A type of metal corrosion probes was proposed using piezoelectric tube stack and electro mechanical 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.

The thin-walled metallic tube-core sandwich structures with convenient preparation, low cost and the ability to form significant plastic deformation have broad application prospects in the field of impact protection. In this paper, the novel metallic tube-core sandwich panels with geometrically asymmetric face-sheets and transverse density gradient distribution of tubes are designed. The dynamic response and energy absorption mechanism of the sandwich panels are studied numerically. The dynamic response process and characteristics of metallic tube-core sandwich panels are obtained, and the effects of detonation height, explosive mass, mass distribution of the panel and transverse density gradient distribution of the tubes on the deformation and energy absorption are discussed. The results show that the dynamic response process of the metallic tube-core sandwich panels can be divided into three stages: core compression, overall deformation, and elastic deformation recovery. With the increase of explosive mass and the detonation height, the central displacement of the back face-sheet of the sandwich panel increases and the energy absorption ratio of the tube-core layer decreases. When keeping the total thickness of the face-sheet unchanged, the sandwich panel with thick front face-sheet and thin back face-sheet has strong ability to absorb energy and resist deformation. The sandwich panel with positive density gradient distribution of cores has strong ability to resist deformation, and the sandwich panel with the negative density gradient distribution of cores has strong ability to absorb energy. The application of the metallic tube-core sandwich panel with an appropriate increase in the thickness ratio of the front and back face-sheets and a positive density gradient distribution of the tubes can better disperse the blast shock wave, enhance the energy absorption efficiency of core layer, and obtain better anti-blast effect.

For the sake of investigating accurately the flutter stability performance of suspension bridges, an aerodynamic force model in which mean wind loads and self-excited forces were integrated was adopted. Based on ANSYS finite element software, time-domain flutter analysis for a long-span suspension bridge with a main-span of 1660 m was conducted, the effect of mean wind loads, geometric nonlinearity and the time step taken for the time domain calculation on the flutter and post-flutter performance of bridges were evaluated following. According to the method presented above, time-domain flutter analysis for the sectional and full-bridge model of a long-span suspension bridge were performed respectively to characterize flutter performance. Numerical results show that the mean wind effects have significant influence on flutter performance of long-span suspension bridges. Neglecting the mean lift and lift moment would overestimate greatly the critical wind speed of flutter. The mean wind drag would causes the vibration amplitude increase in the initial period of motion, but eventually attenuates to zero. The time step set in time-domain simulation must be reasonable, larger time step would result in a larger critical wind speed of flutter. Furthermore, geometric nonlinearities have an inappreciable influence on the flutter threshold, but a significant influence on the motion state of post flutter. As we all know, the linear theory of flutter reveals that bridges will experience a terrible divergence when wind speeds exceed the critical value, but a soft flutter with a smaller amplitude is the final motion state when geometric nonlinearities are involved in the flutter analysis.

The site-city-interaction (SCI) effect will drastically modify the seismic wave field and the response of buildings. Based on the development status of SCI effect simulation approach, taking advantages of the spectral element method (SEM) and the multi-degree of freedom (MDOF) model, (i.e., SEM can efficiently simulate the three-dimensional seismic wave field propagation, and MDOF can simulate a large number of buildings at the same time), and combining with the frequency wavenumber domain (FK) method to input the seismic wave field by applying equivalent seismic loads, the FK-SE-MDOF approach is established. This approach can simulate the oblique incidence input of multiple wave-types (P, SV and SH) in the SE-MDOF coupling model, and solved the problem that the influence of nonlinear characteristics of buildings, spectrum characteristics, seismic wave-type and incidence angle cannot be considered simultaneously in previous three-dimensional SCI effect simulations. Firstly, the theory of the approach is introduced; Then, the correctness of the approach is verified by simulating an existing shaking table test; Furthermore, a series of ideal site-city-interaction models are established, and the influence of incident angle and wave-type on SCI effect is mainly discussed; Finally, some useful conclusions are obtained. The approach can realistically reflect the impact of SCI effects while reflecting the influence of building foundation contours on the seismic wave field. It is suitable for community-scale buildings where it is necessary to consider foundation contour information and can provide quantitative guidance for urban planning, seismic design, risk assessment and post-earthquake rescue.

