twisting Sliding Mode Control (STSMC). The simulation results, obtained using MATLAB®/SIMULINK® under various speeds and mechanical torque conditions, demonstrate the superior performance and robustness of the proposed approaches. This study presents a thorough experimental analysis of a 250 W four-phase 8/6 SRG. The generator was connected to a DC resistive load, and the analysis focuses on assessing its performance and operational characteristics across different rotational speeds. The primary objective is to validate and confirm the efficacy of the SRG under varying conditions. [ABSTRACT FROM AUTHOR]

This paper introduces a novel type of floating machine gun that can be simplified as a self-balancing two-degree-of-freedom mechanical system with distinct vibration characteristics. The model accounts for intricate motion patterns and encompasses numerous potential influencing factors. Multifactor combination optimization of the system represents a pressing engineering challenge. After establishing a simulation model for the machine gun and validating it experimentally, seven factors were chosen as optimization variables. The maximum recoil displacement of the inner receiver (MRD) and the firing rate were chosen to be indicators. Orthogonal combinations and variance analyses were used, and the effects of multiple factors were analyzed using SPSS software; these processes led to a determination of the optimal combination. The results indicated that the piston cylinder pressure, the bi-directional buffer spring energy storage, and the inner receiver mass significantly affected the MRD. Furthermore, the automaton mass and the reset spring energy storage were found to substantially affect the firing rate. Careful analysis of the variance results facilitated the determination of the optimal combination of parameter values. Remarkably, the optimal combination chosen resulted in an MRD reduction of approximately 20.2% and a firing rate increase of approximately 26.6%. [ABSTRACT FROM AUTHOR]

In this paper, based on the non-linear mechanics theory of the drill pipe, a mechanical model of stick-slip vibration of the drill pipe has been established by considering the torsional properties of the drill pipe, kinetic energy and the motion law of the bit. The example calculations and sensitivity analysis of the parameters are carried out. The results show that increasing the rotational speed, viscous damping, length of the drill collar and de-creasing the weight of bit have the effect of suppressing the stick-slip vibration. [ABSTRACT FROM AUTHOR]

This paper is concerned with the stability analysis and design of the n-DOF (n-degree-of-freedom) mass-chain vibration systems containing both semi-active and passive mechanical controllers. Based on Lyapunov's stability theory, sufficient conditions are derived for the n-DOF vibration system containing a semi-active switched inerter and a passive mechanical network with the first-order admittance to be globally asymptotically stable. Furthermore, the optimization designs of a quarter-car vibration control system and a three-storey building vibration system are conducted together with the derived stability results, and the instability cases contradicting the stability conditions are presented for illustration. The optimization and simulation results show that the combination of semi-active and passive mechanical controllers in vibration systems can clearly enhance system performances in comparison with the conventional semi-active or passive control. The novelty of this paper is that the stability problem of a general n-DOF vibration system that simultaneously contains a semi-active controller and a first-order passive controller is investigated for the first time, where such a system combines the advantages of both semi-active and passive mechanical controllers. The investigations and results can provide an essential foundation for further exploring the stability problems of more general systems, and can be applied to the controller designs of many vibration systems in practice. [ABSTRACT FROM AUTHOR]

Wound rotor induction machine (WRIM) has been extensively used in different applications such as medium-power wind turbines and traction systems. Since these machines work under harsh and difficult conditions, condition monitoring of such systems is crucial. Different electrical and mechanical signatures of machines were used for electrical and mechanical fault detection in electrical machines such as vibration, acoustic emission, stray flux, and stator current signature. In recent years, stator current signature analysis due to simplicity, cost-effectiveness, and availability has been considered for fault detection process in comparison with previous conventional methods such as acoustic and vibration. In this paper, a high-resolution technique based on the chirp-Z transform is used for rotor asymmetry fault (RAF) detection in induction machines through stator current signature analysis. In this regard, the Teager-Kaiser energy operator (TKEO) technique for demodulation fault characteristic frequency is used as a pre-processing stage to avoid leakage of the supply frequency. The method has better accuracy due to better spectral resolution and resolvability. Furthermore, computational complexity in the proposed method will be reduced in comparison to the previous conventional ones which have used the Fast Fourier transform (FFT). The proposed technique is tested through synthetic and experimental stator current of WRIM in healthy and faulty conditions with different rotational speeds and fault severities. The results show the validity of the proposed method in rotor asymmetry fault detection through the stator current signature of WRIM. [ABSTRACT FROM AUTHOR]

A steady-state sinusoidal and distortion-free excitation source is very important for the accuracy and consistency of the calibration parameters of micro-electro-mechanical systems (MEMS) inertial sensors. To solve the problem that the current MEMS inertial measurement unit (IMU) calibration device is unable to reproduce the spatial motion of linear and angular vibration coupling, research topics on the coupling vibration characteristics and parameter identification for an electromagnetic linear-angular vibration exciter are proposed. This research paper used Ampere's law and Lorentz force to establish the analytical expressions for the electromagnetic force and electromagnetic torque of the electromagnetic linear-angular vibration exciter. Then, the main purpose of this paper is to establish uniaxial and coupled vibration electromechanical analogy models containing mechanical parameters based on the admittance-type electromechanical analogy principle, and the parameter identification model is also obtained by combining the impedance formula with the additional mass method. Finally, the validity of the coupling vibration characteristics and the parameter identification model are verified by the frequency response simulation and the additional mass method, and the relative error of each parameter identification is within 5% in this paper. [ABSTRACT FROM AUTHOR]

The article offers information on the publications, products and information received as a result of exchange agreements, goodwill, research and subscriptions related to Non-Destructive Testing Topics discussed include several techniques "Ensuring supply security through hydrogen buried pipelines," "Measures to prevent fluorocarbon leakage from refrigeration and air conditioning equipment," and "Application of a hydrogen leak test."

This paper presents the problem of natural vibration of a two-stage hydraulic cylinder subjected to Euler compression load. The considered hydraulic cylinder is freely supported at both of its ends. The linear vibration problem of the telescopic hydraulic cylinder is based on the kinetic stability criterion using Hamilton’s principle and the Bernoulli-Euler theory. The stiffness of the guide and sealing elements between successive stages of the hydraulic cylinder were considered in this paper. These stiffnesses were modelled using translational and rotational springs. The effects of cylinder wall thickness, piston rod diameter, and thickness of guiding and sealing elements on the natural vibration of the system were analysed. Results are presented in the form of characteristic curves on the plane load – natural frequency with different parameters characterizing the considered hydraulic cylinder. [ABSTRACT FROM AUTHOR]