The overburden has the characteristics of soil dynamic nonlinearity and structural layering, which increases the difficulty of free field calculation of foundation with overburden under seismic wave oblique incidence and affects the energy absorption capacity of artificial boundary. They restrict the accuracy and application of seismic wave input. The horizontal layered overburden is taken as the research object, the potential function theory is introduced, the dynamic transitive relation between the amplitude matrix of the top layer and the amplitude matrix of any layer is constructed under seismic wave oblique incidence, and the time domain strain of soil is calculated. Based on the two-dimensional strain state theory, the equivalent linearization method is used to reflect the dynamic nonlinearity of soil, the analytical calculation method for the free field of foundation with nonlinear horizontal layered overburden under seismic wave oblique incidence is established. Then, the nonlinear viscoelasticity artificial boundary element developed by the authors is used to simulate the radiation damping effect of the overburden. In near-field wave analysis, the boundary element parameters change with the dynamic shear strain of the inner soil element, the boundary element has the optimal energy absorption ability. Finally, combined with the equivalent input load obtained from the analytical free field, a seismic wave input method suitable for the foundation with nonlinear horizontal layered overburden under seismic wave oblique incidence is established. This method can achieve wave input for the overburden layer foundation based on the oblique incident waves at deep and surface ground motion. The implementation of wave input based on surface ground motion avoids the process of forward modeling free field through base ground motion. The seismic responses of foundations with elastic horizontal double layers and nonlinear horizontal multiple layers overburden are studied. The results show that the displacements and stresses obtained by wave input have a high degree of fit with the analytical solutions, and the calculation accuracy is high, it can provide a basis for the study of seismic response of embankment dam on the foundation with horizontal layered overburden.

To suppress time-varying vibrations in precision machining processes, a semi-active adaptive PI control method based on magnetorheological elastomer (MRE) was proposed. Firstly, the dynamic model of the MRE isolation system was established based on the variable stiffness isolation principle,and then the semi-active control conditions were derived. Secondly, taking the response acceleration and target acceleration deviation as the input of the PI controller, the optimal PI control parameters under different vibration frequencies and amplitudes were optimized by genetic algorithm, and the frequency amplitude dependent adaptive law was obtained based on the passive reference model.This method does not need to identify the frequency by complicated Fourier transform, and has high real-time performance. Finally, the effectiveness of the designed controller was verified by simulation and experiment. The results show that compared with the traditional PI controller, the proposed method has greater suppression at 40Hz-50Hz and 1.0 m/s2 - 3.0 m/s2 time-varying vibration.

A linear parameter varying(LPV) μ synthesis robust controller is designed for the nonlinearity, uncertainty problem, and the contradiction between multiple performance objectives in solenoid valve semi-active suspension systems. A nonlinear damping force dynamics model of the solenoid valve was established and performed on a bench test to verify the accuracy of the model. A nonlinear LPV model for a seven-degree-of-freedom suspension system was constructed. An LPV-μ synthesis robust controller based on nonlinear and mixed uncertainties is designed with analysis of suspension parameter uncertainties and system modeling errors and consideration of the effects of sensor measurement noise. Finally, the full vehicle solenoid suspension system simulation and real vehicle test were conducted. Simulation results show that the controller reduces the root mean square value of body vertical acceleration for 46.47%, the pitch angle acceleration for 46.47%, and the roll angle acceleration for 50.68% under random disturbance. It has excellent anti-jamming ability and controllability. The test results show that the root mean square values of the vertical acceleration, pitch angle acceleration, and roll angle acceleration are reduced by 36.6%, 30.14%, and 39.47%, respectively, under the LPV-μ synthesis control. In addition, the dynamic deflection of the suspension is ensured to be less than 0.06 m, which verifies the effectiveness of the control strategy.