Taking the power turbine rotor of a shipborne turboprop engine as the research object, a simulated rotor with the same dynamic characteristics as the real rotor of the engine was designed based on the principle of dynamic similarity, and the correctness of dynamic similarity design was verified. A test method for the vibration characteristics of aeroengine rotor under impact load was proposed. The research on the impact resistance of high-speed motor and the vibration characteristics of rotor under the impact load was carried out on the vibration table. The high-speed motor and rotor have a vertical impact resistance of no less than 10g. The transient vibration response and the main frequency components of vibration response of the rotor under impact load were obtained. The research results show that the dynamic characteristics of the designed simulated rotor are basically consistent with the real rotor in engine. The research provides technical support for the development of a shipborne turboprop engine, and also provides a reference for the dynamic test of rotor under large impact load.

During the construction of twin decks, the long-span asymmetrical twin parallel decks represent a unique design, where both the highway and railway are arranged side by side at the same elevation. Due to the disparate dynamic characteristics of the highway bridge and the railway bridge, the considerable variation in wake characteristics of the decks, as well as the pronounced and consequential aerodynamic interference between the asymmetrical twin decks, the vortex-induced vibration (VIV) characteristics of the asymmetric twin decks become considerably more intricate. To comprehensively investigate the impact of interference effects on the VIV behavior of decks, a series of wind tunnel tests and fluid-structure interaction numerical simulations were conducted on twin decks. These experiments and simulations were conducted in the context of a long-span asymmetrical twin separated parallel deck configuration, where the highway deck was designed as a Π-type superimposed deck and the railway deck was a streamlined box deck. The research findings indicate the following: (1) The Π-type highway deck exhibited significant vertical bending and torsional vibrations when exposed to the windward side, showing typical VIV "lock-in" characteristics between the wind speed range and the structural vibration frequencies. However, these vibrations diminished when the deck was on the leeward side. (2) The streamlined railway deck showed no significant vibrations when positioned on the windward side, but substantial vibrations were observed on the leeward side, with amplitudes rapidly rising and falling, without a distinct "lock-in" range. (3) The numerical flow field indicates that the scale and distribution of vortical structures near the deck vary significantly when the highway is located at different positions (windward and leeward sides). The presence of large-scale vortices in the cavity below the bridge deck and the periodic variation of vortical structures are the main reasons for vortex-induced vibration on the windward side. On the leeward side, influenced by the disturbance effect, the scale of vortices in the cavity below the bridge deck decreases, the oscillation frequency of lift changes, and the phenomenon of vortex-induced vibration lock-in disappears. (4) Flow fields and pressure distributions near the railway revealed stable flow patterns when positioned on the windward side, with self-excited lift forces approximating steady forces. However, when positioned on the leeward side, the railway surface experienced a larger negative pressure area due to the interference of the highway wake, leading to significant vibrations caused by the pulsation of the highway wake and resulting in oscillations of the railway's aerodynamic lift. This study systematically investigated the aerodynamic interference effects between asymmetrical twin parallel main girders and their impact on VIV performance. The underlying VIV and aerodynamic interference mechanisms were revealed, providing valuable insights for the engineering design of similar bridges.

