The building foundation elastic pad has become one of the critical vibration control measures for sensitive structures near subway lines.However, its vibration isolation mechanism and the influence of design parameters remain unclear.This paper employs the scaled model dynamic experimental method to systematically investigate the vibration isolation performance of building foundation elastic pad.First, based on vibration isolation theory, the parameters affecting the vibration isolation effect of elastic pad beneath building foundation were derived and analyzed.Then, a scaled model experiment for the “building-elastic pad” isolation system was designed, using actual environmental vibrations from subway-adjacent areas as the excitation source to obtain vibration responses of the building model under various experimental conditions.Finally, by comparing test data in the time domain, frequency domain, and acceleration levels, the vibration isolation effect of the elastic pad and the influence law of key factors were studied.The results show that the elastic pad can effectively reduce the subway-induced vibration response of building structure.Pad thickness, elastic modulus, and working compressive stress are the key factors affecting its isolation performance.Backfill materials around the building foundation are detrimental to the vibration isolation effect of the elastic pad, and a certain vibration isolation design margin should be considered accordingly.The side pad of the building foundation plays a crucial role in subway vibration control, and both the base pad and side pad should be used in combination in practical engineering.By scale model vibration experimental method, the vibration isolation mechanism, effectiveness, and main parameter influence law of the building foundation elastic pad are deeply revealed, providing theoretical and experimental basis for vibration isolation engineering applications of buildings along subway lines.

As an important component connecting transmission towers and conductors, the study of insulator string dynamic response characteristics under dynamic load is vital to ensure the safety of transmission lines.A nonlinear dynamic model of porcelain suspension insulator string under parametric excitation was established; the dynamic response was calculated by using the fourth-fifth order Runge-Kutta method, revealing the parametric vibration mechanism of insulator string system; the effects of excitation frequency, excitation amplitude, and initial perturbation on the dynamic response were analyzed.The results show that parametric vibration of the system occurs when the excitation frequency is about two times that of the intrinsic frequency of the insulator string.Under the action of dynamic load, the parametric vibration occurring in the suspension insulator string is dominated by the first-order parametric vibration, which is consistent with the actual observation.

Extreme value distribution reconstruction is a key issue in structural dynamic reliability analysis, as its accuracy directly affects the estimation of failure probability.The fractional moments-based mixture distribution method based on mixture of the extended inverse Gaussian and log extended skew-normal distributions (M-EIGD-LESND) is an effective approach for extreme value distribution reconstruction.This method uses the flexible M-EIGD-LESND to express the extreme value distribution, in which the model parameters are determined via the fractional moment matching technique.However, during parameter estimation, the selection of the initial weight coefficient and orders of constrained fractional moments mainly relies on empirical assumptions, which may lead to unsatisfactory accuracy of extreme value distribution reconstruction.To address this issue, an adaptive fractional moments-based mixture distribution method was proposed.The maximum likelihood estimation criterion was introduced and combined with the real-coded genetic algorithm to adaptively optimize the initial weight coefficient and orders of constrained fractional moments, thereby improving the reconstruction accuracy of extreme value distributions.Moreover, to effectively estimate fractional moments, the samples of the equivalent extreme value variable were generated using the Generalized F (GF) discrepancy point set.The performance of the proposed method was verified by numerical and engineering examples.The results indicate that, compared with existing methods, the proposed method can more effectively reconstruct the extreme value distribution and achieve higher accuracy in failure probability estimation.

