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This study used the electrodeposition resin molding method (EDRM), an easy and effective technique, to create composite materials. Because it's a new technique, consideration of the impact of various production parameters on composite qualities was necessary. The effects of altering these EDRM voltage and electrical current conditions on the static and dynamic properties of composites were examined and tuned to fit the objective. Three distinct voltage values (100, 150, and 200 V) and five different current conditions (0.5, 0.75, 1.00, 1.25, and 1.50 A) were used for the manufacturing variables. In accordance with that, the effectiveness of heat treatment was also evaluated using two distinct temperature profiles. The bending strength of composites was somewhat influenced by the voltage and current conditions of the EDRM, but not in a particularly significant way. However, the bending strength of composites was significantly impacted by the heat curing temperature as well as the heat curing time. [ABSTRACT FROM AUTHOR]

A bottom–up multi-scale performance transfer chain is developed to ascertain the gradual change in the law of vibration characteristics in spatial steel truss structures under fatigue loading. This chain derives the interrelationship between vibration characteristics and the performance of each structural component. Based on the evolution characteristics of the performance model of the member scale in the transfer chain, a new analytical model of the shape function is established. Building on these foundations, a refined model was formulated to depict the gradual change of vibration characteristics in spatial steel truss systems under fatigue loading. This model integrates the cumulative damage rule, the structural residual performance rule, the finite element method and other pertinent theories. The gradual change in vibration characteristics of a steel truss girder bridge subjected to train loads was analyzed using a self-developed three-dimensional finite element analysis framework tailored explicitly for assessing gradual change issues in spatial steel truss structures. The analysis results indicate that the effective residual cross-sectional area and the structural frequency continuously decline as the service time increases. This comprehensive study advances the understanding of fatigue-induced changes in spatial steel truss structures. It offers analytical perspectives for predicting and mitigating the long-term impacts of dynamic loads on large-scale infrastructural components. [ABSTRACT FROM AUTHOR]

The goal of this study is to solve the problem of the condenser's rotor violently vibrating due to the unbalanced magnetic pulling force (UMP) caused by the dynamic air gap eccentricity of the condenser. To do this, the UMP is theoretically calculated and simulated. The results show that the UMP is a force whose main component is in the natural frequency and that its magnitude is directly proportional to the eccentricity. The modal analysis also shows that increasing the stiffness of the bearing causes a higher critical rotor speed, with the bearing stiffness interval of 1×106 N/m to 1×1010 N/m experiencing significant changes. The explanation is that the rotor is in a mixed mode, with rigid mode dominant or bending mode dominant when the bearing stiffness is between 1×106 N/m and 1×1010 N/m. The critical speed is not significantly affected by the bearing damping. The UMP is put on the rotor surface in a harmonic response analysis. The condenser's rotor is discovered to have a noticeable amplitude peak close to the intrinsic frequency. It is discovered that the amplitude peak decreases as bearing stiffness increases, increases as eccentricity increases, and decreases as bearing damping increases. The first-order force transfer rate peak of the bearing grows and then stabilizes as bearing stiffness increases, but the overall force transfer rate keeps rising. The results demonstrate that condenser rotor vibration can be mitigated by modifying bearing stiffness, damping, and decreasing eccentricity. [ABSTRACT FROM AUTHOR]

The operation condition of axle-box bearings strongly affects the running safety of vehicles. However, the presence of rail welds can impact the wheel-rail interaction system, causing changes in the dynamic response of axle-box bearings and furtherly affecting their health condition. Despite this, there is still a lack of discussion and analysis on the effect of rail welds on dynamic characteristics of axle-box bearings. Therefore, a vehicle-track coupling dynamics model is developed. Besides the rigid vehicle model, flexible track model and wheel-rail contact model, the axle-box bearing model and flexible wheelset model are considered. Among them, the axle-box bearing model accounts for the motion of the roller and cage decentralized into multiple segments. Using modal superposition method, the flexible deformation of the wheelset is calculated and overlapped with its rigid displacement for the flexible wheelset model. The performance of the model is verified through theoretical analysis and field tests. It is crucial to consider the wheelset as flexible in the presence of rail welds and its effects are also researched. Moreover, the effect of the rail weld geometry on the wheel-rail separation is studied, and the consequence caused by rail welds on the bearing damage is discussed under different vehicle speeds. [ABSTRACT FROM AUTHOR]

The escalating severity and frequency of extreme weather conditions, such as typhoons and thunderstorms, exacerbate the failure risk of transmission lines. In this study, a series of wind tunnel tests were conducted to investigate the rain-wind-induced vibrations (RWIVs) on an overhead transmission conductor. First, a conductor sectional model was fabricated to accurately represent the physical appearance and material of the prototype conductor. Then, experimental wind-rain conditions were simulated to investigate the impact of rainfall on the cross-wind buffeting vibration of the conductor, with attempts made to reproduce the phenomenon of RWIVs. Meanwhile, section model vibration tests were conducted on the conductor model with an artificial rivulet to investigate the effects of rivulet position, dynamic characteristics, mass, and wind yaw angle. Finally, high-frequency force balance (HFFB) tests were performed on the same conductor model, and the mechanism of the RWIVs was discussed from the viewpoint of galloping. The results indicated that the presence of rainfall slightly decreased the in-plane vibrations of the conductor when no RWIVs occurred. Due to the interference from the spiral aluminum wires on the conductor surface, this type of conductor is less susceptible to RWIV compared to smooth cables. The conductor model with an artificial rivulet exhibited significant vibrations at position angles 휃 = 48∘–60∘, essentially corresponding to negative Den Hartog coefficients. [ABSTRACT FROM AUTHOR]