At present, the research on the mechanism of rock breaking and vibration effect caused by high-pressure gas blasting is in the primary stage, and the theory is far behind practice. Firstly, the whole process of the interaction between the shock wave, multi-media flow field and hole-wall interface was systematically analyzed. And the calculation model of hole-wall pressure under high-pressure gas blasting with the discontinuous-interface condition of pressure was deduced, which breaks through the over ideal continuous condition of blasting load at the interface of hole wall. Then, a prediction method of ground vibration effect of layered rock mass under high-pressure gas blasting was proposed. By comparing the results of ground vibration effect calculated by the proposed prediction method and the numerical simulation method for the same example, the feasibility of the proposed prediction method was verified. The results show that high-pressure gas blasting is more effective than explosive blasting in controlling the ground vibration effect of layered rock mass on the premise of the same cutting blasting effect. This study can provide important theoretical guidance for the scheme optimization of high-pressure gas blasting and the prediction and control of ground vibration effect, especially for urban underground projects where ground vibration needs to be strictly controlled.

In the missile system, the vibration and impact produced by the engine and pyrotechnics will seriously affect the accuracy and reliability of the warhead, so it is significant to take effective measures to reduce the vibration and isolate the impact. Acoustic black hole (ABH) effect allows altering the phase velocity and group velocity of the wave propagation in a structure by changing the impedance. As a result, the wave is concentrated in the local area of the structure, and energy is efficiently dissipated by a little damping. The ABH with the advantages of high efficiency, light weight, wide frequency, which provides a new idea for structural dynamics control, and has the strong potential and application prospects. In this paper, with the aim of vibration suppression and shock isolation in multistage missile, a kind of structural design schemes (ABH ring) based on the ABH effect are presented to ensure the accuracy and reliability. The dynamics characteristics of ABH ring are analyzed by using the finite element method. It can be seen that the ABH ring has good characteristics about transfer and consumption of energy. The simulation model of ABH ring-warhead is established. By simulating the impact of random vibration and stage separation during flight, the system response characteristics are analyzed and suppression effect is evaluated. The results show that the proposed ABH ring has a good effect of vibration suppression and shock isolation under complex dynamic load: reducing the amplitude and increasing the attenuation rate. This research not only provides ideas for missile vibration reduction and shock isolation, but also effectively broadens the application of ABH new technology.

As a new generation of advanced composites, functionally graded carbon nanotube reinforced composite (FG-CNTRC) has been widely concerned by researchers because of their excellent mechanical properties. In this paper, the FG-CNTRC beam on Pasternak foundation is taken as the research object. Based on different high-order shear deformation theories, a meshless method with interpolation characteristics, the stable moving Kriging interpolation (SMKI) is applied to solve the free vibration and buckling problems of FG-CNTRC beam on Pasternak foundation. Based on stable Kriging interpolation and different high-order shear deformation theory, the displacement field of FG-CNTRC beam is derived. The free vibration and buckling control equations of FG-CNTRC beam on Pasternak foundation are obtained by using Hamilton principle and minimum potential energy principle respectively. The relevant program is compiled by MATLAB. The comparison between the solution in this paper and the analytical solution or the literature solution proves the effectiveness and accuracy of this method in calculating the free vibration and buckling of FG-CNTRC beam on Pasternak foundation. At the end of the paper, the effects of different high-order shear deformation theory, foundation coefficient and carbon nanotube volume fraction on the natural frequency and buckling critical load are also discussed.

Transmission line collapses due to typhoons often occur in the southeastern China, and most studies attribute the collapse to strong winds. However, typhoon landings are often accompanied by continuous rainfall. So, both the wind and rainfall effects should be considered. All the measured data of three typhoons, Mangkhut, Higos and Cempaka, were divided into three groups according to the typhoon regions (typhoon eye, spiral rain band, and peripheral strong wind region) based on the station location and the recorded time, considering the meteorological characteristics of different regions. Then, the correlation between wind speed and rainfall intensity was analyzed to reveal their coupling relation. After that, a refined wind speed and rain intensity joint probability distribution model for different typhoon regions was established. Finally, a case study was carried out through a transmission line, and its failure probability in different typhoon regions was calculated. The results show that the proposed refined wind-rain joint probability model can accurately describe the combination of wind and rain, which has reference value for engineering structure design and performance evaluation.