The traction drive system is the core component that ensures the power performance and safety of  rack vehicles on steep slopes in mountainous areas. Currently, research on the traction drive systems of rack vehicles is limited, with few studies considering the traction characteristic curve. To address this issue, a vehicle dynamics model is established based on vehicle-track coupled dynamics theory and gear dynamics theory, which takes into account the meshing behavior of the traction drive system and the traction characteristic curve. This model investigates the influence of gear meshing excitation on system vibrations and analyzes how traction characteristic parameters affect the vehicle’s dynamic behavior. The results show that a two-stage gear transmission exacerbates transient peak values, introducing more complex meshing frequencies and enriching high frequencies. Increasing the starting torque causes the dynamic meshing force peak to reach 50kN, with gear longitudinal and vertical acceleration peaks increasing by 52.7% and 40.3%, respectively. While improving traction performance, this also leads to a 24% increase in the vertical acceleration of the vehicle body. Increasing the transition speed extends the duration of strong excitation and raises meshing frequencies, but under the limitation of the maximum operating speed, this does not significantly improve acceleration performance. Instead, it results in a 26% increase in the vertical acceleration of the vehicle body and a more than 16% increase in the wheel load reduction rate. In conclusion, for vehicle design and evaluation based on vibration, fatigue, and other key indicators, a two-stage gear transmission model should be used. To balance power performance, safety, and comfort, an appropriate traction mode should be proposed.

Bending stiffness is a critical parameter that reflects the performance of bridge, thus accurate identification of bridge bending stiffness is of great significance. Bridge influence lines can be used to identify the bridge bending stiffness. The key is to select an appropriate bending stiffness deterioration model for simulating the variation of stiffness and an effective optimization algorithm for estimating the parameters of the stiffness model. This paper proposes a novel method for identification of bridge bending stiffness using influence lines and Bayesian optimization. The relationship between the bending stiffness and influence lines is established. Furthermore, an improved Gaussian peak function is introduced to simulate bending stiffness degradation. The feasibility and accuracy of the proposed method are verified by both numerical simulations and laboratory experiments.

Drill string vibration is exacerbated in ultra-deep wells, significantly degrading drilling stability and rate of penetration. To clarify the coupled dynamics of drill strings under complex conditions, we develop a multi-body coupled vibration model that incorporates wellbore constraints, thermo–pressure effects, internal and external drilling fluid forces, and drill bit–rock interaction. The model is solved via the finite element method and validated against laboratory simulations and field measurements. Using parameters from an ultra-deep well in the Tarim Basin, we analyze the influence of weight on bit, rotation speed, and drilling fluid density. Results show that higher rotational speed effectively suppresses stick–slip, an optimal weight on bit exists for maximizing mechanical efficiency, and increased fluid density reduces bit vibration though excessive density may raise bottomhole pressure. This work provides theoretical guidance for vibration control and rate-of-penetration enhancement in ultra-deep drilling.

Delay compensation is the key component to guarantee the successful of real-time hybrid simulation (RTHS). The trend of development for RTHS is that the scale of test structure is larger and larger, the proportion of high-frequency signal in structure response is more and more significant, and the application fields of experiments are also becoming wider. which put forward a higher requirement for time delay compensation. Nevertheless, the compensation capacity for high-frequency signals of existing time delay compensation methods have the limitation. Sliding mode controller combined with discrete model adaptive time-delay compensation method is proposed. In this method, combining with the robustness sliding mode control (SMC), the least square method is used to update the parameters of the discrete model of SMC-hydraulic loading system in real time to compensate the time-delay for high-frequency signal. Real-time load delay compensation simulation of nonlinear servo loading actuator specimen system were conducted. The simulation results showed that the proposed method has better compensation capacity for high frequency signals than the discrete model adaptive time delay compensation (ADM), adaptive time series (ATS), and sliding mode control (SMC) methods. The feasibility and accuracy of the proposed method were also verified in the numerical simulation of RTHS benchmark platform. 

Mode transition enables the LNG-electric hybrid powertrain to adapt to load changes of ships. However, intensive jerk intends to occur during mode transition and increases the risk of shaft breakdown. To address this issue, a driveline dynamics model coupling friction torque of the clutch and the blade frequency torque of the propeller is built, followed by stability analysis considering the change rate of the friction coefficient with slipping speed. Thereafter, dynamics responses are illustrated in terms of the clutch stages of slip, slip-stick and stick. The phenomena of asymmetric stick-slip, side frequencies excited by transition between stick and slip, intensive jerk at the end of slip are found. Further, the effects of clutch pressure, friction coefficient, blade frequency and phase angle are investigated. The results can provide references for the design and optimization of the marine hybrid powertrain.