The present study investigates the vibration analysis of cylindrical shells composed of fiber metal laminate (FML) with embedded piezoelectric layers, undergoing fluid-structure interaction (FSI) and resting on a Pasternak elastic foundation based on the principles of three-dimensional elasticity theory. Using the state space approach, the equations of motion were derived under simply supported boundary conditions. The natural frequencies of the FML cylindrical shell, accounting for the presence of a moving fluid, were computed by solving the eigenfrequency equations. The study examined the influence of various parameters, including boundary conditions, length-to-radius ratio, fluid type, fluid velocity, circumferential wave number, and radius-to-thickness ratio, on glass-reinforced aluminum laminate (GLARE), aramid-reinforced aluminum laminate (ARALL), and carbon-reinforced aluminum laminate (CARALL). A constant composite/metal volume ratio was assumed. The results obtained were validated by comparing with natural frequency values from the existing literature, confirming the agreement and convergence with previous studies. The results confirm that the highest natural frequency values are assigned to the CARALL, ARALL and GRALE structures in descending order. Furthermore, an increase in fluid flow velocity through the cylindrical shell correlates with a reduction in natural frequency. [ABSTRACT FROM AUTHOR]

Highlights In this paper, the mechanical properties and vibration characteristics of Carbon‐Glass Hybrid Fiber Composites (CGHFC) are experimentally investigated with varying axial directions and blending ratios. The experimental results demonstrate a significant increase in the tensile strength of the CGHFC with an increasing content of carbon fibers. The biaxially CGHFC exhibits a maximum static tensile strength of 413.27 MPa in the 0° direction and 466.33 MPa in the 90° direction, surpassing both the quadratic and uniaxial directions. Notably, compared to biaxially oriented glass fiber material, the tensile strength of CGHFC is enhanced by 44.36%, thereby significantly improving its overall performance, making them particularly suitable for blade structures subjected to simultaneous tensile and vibratory loads. By optimizing the fiber orientation and blend ratio, the CGHFC provides good vibration control and fatigue resistance while ensuring high strength, thus maximizing the overall performance and service life of the blades. The results of this paper provide important data and theoretical support for the selection and design of wind turbine blade materials and help to promote the development of composite materials in wind turbine blade structure and design. CGHFCs show enhanced tensile strength with more carbon fibers. Biaxial CGHFCs have max tensile strength at 0° and 90° directions. CGHFCs' strength improves by 44.36% over glass fiber materials. Optimized CGHFCs offer superior vibration control and fatigue resistance. Research supports wind turbine blade material innovation. [ABSTRACT FROM AUTHOR]

To investigate the multifield coupled vibration properties of electric-drive systems of electric vehicles, an improved equivalent magnetic network model of a permanent magnet synchronous motor suitable for variable speed/load and other non-stationary conditions is established by considering the nonlinear factors such as stator slotting, pole distribution, and magnetic saturation. On this basis, a machine-electric–magnetic multi-field coupling dynamics model of the electric drive system is established by comprehensively considering the gear transmission error, time-varying meshing stiffness, etc. The laws affecting the dynamic properties of the electric drive system under excitation of the internal nonlinear factors and external load are investigated. Research shows that electromagnetic excitation exacerbates the vibration amplitude of the gear. Mechanical excitation modulates the current frequency. The system vibration response amplitude trend is consistent with the current low-frequency harmonic components that can be used to monitor the system vibration state. External shock loads have the greatest impact on the vibration of the first-stage active gear and secondary-stage driven gear. The coupling effect of the motor and gear can effectively suppress the shock oscillation caused by a sudden change in the load. [ABSTRACT FROM AUTHOR]

In this paper, an electro-hydraulic exciter controlled by an alternating current distribution valve is proposed, and a systematic analysis of the influence of pipe effect on the vibration characteristics of the electro-hydraulic exciter is investigated by simulation and experiments. The vibration characteristics curves for different pipe parameters are obtained, and the relative errors between simulation and experiment are evaluated. Moreover, a significant regression model of pipe parameters and vibration characteristics of the electro-hydraulic exciter is established by using the quadratic regression analysis method and the Box-Behnken experiment design method. Significant differences in the influence of pipe parameters on vibration characteristics are obtained by ANOVA (Analysis of Variance), and the influence of pipe parameter interaction on vibration characteristics is discussed. The results show that the relative importance of pipe parameters on the vibration characteristics of electro-hydraulic exciter, from high to low, is as follows: pipe diameter, elastic modulus, and pipe length. Notably, there is also an interaction between the pipe parameters, and the significance of these interactions is ranked from high to low as the interaction between the layers of steel wire and diameter, the interaction between diameter and length, and the interaction between the layers of steel wire and length. [ABSTRACT FROM AUTHOR]