(五号加粗) In order to solve the problem of pipeline vibration in power industries such as nuclear power and thermal power, a one-way damped dynamic vibration absorber suitable for three-dimensional pipelines based on fixed point theory was developed and designed. And a key parameter calculator based on visual basic was compiled. The effectiveness of the dynamic vibration absorber in three-dimensional pipeline vibration reduction was verified through finite element simulation, installation location parameter optimization, and experimental verification. The conclusion is as follows: The dynamic vibration absorber developed can effectively reduce the vibration of three-dimensional pipelines. The vibration reduction effect verified by experiment is similar to that verified by simulation calculation.

In order to improve the efficiency and accuracy of CFST void detection， an intelligent recognition method based on FFT (Fast Fourier Transform), MI (Mutual Information) and MiniRocket neural network is proposed in this paper. First, the time domain signal of the CFST percussion wave to be measured is converted to the frequency domain signal using FFT. Secondly, MI is used to establish the correlation between the frequency domain signal and the void state, and the top 30 features with the largest correlation are extracted to establish the data set, which avoids complex mathematical operations and redundant information. A MiniRocket deep learning network is established, and by using fewer parameters and smaller feature sizes improving the speed and accuracy of classification. Finally, the noise robustness of the model is investigated and compared with other algorithms, feature extraction methods and recognition methods. The results show that the proposed method achieves 100 % average prediction accuracy in 100 repetitions of the experiment for different void depths and void widths. At high SNR, this method is less affected. In addition, compared with other algorithms, feature extraction methods and recognition methods, this method has better prediction performance. Therefore, the proposed method has great application potential in the actual intelligent void identification of CFST in the future.

High-velocity and hydraulic kinetic energy fracturing can achieve hydraulic penetration impact with strong dynamic load. This technology mainly utilizes the water hammer effect, which has many unique advantages, such as high peak pressure, high loading rate, and repeated progressive expansion of cracks. The evolution mechanism of rock damage-fracturing process under the hydraulic penetration impact of charged fluid is the core issue in the optimization design of this technology. Therefore, a rock dynamic damage simulation experimental device was employed to conduct a series of rock dynamic failure experiments under strong hydraulic penetration impact. The influence law was analyzed based on loading rate, impact times, and combined repeated impact on rock failure morphology. The results indicate that, If a single hydraulic penetration impact is conducted on rocks, three different rock failure modes are presented in sequence as the loading rate increase. These are near wellbore crushing damage (8.5MPa/ms), forming macroscopic cracks due to the aggregation and concatenation of microcracks (13.4MPa/ms), fluid wedging brittle cracking (15.5MPa/ms). Under repeated impacts with low peak pressure and low loading rate, rock damage and failure exhibit three stages: near wellbore crushing damage (1-2 times), cracks initiation and propagation (3-5 times), and stress compression crushing (6-10 times). As the number of impacts increases, the damage around the hole intensifies, forming cracks of varying length.

The dynamic response of underground structures under traffic loads has a significant impact on their safety and stability during operation. In order to investigate the dynamic response characteristics of the asymmetric integrated underground structure with large cross-section under the action of multi-layer traffic loads, this paper establishes a finite element model based on a typical cross-section of a project, simulates the application of traffic loads on road surface, municipal layer and railway layer, analyzes the vibration response and stress distribution characteristics of the asymmetric integrated underground structures, and explores the superposition law of structural dynamic response generated by the joint action of multi-layer traffic loads. The results show that the vibration response of the asymmetric integrated structure is the highest in the middle of the left top plate of the municipal transportation layer, reaching 0.5~0.7m/s2, and the dynamic stress is the highest at the bottom corner of the rail transportation layer, reaching 0.08~0.1MPa. The subway train load is the main source of the dynamic stress of the structure, but the soil nail support and pile foundation support can effectively reduce the effect of the dynamic stress. The vibration response of the integrated structure is significantly affected by the vehicle load on the ground. During the operation period, special attention should be paid to structures located in densely populated road sections with ground vehicles. The research results can provide reference for optimization design and maintenance of underground asymmetric integrated structures during operation.