The high-soft tower wind turbine has the characteristics of light weight, high towering and low damping, which makes its vibration response more intense under different excitation. It is of great significance to study its vibration law and dynamic characteristics under operating conditions for the safety assessment of the wind turbine. Taking a 140-meter high-soft tower wind turbine tower as the research object, measuring its vibration response signal at different heights, using the spectrum analysis method to analyze its frequency domain characteristics and vibration form; through wavelet packet decomposition and energy entropy calculation principle the measured signal is decomposed and calculated to obtain the energy distribution characteristics and energy entropy of the vibration signal of the tower junction, and the relationship between the two is analyzed; finally, the root mean square (RMS)  value and energy entropy of the vibration signal of each measuring point under different working conditions are counted. , found that: with the increase of power generation, the RMS value of the tower vibration signal has an increasing trend, the vibration energy has a distribution law of first dispersing and then concentrating, and the energy entropy has a trend of first increasing and then decreasing. The essential reason for this change is that with the increase of the impeller speed, the vibration form of the tower structure changes from natural vibration-forced vibration-resonance, which leads to changes in the intensity and distribution of tower vibration energy.

Based on the strongback mechanism, damage control, and replaceable concept, an innovative earthquake resilient strongback-frame structure is proposed to minimize earthquake-induced damage and facilitate quick and economical post-earthquake repairs. To investigate the seismic performance and resilience of the strongback-frame structure, pushover analysis on five structural models was conducted with Sap2000 software. Particular emphasis was taken on the damage mechanism, damage evolution, deformation characteristics, seismic performance, and seismic resilience of the strongback-frame structure. A two-stage calculation method for the residual deformation is proposed to evaluate the seismic resilience of structures subjected to different magnitude earthquakes. The results show that the strongback system can effectively control the lateral deformation pattern of the structure, and the story drift ratio and damage distribute uniformly, which can avoid the formation of the weak-story failure mechanism and improve the seismic performance and collapse resistance of the structure. The strongback system can also effectively mobilize the reserve capacity of the overall structural components, which enhances the overall performance. The stiffness, strength, and energy consumption capacity of the strongback frame are significantly improved, and the pushover curves do not appear the strength softening behavior. After reasonably graded damage design, the replaceable energy dissipation components set in the strongback frame play the first line of defense role to reduce the structural damage and residual deformation, effectively improving the structure's seismic resilience.

Track unevenness is one of the primary sources of excitation that induces coupling vibrations in the vehicle-bridge system. The sensitive wavelength of the coupling vibration in the system has been identified, which holds significant reference value for line management. Firstly, a spatial model of the high-speed maglev train-track beam coupled system is established. In this model, the maglev train is simulated as a multibody dynamic model with 537 degrees of freedom, while the track beam is simulated as a spatial finite element model. The two are coupled through the magnetic track relationship based on PD control theory. Secondly, the Shanghai high-speed maglev is used as the research background, and a 5-car marshalling train crossing a 20-span simply supported girder bridge is selected as the calculation condition to verify the correctness of the model by comparing it with the measured results. Finally, considering the uneven excitation of track harmonics, the effects of different combinations of track unevenness in various directions, different amplitudes of track unevenness, and different vehicle speeds on the sensitive wavelength of dynamic response and ride stability of trains and bridges are discussed. The results indicate that the coupling of lateral and vertical vibrations in the maglev-bridge system is weak. At a design speed of 430 km/h, the sensitive wavelengths of the car body in vertical, roll, and pitch accelerations are 140-180 m, 60-100 m, and 120-160 m, respectively. The sensitive wavelengths of the car body in lateral and yaw accelerations are greater than 200 m. Resonance in the body roll, yaw, lateral, pitch, and vertical directions can be triggered at wavelengths of 80 m, 105 m, 115 m, 140 m, and 160 m, respectively. The response amplitudes of the car body and main beam are generally linearly related to the amplitude of track unevenness. When the amplitude of track unevenness is 1 mm, the peak roll acceleration of the car body does not change significantly with vehicle speed, while the peak accelerations in the other four degrees of freedom decrease with increasing vehicle speed. The vertical acceleration amplitude of the main beam increases linearly with vehicle speed. The lateral and vertical Sperling indicators of the car body indicate that the Sperling index of the car body is less than 2.5, indicating good ride stability for the maglev vehicle.

