In order to solve the problem of energy-efficient control of residual vibration for space flexible manipulator caused by arm-flexibility, a new semi-active vibration control method based on a parallel magneto-rheological damping structure (PMRDS) is proposed. Firstly, the dynamic transmission characteristic of PMRDS is analyzed and a novel solid-liquid two-phase constitutive model of MR damper is proposed to describe the phase transition effect of MR fluid on the boundary condition of flexible manipulator. Secondly, by segmenting the manipulator at the installation position of PMRDS, the rigid-flexible coupling dynamic model of the flexible manipulator with PMRDS is established based on Euler-Bernoulli beam theory and Lagrange equation. Thirdly, the influence of input current, installation parameters of PMRDS and operation parameters of manipulator on system performance is analyzed by numerical simulation. Then, based on the obtained vibration control mechanism, an anti-solidification control strategy is proposed. Finally, the experimental study is carried out by a self-built test bench, the feasibility of PMRDS, the accuracy of the theoretical model and the effectiveness of the anti-solidification control strategy are verified. The results show that the proposed method can effectively suppress the residual vibration of flexible manipulator; compared with the fixed input current control, the anti-solidification control improves the vibration suppression efficiency by 43.23% on average under different operating conditions. The research can provide reference for the application of magnetorheological damping in vibration control of flexible structures.

This study proposes a multiphysics coupling optimization methodology to mitigate electromagnetic noise and cogging torque in external rotor permanent magnet synchronous motors. A slot-pole interaction analysis model is developed, incorporating nonlinear magnetic permeability modulation effects, to elucidate the spatiotemporal distribution characteristics of electromagnetic forces and their resonance mechanisms with structural modes. A novel energy-based method for cogging torque calculation is introduced, achieving a 20% improvement in computational efficiency while maintaining numerical errors below 2% . Furthermore, a cylindrical shell vibration model based on nodal force mapping and a boundary element-based acoustic radiation prediction framework are established. Multiobjective optimization leveraging response surface methodology and a modified particle swarm optimization algorithm is employed to quantify the impact of temperature gradients on permanent magnet performance and nonlinear synergistic effects among parameters. Postoptimization results demonstrate a significant reduction in overall sound pressure level to 27.69 dBA under rated conditions and a 38.5% decrease in cogging torque, validating the effectiveness of the proposed electromagnetic-structural-acoustic codesign approach. This work provides a systematic framework for multiphysics collaborative optimization in high-performance motor design.

In practical engineering applications, bolt-coupled shell structures are susceptible to interface damage and connection failure under sustained vibrational loading, underscoring the critical need for research into their vibration suppression and optimal design. Therefore, this paper investigates the nonlinear vibration characteristics of fiber-reinforced thin-walled conical-cylindrical bolt-coupled shells (FTCBS) with partially attached constrained layer damping (CLD). A novel nonlinear dynamic model is developed, employing the chief-subordinate artificial spring technique to simulate the bolt connection interface and introducing displacement-dependent nonlinear behavior of the bolts. The semi-analytical model is solved using the Lagrange energy equation and the Rayleigh-Ritz method. The model is validated through a self-built vibration test system, and the theoretical results are highly consistent with the experimental results under multiple excitations. Finally, the effects of the quantity of missing bolts, the pattern of missing bolts, and the thickness of the viscoelastic layer damping on the dynamic characteristics of FTCBS are evaluated. This work provides important theoretical support for the vibration reduction design and condition assessment of bolt-coupled shells.

To address the lack of research on the traveling wave vibration characteristics of rotating composite honeycomb sandwich cylindrical shells, this study proposes a semi-analytical model. The model is formulated based on the first-order shear deformation theory, the Ritz method, the domain decomposition method, and Jacobi orthogonal polynomials, aiming to predict both the natural frequencies and the forward and backward traveling wave frequencies under rotational conditions. The key model parameters are systematically determined through convergence analysis. The accuracy of the model is validated through comparisons with existing research cases and experimental test results. The results show that the model corresponds well with the results in the corresponding literature, and the maximum error between the model and the experimental results is 5.5 %. Furthermore, the effects of boundary stiffness loss and thickness ratio on the rotational traveling wave vibration frequencies, modal step regions, and critical rotational speeds are examined. The results show that the change of rotational speed will lead to complex frequency steering and modal shape exchange. In the high-order mode, the sensitivity of the frequency turning point to the boundary stiffness and speed decreases. In addition, properly increasing the thickness ratio of fiber layer can help to improve the structural stiffness.