As a widely used passive vibration control device, the fluid viscous damper exhibits mechanical performance alteration throughout the entire service life. To explore the mechanical parameter changing mode and reveal the mechanism of performance alteration, experimental and simulation studies were conducted with oil leakage and temperature effects as the main influencing factors. Firstly, cyclic tests and viscousity-temperature analysis were carried out on viscous dampers under different oil leakage levels and ambient temperatures, respectively. Secondly, fluid dynamics simulations were performed to obtain the alternating tendency of the hysteresis performance. Finally, an analytical model reflecting the performance alteration of viscous dampers under combined oil leakage and temperature effects was established and verified. The results show that oil leakage will cause a “zero-force gap” appearing in the hysteresis loop, of which the length is proportional to the leakage level. Temperature increase will lead to a decrease in the damping coefficient, which affects the peak damping force. The established performance alteration model can accurately reflect the changes in mechanical performance of viscous dampers.

Because of its simple and reliable connection, as well as the advantages of space saving and weight reduction, the wedge-shaped ring connection structure is often used in torpedoes, aerospace vehicles and other weapons and equipment. Aiming at the problems of complex mechanism model, small sample size and class imbalance of wedge-shaped ring connection structure, a method of Pre-tightening state identification based on the siamese neural network is proposed in this paper. A time-frequency feature enhancement technology is used to improve the efficiency and effect of model training. Based on the enhanced features, a three-layer siamese neural network classification model is established to realize the macroscopic classification of Pre-tightening state identification of wedge-ring connection structure. On this basis, in order to guide the precision assembly, the feature clustering effect of siamese neural network is deeply analyzed by feature visualization technology. The pre-tightening state quantitative characterization model is established by using two-dimensional features, and the target state clustering center and acceptance domain are introduced to realize the quantitative evaluation of the pre-tightening state of the wedge-ring connection structure. Experiment has verified the effectiveness of the proposed method. The research results provide a new technical approach and solution for Pre-tightening state identification of wedge-ring connection structure.

In the flat finned tube heat exchanger working in low temperature and high humidity environment, frost phenomenon is easy to occur, resulting in increased energy consumption and failure rate. The vibration effect on the microdroplet at the initial stage of frost formation can accelerate the sliding process of the microdroplet and thus achieve the effect of frost formation. The growth process of microdroplet in the early stage of frosting was numerically simulated and analyzed, and the growth characteristics of microdroplet on different surfaces were obtained and verified by the literature values. Then, the effects of different vibration frequencies were studied by using the data of microdroplet at different times through numerical simulation, and finally an experimental platform was built for verification. The results show that for different surfaces, the larger the surface contact Angle is, the slower the growth rate of microdroplet is. The optimal vibration frequency corresponding to different volumes of microdroplets is different. When the volume of microdroplets is small, the higher vibration frequency makes the microdroplets oscillate back and forth on the wall surface of the base tube, which is not easy to slip off. When the volume of microdroplets is large, the higher vibration frequency is conducive to the microdroplets overcoming the wall friction and the droplet sliding off.

To address the problem that the remaining useful life prediction accuracy of a component is affected by environmental changes during operation, a kernel density estimation remaining useful life prediction model considering the impact of environmental shocks is proposed. Firstly, the non-parametric estimation method of adaptive kernel density is used to model the continuous natural degradation process of the component; secondly, assuming that the impact of the harsh environment on the component is the random shocks on the component, the remaining useful life prediction model is established by introducing a virtual age function and a variable sudden failure threshold under the consideration of changing the operating environment conditions to correlate the impact on the component with the continuous degradation process stochastically, and its reliability is analyzed. Finally, the accuracy and validity of the proposed model are verified by the experimental simulation analysis of wind turbine degradation data and gearbox wear measurement data.

