Resonance Speed Research Articles

Alfvén waves in the solar corona: resonance velocity, damping length, and charged particles acceleration by kinetic Alfvén waves.

Recent advances in heliospheric exploration spurred by NASA's Parker Solar Probe (PSP) mission require a deeper understanding of the intricate dynamics of the solar corona and wind. This study provides a detailed examination of kinetic Alfvén waves (KAWs) within the RSun range, a region only briefly explored in future PSP passages. Employing the framework of kinetic plasma theory and incorporating a non-thermal Cairns velocity distribution, we investigate the impact of the non-thermal index parameter on the resultant resonance velocity . The results reveal a notable change in the distance (RSun) over which the particles transport energy and the magnitude of resonance velocity for . We also derive the perpendicular resonance velocity and the group velocity expressions of particles and KAWs, respectively. We find that and the normalized group velocity are significantly influenced by . In contrast to the resonance speed and group velocity, the damping length of KAWs is evaluated for different parameters. We find that KAWs experience accelerated damping and exhibit an increased damping length for . We evaluate KAWs by the influence of the magnetic field, variation in height relative to the solar radius RSun, and the electron-to-ion temperature ratio . Collectively, these findings illustrate that KAWs not only are important for heating processes but also accelerate charged particles across considerable distances within the solar corona and solar wind regions. The analytical insights gleaned from this study find practical application in understanding wave phenomena in the solar and heliospheric regimes, particularly exploring the role of non-thermal particles in observed heating processes.

Dynamic Interaction Analysis of a Coupled System of Permanent Maglev Train and Flexible Track Beam

Vehicle–track beam coupling resonance greatly influences the vibration response of the suspended permanent (SPML) system. Therefore, the study established the coupled dynamic model of the SPML train and the track beam using. The model is used to analyze the dynamic response of SPML trains when passing through the long-span flexible track beam at resonance speed. The accuracy of the model was verified by field tests, which simulated and compared the dynamic responses of maglev train and track beam systems at different running speeds. Furthermore, the coupled vibration response of the train and track beam at resonant speed are investigated to gain insight into the mechanism and vibrational properties of the SPML system in a resonant background. It shows that the dominant frequency of the train, suspension frame, and track beam is 6.74[Formula: see text]Hz. They result in resonance in the SPML system at 30[Formula: see text]km/h. Further analysis shows that adjusting the vertical distance between the mass center of the vehicle and the track beam can effectively alleviate the resonance between the vehicle and the track. Additionally, deformation at the ends of the long-span track beams affects the levitation force and gap of the suspension frame, offering valuable guidance for SPML system design.

Simulation and experimental analysis of traveling wave resonance of flexible spiral bevel gear system

Considering the traveling wave resonance (TWR) phenomenon of the spiral bevel gear system in the aero engine accessory casing, the flexible spiral bevel gear model is established by three-dimensional (3D) shell element and beam element. The dynamic model of flexible bevel gear system considering the change of meshing teeth pairs in the operating process is established by component mode synthesis (CMS) method and rotational modal projection method. The proposed model is verified by finite element (FE) solid model and experiment test results. On this basis, the TWR phenomenon of the bevel gear system is studied in combination with dynamic response and vibration stress experimental test. The results show that the bevel gear system has 3 nodal diameter resonance speeds within the actual operating speed range, which are one 1st nodal diameter resonance of pinion and two 1st nodal diameter resonance of gear. When the bevel gear system operates at TWR state, the amplitude corresponding to fm ± m·fr (fm is meshing frequency, m is nodal diameter number, fr is shaft rotational frequency) is larger than that corresponding to fm in the Fast Fourier transform (FFT) spectrum of the of the gear foundation vibration stress, and the vibration stress cloud map of the gear foundation shows the corresponding nodal diameter vibration shape. The research results provide a theoretical basis for feature recognition and influence law evaluation of TWR of bevel gear system.