The flow around the rectangular cylinders with different aspect ratio is different. Three-dimensional large eddy simulations of flow around the 1:1 rectangular cylinder and 5:1 rectangular cylinder under a Reynolds number of 2000 are carried out to deeper understand the effect of corner chamfers on aerodynamic force characteristics and flow field of rectangular cylinders. The corner chamfered ratios ξ = C/D = 0%, 10% and 20% are selected to investigate, in which C and D are the corner chamfered size and the cylinder width, respectively. The lift and drag coefficients, Strouhal number, pressure coefficients, reattachment length and wake length are analyzed in detail. The results indicate that the effect of corner chamfers on aerodynamic force characteristics and flow field of rectangular cylinder is influenced by aspect ratio. As the chamfered ratio increases, the 1:1 and 5:1 rectangular cylinders exhibit a consistent trend in the mean drag coefficient variations; however, significant differences emerge in the trends of the fluctuating lift coefficients and Strouhal numbers. By introducing corner chamfers, the mean pressure coefficients on the side surfaces of the 1:1 rectangular cylinder increase while the fluctuating pressure coefficients on that decrease; the peak position of the pressure coefficients on side surfaces of the 5:1 rectangular cylinder move upstream. Both primary side-surface bubbles of the 1:1 rectangular cylinder and main bubbles of the 5:1 rectangular cylinder are affected by the corner chamfer, showing a shrinking trend. However, the variation trends of the length of wake region for the 1:1 and 5:1 rectangular cylinders are not the same. The instability of the attached flow may be the reason causing the difference of aerodynamic force characteristics of the 1:1 and 5:1 rectangular cylinders under chamfering.

A novel enhanced finite element method (EFEM) for the vibration analysis of two-dimensional linear elastics is presented in this work. The interpolation cover functions in the enhanced elements are the linear Lagrange polynomial basis functions and a set of harmonic trigonometric functions. The harmonic trigonometric function originates from the spectral method, so the proposed method can be regarded as a combination of the classical finite element method and the spectral technique. The interpolation cover functions can be directly applied to the finite element model using low-order elements without any mesh adjustment. Meanwhile, the linear dependence problem in the EFEM is investigated in this work, and a simple and effective scheme is proposed to eliminate the linear dependence problem and ensure that the coefficient matrix in the EFEM is sparsely symmetric positive definite. Because the standard finite element approximation space is enhanced by the interpolation cover functions, the proposed EFEM in this work can obtain precise numerical solutions for the vibration analysis of two-dimensional linear elastic solid by even using a rough mesh, thus can reduce the cost in mesh generation. Several typical numerical examples show that, compared with classic quadratic finite elements, the EFEM proposed in this work can not only provide more accurate numerical results, but also have higher computational efficiency. 

Based on measured data of Typhoon "Doksuri" (No. 2305) from a wind lidar deployed on Dadeng Island, Xiamen, five typical periods during its passage were selected to analyze the mean and fluctuating wind characteristics at five altitude levels. The aim was to elucidate the evolution patterns of the wind fields in coastal areas across different typhoon regions during the typhoon’s movement. Results indicate that mean wind speed increases with height, while wind direction trends remain consistent across all levels. The wind speed profiles exhibit distinct variations in the outer rainband region, the inner rainband region, and the eyewall region. In the strong wind zone of the eyewall, the ratio of the three-component turbulence intensities is 1:1:0.38, with the lateral component exceeding recommended values in design codes while the vertical component is relatively smaller. Moreover, turbulence intensity is notably higher before landfall. The gust factor decreases with increasing mean wind speed, and a nonlinear fitting provides a more accurate representation of its relationship with turbulence intensity. Significant differences are observed in the turbulence integral scale across different typhoon regions, with a marked increase in the eyewall region. Measured PSDs follow the -5/3 decay law at high frequencies but display distinct multi-peak features in the energy-containing range, with a significantly higher vertical peak frequency. The Von Karman spectrum fits the energy peak region better than the Kaimal spectrum.