The operation and service performance of ballasted track on bridges face significant challenges due to high-speed railway train operations. To investigate the mechanical characteristics of ballasted track on bridges, field experiments were conducted. A coupling model of ballasted track on a simply-supported girder bridge was established using the coupling method of discrete element and multi-flexible body dynamics and analyzes the changes in ballast bed settlement deformation, stiffness and energy with increasing load cycles. The findings reveal that dynamic loading alters the original contact state of ballast particles, displaying notable anisotropy vertically and longitudinally and isotropy horizontally. The vibration of ballast particles on bridges is more pronounced than on the subgrade, with vibration acceleration under the sleeper at 150mm depth on the bridge being 2.89 times that on the subgrade foundation. As the system stabilizes, the interlocking effect among granular ballast particles strengthens, reducing mutual sliding and increasing ballast bed stiffness by approximately 7.8–9.5% compared to the initial state, while total energy and dissipated energy gradually decrease. It is recommended to monitor the quality of ballast particles under the sleeper of ballasted tracks on bridges, implement vibration mitigation measures, or periodically replace ballast particles. [ABSTRACT FROM AUTHOR]

In order to reduce the vibration localization of multistage blade-disk system of aeroengine compressor, the integral model and substructure model of multistage blade-disk system are established by using substructure modal synthesis method, and the dynamic characteristics of two models are analyzed and the accuracy of the substructure model is verified by comparison. Based on the substructure model, two optimization algorithms of the random wear mass and the snake optimization are proposed. The results show that the vibration amplitudes of the two models are in good agreement in the first 200 modes, and the substructure model meets the requirement of analysis accuracy. Both optimization algorithms can effectively reduce the degree of the vibration localization of the mistuned blade-disk system. The random wear mass algorithm can quickly reduce the amplitude of the blade. The snake optimization algorithm can find the global optimal solution with enough iterations. The results show that the maximum vibration amplitude and the vibration localization factor after optimization are reduced by 5.72 % and 12.0 % respectively by using the random wear mass algorithm, and that of 9.13 % and 16.7 % respectively by using the snake optimization algorithm. The analysis method presented in this paper takes into account the analysis efficiency and analysis precision, it can be used for dynamic analysis and vibration reduction optimization of large power machinery such as aeroengine and gas turbine, and provides a basis for further improving the reliability and service life of aircraft. [ABSTRACT FROM AUTHOR]

In this study, we investigated the natural dynamic characteristics of bi-directional (2D) functionally graded material (FGM) beams using differential quadrature method (DQM). The higher order shear deformation theory was used to reconstruct the displacement and strain fields at any point on the beam. The resulting equilibrium equation of elasticity was expressed by stress is equivalently integrated along the height direction of a rectangular beam, which helps derive the ordinary differential characteristic equations of the free vibration problem of 2D FGM beams, including the natural frequency and the triple-coupled mode functions. Then, using the DQM, the eigenvalue problems of the derived differential equation for free vibration of 2D FGM beams were transformed into a set of algebraic equations representing the eigenvalue problems. The obtained algebraic equations were solved using the orthogonal triangular decomposition method (QR). First, several orders of natural frequencies of the free vibrations of 2D FGM beams were calculated sequentially, and then, the triple-coupled mode functions were obtained together. Numerical examples were used to illustrate the effects of the thickness ratio, grading indexes, and the supported edges on the natural frequency in detail. Numerical results validated the feasibility and accuracy of the developed DQM for solving the problem of free vibrations in 2D FGM beams. [ABSTRACT FROM AUTHOR]

Optical mirrors have high requirements for surface precision, requiring ultra-precision processing. The revolving movement of a computer-controlled optical surfacing (CCOS) grinding system will induce vibrations in a five-degrees-of-freedom hybrid processing robot (5-DOF-HPR) and a flexible support system (FSS) in a large optical mirror processing system (LOMPS). As a result, the mirror surface will vibrate, which will ultimately affect the surface accuracy of the final optical mirror. Therefore, the differential equation representing the vibration of the 5-DOF-HPR is established based on the spatial beam unit, which transforms the generalized coordinates into modal coordinates, thereby removing the coupling terms of the vibration differential under generalized coordinates. At the same time, a dynamic analysis of the CCOS grinding system is performed, and the magnitude and direction of the centrifugal force and reaction force are calculated. Then, the natural frequencies of the 5-DOF-HPR and the FSS are measured experimentally and compared with the simulation results; thus, the accuracy and effectiveness of the model are verified. Finally, the vibration characteristics of the processed optical mirrors under different influencing factors are obtained. A theoretical and experimental basis for parameter optimization and path planning of the LOMPS is provided to improve the surface accuracy of the processed optical mirror. [ABSTRACT FROM AUTHOR]

In rotating machinery, the condition of rolling bearings is paramount, directly influencing operational integrity. However, the literature on the fault evolution of rolling bearings in their nascent stages is notably limited. Addressing this gap, our study establishes an innovative nonlinear dynamic model for early fault evolution of rolling bearings based on collision impact. Firstly, considering the fault evolution characteristics, the influence of the rolling element and fault structure, the dynamic model of early fault evolution between the rolling element and the local fault is established. Secondly, according to the Hertzian contact deformation theory, a nonlinear dynamic model of rolling bearings expressed as mass-spring is established. Thirdly, the energy contribution method is used to integrate the fault evolution model and the nonlinear dynamic model of the rolling bearing. A nonlinear dynamic model of early fault evolution of the rolling bearing is proposed by using the Lagrangian equation. Comparing the simulation results of the nonlinear dynamic with the experimental results, it can be seen that the numerical model can effectively predict the evolution process and vibration characteristics of the fault evolution of rolling bearings in the early stage. [ABSTRACT FROM AUTHOR]