Aiming at the problem that it is difficult to recognize the caving coal gangue in the process of fully mechanized caving mining under the background of strong noise, a coal and gangue recognition method fusing low-level auditory feature Mel spectrum and high-level auditory feature auditory neurotransmitter firing rate is proposed. Firstly, according to the frequency spectrum characteristics of the sound signal of the tail beam of collapsed coal and gangue impact hydraulic support, an auditory model suitable for the coal gangue recognition task is established based on the auditory neural filter bank model. Then, the auditory model is used to analyze the sound signal of collapsed coal and gangue to obtain auditory neurotransmitter firing rate. Afterwards, the auditory neurotransmitter firing rate is fused with the peak feature extracted by Mel spectrum to obtain the auditory perception diagram of coal and gangue sound. Finally, coal and gangue were recognized with the ConvNeXt model based on the fusion auditory features constructed. The experimental results showed that the proposed coal and gangue recognition method with fusion auditory features had high recognition accuracy under different signal-to-noise ratios, and its superiority was particularly evident under the condition of large background noise (signal-to-noise ratio of -5dB), with accuracy reaching 91.52%, which was significantly superior to the method using low-level auditory features and spectrum as recognition features and using time-frequency domain features combined with machine learning, verifying the robustness of the proposed method to noise.

To improve the re-centering capacity of damper, a dual self-centering driven system composed of reset spring and shape memory alloy (SMA) is proposed. A novel dual self-centering friction damper is designed, and its configuration and working principle are summarized. The effects of preloading force, loading displacement amplitude and the reset spring module stiffness on the re-centering and energy dissipation capacity were investigated by cyclic loading tests. The simplified mechanical model of the damper is established, and the analysis of numerical simulation is carried out. The results show that although increasing the preloading force can improve the energy dissipation capacity of the damper, it also increases the residual deformation rate. Under relatively large preloading force and loading displacement amplitude, the reduction of residual deformation rate caused by dual self-centering driven system is obvious, which is beneficial to improve the re-centering capacity of the damper with high energy consumption demand. The hysteresis curves and mechanical performance parameters of the damper obtained by simplified mechanical model and finite element simulation using OpenSees match well with the experimental results, which verifies the accuracy of the mechanical model. The contribution of each functional component to the overall performance of the damper is analyzed by finite element simulation. The analysis results reflect that the friction energy dissipation device has a good contribution to the overall energy dissipation capacity of the damper, and the contribution of the reset spring to the re-centering capacity of the damper becomes obvious with the increase of the preload.

With the development of heavy haul railway in China, the axle load of heavy haul freight vehicles is increasing, and the problem of wheel flat is also increasingly prominent, this problem lead to a dramatic increase in dynamic wheel rail loads. In this paper, a rigid-flexible coupling dynamic model of heavy haul freight vehicle-track is established, and the influence of wheel flat on vertical force and longitudinal creep between wheel and rail is investigated under different braking conditions of heavy haul freight vehicles, and the limit value is calculated. The results show that the P1 and P2 forces of the vehicle increase with the increase of the length and speed of the wheel flat, and the emergency braking condition is greater than the normal braking condition. The wheel/rail vertical force of the empty car is far less than that in the load car, but the wheel/rail vertical force fluctuation of the empty car will be greater under the effect of the flat. On the other hand, the braking of the vehicle will lead to changes in the longitudinal creepage and the longitudinal creep force. At the same time, the longitudinal creepage and the longitudinal creep force will fluctuate under the action of the wheel flat. The larger of the wheel flat, the greater the fluctuation. According to the wheel/rail vertical force and wheel load reduction rate specified by the state, the wheel flat limit value of the vehicle under different working conditions is calculated. Combining the empty and load vehicles as well as the braking conditions, the limit value of wheel flat of the heavy haul freight vehicle is obtained as 38mm.. The study will provide relevant guidance for the operation and maintenance of heavy haul freight vehicles.