A three-dimensional numerical model was established using STAR-CCM+ software to investigate the flow characteristics of severe slugging, with a focus on its flow mechanisms and axial flow patterns. The results show that severe slug flows can be divided into four different flow stages according to the different flow characteristics, they can also be divided into three types: SSI, SSII, and SSIII. During the liquid-gas eruption stage, the gas breaks through the liquid plug axially from both sides of the liquid plug, leading to biased flow and resulting in an asymmetric distribution of gas and liquid phases across the riser cross‑section. The inlet gas mass flow rate influences the frequency of severe slugging, thereby affecting the structural stability of the pipeline. The period and amplitude of pressure fluctuations in the riser are inversely proportional to the inlet gas mass flow rate.

The grouting sleeve connection of prefabricated concrete structures is affected by many factors in practical projects, and there are often certain quality defects. It is very important to choose an efficient and reliable method to detect and evaluate the connection quality. A dynamic response-based inspection and evaluation method for grouting sleeve connection quality of prefabricated concrete columns is proposed. The effectiveness of the proposed method is verified with numerical simulation and indoor tests. The research results show that the sleeve grouting connection defects ( grouting is not full, and the slurry layer is not dense ) will lead to a decrease in the natural frequency of the assembled concrete column. The natural frequency can be used as an evaluation index for the sleeve grouting connection defects. The dynamic characteristics of the assembled concrete column are tested to obtain its natural frequency. Combined with the numerical simulation of the connection defects ( including type and degree ) column natural frequency reference library, the comparison coefficient Pij can be used to determine whether the sleeve grouting connection defects exist or not and the type and degree of the defects. Based on the dynamic response, the detection and evaluation of the grouting connection quality of the assembled concrete column sleeve can be effectively realized.

Rotor is a key part of rotating machinery, and the high amplitude vibration of the rotor system caused by unbalance often occurs. Therefore, achieving high-efficiency and accurate dynamic balancing of rotors is an important task of healthy monitoring and maintenance. There exist some shortages in traditional optimization algorithms of dynamic balancing. For instance, the vibration information obtained by a single sensor cannot reflect the overall vibration of the system, and the optimal target of balancing is relatively single. Therefore, this paper carries out the research on holo-balancing of flexible rotors based on multi-objective intelligent optimization. Based on the comprehensive capacity of information extraction in holospectrum, three targets, the average value, the maximum value and the extreme difference of residual vibration are selected to measure the balancing state of the unit. The optimal evaluation function of multiple targets is introduced to solve the coordination problems of above three optimal targets. In terms of optimization algorithm, an improved differential search algorithm is proposed to improve the efficiency and accuracy of dynamic balancing. Relevant balancing experiments show that the vibration reduction ratio of this method is as high as 85.3%, which further verifies the reliability and practical value of the proposed method.

Bridge structural health monitoring data are often contaminated with a large amount of complex noise. Without dimensionality reduction, relying solely on neural networks cannot effectively identify structural damage. To this end, a structural damage identification via a synergy of model order reduction and fully convolutional networks was proposed. Proper Orthogonal Decomposition is used to extract features from structural dynamic response data, and a reduced order model (ROM) is constructed to dynamically reflect the damage state of the structure. A Fully Convolutional Network (FCN) is then employed to perform deep learning on the reduced data, with the network architecture and hyperparameters optimized to improve the accuracy and generalization capability in recognizing different damage states. Numerical simulations and laboratory tests of a moving-vehicle bridge model are conducted to validate the proposed method. The results show that model order reduction can reduce the interference of complex noise,enhance data quality and accelerate dataset construction, while also enabling the tracking of structural damage evolution and significantly improving model generalization. The fully convolutional network preserves the spatial structure of dynamic response data from multiple measurement points and can accurately identify structural damage states after training, achieves the damage identification accuracy exceeding 98.67%, offering meaningful reference value for structural health monitoring of bridges.

An approximate separation method for the transmission line subsystem is established, which considers the line-tower coupling and employs an objective optimization method to determine the elastic support constraint stiffness of the isolated transmission line subsystem under wind-induced vibration. Taking a typical transmission line-tower system with the wind direction perpendicular to the line as the case study, the fluctuating wind field was simulated and the structural wind-induced vibration response was calculated. A systematic analysis of the transferred dynamic load characteristics was conducted, compared with those obtained under the traditional fixed support boundary conditions. It indicates that the vibration of the transmission tower along the line direction has a mitigating effect on transmitting loads, but tending to weaken as the wind speed increases. The intensity would be overestimated when using the traditional fixed support boundary constraints, and it exhibits significant fluctuating effects both along and across the line direction. Current Chinese design codes for transmission lines, which consider only the perpendicular component while neglecting the parallel one, may therefore entail a risk of insufficient safety margin in assessing strong wind loads.