AbstractIn modern engineering practice, the simultaneous exposure to high temperatures and vibrations can threaten the security of the structure. In this paper, a novel additional damping structures with entangled metallic wire material (EMWM) are proposed and its vibration characteristics at high temperature are investigated. Firstly, a thermal/vibration coupling test platform of additional damping structures is designed and constructed, and a high-temperature vibration pickup method is adopted to extract the response signals. On this basis, the 5–400Hz frequency sweep tests are carried out under the unilateral constraint condition. The effects of excitation magnitude, ambient temperature and EMWM thickness on the vibration parameters are analyzed. The vibration performance is evaluated by modal identification and loss factor by half-power method. The results show that the damping performance of the constrained damping structure and insertion damping structure is better than that of the free damping structure under different excitation levels; the increase of the ambient temperature generates a greater influence on the vibration damping performance of the structure, but it still has a good stability; the amplitude change of the structure is more apparent through the increase of EMWM thickness, and the vibration damping performance is more superior. Under extreme engineering environments, a new approach to plate damping structures is provided that still maintains excellent performance. [ABSTRACT FROM AUTHOR]

The rolling bearing is an important supporting part of the spindle drive system of the computer numerical control machine tool. The defects of the bearing assembly affect the performance and work efficiency of the whole computer numerical control machine tool drive system. To investigate the difference in internal dynamic characteristics of bearings under the condition of defects, the dynamic characteristics of the defective bearings were investigated with 7002C angular contact ball bearings as the research object. Firstly, the dynamic model of bearing assembly with pitting defects was constructed by using finite element simulation software. Then, the simulation results and theoretical calculation results of the ball rotation speed of the bearing at different speeds were compared. Finally, the dynamic characteristics of the defects of the outer ring, the ball, and their compound defects were comprehensively analyzed. The research results show that the shear stress of composite defects is higher than that of the single defects, and the shear stress fluctuates sharply. Different fault states show the difference in vibration signals. Ball defects show little fluctuation, outer ring defects are stable, and compound defects are the most unstable and have the largest vibration amplitude. The ball' s rotational velocity exhibits irregular and inconsistent variations, and the ball defects, outer ring defects, and compound defects exhibit similar but slightly different periodicity and peak-valley delay on the velocity curve. The constructed finite element model can be used to study the dynamic characteristics of rolling bearings under different fault states and can provide some important references for the optimization design of bearings. [ABSTRACT FROM AUTHOR]

In order to obtain the vibration response characteristics of the propeller spindle system effectively and accurately, and provide the basis for the subsequent fault diagnosis, the modal simulation and test of the spindle model were carried out. With the propeller set as eccentric mass, the amplitude and torsion angle of the spindle model were simulated under the condition of excited vibration and unexcited vibration respectively, and the frequency response of bending and torsion under the coupled condition was obtained. The newmark-β method was used to solve the transient response of the bent-torsional coupling model. The results shows that when the propeller spindle system undergoes rotation at a specific frequency and experiences bending vibration excitation force, the latter will induce torsional vibration response. Moreover, the amplitude of the torsional vibration response varies with changes in the frequency of the bending vibration excitation force. [ABSTRACT FROM AUTHOR]

The oil‐immersed transformer is a crucial power equipment in power system, which is prone to abnormality or failure under long running. In order to improve the level of operation and maintenance and ensure the safe and reliable operation of the power grid, it is necessary to diagnose the fault of the oil‐immersed transformer in time. Most of the traditional fault vibration methods are off‐line detection, and are easily disturbed by mechanical deterioration. In order to solve the above problems, this paper established a 3D electromagnetic and stress coupling simulation model of oil‐immersed transformer by finite element simulation software. The vibration characteristics of oil‐immersed transformer core winding are obtained, and at the same time, this paper obtained the vibration signals at different positions on transformer core winding and oil tank. According to the vibration signal of the transformer, the best measuring point position of the tank wall is proposed to accurately reflect the vibration characteristics of the transformer. The signal data is preprocessed by CEEMDAN decomposition method, and the signal data is classified by GWO‐BP composite classification algorithm. This paper proposed an online transformer fault diagnosis method based on vibration signal, which achieves the purpose of accurately diagnosing oil‐immersed transformer faults. The test results show that in the case of oil‐immersed transformers the accuracy of the proposed transformer fault diagnosis method is more than 93%, which provides important guiding significance for the safe and stable operation of the transformer. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