In this paper, a dynamic modeling and signal processing framework integrating Doppler compensation is proposed for the accurate prediction of broadband noise characteristics in external-rotor permanent magnet synchronous motors (ERPMSM). First, a multiphysics coupling model incorporating tangential electromagnetic forces is established, with its spatiotemporal distribution validated through finite element analysis. Subsequently, multi-channel synchronous signal acquisition is implemented using a uniform circular microphone array, combined with a time-varying spatial filtering and reordering strategy to dynamically correct spectral distortion induced by time-varying sound propagation paths. Furthermore, a boundary element method modified by a dynamic Green's function is employed to precisely characterize the radiation behavior of moving acoustic sources. Experimental results demonstrate that the proposed method significantly reduces sound pressure level prediction errors, enhances the identification accuracy of high-frequency harmonics, and maintains stable spatial directivity prediction capability under all operating conditions.

Clamps are key local constraint components that affect the modal characteristics of spatial fluid-conveying pipe systems. However, a unified representation of clamp constraints within the absolute nodal coordinate formulation (ANCF) remains insufficiently developed. The mechanisms of clamp-mediated coupled vibration and frequency veering also require further clarification. A dynamic model for multi-clamp spatial fluid-conveying pipe systems is established within a three-dimensional ANCF framework. By expressing local translational and rotational clamp deformations in terms of ANCF generalized-coordinate increments, parameterized equivalent single-clamp and double-clamp models are derived based on the principle of virtual work. The proposed model is validated against modal experiments and a finite element model. Clamp-position and directional-stiffness sensitivities are analyzed to identify critical clamps. The clamp-mediated frequency-veering behavior is further investigated through mode exchange and modal strain-energy redistribution. The results indicate that single clamps mainly induce local frequency modulation, whereas double clamps more readily alter inter-pipe coupling by constraining the relative displacement and rotation between adjacent pipes. Frequency veering is accompanied by mode exchange, reconstruction of dominant vibration regions, and redistribution of strain energy among pipes. Additional clamp-adjustment experiments are conducted to further verify the predicted frequency-variation trends. The proposed framework provides guidance for support-layout optimization and vibration control of complex spatial pipe systems.

In this study, an accurate subdomain method is proposed for calculating electromagnetic force density. This approach divides the computational domain into multiple subdomains, significantly enhancing the precision in capturing variations in the electromagnetic field. The effects of tangential electromagnetic force waves, harmonic current amplitude, and stator tooth saturation are also considered, thus significantly improving the accuracy of the results. Building on this foundation, a robust equivalent theoretical model of the stator core shell is developed, and the stator’s natural frequency is calculated using the energy method. The model’s accuracy is confirmed through modal experiments. Furthermore, the frequency response function of the stator in low-order modes is determined, and the acceleration spectrum and electromagnetic force wave for each mode of the prototype stator are derived using the linear superposition principle. Compared to the established electromagnetic-structural coupling finite element model, the methodology introduced in this study reduces the computation time by 59.3 %.

A unified high-order shear deformation model is developed for vibration analysis of arbitrarily spatially shaped braided shells with graded coatings. The model combines equivalent-property evaluation of braided composites, generalized higher-order displacement and stress fields, displacement compatibility conditions, and virtual-spring connections to describe coupling effects between adjacent substructures and arbitrary boundary constraints. Based on the Lagrange method, the governing equations for free and forced vibrations are derived, and the stiffness and inertia contributions of graded coatings are incorporated consistently. The proposed model is validated through convergence analysis, finite-element comparisons, and vibration experiments. For uncoated shells, the maximum deviations between the predicted and reference natural frequencies are 3.5% for free boundary conditions, 2.06% for complex boundary conditions, and 0.95% across different thickness-to-radius ratios, demonstrating the applicability of the proposed model to both thin and moderately thick shells. Experiments on coated and uncoated L-shaped specimens show that the maximum modal-frequency error is below 2.92%, while the graded coating reduces the resonance response by up to 22.6%. Parametric results further clarify the effects of braiding angle, thickness-to-radius ratio, and spatial angle on frequency splitting, modal coupling, and vibration attenuation, providing a theoretical basis for the vibration-resistant design of complex braided shell structures.