To suppress the torque ripple in permanent magnet synchronous motor (PMSM) caused by complex disturbances, parameter perturbations, and measurement noise, a Super Twisting Sliding Mode Observer based Improved Equivalent-Input-Disturbance (STSMO-IEID) control method has been proposed. Specifically, a PMSM model that accounts for periodic disturbances and parameter perturbations is established. Based on this model, an STSMO-EID structure is designed, and the nonlinear estimation structure is subsequently analyzed in the frequency domain using the description function method. To enhance the structure, an improved second-order filter suitable for the nonlinear estimation structure has also been developed, further designed an STSMO-IEID estimator to estimate the unknown system disturbances for compensating. Then, the stability of the observer was proved using a quadratic positive definite Lyapunov function, and the global stability of the system was also demonstrated. Finally, experimental results demonstrate that the proposed method suppresses approximately 77%, 69%, and 54% of steady-state speed fluctuations compared to uncompensated method, conventional EID method, and the proposed method employing a first-order low-pass filter, respectively. Under extreme operating conditions, suppression rates reach 64%, 47% and 19% respectively, which fully demonstrates the superiority of the strategy in terms of steady-state tracking accuracy and disturbance suppression.

To address the demands for high-speed, macro-stroke, and high-precision motion in micro-nano manipulation fields such as semiconductor testing and cell puncture, a drive-structure integrated piezoelectric compliant actuated by the macro fiber composite (MFC) is proposed, and a cross-scale linear stick-slip motion platform is designed. The MFC exhibits bipolarity and a wide voltage tolerance range. Its symmetrical layout ensures consistent bidirectional motion while delivering greater output displacement, balancing macro-stroke capability, nanometer-level resolution, and high motion speed under low-frequency actuation. Then, a finite element method was employed to establish an analytical model of the compliant driving unit, and the output displacement and natural frequency were simulated. Finally, an experimental system was constructed to evaluate the platform’s performance. Experimental results demonstrate that during single-step motion, the platform achieves a maximum output displacement of 146.45 µm under a sinusoidal voltage of -400 to 800 V, with a motion resolution of 4.7 nm. During continuous stepping motion, the maximum effective single-step displacement under a sawtooth voltage of -400 to 800 V was 156.81 µm, with a stepping resolution of 3.1 nm and a travel range of 12 mm. Within the 1445.61 µm range, the maximum forward and reverse motion deviation is 5.87%. Moreover, a motion speed of 1.62 mm/s is achievable at a driving frequency of 10 Hz, and the platform maintains an effective single-step displacement of 54.63 µm under a 4 kg load. Experimental testing validates the effectiveness and output performance of the designed stick-slip platform.

During the operation of spinning pipes conveying fluid, coupled thermal-fluid-solid multiphysics effects can induce complex vibration behaviors, leading to dynamic instability and posing significant threats to structural safety. This study therefore focuses on the vibration and stability issues of spinning pipes conveying fluid under nonlinear stress-temperature conditions. First, based on Hamilton's principle and thermoelastic theory, the lateral vibration control equations for spinning pipes conveying fluid under thermal loading are established. Subsequently, the partial differential control equations of the pipe system are discretized using the Galerkin method, and the complex natural frequencies of the system are solved. Finally, the dynamics of the pipe system are thoroughly investigated, examining the influence of key parameters—spinning speed, mass ratio, flow velocity, vortex-induced vibration ratio, and thermal load—on the system's vibration characteristics and stability. Results indicate that fluid-structure interaction, vortex-induced vibration ratio, and temperature effects significantly impact system stability, while spinning speed primarily affects the system's natural frequency. Increases in temperature variation and vortex-induced vibration ratio substantially lower the system's critical instability threshold, while mass ratio exerts minimal influence on pipeline stability. Additionally, variations in thermal loading and vortex-induced vibration ratio exert certain effects on the system's complex modal motion.