Static and Dynamic Stress of the Combined Rotor with Curvic Couplings Considering the Rough Three-Dimensional Interface at Extreme Operating Conditions

The curvic coupling, as one of the common connecting structures for gas turbine combined rotors, is more susceptible to various dynamic and static loads at extreme operating conditions. But, traditional combined rotor models tend to neglect the influence of the connection structure, especially failing to consider the contribution of the curvic coupling interfaces. To address this problem, this paper establishes a solid geometric model of the combined rotor with curvic couplings considering the rough three-dimensional interfaces. The effectiveness of the proposed model method is indirectly verified through the compression tests and modal tests. Subsequently, combined with finite element calculations, the mechanical properties of the rotor with curvic couplings considering the rough interface are analyzed under static and dynamic load conditions. The results indicate that the roughness of the interface significantly affects the deformation of the contact surface under static load, but its impact on the overall deformation of the rotor is relatively insignificant. The dynamic stress at the interface exhibits periodic variations at the resonance speed. At the maximum operating speed, the dynamic stress is influenced by the magnitude of imbalance. The aforementioned methods and conclusions provide a reference for the design research and engineering application of combined rotors.

An Approach to Quantifying the Distribution of Resonance and Cancellation Train Speeds of Railway Bridges with Random Uncertainties

An Approach to Quantifying the Distribution of Resonance and Cancellation Train Speeds of Railway Bridges with Random Uncertainties

Analysis of Reverse Whirl Characteristics of a Rub-Impact Rotor System

The rub-impact fault between the rotor and stator of the aeroengine can lead to a reverse whirl phenomenon, which will induce the instability of the rotor system. This paper uses the bending–torsion coupled vibration signal to analyze the reverse whirl characteristics of the single-rotor system under single-disc and multidisc rub-impact faults. In the full-spectrum analysis of the bending direction, the reverse whirl frequency, which is the nonpower frequency component caused by rubbing, is found. This whirl frequency leads to the period-doubling bifurcation and the reverse whirl phenomenon of the system. In the analysis of the torsional direction, it is found that the torsional signal can better reflect the different types of rub-impact faults. Further research shows that the unbalanced phase between the rubbing discs is a crucial parameter influencing the bending–torsion coupled vibration and the whirl characteristics of the rotor system. An experimental platform with nonuniform clearance is designed and manufactured to reproduce the reverse whirl phenomenon. The reverse whirl motion near the second-order superharmonic resonance speed is designed to verify the mechanism of the reverse whirl.

Composite failure analysis of an aero-engine inter-shaft bearing inner ring

The inter-shaft bearing is a critical component in dual rotors aero-engine. Due to the complex and severe loads caused by the interactive excitation of HP and LP rotors during operation, the inter-shaft bearing is prone to damage accumulation and failure. Focusing on a typical failure of inter-shaft bearing inner ring fragmentation and cannot be spliced together completely in high thrust-weight ratio turbofan engine, this paper conducted morphological investigation, fractographic analysis, vibration signal processing, finite element numerical simulation, and fully studied the failure mechanism of this failure.The results indicated that: there exists an uncoordinated resonance speed of the HP rotor in close proximity to the operating speed. This puts the rotor in non-synchronous procession state, accompanied by the uncoordinated angular displacement of the inner and outer rings, which resulting in a lager rolling dynamic load in bearing inner ring. This further leads to high tangential impact load at the root fillet of the anti-rotation pin, causing significant stress concentration, and eventually leads to the generation of initial cracks. These cracks persist and propagate into fatigue oblique fracture over time. After oblique fracture, the modal frequencies of the inner ring become more dispersed. Under the rolling dynamic load (traveling wave load), nodal diameter vibration occurs, causing high stress vibration fatigue damage, and ultimately leading to multiple-point simultaneous fragmentation.The investigation suggests that reducing the stress levels at the root fillet of the anti-rotation pin of the inner ring is an effective approach to prevent bearing failure. This can be achieved through two methods: one is optimizing the rotor structure to decrease the rolling dynamic load on the inner ring, the other is eliminating the anti-rotation pin and appropriately reducing the tightening torque of the compression nut and the interference between the bearing inner ring and the HP turbine rear journal.