Metamaterials are employed to modulate the propagation of forced vibrations. The periodic structure inherently influences self-excited vibrations. Theoretical researches on the nonlinear dynamics and stability of a metamaterial rotor/seal system are presented in this paper. The nonlinear model of the metamaterial rotor/seal system is established. The instability threshold speed is calculated by the eigenvalue theory. Then the nonlinear differential equations are solved using the numerical integration method, and the dynamic behaviors including bifurcations are obtained. Also, the instability threshold speed is validated by the nonlinear responses. The results show that the local resonance bandgap generated by the metamaterial cannot forbid the propagation of the fluid-induced vibration in the rotor/seal system. The metamaterial can forbid the propagation of the instability vibration as incorporating the damping. This research provides a theoretical basis for suppressing self-excited vibrations in metamaterials and has potential for engineering applications.

This paper addresses the multi-physical field coupling problem of electromagnetic vibration in permanent magnet synchronous motors (PMSMs), and presents a fast calculation method for multi-harmonic decoupling of electromagnetic forces based on subdomain analysis and an equivalent ring model. This method breaks through the simplifying assumptions of traditional models regarding the non-uniform distribution of tangential electromagnetic forces and high-frequency nonlinear effects. By introducing a modified modal participation factor and an orthogonal anisotropic stiffness superposition criterion, it achieves a low-order modal frequency error of <7% for the stator-winding system and constructs a nonlinear mapping model between tangential forces and high-frequency vibrations. Compared with existing studies that neglect the non-uniform distribution of tooth surface forces and end constraint effects, the proposed method exhibits spectral localization accuracy better than 5% in the low-frequency band (<3 kHz) and improves computational efficiency by 80%. It significantly alleviates the modeling complexity of traditional finite element methods under multi-speed conditions and high-frequency prediction deviations. Experimental verification shows that this method can accurately characterize the electromagnetic vibration characteristics of motors, providing an effective technical approach for the early suppression of motor vibration and noise.

Under actual operating conditions, structures with bolted connections can develop localized bolt loosening due to external excitations, which may result in structural disintegration or other hazards. To tackle this issue, the current study presents the theoretical model for the analysis of natural characteristics of a fiber-reinforced composite thin-walled cone-cylinder joint shell (FTCCJS) under conditions of partial bolt loosening. Firstly, the classical laminated plate theory and Love's thin-shell assumption are utilized to establish a theoretical model of the FTCCJS under partial bolt loosening, and the virtual artificial spring technique (primary and secondary springs) is introduced to equivalently represent arbitrary bolt connection states. Then, an orthogonal polynomial method is employed to construct the displacement field function, and in combination with the Rayleigh-Ritz method, the natural characteristics of the FTCCJS with partially loosened bolts are solved. Subsequently, using a TC300/epoxy resin-based FTCCJS as the test specimen, a modal experiment with single-point hammer excitation and multi-point response measurement is carried out. Through comparison of experimental results and theoretical calculations, it is found that the error in the first four natural frequencies of the FTCCJS with partial bolt loosening ranges from 0.3% to 5.5%. Furthermore, the mode shapes derived from both methodologies show a high degree of congruence, confirming the validity of the theoretical model. Finally, by varying the number, degree, and pattern of bolt loosening, the impact on the natural frequencies of the FTCCJS is evaluated. This research offers valuable reference data for forecasting the natural characteristics of bolt-connected shell structures.

For the problem of reducing unfavorable vibrations stemming from unbalanced rotors in rotor dynamic systems, a dynamic model consisting of two space rotors and a rigid frame is proposed. Delving into the self-balancing characteristics of the system based on the principle of self-synchronization aims to reduce the dynamic loads transmitted to the foundation due to the unbalanced rotor while concurrently reducing noise pollution. Firstly, vibration synchronization theory including self-synchronization and stability is formulated using average methods, Lyapunov theory, and the Kronecker product. Then, the impact of crucial dynamic parameters, such as the mass, axial distance, and initial phase of the unbalanced point, on the stable synchronization states and self-balancing properties in specific resonance regions of the system is qualitatively analyzed. Moreover, simulations are carried out to investigate dynamic characteristics and verify the accuracy of the numerical qualitative analysis results. Through phase portraits, the stability of essential synchronization states is examined. Results show that the self-balance of the system in partial degrees of freedom can be achieved in the first sub-resonance region for specific rotor configurations, and the corresponding synchronous state is not affected by the initial value and velocity of the phase difference. This research serves as a reference for the self-synchronization theory of space rotors and provides a novel scheme for the problem of vibration suppression in rotor dynamic systems.