Aiming at the real-time requirement of online vibration detection of power equipment, a new type of magnetic circuit-vibration circuit coupling model of a reactor based on the principle of mechanical-electrical analogy is proposed. According to the structural characteristics of the reactor core column, an equivalent magnetic circuit model considering the air gap between the core discs and the magnetic flux diffraction is established to calculate the magnetic flux density and excitation current accurately. Considering the combined effect of the equivalent force of magnetostriction of the core and the Maxwell force between the discs, a real-time calculation method for the core vibration characteristics based on the equivalent vibration circuit model of the reactor is proposed, and the calculation time reaches the second level. By building a vibration experiment platform for the reactor, parameters such as the vibration displacement and acceleration of the reactor core are measured. The error of the displacement and acceleration calculation results are less than 12.5% and 10% respectively. Meanwhile, the interaction effect between the magnetostrictive force and the Maxwell force between the discs is analyzed, verifying the accuracy of the established model. 

To investigate the influence of the crystalline structure of granite on the macro and mesoscopic failure characteristics under medium strain rate impact, a three-dimensional Grain Based Model (GBM) that can reflect the mesoscopic structure of minerals was constructed using Particle Flow Code (PFC). This model comprehensively considered 14 types of contacts between intra- and inter-granular minerals of the same and different types within granite, and the meso-mechanical parameters for each contact type were calibrated through parameter inversion. Based on the established GBM, drop hammer impact simulations at various heights were conducted to systematically analyze the evolution of the meso-force chain network, crack propagation patterns, and macroscopic fragmentation morphology of the specimens. The results indicate that under medium strain rate impact, the internal force chains in granite undergo four successive evolutionary stages: initiation, enhancement, coalescence, and disintegration. Among these, the intergranular force chains of feldspar dominate in quantity. Crack propagation is primarily tensile, with intergranular cracks of feldspar being the main type leading to specimen failure. The evolution of fragments exhibits a dynamic process from localized initiation to overall fragmentation. As the impact height increases, the force chain network transitions from sparse to dense, the number and distribution range of cracks significantly expand, fragment sizes noticeably decrease, and the quantity of intergranular cracks in feldspar consistently remains predominant.

To investigate the morphological characteristics and load response patterns of wave excitation induced by underwater explosions, a series of underwater explosion experiments were conducted. The formation mechanism of jet-type wave excitation was explored, and the temporal variation of wave loads was analyzed. A numerical model of wave excitation due to underwater explosions was developed using the LS-DYNA finite element software based on the S-ALE (Structured Arbitrary Lagrangian–Eulerian) algorithm. The model was validated against experimental results to ensure its reliability. Further parametric studies were carried out to examine the effects of stand-off distance, detonation depth, and explosive charge weight on the wave excitation pressure peak and impulse load. The results show that with increasing stand-off distance and detonation depth, both the pressure peak and impulse load initially increase and then decrease. With increasing explosive charge weight, both parameters exhibit an overall upward trend, though fluctuations are observed during the process. As the wave propagates to a certain distance, its shape becomes more regular and wave crests appear; at this stage, the attenuation of the pressure peak and impulse load slows down with increasing scaled distance, and in some cases, even reverses to a slight increase.

To study the mechanical response and damage characteristics of freeze-thaw (FT) treated steel fiber reinforced concrete-sandstone composites under cyclic impact loading, composite specimens with different thickness ratios of sandstone layers were prepared. Cyclic impact tests of the composite specimens after FT were carried out using split Hopkinson compression bar system. The effects of FT cycle number and thickness ratios of sandstone layer on the failure mode, anti-cyclic impact times, dynamic peak stress reduction (DPSR), energy dissipation and micro-visual damage characteristics of the composite after cyclic impact were systematically analyzed. Results showed that FT cycles lead to a decrease in the proportion of micropores in the composite body and an increase in the proportion of medium pores and large pores. With the increase of the thickness ratio of the sandstone layer, the proportion of micropores decreased while the proportion of medium pores increased. After cyclic impact, the unfreeze-thaw composite specimens still maintained a good interfacial bonding state. After 40 FT cycles, the crack number in the concrete layer increased significantly, and typical transgranular cracks appeared in the sandstone layer, in addition, the degree of cementation in the interfacial transition zone decreased. With the decrease of the thickness ratio of sandstone layer, the FT damaged composite specimens gradually changed from tensile failure to edge shear failure. For unfrozen composite specimens, a higher proportion of sandstone layers results in stronger resistance to cyclic impact and a smaller increase in DPSR. After multiple FT cycles, however, a higher sandstone proportion leads to opposite trends in the number of cyclic impacts and DPSR increase.