Aiming at the problem of non-uniqueness of solution and singular integral in acoustic boundary element method, based on the idea of CHIEF method, the conventional boundary element equation and the equivalent source equation are combined, and the coupling equivalent relation between the coefficient matrix of the two equations is used to indirectly replace the singular coefficient matrix in the conventional boundary element method, and then a coupled CHIEF method with unique solution in full frequency domain, high computational accuracy and high stability is proposed. In this method, the equivalent source equation is used as the supplementary equation, which not only solves the failure of the interior point supplementary equation of the traditional CHIEF method, but also avoids the direct calculation of singular integrals by the indirect substitution of matrix, which significantly improves the computational efficiency and accuracy. Through typical examples of acoustic radiation and scattering, the results of the proposed method, conventional boundary element method, conventional Burton-Miller method and equivalent source method are compared. The results show that not only the unique solution can be obtained in the full wavenumber domain, but also the calculation accuracy and efficiency of the proposed method are better than those of the conventional boundary element method and the conventional Burton-Miller method, and the condition number of the coefficient matrix is much lower than that of the equivalent source method.

To achieve the purpose of multi-level protection of the main structure and reduce the residual deformation of conventional energy dissipation dampers under strong earthquakes, A novel variable hysteresis performance damper based on shape memory alloy (SMA-VHD) is proposed. This paper elucidates the damper's configuration, variable hysteresis performance, and working mechanism. A refined finite element model of the damper is formulated by leveraging the outcomes of plate specimen tests using SMA. The hysteresis performance study and parametric investigations are based on the verified finite element model. Finally, the multi-level seismic performance of a double-column RC bridge bents with additional variable hysteresis performance damper is studied by dynamic time-history analysis. The results indicate that SMA exhibits a distinctive stress-strain relationship resembling a flag, which shows good self-centering capability. The SMA-VHD actualizes variable hysteresis performance, with the hysteresis response transitioning from rectangular to flag-shaped as the damper deformation increases, accompanied by a prominent multi-level platform. Applying SMA-VHD to RC bridge bents imparts multi-level seismic performance and enhances the structure's seismic performance.

The nonlinearity in the multi-mesh gear train due to the periodically time-varying mesh stiffness, contact loss, and the couplings between the multi-mesh stiffnesses are considered. The nonlinear oscillation is investigated by the homotopy analysis method (HAM). And closed-form approximations for the primary resonance, sub-harmonic resonance, and super-harmonic resonance are obtained. In contrast to the method of multi-scale (MMS), the HAM is independent of the contact loss ratio. Results indicate that with large contact loss ratios over 30%, the amplitude-frequency curves obtained by HAM agree better with the numerical integration (NI) results than those obtained by the MMS. This study lays a higher accurate foundation for more complex nonlinear dynamic analysis of gear sets.

The frequent transient process of pumped storage power station has an important effect on shafting vibration, so it is very important to establish a coupling model between the regulation system and shafting which can reflect the transient response of hydropower units for the safe operation of pumped storage power station. In this paper, a transient coupling model between the regulation system and the shafting system considering multiple vibration factors is established based on the torque equation derived from the Lagrangian formula. The dynamic response process of the shafting under different load rejection is calculated, and the influence of the eccentric mass of the generator and the excitation current of the generator on the transient process of the shafting is analyzed. It is found that the more the load is rejected, the more severe the vibration of the shafting in the process of dynamic response. After 30 %, 60 % and 100 % load rejection, the amplitude of the generator rotor in the x direction is increased by 68.7 %, 109.3 % and 126.3 % respectively compared with that before load rejection. The larger the eccentric mass of the generator is, the higher the amplitude of the shaft system of the hydro-generator set in the dynamic response process is, and the more unstable the system is. The larger the excitation current is, the smaller the amplitude of the shaft system in the response process is, which is more conducive to the stable operation of the system. The purpose of this paper is to provide a method for the establishment of the transient coupling model of the regulating system and shafting system of hydro-generator set, discuss and evaluate the parameter sensitivity of the transient coupling model under load rejection, and ensure the safe and stable operation of the unit under the transient state.