Effects of turbulence integral length scales on aerodynamic characteristics and displacement responses of a square prism

This paper investigates the influence of the inflow turbulence integral length scales on the aerodynamic forces on a surface-mounted finite-length square prism and its displacement responses by computational fluid dynamics simulations. Four turbulent inflow conditions with the same mean wind speed and turbulence intensity but different longitudinal and transverse turbulence integral length scales are generated for the simulations. First, the wind pressures and forces on a rigid square prism model and the shear layer characteristics are simulated by large eddy simulations. The simulation results show that the mean characteristics of the wind pressures and shear layers are not sensitive to the turbulence integral length scales. However, the root mean square (RMS) wind pressures on side faces and RMS across-wind forces are increased with the longitudinal turbulence integral length scale, and the mechanism is analyzed by the proper orthogonal decomposition. Second, the displacement responses at the mean wind speed of vortex-induced resonance are computed based on an aeroelastic square prism model by fluid–solid interaction simulations. The RMS displacements of the model are observed to be more sensitive to the transverse turbulence integral length scale rather than the longitudinal turbulence integral length scale. Finally, the influence of the turbulence integral length scales on the Reynolds stresses around the square prism is presented and discussed.

Numerical Simulation of Residual Stresses and Structural Vibration of Welding Repaired Blades

Abstract Taking a typical aero-engine high-pressure compressor blade as the research object, the Gauss heat source was used to numerically simulate the repair process of blade surfacing welding. The temperature data and stress data of the blade were obtained when the heat source velocity was 1 mm/s, 2 mm/s, and 4 mm/s, respectively. The results showed that both the temperature and stress values decreased with the heat source velocity increasing. Then, the residual stress of the repaired blade is introduced into the modal analysis module as prestress, and the Campbell diagram is drawn to analyze the natural frequency and speed margin of the blade respectively. The results show that as the heat source speed increases, the frequencies of each order of the blade decrease. The speed margin of each resonance point is greater than 10%, and the modal dynamic stress corresponding to the resonance speed can be used as the primary criterion for blade failure.

A broadband and multiband magnetism-plucked rotary piezoelectric energy harvester

This study introduces a broadband and multiband piezoelectric energy harvester characterized by an E-shaped structure based on the rotational magnetic excitation. The piezoelectric oscillator is comprised of a trio of piezoelectric beams, which is like the letter 'E'. To elucidate the harvester's performance, this work employs both finite element analysis and experimental methods to explore the effects of pivotal parameters. Length ratio (Lr) and mass ratio (Mr) can influence the first two modes of vibration of the E-shaped oscillator. Lr = 1.0 and Mr = 3.0 are the critical points for mode transition of the E-shaped oscillator. Changing the added mass can reduce the gap between the resonance speed regions of the inner and outer beams, thus achieving the purpose of broadband. When piezoelectric patches are arranged in a "品" shape on the inner and outer beams, the total output power of a single oscillator can reach 5.33 mW, with the inner and outer beams contributing 4.01 mW and 1.32 mW respectively. Besides, when rotating magnets are two, a single piezoelectric oscillator can have 9 effective working regions. These can enhance the efficacy of energy harvesters, particularly in the realm of autonomous and self-powered systems.