The development of impact-resistant designs for ship main engine structures has garnered significant attention from the scientific community. As the primary load-bearing components, main engine support structures undergo significant dynamic loads during underwater explosions and other impact events. The present study employs the equivalent static method as the load equivalent approach to perform structural topology optimization for ship main engine supports. In order to achieve a reduction in weight while meeting established strength requirements, a mathematical model for topology optimization was established. This model is characterized by its ability to minimize structural compliance while imposing both stress and volume constraints. In addition, the optimization results were validated under typical impact conditions. A comparison of peak stresses at critical locations and the overall mass of the support structure before and after optimization was conducted to confirm the feasibility and effectiveness of topology optimization based on the equivalent static method. The findings indicate that this approach successfully achieves structural lightweighting while maintaining strength, thereby providing a foundation for the development of impact-resistant designs for marine main engine support structures.

Based on the peridynamic method, a numerical model is developed to simulate damage and crack propagation in a flat glass plate subjected to rigid-body impact, accounting for structural fracture and crack evolution. The validity of the model is verified through edge-on impact tests and impact experiments on square glass plates. On this basis, the effects of impact angle and impact velocity of a rigid sphere on the damage severity, crack morphology evolution, and crack propagation mechanisms of the glass plate are systematically investigated. The results show that the impact angle plays a critical role in governing crack types and propagation paths. At a low impact angle (15°), tangential momentum dominates the failure process, leading to the formation of spallation bands and fan-shaped cracks along the impact trajectory. At intermediate impact angles (30°–45°), the combined effects of tangential and normal momentum result in a mixed crack pattern, evolving from fan-shaped cracks to a combination of radial cracks and localized perforation. At high impact angles (60°–90°), the failure process is dominated by normal momentum, and radial cracks prevail, accompanied by the formation of circumferential cracks and branched crack networks. Impact velocity has a pronounced influence on damage evolution: at low velocities, radial cracks are predominant, whereas increasing velocity promotes the development of circumferential cracks and the formation of complex radial–circumferential crack networks. Overall, higher impact velocities lead to larger maximum impact forces and more severe damage, with the number of damaged material points increasing approximately linearly with the initial impact velocity.

In order to enhance the energy concentration of time-frequency representation methods and provide a more accurate two-dimensional group delay (2D GD) trajectory estimation for rotating machinery fault pulse signals, the Local Maximum Transient Extraction Transform (LTET) method is proposed to optimize the diagnosis of rotating machinery faults. Firstly, a second-order strong frequency varying signal model is constructed, and the Short-Time Fourier Transform (STFT) is conducted on it. Then the reason for the energy divergence phenomenon present in the transient extraction transform is derived. Based on the relationship between the local maxima of STFT in the time domain and the 2D GD trajectory, the Local Maximum Transient Extraction Operator (LTEO) is designed, obtaining a more concentrated time-frequency representation and a more accurate 2D GD trajectory. Finally, simulated fault signal of rotating machinery is constructed and real signal collection experiment is designed to collect fault signals from bearing, gear, and piston pump. Verification experiments and comparative experiments are designed to validate the excellent performance of LTET and comparing it with four time-frequency analysis methods. Results indicate that LTET achieves better energy concentration, less interference in the 2D GD trajectory, stronger noise robustness, and clearer transient features of faults. 

