The rod string is a thin rod string composed of a coupling and a rod connected by threads. The research on the dynamic behavior of the sucker rod string is the basis to prevent the failure of the sucker rod string and reduce the operation cost of the oil well. In view of the coupling vibration of rod string，it is proposed that the torsional torque generated by the friction force between the rod and tubing is the excitation of torsional vibration. Considering the influence of friction force on the coupling vibration of rod string，a simulation model of the coupling vibration of rod string in one directional well with initial bending is established under the conditions of displacement excitation at the top，load excitation at the bottom，trajectory excitation at the curved hole and tubing constraint. The four-order Runge-Kutta method is used to solve the simulation model and to simulate the dynamic behavior of the rod string. The simulation results show that： both longitudinal and transverse vibration simulation results are affected by the coupling vibration of the rod string. The effect on longitudinal vibration is not obvious. The contact force between the rod and the tubing in the inclined section of the oil well is high，and the collision in the compressed section of the rod string is serious. Hence，the inclined section of the oil well and the compressed section of the rod string are dangerous points for eccentric wear. Under normal preload conditions，the torsional vibration of the rod string is not sufficient to cause the rod string to trip. However，when the preload force of the coupling drops below the maximum torque of the rod string，torsional vibration may cause the rod string to trip. The research provides a theoretical basis for analyzing the failure mechanism of pumping rods，improving the working life of pumping rods and optimizing the design of pumping rods.

Brake disc bolts are important to ensure the braking reliability and the operation safety of electric multiple units （EMU）. Based on the load test technique of braking disc bolts， an experiment was conducted on the wheel-mounted braking disc bolts of the Chinese high-speed train to obtain the data of the dynamic loads，including the tensile load，the radial bending moment and the circumferential bending moment. By establishing a finite element model of the wheel-mounted braking disc bolts with the wheel-rail contact，the bolt loads under high-speed rotation are simulated and compared with test results. According to the test results and the simulation results，it indicates that the braking disc bolt loads are closely related to the operating speed of EMU. The higher the operating speed is，the bigger the variation of the bolt load will be. The loads of the braking disc bolt change periodically with the wheel rotation. When the wheel rotates once，the bolt load changes once. Meanwhile，there are some small waves on each load signal，which is caused by the wheel-rail excitation. With an increase of the operation speed，the vibration of wheel increases，and the bolt load fluctuation also increases. The results of the finite element model show that the values and directions of the radial bending moments at different positions are inconsistent. Due to the asymmetry of the wheel structure，the radial bending moment at the left cross section of the bolt is bigger than that of the right cross section.

Based on the strain gradient nonlocal Biot theory，the analytical solution of the dynamic response of the tunnel lining under the action of P-wave is obtained by using the wave function expansion method and the boundary conditions between saturated soil and lining with the deeply buried circular lining as the research object. The influence of non-local parameters and size factors on the dynamic stress concentration factor （DSCF） is investigated for different incident P-wave frequencies. The results show that when the incident wave frequency is low，the non-local parameters and size factor have almost no effect on the DSCF. As the incident wave frequency increases，the effects of the non-local parameters and size factor on the DSCF become more and more obvious. The non-local parameters are negatively correlated with the DSCF，and the size factor is positively correlated with the DSCF. The maximum dynamic stresses in the lining appear on the right side of the lining. With an increase of frequency，the DSCF in the lining shows obvious radial direction and the dynamic stresses in the lining appear in the right side of the lining. The maximum dynamic stresses in the lining all appear on the right side of the lining，With an increase of frequency，the DSCF in the lining shows obvious fluctuation along the radial direction，and the non-local parameters and size factor have little influence on the distribution pattern of the cyclic stresses in the lining.

In this paper，the timing transmission gear of a certain type of domestic marine 20V diesel engine is taken as the research object. Aiming at solving the problem of frequent broken teeth fault，considering the influence of various types of internal and external comprehensive excitation，the lumped parametric bending-torsion coupling dynamic model of multi-branch gear transmission shaft system of diesel engine is established. Based on Newmark step-by-step integration method，the forced vibration response is predicted，and the accuracy of the model is verified by the actual test data. Considering the influence of dynamic load，the traditional tooth root bending stress load spectrum is modified，and the strength fatigue check of the faulty gear is carried out. The results show that the peak value of the response energy at the driven timing gear of the fuel supply cam end of the diesel engine is 5.2 times that of the peak value of the response energy at the flywheel end，which indicates that the speed fluctuation at the driven gear of the timing gear is too large and the torsional vibration characteristics are poor. At this time，the bending fatigue safety factor of the tooth root is only 1.35，which is in the general reliability range and is prone to tooth breakage. Based on the engineering practice experience，the vibration optimization design scheme of the fault gear transmission system is proposed to improve the bending fatigue safety factor of the fault gear by 1.61 to ensure the safe and stable operation of the shafting. The research results reveal the mechanism of timing gear tooth breaking fault from the perspective of dynamics，provide some theoretical guidance for accurate prediction of tooth root bending stress and performance optimization，and provide theoretical support for vibration response analysis and vibration and noise reduction of diesel engine timing gear shaft system.