The steel bridge tower is one kind of tall and slender structure which is highly sensitive to wind loads and prone to vortex-induced vibrations (VIVs). To investigate the VIV characteristics of a 217-meter-high steel bridge tower, 1:100 scale free-standing aeroelastic model wind tunnel tests were conducted. The experimental results show that in-phase VIVs occur in the low wind speed ranges, and out-of-phase VIVs occur in the high wind speed ranges at the wind directions range of 0° - 30°. The most unfavorable wind directions of in-phase and out-of-phase VIVs are 0° and 10°, respectively. In-phase along-wind displacement and out-of-phase torsion angle are 609.5 mm and 4.3°, respectively. Furthermore, the VIV triggering mechanisms were studied by computational fluid dynamics (CFD). The numerical simulation results show that the frequency of alternating vortex shedding near the two tower columns is close to the fundamental natural frequency, and the periodic pressure difference generated by this phenomenon leads to in-phase and out-of-phase VIVs. The findings and conclusions of this study provide some reference for the wind-resistant design of similar steel bridge towers.

Six full-scale square concrete filled steel tubular (CFST) stub columns with the cross-sectional width of 800 mm were tested under constant axial loading and cyclic lateral loading. With the increase of the width-to-thickness ratios B/t of 50, 80 and 100, the influence of the confinement effect provided by steel tube to core concrete on the failure mode, hysteretic behavior, ductility, stiffness, and energy dissipation of the CFST columns was investigated. It can be found that 1) the failure mode of all specimens was the compression-flexural failure with the local buckling of steel tube and the crushing of core concrete at the bottom of the columns. 2) With the decrease of the width-to-thickness ratio (the confinement effect improved) the influence of the ductility of columns is not significant, and comparison with the scale columns, the ductility performance of the full-scale columns decreases obviously. 3) The effect of the width-to-thickness ratio on the stiffness degradation and energy dissipation of the full-scale columns is not significant, and with the decrease of width-to-thickness ratio, the cumulative energy of the specimen increases. 4) As the width-to-thickness ratio decreases with the increase of the confinement effect, the compression and flexural capacity increases, but the increased extent of the compression and flexural capacity is smaller than that of the current codes. In addition, according to the current design codes of China and Europe, the predicted values are large than that of experimental values of the full-scale CFST column. The calculated formulas in the code of America is very conservative.

To enhance transverse stiffness of a long-span railway suspension bridge, a composite-spatial cable structure consisting of main and secondary diagonal cables is proposed. Then, the parameters of diameter of composite-spatial cables, anchorages of main diagonal cables with stiffening beams and the surface, and the number of secondary diagonal cables on transverse deflection-span ratio of the bridge are optimized by the effective utilization of the materials and static analysis method. Finally, the analysis method for coupling vibrations of wind-vehicle-bridge system is used to obtain the limit of transverse deflection-span ratio of the bridge based on the driving performance, and the influence of the main and secondary diagonal cables on the enhancement rate of the limit of transverse deflection-span ratio is analyzed. The results show that on the basis of considering the effective utilization rate of composite-spatial cables, anchorages of main diagonal cables and stiffened beams should be located near 1/4 of the main span, and it is optimal when the vertical distance between anchorages of main diagonal cables with stiffening beams and the surface and the tower is equal, and it is enough to set a secondary diagonal cable for each group of composite-spatial cables; in the optimal layout of composite-spatial cables, transverse deflection-span ratio of the bridge can be reduced by 14.18%, the limit of transverse deflection-span ratio can be increased by 16.79%.