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In order to ensure the vibration safety of rotor systems in the next generation of aero-engines and reduce the impact of misalignment faults, the effect of support misalignment on the vibration characteristics of rotor systems under ultra-high operating speeds is investigated in this paper. Firstly, an analytical excitation model of the rotor systems under ultra-high operating speeds is established, considering the impact of the support misalignment. Then, based on the model of the misaligned combined support system, the dynamic model of the flexible discontinuous rotor support system with the support misalignment is presented. Subsequently, based on the established model, the effects of support parameters and support misalignment amounts on the vibration characteristics of the rotor support system are analyzed. Finally, experimental validation of the research findings is conducted. The research result shows that the support misalignment increases the vibration response of the rotor, reduces the vibration reduction efficiency of the combined support system, and consequently decreases the vibration safety of the rotor support system. [ABSTRACT FROM AUTHOR]

Radial gate, a spatial frame structure, is the key factor to control water discharge in dam structure and storm surge barriers. However, the fluid-induced vibration (FIV) problem always occurs owing to fluctuation loads exerted on the gate, threatening the safety of hydropower stations. In this work, two fluid–structure interaction (FSI) modal analysis methods—the coupled acoustics–structure method and the added-mass method—are provided. Further, a comprehensive investigation on the vibration characteristics of the spatial radial gate, considering spatial structural characteristics and the FSI effect, is conducted. The numerical results revealed that the feasibility of the proposed coupled acoustics–structure method in analyzing FSI modal analysis was demonstrated; moreover, a reasonable length of the fluid domain in front of the skinplate existed for efficient computation. Meanwhile, through the added-mass method, the rational added-mass discount factor of hydrodynamic loads obtained from the Westergaard formula was provided. The FSI effect induced whole-gate rotation vibration streamwise around trunnion pins, significantly reducing the gate's fundamental vibration frequency. In addition, three typical dynamic-instability vibration patterns of radial gates were presented. These patterns were affected by spatial structural characteristics and FSI. It was demonstrated that the struts and skinplate coupled bending–torsional vibration would cause the radial gate frame structure to fail catastrophically. The proposed insights can provide guidelines of vibration characteristics analysis of the radial gate submerged in flow water in reservoir and storm surge barriers. [ABSTRACT FROM AUTHOR]

In order to develop green energy, reduce carbon emissions, and alleviate global warming and the green energy crisis, many researchers focus on wave energy, using a device to convert wave energy into electricity. The three main types of wave energy converters are the overtopping type, the oscillating water column type, and the oscillating body type, and for most of them, the power generation efficiency is low. The research team in this paper proposed a wave energy converter for a wave-induced oscillation heave plate. The plate vibrates up and down under the action of waves, and the captured energy of the vibrating plate transfers the energy to the generator, so as to generate electricity. There is electricity only when there is vibration; therefore, the vibration characteristic of the converter is crucial to power generation. So, the vibration characteristics of the energy capture structure of the converter were studied experimentally. The test results show that the energy harvesting device can vibrate, and the vibration effect is good, which further indicates that the device can generate electricity. The effects of different wave conditions and system stiffnesses on amplitude and corresponding amplitude were studied, and the amplitude increases with the increase in wave height and period and decreases with the increase in system stiffness. The amplitude response decreases with the increase in wave height and system stiffness. Under the test conditions, the maximum amplitude of the system is 6.23 cm (when the wave period is 1.40 s, the wave height is 0.25 m, and the system stiffness is 1735.62 N/m), and the maximum amplitude ratio is 0.34 (when the wave period is 1.1 s, the wave height is 0.10 m, and the system stiffness is 1735.62 N/m). [ABSTRACT FROM AUTHOR]

Taking the wheelset and axle-box bearings of a high-speed train as research objects, the vehicle track coupling dynamics model including the wheelset and axle-box bearings are built to study the contact vibration characteristics of the internal structure of axle-box bearings under the track excitation of Beijing-Tianjin rail and wheel flat. The results show that when the flat defect of the wheel occurs, it causes high-frequency vibration of the axle-box in the vertical and lateral directions. With the increase of wheel flat scar length, the high-frequency component of the roller-outer raceway contact load increases, which causes the medium and high-frequency excitation of the bearing rollers and outer raceways, and accelerates the fatigue failure of the bearings. When the flat length exceeds 30 mm, the contact load in No.0 raceway area changes greatly. Compared with the maximum roller-outer raceway contact load at the flat length of 10 mm, the average roller-outer raceway contact load at the flat length of 50 mm increases by 33.38%. When the train speed is about 250 km/h, the safety threshold of wheel flat length should be limited to 30 mm to minimize the high-frequency vibration on the wheel-rail structure caused by long wheel flat. [ABSTRACT FROM AUTHOR]

A dynamic pitch strategy is usually adopted to improve the aerodynamic performance of the blade of a wind turbine. The dynamic pitch motion will affect the linear vibration characteristics of the blade. However, these influences have not been studied in previous research. In this paper, the influences of the rigid pitch motion on the linear vibration characteristics of a wind turbine blade are studied. The blade is described as a rotating cantilever beam with an inherent coupled rigid-flexible vibration, where the rigid pitch motion introduces a parametrically excited vibration to the beam. Partial differential equations governing the nonlinear coupled pitch-bend vibration are proposed using the generalized Hamiltonian principle. Natural vibration characteristics of the inherent coupled rigid-flexible system are analyzed based on the combination of the assumed modes method and the multi-scales method. Effects of static pitch angle, rotating speed, and characteristics of harmonic pitch motion on flexible natural frequencies and mode shapes are discussed. It shows that the pitch amplitude has a dramatic influence on the natural frequencies of the blade, while the effects of pitch frequency and pith phase on natural frequencies are little. [ABSTRACT FROM AUTHOR]