An interval model was established to analyze the normal contact stiffness of a mechanical joint. The model takes into consideration the uncertain parameters such as asperity radius of curvature, distribution density, and asperity height variance. To address the limitations of traditional contact stiffness models in determining the reasonable range of normal contact stiffness, the KE elastic-plastic contact stiffness model and Legendre polynomials were utilized. The model was validated by comparing it with contact stiffness test data and traditional model solution results. The feasibility and accuracy of Legendre-scanning method were proved by the results. The results show that the rough surface topography parameters have a significant impact on normal contact stiffness, with the uncertainty of asperity height variance having the greatest influence. As the dimensionless contact distance decreases, the degree of influence increases. The establishment and analysis of the interval model for normal contact stiffness in mechanical joints can serve as a reference for further research on joints.

The bolted connection joints of transmission towers often experience loosening due to transverse cyclic loads, resulting in damage to the transmission towers. Currently, many single-bolt tests conducted on vibration test machines and finite element studies are not applicable to the actual working conditions of angle steel-bolt group joints due to bolt constraint issues. To address this problem, a refined bolt model considering thread incline is established in ABAQUS. The applicability of the finite element model is verified based on the results of fastener tests. The bolt model is then extended to complex single-limb, single-wrap, and double-wrap angle steel-bolt group joint models to analyze the loosening mechanism and pre-tension variation process of bolt group joints under transverse vibration loads. The analysis results show that under transverse cyclic loads, the pre-tension alternates between increasing and decreasing. The thread contact surface enters the slip state before the pressure surface of the bolt head. With an increase in the friction coefficient and pre-torque, the decreasing trend of pre-tension becomes smaller. With an increase in vibration amplitude, the decreasing trend of pre-tension becomes larger. The vibration frequency has a negligible impact on bolt loosening. The degree of bolt loosening in single-wrap and double-wrap joints gradually decreases from the outer side to the inner side. Applying preload will reduce the tendency of bolt loosening to some extent. The degree of loosening for double-limb single-packet joint bolts decreases by 16% to 23.24%, and for double-limb double-packet joint bolts, it decreases by 2.63% to 3.80%. Therefore, it is important to monitor the easily loosened bolt locations in actual engineering to ensure the load-bearing capacity of the joints.

The early warning of faults in hydropower units is greatly affected by the warning indicators. However, these indicators are mostly based on single sensor signal and information, and therefore limited in their abilities to comprehensively characterize the unit operating status. To address this issue, a method combining Integrated Multi-Sensor Genetic Programming (IMSGP) and Weighted Euclidean Distance Index (WEDI) is proposed. First, multiple sensor signals are preprocessed to eliminate interference. Next, multivariate features are extracted from the preprocessed signals to construct the original warning feature set. Then, the Composite Detection Index (CDI) is used for feature selection, and IMSGP is investigated for feature construction. Finally, Principal Component Analysis (PCA) and the Euclidean distance are used to construct WEDI for identifying abnormal states of the unit. Through analysis of hydropower unit data, the ability of the proposed method on detecting early faults and achieving effective fault warning were verified.

In the realm of fluid-structure interaction dynamics, the traditional Housner model plays a pivotal role in engineering design. However, its theoretical derivation is limited to regular water tanks, employing a concentrated mass overall model to describe the global effect of liquid oscillations. This approach inadequately captures the finely detailed responses of irregularly shaped liquid storage structures, necessitating the development of a distributed additional mass model suitable for simulating oscillations in irregular water bodies.Through potential flow theory, a modal synthesis model is derived, achieving the decoupling of distributed mass and the vibrational acceleration of the liquid storage tank wall. This model effectively disentangles distributed impulse mass and convective mass. Moreover, the vibrational mode analysis of solid grids is applicable to the dynamic analysis of water bodies with arbitrary shapes. The model's accuracy and reliability are verified through comparisons with detailed Computational Fluid Dynamics (CFD) simulations.Finally, utilizing the proposed model, this study investigates the dynamic response patterns of safety tanks with irregular shapes in nuclear power plants at various water levels and sway grid distributions. The applicability of the model in engineering scenarios is demonstrated.

