Planetary gear transmission systems are extensively used in industrial applications. Due to their compact and complex configurations, mechanical components are prone to failure during long-term operation. Compared to fixed-axis gear systems, planetary gear systems exhibit multiple excitation sources and time-varying signal transmission paths stemming from their intricate structural and kinematic characteristics. Consequently, condition monitoring techniques based on fixed vibration measurement points face significant challenges in compound fault diagnosis, especially when a planet gear fault is coupled with a bearing fault. To address these issues, this study proposes a non-contact torsional vibration monitoring and residual vibration analysis method utilizing laser doppler vibrometry (LDV). The laser beam is positioned on the low-speed shaft surface to directly acquire torsional vibration information from the gear system. To mitigate the impact of measurement noise on fault feature extraction, a hybrid denoising strategy combining cepstrum-based soft-threshold editing and median filtering is developed to suppress pseudo-vibration artifacts and random impulse noise, respectively. For different types of compound faults, a progressive residual vibration decomposition framework is established. This framework systematically peels off residual broadband response and residual meshing sideband components from the torsional vibration signal. Specifically, optimized filtering is applied to the broadband response obtained via cepstrum short-pass to extract the second-order cyclostationary features of bearing faults. Concurrently, a phase self-demodulation-based order domain resampling method is proposed to highlight gear fault features by reconstructing meshing sideband residual signals of different orders. Experiments involving tooth spalling on planetary gears and raceway spalling on the sun gear bearing demonstrate that the proposed method can effectively achieve non-contact compound fault diagnosis for planetary gear systems. Compared to conventional flexible synchronous averaging and accelerometer-based methods, the proposed approach exhibits superior performance in early-stage planet gear fault detection under varying speeds.

To effectively detect and localize vibration faults such as clamp loosening in aero engine accessory pipes, this paper proposes a novel diagnosis method based on dynamic responses of accessory pipes and transmissibility functions. The dynamic model and equation of the faulty pipe are established based on the principle of structural similarity and dynamic similarity, where the impact of the fault is simulated as an additional nonlinear load acting on related position of the pipe. Through the analysis of structural dynamic characteristics, the relationship between dynamic responses and fault occurrence and location is derived and analyzed, a fault diagnosis method based on transmissibility function is then proposed, and the operating process of the method is summarized as well. The accuracy and practicality of the proposed fault diagnosis method are verified through multiple experimental examples. Theoretical analysis and testing results show that the diagnostic method proposed in this paper can accurately detect and localize the existence and position of the clamp loosening fault. Meanwhile, this diagnostic method is suitable for single and multiple clamp loosening faults in aero engine accessory pipes.

Vibration and temperature signals from bearings contain rich fault characteristic information, making them crucial for condition monitoring and fault diagnosis of traction motor bearings in heavy-haul locomotives. This study establishes a thermo-vibration coupling dynamics model for heavy-haul locomotive traction motor bearings, based on vehicle-track coupled dynamics. The model considers the nonlinear normal contact and tangential friction effects between the roller, raceway, as well as their defect areas. The influence of raceway defects in motor bearings on the thermo-vibration coupling characteristics of the traction motor is investigated. Additionally, the mapping relationship between defect width and both vibration response and bearing temperature rise is constructed. Results indicate that when the defect width reaches 1 mm, distinct fault characteristic frequencies appear in the vibration signal spectrum. The root mean square frequency, a frequency-domain statistical indicator, shows an increasing trend across the entire defect width range, while the frequency standard deviation is more sensitive to early defects. Time-domain statistical indicators of vibration signals, such as root mean square (RMS) and kurtosis values, are relatively sensitive to outer raceway defects. Conversely, inner raceway defects lead to a rapid temperature increase in the traction motor bearing, which is prone to triggering temperature rise alarms.