Approximately 90% of mechanical failures stem from fatigue, and acoustic emission (AE) monitoring has shown promise in evaluating such damage. AE signal characteristics, such as event count, amplitude, and hit rate, are directly linked to fatigue progression and allow real-time tracking of critical damage stages. However, traditional feature-based methods often suffer from noise and interference from work hardening and user-defined settings, reducing accuracy. This study introduces an adaptive threshold waveform processing method that filters noise and enhances high-energy events. Analyzing these signals with the Bhattacharyya coefficient (BC) enables real-time fatigue assessment. Fatigue tensile-compression tests were conducted on medium-carbon steel, with concurrent real-time recording of surface temperature changes in the specimens. During the slow crack growth phase, an increase in local temperature corresponded with a turning point in the BC evolution trend, indicating that this method can reliably reflect the fatigue damage state of structures in real time. The effectiveness of the proposed method was validated through high-cycle fatigue experiments, demonstrating its applicability in practical fatigue damage scenarios. Furthermore, the computational cost analysis indicates that the proposed AHIE+BC framework achieves a data compression rate of approximately 20%, significantly reducing the computational burden while maintaining effective damage representation. These results highlight the method’s potential for efficient and accurate fatigue assessment in real-time structural health monitoring applications.

In addition to blade-to-casing rubbing, drum-to-labyrinth rubbing is another common interaction in aero-engines. In this study, the labyrinth seal is simplified and modeled as an inner ring. First, considering the flexibility of both the drum and inner ring, a novel rubbing force model applicable to drum-inner ring rubbing is proposed, and this model is partially validated with the measured vibration responses. Incorporating both drum-inner ring rubbing faults and bolt joint effects, a dynamic model of the shaft-disk-drum-inner ring-vane-casing system (SDDIRVCS) is established with beam-shell hybrid elements to investigate the nonlinear dynamic responses induced by rubbing at various rotational speeds. The established dynamic model of the SDDIRVCS is validated by the comparison of its modal characteristics with those obtained from the ANSYS simulations. The results indicate that the rotor spectrum is dominated by odd-multiple harmonics, while the stator spectrum exhibits prominent even-multiple harmonics. Moreover, the rubbing location between the drum and the inner ring varies with the dynamic behavior of the rotor system.

Cracks in disc components can significantly reduce their service life. Most existing studies on cracked discs assume predefined crack paths (such as tangential or radial cracks) and rarely analyze the stress of the cracked disc during vibration. Additionally, dynamic models of the disc typically involve a significant number of degrees of freedom, resulting in substantial computational time when calculating the stress response. To address these issues, this paper conducts vibration experiments to determine the crack paths in discs and develops a reduced-order dynamic model of the disc with breathing crack based on shell theory. The proposed model in calculating stress is validated through comparison with the experimental results. Finally, the actual crack paths are introduced into the dynamic model, and the dynamic stress variation of the disc during crack propagation is studied by simulation and experiment. The results show that the crack in the disc exhibits the breathing effect during propagation, which induces nonlinear vibration of the disc. Moreover, as the crack propagates, the maximum stress at the disk root gradually decreases, and the decreasing rate becomes slower and slower. In contrast, the maximum stress at the crack tip decreases linearly.

The rotor system may be subjected to base motion excitation in addition to unbalanced excitation. Moreover, bearing loads can be simultaneously influenced by the base motion and bearing misalignment caused by assembly errors, potentially causing excessive axial load. To study the vibration characteristics of rotors and the contact characteristics of bearings, a new bearing contact force model of the misaligned angular contact ball bearing is proposed and the proposed bearing model is verified by the measured vibration acceleration responses. Incorporating both base motions and bearing misalignment, a dynamic model of a rotor-bearing system is established. The findings reveal that as the rotating speed of the base increases, the amplitude of the variable compliance vibration frequency of the bearing gradually increases because the base motion intensifies the variable compliance vibration of the bearing and some harmonic frequencies and combined frequencies can be observed. Additionally, base motion significantly amplifies the axial force of the bearing, with the axial load rising by approximately 28 times compared to the system without base motion excitation. Both the base motion and bearing misalignment can change the contact zone for the bearing and base motion can cause the ball and raceway to always maintain contact.