Abstract In this paper, an electro-hydraulic exciter controlled by an alternating current distribution valve is proposed, and a systematic analysis of the influence of pipe effect on the vibration characteristics of the electro-hydraulic exciter is investigated by simulation and experiments. The vibration characteristics curves for different pipe parameters are obtained, and the relative errors between simulation and experiment are evaluated. Moreover, a significant regression model of pipe parameters and vibration characteristics of the electro-hydraulic exciter is established by using the quadratic regression analysis method and the Box-Behnken experiment design method. Significant differences in the influence of pipe parameters on vibration characteristics are obtained by ANOVA (Analysis of Variance), and the influence of pipe parameter interaction on vibration characteristics is discussed. The results show that the relative importance of pipe parameters on the vibration characteristics of electro-hydraulic exciter, from high to low, is as follows: pipe diameter, elastic modulus, and pipe length. Notably, there is also an interaction between the pipe parameters, and the significance of these interactions is ranked from high to low as the interaction between the layers of steel wire and diameter, the interaction between diameter and length, and the interaction between the layers of steel wire and length.

Abstract In rotating machinery, the condition of rolling bearings is paramount, directly influencing operational integrity. However, the literature on the fault evolution of rolling bearings in their nascent stages is notably limited. Addressing this gap, our study establishes an innovative nonlinear dynamic model for early fault evolution of rolling bearings based on collision impact. Firstly, considering the fault evolution characteristics, the influence of the rolling element and fault structure, the dynamic model of early fault evolution between the rolling element and the local fault is established. Secondly, according to the Hertzian contact deformation theory, a nonlinear dynamic model of rolling bearings expressed as mass-spring is established. Thirdly, the energy contribution method is used to integrate the fault evolution model and the nonlinear dynamic model of the rolling bearing. A nonlinear dynamic model of early fault evolution of the rolling bearing is proposed by using the Lagrangian equation. Comparing the simulation results of the nonlinear dynamic with the experimental results, it can be seen that the numerical model can effectively predict the evolution process and vibration characteristics of the fault evolution of rolling bearings in the early stage.

Gas foil bearings, which are oil-free and exhibit low energy losses, are used in high-speed rotating machinery. Because gas is used as the working fluid, there is a need to improve damping performance using support structures. Additionally, the support structure, which becomes increasingly complex shaft performance, needs to be simplified. This study proposes a new bump mesh foil bearing focusing on the support structure and experimentally verifies its static and dynamic characteristics. The bump metal mesh foil bearing is a simple structure that combines a bump shape and metal mesh. Static load and hammering tests were conducted to evaluate the static characteristics, and the frictional torque and vibration at high-speed rotation were measured to evaluate the dynamic characteristics. The bump metal mesh foil bearing exhibited excellent damping performance owing to the friction damping caused by the bump shape and metal mesh; however, the rigidity of the bump metal mesh foil bearing was reduced. The bump metal mesh foil bearing exhibited the same level of lifting performance as the bump foil bearing, and vibration reduction at high-speed rotation was confirmed. Thus, the combination of the bump foil and metal mesh bearings yielded good results in terms of vibration characteristics.

To suppress the influence of complex field path excitation on the seeding quality of a corn no-till planter, a method for optimising the parameters of connecting parts is proposed in this study. Firstly, a twelve degrees of freedom model of the whole tractor-planter is established, and the corresponding differential equations are solved for the vibration characteristics. Then the key parameters of vibration characteristics are determined by sensitivity analysis based on the Matlab/Simulink model. On this basis, the gray wolf optimisation algorithm is introduced to address the global optimal solutions of connecting part parameters. Finally, the effectiveness of the proposed method is verified through numerical simulations and field experiments. The simulation results indicate that compared with the results before the optimisation, the vibration accelerations of corn no-till planter in the vertical, roll and pitch directions are reduced by 15.8%, 14.3% and 16.4%, respectively. The field experiment results further verify the validity of the proposed method. • A twelve degrees of freedom system of whole tractor-planter is proposed. • The key parameters for vibration response of corn no-till planters are determined. • The global optimal solutions of key parameters are achieved by the proposed method. [ABSTRACT FROM AUTHOR]

This paper investigated the fluid–structure interaction vibration response of an aircraft liquid-filled pipeline under external random vibration and internal pulsating pressure. First, the fluid–structure interaction solution is theoretically analyzed, and the advantages and disadvantages of the direct coupling method and the separation coupling method are compared, with the latter chosen as the simulation analysis method in this study. Second, taking the U-shaped oil pipeline of an aircraft engine as an example, simulation modeling was performed to compare and analyze the fluid–structure interaction vibration response of aircraft liquid-filled pipelines under different working conditions, obtaining the vibration response characteristics of stress danger points under various conditions. Finally, a test bench for an aircraft liquid-filling pipeline was built to explore the influence of external random vibrations with different kurtoses, different pipe wall thicknesses and different working conditions on the vibration response danger points of aircraft liquid-filling pipelines, verifying the simulation conclusions and providing a basis for aircraft liquid-filling pipeline design. [ABSTRACT FROM AUTHOR]