Bearings were critical components in rotating machinery, and their fault diagnosis was essential for operational safety. Traditional methods struggle with strong noise and dynamic temporal features, while existing Transformer-based models have limitations in feature embedding and trend modeling. To address these issues, this paper proposes FreqTimeFormer (FTF), a novel time-frequency joint diagnostic model. FTF introduces a time-frequency cooperative strategy to guide its Transformer architecture, enabling differentiated processing of features from both domains and reducing the representation complexity of vibration signals. Specifically, the model employs a Shift-Scale Embedding (SSE) instead of traditional linear embedding, which constructs cross-scale feature mappings to enhance deep associations between time and frequency domains. For classification, a Multi-feature Joint Classifier (MJC) is designed, integrating multi-scaled hierarchical convolution and pooling pathways to extract key frequency components and temporal evolution trends separately. This enables decoupled fusion of time-frequency features and achieves a robust deep representation of fault patterns. Tests on the CWRU bearing dataset show that FTF achieves an average accuracy of 99.87% in 10-class fault diagnosis, with 70% of faults identified at 100% accuracy. Under complex conditions, the model reaches a transfer recognition averaged accuracy of 92%, demonstrating high diagnostic precision and convergence performance. The proposed method offers a reliable solution for bearing fault diagnosis in challenging environments.

In order to obtain the vibration characteristics of the EV56 source controllable vibrators, the operating load of the seismic vibrators was used as the excitation condition. Measurement points were set up on the main structures of the seismic vibrators and the vibration responses of the main components of the vibrator were measured under linear sinusoidal excitation loads and random loads. The comparative analysis of time-frequence vibration characteristics was conducted on the of each measurement point on the components. The results show that the vibrations of the main components of the EV56 seismic vibrators in the x and y directions are asynchronous, and there are significant differences in the vibration amplitudes among the various measurement points on the components. When the frequencies are 9 Hz, 18 Hz, 27 Hz, and 90 Hz, the I-beam plate and the top plate exhibit an obvious vibration amplification effect in the x and y directions; when the frequency increases to 110 Hz, the vibrator achieves the maximum vibration amplification in all directions. The vibration intensity of the vibrator components connected to Column 2 is the highest, and the vibration response intensity of the top plate is higher than that of the I-beam plate. The test results provide a reference for the performance improvement and structural optimization of the EV56 vibrator.

New sawtooth anti-slide piles exhibit excellent mechanical properties under static loading. To investigate their seismic performance, shaking table model tests were conducted to compare conventional anti-slide piles with sawtooth anti-slide piles. Using a similarity ratio of 20:1 and the El Centro earthquake wave as input, the slope deformation characteristics, acceleration responses, and peak dynamic earth pressure distributions were systematically analyzed under varying seismic intensities (0.1g, 0.2g, and 0.3g). The results indicate that: (1) Macroscopic Observations: The sawtooth anti-slide piles significantly delay the expansion of slope cracks. The critical peak accelerations for cracking at the rear and front edges of the slope were 0.2g and 0.3g, respectively—representing an improvement over the 0.1g and 0.2g observed for conventional piles. The separation displacement at the pile top was only 0.4 cm, merely one-third of the 1.2 cm recorded for conventional piles, and the volume of soil sheared out at the slope toe was notably smaller. (2) Acceleration Response: At a seismic intensity of 0.3g, the peak acceleration below the slip surface decreased by 6.7%, while the reduction at the slip surface stabilized at 2.1%. (3) Frequency Response: the response amplitudes at all measuring points of the sawtooth pile show a significant reduction compared to those of the conventional pile within the low-frequency range f1. In the medium-to-high frequency ranges f2 and f3, the reduction effect is even more pronounced at the slip surface within the loaded section. (4) Peak Dynamic Earth Pressure: Both pile types exhibit a non-linear "weak bedrock response – sudden increase at the slip surface – peak in the sliding mass – upper attenuation" profile along the elevation. The sawtooth geometry helps disperse shear stress and alleviate the concentration of dynamic earth pressure. The study demonstrates that the geometric configuration of the sawtooth blocks significantly weakens seismic energy transfer and effectively controls dynamic responses. The seismic performance of sawtooth anti-slide piles is markedly superior to that of conventional piles, providing a new theoretical basis and technical support for landslide prevention and mitigation engineering.