In the practical engineering application, the bolt connection is commonly used for the assembly of shell structures. High external excitation can lead to partial bolt looseness, further causing interface sticking, sliding or even separation at the connection, resulting in complex nonlinear dynamic problems for bolted shell. Understanding the nonlinear vibration characteristics of fiber-reinforced composite thin-walled conical-cylindrical coupled shells(C-C) under partial bolt looseness is crucial. Therefore, this article investigates the nonlinear vibration mechanism of the C-C under partial bolt looseness. The kinematic equations of conical-cylindrical coupled shells are established by adopting the Lagrange energy equation on the basis of the energy method. The displacement admissible functions of orthogonal polynomials are utilized in combination with the Rayleigh-Ritz method to analyze the vibration characteristics of the C-C. Meanwhile, Jenkins elements are set up at the joint of the substructure shells, and the equivalent stiffness and damping of the bolt connection are obtained by adopting the virtual artificial spring technology to simulate the stick-slip state of the bolt connection, so as to describe the nonlinear behavior of the bolt connection reasonably. The precision of the theoretical model is confirmed by comparing data obtained under different excitations with theoretical calculations using a self-built vibration testing system. Finally, the nonlinear vibration characteristics of the C-C are assessed in terms of different number of bolt looseness, degrees of bolt looseness and forms of bolt looseness. This study provides reference for predicting and evaluating the health state of the bolted shell.

In this paper, a new suspension vibration reduction structure is proposed by topology analysis of the suspension structure. The ISD (Inerter-Spring-Damper) suspension is dynamically modeled, and the vehicle vibration response is obtained by solving the dynamic differential equation.The vibration transmission characteristics of ISD suspension and its dynamic performance under various road conditions are studied. By comparing and analyzing with single-stage ISD suspension and hybrid ISD suspension, the suppression of resonance peaks during vibration transmission by the proposed two-stage ISD suspension is studied. The mapping relationship between suspension parameters and transmission characteristics has been clarified. The dynamic response of ISD suspension structure is discussed. The results show that, the peak of the transfer function gain of two-stage ISD suspension is significantly reduced compared to single-stage ISD suspension and hybrid ISD suspension, and indicates that the newly designed structure has excellent vibration reduction effect. Properly increasing the spring stiffness and inertia coefficient while meeting the requirements of vehicle acceleration gain can have a positive improvement effect on vibration reduction. Therefore, by comparing multiple indicators, it can be shown that the new suspension has a positive effect on improving the vibration reduction effect, which can effectively suppress the vibration.

This article systematically investigates the vibration characteristics of functional gradient carbon nanotube reinforced composite truncated conical shells under arbitrary boundary conditions. First, a structural dynamic model is developed based on the first-order shear deformation theory. The mid-surface displacement field is constructed using Jacobi polynomials to accurately capture the deformation behavior of the shell under complex boundary constraints. Subsequently, the governing equations for free vibration are derived via the Lagrange energy method, and a solution framework for the forced vibration response under single-point pulse excitation is established using the modal superposition approach. The proposed model is validated through comparison with existing literature and finite element results, confirming its accuracy and effectiveness and providing a solid theoretical basis for subsequent vibration analysis. Finally, the effects of carbon nanotube distribution patterns, weight fractions, and fiber laying angles on the structural vibration response are systematically analyzed, yielding a set of engineering-relevant conclusions with practical significance for structural design and vibration control.

This paper investigates the coupling dynamic characteristics of a double-beam structure with two linear oscillators that generate harmonic concentrated excitation and the vertical elastic support boundary, including the Sommerfeld effect and the synchronization behavior. The governing equations of motion with boundary conditions are developed using Hamilton's principle. The Sommerfeld effect near the resonance region is characterized by transient power balance analysis, and the critical power of the motor is given to allow the system to pass through the resonance region. The theoretical condition for the synchronous behavior of two linear oscillators is derived using the average method, and its stability is also determined. The synchronization characteristics are analyzed and compared with the numerical steady-state response of typical physical parameters. Results show good agreement. Further, on the condition of the linear oscillators exhibiting synchronous behavior, sensitive working regions and parameters are sought to suppress the dynamic loads transmitted from the system to the foundation. The parameter optimization results show that the stable phase difference plays a crucial role in vibration suppression within the appropriate range of sensitive parameters. This study effectively extends the theoretical criteria for synchronous behavior on complex structures and is expected to provide ideas for vibration suppression strategies of multi-driving sources acting on multi-groups of elastic structures.