To investigate the difference of wind-induced swing characteristics between long span conductors and jumper lines, a refined finite element model coupling the jumper lines, long span conductors and insulator strings is constructed. The research elucidates the different dynamic characteristics, included mode and aerodynamic damping ratio, between the conductors and jumper lines. Combining with the frequency-domain method, multiple cases are calculated to analyze the effect of wind field and line parameters on the dynamic response of conductors and jumper lines. Results show that: The fundamental frequency of jumper lines is approximately 1.5~2.0 times that of conductors. The effect of aerodynamic damping on jumper lines is much smaller than that of conductors. The dynamic response of conductors is dominated by the background response, while the resonance response is not significant. However, the resonance response increases the wind -induced swing response by more than 30%, which should be considered in the wind-resistance design of jumper lines. The resonance response characteristics of jumper lines are determined by their own dynamic characteristics, and are relatively less affected by the upstream wind. The fundamental mode plays a decisive role in the resonance response of jumper lines. Based on the quasi-static and inertia force method, this paper derives the resonance part of peak fluctuating wind force for jumper lines, introduces the resonance factor, and amend the gust response coefficient. The amended gust response coefficient increases by about 9%~12% compared to the code.

In order to investigate the influence law of material performance parameters on the dynamic characteristics of the fluid-elastomeric damper, the variation of load-displacement curve, elastic stiffness, damping stiffness and loss factor of the fluid-elastomeric damper with the difference of rubber hardness and damping fluid viscosity were studied by electro-hydraulic servo dynamic testing machine. The test results showed that more than 91.5% of the elastic stiffness of the fluid-elastomeric damper is provided by the rubber part, and the elastic stiffness increases with the increase of rubber hardness. More than 84.8% of the damping stiffness of the fluid-elastomeric damper is provided by the damping fluid, and the damping stiffness and loss factor increase with the increase of the viscosity of the damping fluid and decrease with the increase of the shear amplitude. The greater the viscosity of the damping fluid, the greater the decrease of the damping stiffness and loss factor. When the viscosity of damping fluid increases from 2000 mm2/s to 10000 mm2/s, the damping stiffness of the fluid-elastomeric damper increases from 2420 N/mm to 5163 N/mm. when the shear amplitude increases from 0.2 mm to 1.5 mm, the damping stiffness decreases by 18.5% and 40.1%, respectively. The above conclusions can provide a basis for the selection of materials for fluid-elastomeric damper.

The accurate explanation of the tooth deregulation or back meshing induced by the backlash can provide theoretical guidance for the optimal design of the gear structure. Based on the Johnson contact force model, the dynamic meshing force calculation model of involute internal meshing spur gear transmission system is constructed, which takes into account the time-varying backlash and energy dissipation in the meshing process, according to the meshing principle of internal meshing spur gear and the force of gear teeth, the meshing process is decomposed, and the nonlinear dynamic model of involute internal meshing spur gear system with five meshing states under time-varying backlash is established. Five different Poincaré maps are constructed to clarify the characteristics of five-state meshing behavior, and the generation mechanism of multi-state meshing behavior of the system is revealed by phase diagram and dynamic meshing force time history diagram. The results show that with the gradual increase of the meshing frequency, the single-tooth and double-tooth surface meshing occurs in the system, and the sudden change of the dynamic meshing force in the direction leads to the meshing between the gear teeth and the back of the single-tooth and double-tooth, resulting in the impact vibration behavior between the gear teeth. Even if the system shows a stable meshing state, the single and double teeth dismeshing still occurs. The previous dynamic model of internal meshing gear system can not reveal its multi-state meshing characteristics. Aiming at the multi-state meshing behavior, this paper analyzes the nonlinear vibration characteristics of internal meshing gear transmission cycle.