DYNAMIC RESPONSE OF ELASTICALLY-SUPPORTED BRIDGE UNDER OPPOSITE MOVING HIGH-SPEED LOADS

This paper explores the design parameters for elastically supported (ES) bridges, particularly for short to medium under the influence of high-speed trains. It introduces a non-dimensional mathematical framework that conceptualizes the ES as a Euler-Bernoulli beam supported by elastic bearings at its ends and subjected to evenly spaced moving loads. The framework highlights various resonances and speed ratios for cancelling out specific effects based on the stiffness parameter and the distance between loads. The analysis indicates that most of the maximum displacement occurs near the beam's midpoint. Additionally, it shows that lower resonance speeds coupled with higher stiffness parameter values can result in significant amplification of displacement response due to cumulative forces acting on the system. This amplification is a consequence of the cumulative forces acting on the system. Hence, this research provides valuable insights for designers and engineers to optimize foundation design, thereby reducing structure-borne vibrations transmitted to the ground.

DYNAMIC RESPONSE OF ELASTICALLY-SUPPORTED BRIDGE UNDER OPPOSITE MOVING HIGH-SPEED LOADS

This paper explores the design parameters for elastically supported (ES) bridges, particularly for short to medium under the influence of high-speed trains. It introduces a non-dimensional mathematical framework that conceptualizes the ES as a Euler-Bernoulli beam supported by elastic bearings at its ends and subjected to evenly spaced moving loads. The framework highlights various resonances and speed ratios for cancelling out specific effects based on the stiffness parameter and the distance between loads. The analysis indicates that most of the maximum displacement occurs near the beam's midpoint. Additionally, it shows that lower resonance speeds coupled with higher stiffness parameter values can result in significant amplification of displacement response due to cumulative forces acting on the system. This amplification is a consequence of the cumulative forces acting on the system. Hence, this research provides valuable insights for designers and engineers to optimize foundation design, thereby reducing structure-borne vibrations transmitted to the ground.

Numerical and experimental analysis on the whirl orbit with inner loop in cracked rotor system

Cracks in rotor systems are generated because of internal as well as external heavy loading conditions. The external loading conditions could be attributed to thermal gradients (such as in turbomachinery) or other environmental conditions that result in cracks developments. The internal loading conditions can be attributed to cyclic fatigue loading during continuous and recurrent shaft's running which is the most common cause for cracks propagation. The presence of cracks in rotor systems induces nonlinearities into the system which affects its whirl response. Many published literature on cracked rotors have indicated that when the rotational speed is at sub-critical resonance of order 1/n (1/2, 1/3,1/4, etc.…) of the critical rotational speed, the fundamental whirl orbit takes patterns including inner loop/loops of order (n-1) or outer loop/loops of order (n+1) depending on the critical whirling direction. The present study investigates the strong impact of the magnitude of unbalance force on whirling pattern with inner loop in a cracked rotor. Numerical analysis is carried out on the mathematical model of the considered cracked rotor. The unbalance force magnitude is observed to be the main factor affecting the inner loop pattern in the whirl orbit rather than the ½ of the critical resonance speed. Accordingly, the appearance of inner loop in shaft's whirl orbit due to crack propagation in the rotor system is found here to be present before and after passing through resonance speed. This inner loop whirl orbit pattern is not restricted to be associated with ½ of the critical rotational speed as believed in plenty of literature. This kind of whirling is observed to be strongly depending on the unbalance force magnitude rather than the subcritical resonance speed. The experimental results also validate the numerical simulation findings. Therefore, the whirl orbits of the cracked rotor can be categorized into pre-resonance whirl orbit (Pr-WO), resonance whirl orbit (R-WO) and post-resonance whirl orbit (Po-WO) based on the magnitude of the unbalance force. The resultant numerical and experimental findings on the whirl orbit with inner loop can provide a robust insight into the cracked rotor whirl behavior.

Phase shift-based resonance assessment for in-service high-speed railway bridges

Resonance in high-speed railway bridges can deteriorate the structural integrity and running safety of a train; thus, the resonant speed needs to be identified. Previous studies have proposed resonant conditions analytically, but their applications to in-service bridges are limited. Free vibration after the passage of a train was utilized to assess resonance, but it could not capture the natural frequency of the coupled system because the train-bridge interaction was neglected. This study proposed a practical framework for quantifying the resonance in a high-speed railway bridge using a phase shift. The static displacement of the railway bridge was numerically reconstructed using the train loading history. Phase angles were extracted by comparing the static and dynamic displacements, which were directly utilized to develop a novel resonance indicator in this study. Numerical simulations and field demonstrations validated the applicability of the proposed method for understanding the resonance behavior of full-scale railway bridges.