Facing the lack of experiment data, a model updating and virtual verification method considering modelling uncertainty is proposed to obtain accurate thermal-mechanical coupling finite element model (FEM) for launch vehicle strap-on structures. The proposed method makes full use of the experiment data of previous model and enable the new developing model without any experiment data, through the virtual mapping, verification and calibration based on the generalized theoretical model of friction heat. Firstly, the FEM of previous model is established and calibrated through the Bayesian updating framework. And then, determine the undetermined coefficients in theoretical model to reduce the discrepancy between theoretical value and simulation result. Finally, verify and calibrate the FEM of new developing model based on the theoretical model. The proposed method is performed to solve digital modeling and verification problem of a novel developing strap-on structure without sufficient experiment data and the result shows the calibrated FEM has higher accuracy and reliability.

A type of metal corrosion probes was proposed using piezoelectric tube stack and electromechanical impedance (EMI) technique. The probe consists of a piezoelectric tube stack and a metal bar. The transfer matrix model of the multilayer structured probe in longitudinal vibration mode was established, and the electrical impedance was derived to solve the first resonance and anti-resonance frequencies. The theoretical results were validated by comparing them with those of the special cases in the published literature. In addition, the probe performance was studied systematically through theoretical analysis, artificial uniform corrosion experiments, temperature-sensitive experiments, accelerated corrosion tests, and wireless impedance measurement experiments. The results show that the first resonance and anti-resonance frequencies of the probe are increased with the decrease of the bar length, the increase of the corrosion days, and decreased with the increase of temperature. The measured impedance spectra of the wireless impedance measurement system are very consistent with the test results of the traditional impedance analyzer. The present study provides an important reference for developing the novel metal corrosion probes of wireless quantitative measurement.

Aiming at the vibration problem of the rub-impact rotor-runner system in axial-flow hydrogenerator set caused by misalignment of coupling Angle, based on the modified LuGre friction model,the expressions for the rub-impact forces of runner blades under the misalignment fault are derived in this paper. On this basis, the system dynamic model is established which comprehensively considers external excitations including unbalanced magnetic pull force. The influence of the misalignment angle on the vibration characteristics of the system is studied by numerical method, and the stability of the periodic solution of the system with the speed as the control variable is analyzed based on Floquet theory. The results show that the existence of misalignment significantly changes the dynamic characteristics and increases the possibility of system instability. In addition, the effect of the misalignment angle on the vibration response of the rotor and the runner is quite different. With the increase of the misalignment angle, the runner vibration varies obviously and the degree of rub-impact is worse. The research results in this paper can provide references for the safe operation and stability analysis of axial-flow hydrogenerator set.

In order to reveal the influence of the confining pressure on the formation and expansion mechanism of rock fissures under particle impact, particle impact rock-breaking experiments and micro-nano industrial CT scanning experiments were carried out, which clarified the influence of the confining pressure on the characteristics of the rock fissure expansion under the action of particle impact; and numerical simulations were carried out on the particle impact under the conditions of different confining pressures, to analyze the evolution process of the rock's stress and fissure fields, and to reveal the intrinsic mechanism of the confining pressure influencing the expansion of fissures. The results show that after the particles impact the rock, a fracture zone and intergranular main crack propagation zone are thus formed in the rock. The shear stress and tensile stress caused by compressive stress are the main reasons for the formation of the fracture zone, while the formation of the intergranular main crack propagation zone is mainly due to tangential derived tensile stress. The confining pressure induces prestress between rock particles such that the derived tensile stress needs to overcome the initial compressive stress between the particles to form tensile fractures. And the increase in the confining pressure leads to increases in the proportion of shear cracks and friction effects between rock particles, resulting in an increase in energy consumption for the same number of cracks，which inhibits the formation of the fracture zone and intergranular main crack propagation zone.