As the main component of the train body structure, the truss-cored flat panel is situated close to the wheel-track noise source and has a large area for noise radiation, and its acoustic performance directly influences the riding comfort of trains. This paper first establishes the wavenumber finite-element model and a sound-insulation prediction model for an aluminum truss-cored train floor using wavenumber finite elements and boundary integral equations. The wavenumber, transmission loss, and eigenvectors of the structure are calculated. The dispersion characteristics, sound-insulation performance and cross-sectional wave-modes of elastic waves are studied. The calculated results are compared with the prediction given in the references to verify the proposed model. Furthermore, this paper investigates the effects of the core layer's topological geometry of the extruded panel on the sound-insulation characteristics of aluminum extruded panels. The results show that varying the topological configuration of the core layer significantly changes the variation pattern of dispersion curves of elastic waves, which affects the sound-insulation properties of aluminum extruded panels. By comparing the topologies of classic extruded structures, it is found that the ‘herringbone’ ribbed plate structure has a relatively higher sound-insulation level and lower mass. This study can provide a reference for designing quiet and lightweight extruded panels.

Adaptive decomposition, reconstruction, and denoising of bridge structure monitoring signals are critical parts in the research field of bridge health monitoring. To provide efficient and effective time-frequency domain denoising methods for these signals, an Adaptive Variational Mode Decomposition and Reconstruction (AVMDR) method was proposed for signal denoising, which can overcome the disadvantage of VMD (Variational Mode Decomposition) type methods that the number of decomposition components needs to be determined inadvance. The Empirical Mode Decomposition (EMD) method was introduced to adaptively determine the number of decomposition components, and then the Multi-scale Principal Component Analysis (MSPCA) was used to denoise each component and reconstruct the signal. The denoising performance of the proposed AVMDR method was validated and compared using both simulated signals—linear stationary and nonlinear non-stationary signals with varying noise levels—and real signals obtained from two cable-stayed model bridges. The results indicate that the AVMDR method outperforms other commonly used methods in terms of denoising performance, achieving optimal scores across all denoising performance evaluation metrics. Moreover, the AVMDR method can effectively retain more structural information while eliminating noise.

As the thermonuclear fuel container in inertial confinement fusion (ICF), the surface quality of the target capsule directly affects the success of ICF experiments. Therefore, it is crucial to inspect the morphology of ICF microspheres before fabrication. To address the issue of secondary damage to the surface of ICF microspheres during manipulation by current detection equipment, a bulk acoustic wave-driven microsphere manipulation device is proposed. This device excites an out-of-plane bending vibration mode in a vibrator composed of a piezoelectric ceramic and a metal substrate, creating an acoustic field within the liquid. The ICF microspheres are then driven by non-contact acoustic radiation forces, enabling non-destructive manipulation during ICF microsphere inspection. To analyze the relationship between the vibration of the manipulation device and the generated acoustic field, we developed an electromechanical coupling dynamics model of the vibrator using the transfer matrix method. This model comprehensively considers factors such as the size, material, boundary conditions, arrangement of piezoelectric ceramic sheets, excitation voltage, and additional load from water of the vibrator. Using this model, we calculated the vibration modes of a non-resonant traveling wave and two resonant standing waves, along with three corresponding acoustic fields. Based on calculation results, we fabricated and assembled the prototype. Vibration characteristics and manipulation performance of the prototype were studied through experiments. The results indicate a good agreement between theoretical calculations and experimental tests regarding the vibration characteristics of the acoustic manipulation device, validating the correctness of the established dynamics model. Both non-resonant traveling waves and resonant standing waves can effectively manipulate ICF microspheres, with the resonant standing wave achieving faster microsphere movement. This confirms the feasibility and effectiveness of the proposed acoustic manipulation method. Furthermore, based on the modal switching measurement and control method, the device can classify ICF microspheres by diameter without the need for a microscope.