Study on Torsional Vibration Response Characteristics of Marine Propulsion Shafting

_ The paper establishes the lumped parameter vibration mathematical model of shafting and uses the system matrix method to calculate and analyze steady-state frequency domain vibration characteristics of the shaft system in the range of diesel engine speed. Then in order to further study the transient torsional vibration of the shaft system under the resonance speed point, the state space method and finite element analysis method were used to compare and analyze the transient time domain response characteristic curve of the shaft system; finally, the test data of the real ship was compared with the theoretical calculation results, which verified the correctness of the mathematical model and the theoretical calculation method. This study has certain theoretical significance for carrying out the design of low-noise and vibration of shaft systems and improving the safety of ship navigation. Keywords shafting torsional vibration; transient time domain; finite element method; vibration test

Fluid-solid interaction simulations of an aeroelastic square prism in sinusoidal oscillatory flows

This study numerically investigates the aerodynamic and aeroelastic characteristics of a square prism (aeroelastic model) and wind field around it in sinusoidal oscillatory flows (SOFs). The reliability of the fluid-solid interaction (FSI) simulation is validated by a free vibration test and wind tunnel tests in smooth flow and SOF. The effects of the amplitude and frequency of SOFs are studied at the mean wind speed of vortex-induced resonance. The results show that increasing the amplitude and frequency of SOFs will amplify the root mean square (RMS) along-wind and across-wind base shear forces of the aeroelastic model but decrease the RMS across-wind displacement at the top of the aeroelastic model. The spectral analysis of the base shear forces indicates that the influence of vortex shedding on the across-wind base shear force is reduced by either increasing the amplitude or increasing the frequency of SOFs. The mean and instantaneous wind fields around the aeroelastic model in SOFs and smooth flow are compared, and the wake characteristics of the aeroelastic model in SOFs are analysed by dynamic mode decomposition. It is observed that when the frequency of SOFs is 1.5 times as large as the fundamental natural frequency of the aeroelastic model, the regular vortex shedding process is substantially affected.

Vibration analysis of a rotor-bearing system using magneto-rheological elastomers

Magneto rheological materials are considered as a promising adaptive means of vibration control. This paper proposes a new configuration of smart bearings comprising magneto-rheological elastomer (MRE) layer inserted between the bearing pedestal and the foundation. This configuration provides a directional vibration controllability in both horizontal and vertical directions of a rotor-bearing system. The effect of using MRE layer on the vibration response and the resonant speeds of a rotor-bearing system is investigated. The finite element method is used to derive a dynamic model for the rotor-bearing system using shaft elements based on the Rayleigh beam theory and accounting for the gyroscopic effect and internal damping of the shaft. Simulation results reveal that the use of MRE materials in passive mode leads to downshifting of the first two resonant speeds and the attenuation of the steady state vibration response of the rotor bearing system in the horizontal and vertical directions at the resonance frequencies. When the MRE layer is subjected to a magnetic field generated by an electric current produced in the magnetic coil, the horizontal and vertical vibration responses are increased at the resonant speeds but decreased at other rotational speed ranges. Furthermore, the first two resonant speeds in the horizontal and vertical directions decrease further with the increase of the electric current.