Due to their lightweight characteristics, spatial thin-film structures can generate vibrations far exceeding their film thickness when subjected to external loads, which has become a key factor limiting their performance. This study examines the vibration characteristics of tensioned membrane structures with non-uniform elements subjected to impacts in air, leveraging the Absolute Nodal Coordinate Formulation (ANCF). This model takes into account the wrinkling deformation of thin films under pre-tension and incorporates it into the dynamic equation derived using the absolute node coordinate method. A detailed discussion was conducted on the influence of non-uniform elements, situated at different locations and side lengths, on the vibration characteristics of the thin film. The analytical results obtained from the vibration model were compared with the experimental results, validating the effectiveness of the vibration model. This provides a theoretical foundation for the subsequent vibration control of thin films. [ABSTRACT FROM AUTHOR]

In this paper, the vibration characteristics (free vibration and forced vibration) of fiber-reinforced thin-walled conical–cylindrical composite shells (FTCCS) are analyzed by combining theory and experiment. Based on the classical shell theory and Kirchhoff–Love assumption, the overall structure of the FTCCS is theoretically modeled. The artificial spring technology is used to simulate the arbitrary boundary conditions at the joint, which is divided into a main spring and a secondary spring. At the same time, the displacement functions of the two sub-structure shells of the FTCCS are established by the orthogonal polynomial method, and the energy function of the FTCCS is constructed according to the continuity condition of the bolt joint. Then, the vibration characteristics of the FTCCS are solved using the Rayleigh–Ritz method and the modal superposition method. Finally, the TC300/epoxy resin-based fiber-reinforced thin-walled conical–cylindrical composite shells are selected as the research object, and the rationality of the mathematical model is verified by pulse, frequency sweeping and resonance excitation tests. The experimental results show that the errors between the natural frequency and the resonance displacement calculated by the theory and the experimental results are 1.75–4.76% and 3.79–9.28%, which confirms the rationality of the proposed model. By changing the length of the shell, the lamination angle and the semi-cone angle of the conical shell, the vibration characteristics parameters under different conditions are calculated to evaluate the influence of three physical parameters on the vibration characteristics of the FTCCS. [ABSTRACT FROM AUTHOR]

To research the vibration problem caused by bearing assembly errors in machine tool spindles, a special test rig for rolling bearing misalignment is designed and built. The dynamic model of the spindle-bearing-pedestal system of the test rig is established, and the characterization method for bearing parallel and angular misalignments is given through the Hertz contact theory. The effect rule of the misalignment level on spindle vibration response is studied by simulation and experiment, and the system dynamic model and bearing misalignment model are verified. On this basis, the vibration characteristics of the spindle system under the joint effect of raceway misalignment and waviness are further analyzed. The numerical and experimental results show that when the bearing is in the misalignment state, the excitation of bearing variable compliance increases. The assembly errors of the bearing raceway lead to the deviation of the centroid motion trajectory of the spindle tool end, which seriously affects the machining accuracy of the machine tool. In the case of severe angular misalignment, the system shows chaotic motion, indicating that the instability of the system is enhanced. The impact of angular misalignment on system vibration is greater than parallel misalignment, so bearing ring tilt should be avoided as far as possible in practice. In addition, it is also found that the variation of excitation amplitude of bearing waviness caused by raceway tilt is related to the relationship between the number of waviness and ball number. [ABSTRACT FROM AUTHOR]

• A dynamic model of bolted joint rotor system considering rubbing and pedestal looseness fault is established. • The effect of the rubbing fault on dynamic properties of the bolted joint was evaluated. • The effect of the rubbing-pedestal-looseness coupled fault on dynamic properties of the bolted joint was studied. • Experimental studies is conducted on a bolted joint rotor-bearing test rig with pedestal and rubbing device. Rotor-stator rub and pedestal looseness are common faults in rotating machinery, such as large gas turbines that typically use bolted joint structures to fasten adjacent disks together. It is of great significance to investigate the vibration behaviors of the bolted joint rotor-bearing system with pedestal looseness and rubbing coupled fault, which can provide proofs for the fault diagnosis. In the present work, a dynamic model of the bolted joint rotor-bearing system with coupled fault is developed by using the finite element (FE) method, and then the vibration characteristic analysis is carried out. The rotor shafts that connected by the bolted joint element (BJE) are discretized as two sets of Timoshenko beam elements. The BJE is composed with four springs (two linear translational springs and two rotational springs with piecewise-linear stiffness). The interactions of rotor-stator contact are then modeled based on the Hertz contact theory and Coulomb's friction law, and the bearing forces are also calculated based on the Hertz contact theory. Moreover, the pedestal looseness fault is modeled through the piecewise-linear stiffness spring. The equations of motions of the bolted joint rotor-bearing system with coupled fault are then developed through FE theory and solved by the Newmark method. The dynamic responses are then calculated, and the frequency spectrums, bending stiffness of bolted joint, and vibration responses under different rotation speeds under the coupled fault are analyzed. The experimental study is finally conducted based on a bolted joint rotor test rig. Simulation results are in agreement with experiment results. The research results can provide a basis for understanding the rotor dynamic features of a bolted joint rotor system with coupled faults of rubbing and pedestal looseness. [ABSTRACT FROM AUTHOR]