To upgrade the level of rural housing to meet the increasing demand for comfort, safety, environmental protection and energy saving, a light frame structure system housing was proposed and designed. The light frame structure system takes a steel frame as the main structural body and ALC wall panel as the filling wall. A full-scale shaking table test has been carried out to verify its seismic performance and to study the seismic behavior and seismic response law of the light frame structure system under earthquake action on beam-column joints, wall-slab joints, and the building structure. The test results show that the wall panel has not fallen off, the joint connection is intact, and the structure has not collapsed. With the increase of input seismic intensity, both the acceleration amplification factor and relative displacement increase, while the natural frequency of the structure decreases gradually. Throughout the test, the main structural members remain elastic, and the inter-story displacement angle of the structure under a fortification earthquake of 6-degree is less than 1/250. Under the action of rare earthquakes of 7th intensity and 8th intensity, the inter-story displacement angle of the structure exceeds 1/250, but the structural deformation can be reduced by tensioning reinforcement support. The light frame structure system exhibited excellent seismic performance and can be used to improve the level of rural housing in the 6th intensity seismic fortification area. For seismic fortification areas above 6th intensity, the seismic performance can be enhanced by increasing the tension of tie bars.

The combined seismic isolation bearing is composed of a sliding friction bearing and an elastomeric bearing. The bearing system offers a substantial vertical support capacity, various post-yield stiffness choices, and the ability to separate the bridge’s vertical support system from the horizontal support system. To investigate the seismic performance of the combined seismic isolation bearing system, by way of example of a continuous beam bridge with each continuous unit of (4 × 40) m spans, the OpenSees software was used to model with the conventional spherical steel bearing, full sliding friction bearing and combined seismic isolation bearing support systems to obtain the longitudinal seismic response of the bridges, respectively. The influence of seismic parameters such as sliding friction coefficient and shear stiffness on the seismic performance of the combined seismic isolation bearing was discussed. The results demonstrated that the combined seismic isolation bearing exhibits excellent seismic performance and self-centering ability. The seismic performance of the combined isolation bearing will be affected by the sliding friction coefficient and shear stiffness. By selecting appropriate seismic parameters, the maximum displacement demand of bearings, the residual displacement of bearings, and the seismic response of the piers can be effectively controlled.

The strong surface impact loads caused by dynamic compaction and construction operations have significant implications on the surrounding environment. Traditional research methods often simplify the impact load as a triangular load for calculation. However, this simplification does not consider the energy loss during impact, leading to overestimation in the calculation results. This paper is based on the measured data from an actual dynamic compaction project. After validating the numerical method’s feasibility, a parametric analysis of key influencing factors is conducted. The paper proposes a reasonable reduction coefficient to modify the current triangular loading model. The objective is to improve the accuracy and applicability of the model for dynamic compaction projects. The calculation results indicate that the magnitude of impact energy and the soil parameters of the site are critical factors influencing the impact vibration response. It is suggested that for impact energy levels categorized as low, medium, and high, the reduction coefficients for medium-soft soil can be set as 0.85, 0.6 and 0.5, respectively. For medium-hard soil, the reduction coefficients can be set as 0.9, 0.7 and 0.6 for the corresponding low, medium, and high energy levels.

The ground motion of pulse type near fault has the characteristics of higher frequency, faster speed and more concentrated energy than that of a distant site, which has serious harm to engineering structures. With abundant water resources, frequent and high-intensity earthquakes occur in Western China, and many high dams are located near fault zones. The permanent deformation and slope safety of high dams under near-fault ground motion are very important. A random pulse ground motion model is established based on the pulse ground motion records of the Jiji near fault in Taiwan Province. Finite element analysis is carried out on the Gushui 250 m grade engineering panel dam, and stochastic dynamic analysis and reliability analysis are carried out on the displacement and slope slip of the high earth-rock dam by the direct probability integral method. The results show that pulse ground motion significantly affects on the vertical deformation and slope stability of high earth-rock dams. The seismic safety and seismic capability of high earth-rock dams near faults with high seismic risk are evaluated comprehensively.