Electromechanical coupling dynamics of dual-motor electric drive system of hybrid electric vehicles

In this study, to investigate the electromechanically coupled dynamics of a dual-motor electric drive system (DEDS) of hybrid electric vehicles under typical conditions. Considering the time-varying stiffness of gears, a dynamic model of the gear system and permanent magnet synchronous motor (PMSM) was developed, and a comprehensive electromechanical coupling dynamics model of DEDS applicable to coupling dynamics analysis was obtained. Based on this model, the impacts of the transmission error and electromechanical coupling effect on the dynamics of DEDS under steady-state and acceleration conditions were simulated and analyzed. This study demonstrates the significant impact of transmission errors on the dynamic load of high-speed gear pairs and the speed synchronization characteristics of the system. The study also reveals that the electromechanical coupling effect exacerbated the fluctuation of the gear dynamic load. During the speed change process, the electromechanical coupling effect did not introduce new resonance points. However, transmission errors tend to induce low-frequency resonance of the gear dynamic load and speed synchronization error (SSE). In addition, when the system is operated near the resonant speed, a large torsional vibration dominated by the resonant excitation frequency is generated, distinguished using the current signal to assess the resonance risk. The research results are important for the integrated design and condition monitoring of DEDS and offer valuable insights for enhancing the operational efficiency and reliability of the system.

Modeling of flexible bevel gear rotor systems: Modal and dynamic characterization

Bevel gears, a crucial part of aircraft transmission systems, are more susceptible to wheel body vibration issues as lightweight requirements rise. In the past, the gear wheel body was often considered rigid while assessing the dynamic properties of gear systems. Constructing a bevel gear model with a thin-walled structure might not be appropriate for this modeling technique; this research suggests a dynamic model that considers the flexibility of bevel gears. The web and teeth structure of the gear are preserved by realistic modeling using three-dimensional hexahedral components. The component mode synthesis (CMS) approach reduces the model order for increased computational efficiency. To confirm the accuracy of the modeling method, the modal frequencies and vibration shapes of the proposed model single-gear shaft are compared with results from experiments and ABAQUS. By contrasting ABAQUS system-level meshing modal frequencies and vibration shapes, the accuracy of the system model assembly is further confirmed. The model examines the impact of bevel gear flexibility on the modal frequencies, modal vibration shapes, and system dynamic properties. The mode shape diagram at dangerous modal frequencies found using the modal strain energy technique and the vibration displacement cloud maps at resonance speeds computed using the Newmark-β method are mutually verified, and this demonstrates that lightweight bevel gears are more susceptible to excitation due to nodal diameter type vibrations. Proposed and traditional models anticipate substantially different resonance speeds since the traditional model assumes that the gear, being a rigid disk, can only excite the shaft's bending mode of vibration. The proposed model provides a more comprehensive description of the dynamic characteristics of bevel gear systems, providing a theoretical basis and optimization tool for the high-performance design, vibration reduction, and noise control of high-speed lightweight gear transmission systems.

Eight-link pressure mechanism and its dynamic simulation based on improved ant colony algorithm optimization

Abstract In recent years, the optimization of eight-link pressure mechanism using ant colony algorithm is a research hotspot, but given the limitations of traditional ant colony algorithm, this paper improves the ant colony algorithm based on the SSA-IACO algorithm and develops the application and analysis of eight-link pressure mechanism and its dynamic simulation. Through the study of parameter settings before and after optimization, simulation analysis and other aspects, it is concluded that: the efficiency of the new scheme optimized by the improved ant colony algorithm is 88.86% higher than the original scheme. The stator power is reduced by 4.10% and the power factor is increased by 14.67% on average over the original scheme. The maximum magnitude of the free end torsion angle of the crankshaft system is 0.16 degrees, and the increased resonance speed is about 1800 rpm. The maximum torsion angle of the main harmonic (6th harmonic) is reduced from 0.54 to 0.16, and the damping effect is noticeable. When 0.7 ≤ ρ 0.8, and ρ is close to 0.7, the algorithm performs better. When 0.15 ≤ θ 0.2, and the value of θ is more comparable to 0.15, the algorithm obtains the optimal solution and the execution time is shorter than the [0.7,0.2] combination.