The incipient fault characteristics of planetary gearbox are weak and difficult to effectively identify under strong background noise interference and variable working conditions. To address these issues，an improved feature mode decomposition （IFMD） algorithm is proposed to extract the weak fault characteristics of planetary gearbox under time-varying speed conditions. Firstly，for the key input parameters of the FMD algorithm，such as the number of decomposition mode n，the number of filter K，and the length of filter L，which need to be set manually and lack adaptability，an adaptive scale space spectrum segmentation method is proposed to determine the required number of decomposition modes n. On this basis，the Spectral Gini Index （SGI） is used as the objective function，and particle swarm optimization algorithm is used to automatically determine the optimal filter number K and filter length L. Subsequently，the IFMD is applied to perform optimal modal decomposition on the fault signal under the optimal parameter combination，and the decomposed component with the highest SGI value is selected as the sensitive modal component. Finally，significant fault feature orders are extracted from the envelope order spectrum of sensitive component to accurately diagnose the fault type and location of planetary gearbox. The analysis results of variable speed simulation signals and engineering experimental data indicate that compared to the PSO-VMD method，MED method，SGMD method，and fast spectral kurtosis method，the proposed method can extract weak fault information more clearly and comprehensively，thereby improving the characterization ability and diagnostic accuracy of early fault features of planetary gearbox under time-varying speed conditions.

Direct measurement of dynamic loads on engineering structures is challenging due to environmental constraints. Therefore，the indirect identification or reconstruction of dynamic loads，using dynamic response information，has emerged as a highly effective method. Over decades，dynamic load identification has evolved，resulting in a series of valid solutions. This paper begins by reviewing the research history and main achievements of dynamic load identification methods. It provides a systematic exposition of typical frequency domain and time domain methods，as well as dynamic load identification methods which are based on various approaches such as function fitting，regularization strategies，Bayesian frameworks，and data-driven techniques. The advantages and disadvantages ，as well as application scope of each method，are also discussed. Additionally，this paper summarizes common issues in the load identification process，including uncertainties in structural parameters and input conditions. Identifying the position of dynamic loads is also a crucial aspect of the dynamic load identification problem. This paper analyzes the methods currently available for position identification. This paper delves into the engineering applications of dynamic load identification methods and analyzes the limitations of current methods. Considering the current challenges in the field of dynamic load identification and the increasing demands in practical engineering applications，the paper anticipates the technical difficulties that need to be addressed. It also discusses potential future development directions and key areas in dynamic load identification.

Aircraft often operate in complex and variable dynamic load environment，and dynamic load localization is the primary problem that needs to be solved in this field. This paper focuses on the dynamic load localization requirements of common and prone to abnormal vibrations in aircraft structures. Combining deep neural network，a rapid dynamic load localization method for aircraft structures is developed. By using Long Short-Term Memory （LSTM） neural network，the inverse implicit function model which can accurately describe the corresponding relationship between the dynamic load location and vibration response of the structure is constructed. A dynamic load localization method based on the LSTM neural network classification model is proposed. A simplified finite element model of the entire aircraft structure is established to simulate several typical dynamic load conditions that the aircraft may encounter during actual flight. The noise resistance and robustness of the established deep neural network are also studied. The simulation results show that the proposed method can accurately identify the location of dynamic loads under various load conditions，and can still maintain high locating accuracy under the measurement noise level of 10 dB and the parameter perturbation of 2.8%.

Sparse regularization has been proven to be effective in addressing the ill-posed problem in moving force identification （MFI）. However，existing methods often neglect frequency characteristic disparities between static and dynamic components in moving loads，thereby limiting the identification accuracy. Therefore，an MFI method integrating response prior information and weighted dictionary is proposed. A linear relationship between vehicle-induced bridge responses and moving vehicle loads is established in bridge-vehicle system. Once frequency domain analysis is separately performed on bending moment and acceleration responses，the obtained frequency prior information is then employed to construct weighted dictionaries that correspond to both static and dynamic load components. Subsequently，the static and dynamic components of moving loads are individually solved by alternating direction method of multipliers （ADMM）. The effectiveness of proposed method is demonstrated through numerical simulations on a real bridge，and a series of MFI experiments are conducted in laboratory. Results show that the weighted dictionaries considering response prior information significantly improves the accuracy of force identification and enhance its robustness to noise.

The fatigue failure of the structure under vibration conditions has brought hidden dangers to its own service life and the personal safety of the user. At present，there are solutions for the structural vibration fatigue such as adding reinforcement bars and laying a large amount of damping materials，but the efficiency is often low and the additional mass is excessive. In order to solve the above problems，an additional acoustic black hole （ABH） is installed on the structure to reduce the stress amplitude and extend the service life by reducing the structural response. Using a cantilever plate as the reference structure，the steady state dynamics analysis is carried out by the finite element method. The results show that the stress response at the gap of cantilever plate is significantly reduced after the addition of rectangular acoustic black hole （RABH）. Through stress and fatigue experiments，it is verified that additional RABH can reduce the stress response at the dangerous point of the structure and extend the vibration fatigue life of cantilever plate structure.

A novel vibration method，the master-slave distributed vibration test method，was proposed. Aiming at its control requirements，an online waveform replication technique for vibration loads was developed and an integrative prototype system with measuring and controlling functions was constructed. Therein，a signal processing method of frame segmentation and reconstruction was proposed for solve the problem that time waveform replication for long-duration continuous vibration loads. A method for dynamic transfer function estimation based on sample database construction and weighted average was proposed to reduce the influence of nonlinear property on control precision. A spectrum correction method was introduced to improve the frequency domain control accuracy. A test with 1 master vibrator and 2 slave vibrators was performed using the developed online vibration load replication control technique，and the results show that the technique has a high replication precision in both time domain and frequency domain，has a subsecond overall delay time，and has a subpercent overall root-mean-square error. The technique can provide a key technique for supporting online distributed vibration tests.