Schemes of testing means to determine technical and vibration parameters of manual nut wrenches are analyzed. The improvement of bench testing methods is considered. A test scheme is proposed in which a manual nut wrench is installed on a device that simulates the work of an operator when screwing/unscrewing nuts and bolts. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Pipeline maintenance technology based on pipeline intelligent plugging robot (PIPR) has become an effective method for failure accident prevention of high-pressure subsea oil and gas pipelines. However, during the plugging operation, the vortexes and pressure fluctuation are presented under turbulent flow field excitation, which may lead to vortex-induced vibration and failure of the plugging operation. Therefore, in order to ensure the reliability of pipeline plugging, the vibration characteristics are analyzed using numerical simulation, providing guidance on the structural optimization of PIPR's end face. Firstly, the flow field characteristics under different PIPR's end faces are investigated. Secondly, an experimental scheme is designed based on Latin Hypercube Sampling Design (LHSD) optimized by greedy strategy. A mathematical model of the end face's parameters and pressure gradient is established using a back propagation (BP) neural network. Then, an improved whale optimization algorithm (IWOA) is proposed to optimize the end face's parameters to minimize the pressure gradient of the flow field. Finally, the experimental study is performed to observe the turbulent flow field and pressure fluctuation to validate the optimization results. The results demonstrate that the PIPR's end face has a great influence on the vortex-induced vibration response. After structural optimization, the average pressure gradient of the optimal PIPR's end face has decreased by 84.69% and 54.55% before and after the plugging process, compared to the original end face. This study can provide a reference for pipeline plugging operations, which is significant for preventing pipeline failure accidents. [ABSTRACT FROM AUTHOR]

Paulownia has usually been an important material for making resonant components of musical instruments, which has a significant influence on the sound quality of musical instruments. This study utilized a generalized regression neural network （GRNN） to develop the sound quality evaluation model of Yueqin based on the vibration performance of the soundboard. In this study, nine Yueqins were fabricated, and a prediction model for the sound quality of Yueqins was proposed based on their sound qual‐ ity evaluation and the soundboard information of prepared Yueqins. Out of a total of 180 sets of data, 135 sets of data were randomly selected for training and the remaining 45 sets of data were used for validation. A model for evaluating the acoustic quality of Yueqin instruments was established using principal component analysis method and GRNN, and simulation prediction was performed. The results showed that based on the vibration characteristics of the soundboard, the prediction of the Yueqin sound quality can be achieved by using the Matlab simulation, and the accuracy of the prediction can reach 91. 41%. In addition, this study demonstrated that the dynamic elastic modulus, acoustic radiation damping coefficient, elastic modulus, elastic and shear modulus ratio, acoustic impedance, loss tangent angle, and acoustic conversion efficiency of Paulownia wood resonator plates were all key factors influencing the acoustic quality of the finished Yueqin during its preparation. [ABSTRACT FROM AUTHOR]

Steel spring floating slab track (SSFST) is an effective vibration and noise reduction measure, which is gradually used in urban rail transit in recent years. In order to better solve the problems of vibration noise and abnormal rail corrugation on metro lines, the dynamic model of vehicle-track system including metro vehicle and track structure is established by using the simulation software. The relationship between the passing frequency of vehicle and the vibration frequency of track structure, as well as the resonance characteristics of the elastic track structure are analyzed so as to obtain cause of rail corrugation on SSFST. The results show the following: (1) It is a more obvious resonance phenomenon between the inner rail and the floating slab at the vibration frequency of 116 and 161 Hz (R300 m), 262 Hz (R1000 m) and 320-387 Hz (R1500 m), and the simulation of rail corrugation wavelength is closer to field measured data. (2) Comparing the vibration frequency distribution of ordinary track and SSFST under the same curve radius, the rail corrugation is related to the natural vibration characteristics of track structure. (3) The vibration characteristics of the track structure and the periodic wear characteristics of the rail are the key factors for the formation of rail corrugation. [ABSTRACT FROM AUTHOR]

Research on the vibration characteristics of the drill rod system in a coal mine drilling robot is essential for the prediction and control of drilling trajectories. Considering the complex interaction mechanisms between the drill rod system and coal seams during horizontal drilling, an experimental platform and vibration monitoring system for the coal mine drilling robot were established. Horizontal drilling experiments were conducted under various layering conditions of soft and hard coal seams and different seam inclination angles. The empirical mode decomposition method was used to decompose, filter, and reconstruct the collected data to eliminate noise interference and study the vibration characteristics of the drill rod system under interlaced soft and hard inclined coal seams. The results showed that as the inclination angle of the coal seam increased, the longitudinal, transverse, and torsional vibration amplitudes of the drill rod system increased when the robot was drilling through hard→medium-hard→soft or soft→medium-hard→hard coal seams. At the same inclination angle, the vibration amplitudes in the longitudinal, transverse, and torsional directions were higher when drilling through soft→medium-hard→hard coal seams than through hard→medium-hard→soft seams. When the inclination angle was small, the interlaced soft and hard coal seams had a greater impact on the drill rod system's vibration characteristics, whereas at larger angles, the seam inclination angle had a more significant effect than the layering. Moreover, larger sand and gravel particles had a certain impact on the vibration of the drill rod system.