The rectangular hollow section pier of a railway high-pier long-span simply-supported beam bridge is taken as the research object,calculation model for four kinds of pier heights were constructed, and factors such as the position of truncation and the number of reinforcement bars were considered. IDA analysis is carried out by using Opensees software to build a single pier calculation model, and the elastic-plastic seismic response characteristics of railway high piers are summarized and suggestions on seismic design is put forward. The results show that when the ratio of longitudinal reinforcement is between 0.63 and 0.89%, the pier height is less than 42 meters and the longitudinal reinforcement length is arranged over the pier, the section of hollow pier bottom is weak.When the height of the pier is greater than 67 meters and the longitudinal reinforcement is divided into sections, the section at the bottom of the hollow pier, the section at the truncation of the longitudinal reinforcement and a section in the pier may be the weak part, but the section at the bottom of the hollow pier is the area where the plastic hinge appears first.The plastic hinge in pier shaft can be produced only when it is stimulated by strong ground motion. The influence of ground motion peak acceleration should be considered in the selection of longitudinal reinforcement.Increasing the number of reinforcement bars at pier bottom is beneficial to reducing the plasticity of pier bottom section in general, but it may not improve the seismic performance of the whole pier under strong earthquakes. For high piers, when there are two or more plastic hinge areas in pier shaft, it is suggested to use the coefficient of curvature ductility as the evaluation index.

Cable is an essential force transmission component of the cable supported structures, and its cable force directly affects the service condition and lifespan of the structures. In general, for cable supported structures with locally rigid coupling, the cable strand vibration is independent and coupled. the vibration characteristics of the parallel strand cables are different from those of the single cable strand or the cables with good integrity. In order to effectively identify the tensions in the parallel strand cables with rigid couplings, Firstly, the model of multi-strand coupled system was established and the vibration equations of the system was derived, According to the vibration equations of the system, the parametric analysis of vibration characteristics was performed on the coupled system; Then, combined the filled function method and optimization theory, the identification algorithm for cable force of multi rigid couplings cable strands was constructed, the global identification of cable force was realized; Finally, the correctness and reliability of the algorithms were demonstrated by the experiment and finite element simulation. The results show that the rigid coupling ensures that each cable strand vibrates synchronously, the natural vibration frequencies of the parallel strand cables appear fractional frequency doubling, and there are local differences in the overall vibration modes; The cable force identification algorithm based on global optimization theory proposed in this paper exhibits low requirements for initial values, high calculation accuracy, and convergence efficiency, and can be extended to other parameter identification problems.

The parameter tracking robust observer design method is proposed for a class of quadrotor UAV subject to vibration. Firstly, the auxiliary filter is constructed to excite the vibration properties. Meanwhile, filter parameters are adjusted to reject the adverse effect of noise acting on the auxiliary state variables. The active vibration suppression can be simplified to the constant parameter estimation problem, which avoids the coupling of the estimated values and the operation of redundant parameters. Then a cascade structure of frequency parameter observer and tracker is designed to accurately estimate the vibration information. According to the above analysis, the compensation signal is reconstructed by auxiliary variables and frequency parameters. As a result, satisfactory vibration suppression performance can be achieved in combination with the controller. The designed observer has strong robustness without the phase lag caused by the time varying signal, which is often occurred in the conventional tracker. Finally, the performance of the system is demonstrated using the Lyapunov theorem, and the simulations are used to illustrate the effectiveness of the proposed method.

A friction self-centering brace with displacement amplification function (SC-DAFB) is proposed to address the insufficient energy dissipation capacity of traditional self-centering braces and the self-centering capacity of displacement amplification dampers. SC-DAFB is based on the working mechanism of bridge amplification and has a basic structure and working mechanism that are explained in detail. The formula for calculating the restoring force of the brace at each loading stage is derived, and the low-cycle reciprocating loading test of 6 groups of SC-DAFB under different working conditions is carried out. The key mechanical properties of SC-DAFB, such as load bearing capacity, hysteresis curve, energy dissipation and residual displacement, are obtained and compared. The results show that reducing the initial amplification Angle can effectively improve the bearing capacity and energy dissipation performance of the brace. When the self-centering ratio is 1.3, the yield load and maximum load of the brace at the initial amplification angle of 30° increase by 47.6% and 29.4%, respectively, compared with the brace without displacement amplification. The theoretical calculation and the experimental results show good agreement, verifying the accuracy of the theoretical restoring force model.