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.

A mechanical impact oscillator with a pre-compressed spring is considered. The Poincaré map composed of smooth flow map and discontinuous map is constructed, and a numerical calculation method of Floquet multipliers is given. The periodic attractor patterns and their parameter regions of the system in the two-parameter plane are obtained by numerical simulation. The bifurcation characteristics of period-1 attractors and the discontinuous bifurcation behaviors, such as discontinuous grazing bifurcation, bifurcations induced by grazing and period-doubling, subcritical period-doubling bifurcation and crisis, are studied by applying continuation shooting method and cell mapping method, and the formation mechanism of hysteresis and subharmonic inclusions regions is revealed. In the transition between adjacent 1–m and 1–(m+1) attractors, the hysteresis and subharmonic inclusions regions are created by discontinuous grazing bifurcations. However, they are respectively created by grazing induced saddle-node and period-doubling bifurcations as the pre-compression is equal to 0. The results can provide guidance for the parameter design and optimization of mechanical impact system with a pre-compressed spring.

The strain produced by impact load on a structural is much greater than the static load. It is of great significance to identify the impact load accurately. The method proposed aims at the prominent contradiction of inconsistent sample length between impact load and response signal. The method was based on linear model and the experiment was carried on a steel pylon structure. Firstly, the feature extraction of vibration signals was carried out based on the impact response signal decomposition theory. Then, the load and response signal sample characteristics are mapped to realize the impact load identification based on the long short term memory neural network (LSTM). The results show that the correlation coefficients between the true and predicted load are more than 94% and the RMSE (root-mean square error) are less than 0.6.

An effective reliability-based topology optimization method is proposed for the design problem of continuum structure considering the uncertainty of load amplitude and frequency of harmonic excitation. A reliability design optimization model of minimizing structural volume ratio under probabilistic reliability constraint is established, in which the limit state function is the sum of the amplitude squares of the degrees of freedom concerned. The analytic sensitivity formulations of limit state function with respect to design variables and random variables are derived using adjoint variable method. The Performance Measure Approach (PMA) is used to achieve reliability analysis, and the method of moving asymptotes (MMA) is used to update design variables. Finally, three numerical examples and Monte Carlo simulation are tested to verify the effectiveness and stability of the proposed method for the design problem of continuum structure under uncertain harmonic excitation. The influences of the uncertainty of amplitude and frequency of harmonic excitation, reliability index, and coefficient of variations on the optimization results are also discussed.

Based on the characteristics of ABH (acoustic black hole) arc beam with small volume and rich modal frequencies, ABH (acoustic black hole) arc beam is periodically distributed on the straight beam as an additional structure and coupled with the straight beam to promote the local resonance effect and broaden the low-frequency band gap, and a new local resonance acoustic metamaterial is constructed. For local resonant metamaterials, the semi analytical theoretical analysis model is established by using the Gaussian expansion method. The internal connection and periodic boundary conditions are treated based on the null space method. The accuracy of the semi analytical theoretical analysis model is verified by the finite element method. The energy band structure is analyzed and calculated, and the influence mechanism of structural parameters and ABH effect on Bragg band gap and local resonance band gap is studied. The results show that the semi analytical theoretical model can effectively calculate the band gap of the structure, and the notch mechanism with arc ABH can promote the local resonance effect of the structure and effectively reduce the vibration of the main beam.

Structural parameters are the key factors affecting mechanical properties of rolling lobe air spring (RLAS), and the structural parameters of rolling lobe air spring with complex piston contour has characteristics of complex structural parameters, nonlinear mechanical properties and load-carrying capacity changing with the working height. Therefore, it is an important way to analyze and optimize the mechanical properties of air springs in the design stage by establishing a unified model of nonlinear structural parameters based on key design parameters. In this paper, in order to solve the modeling problems of structural parameters of RLAS with complex piston contour composed of straight line and arc, the dynamic change of outer diameter of rubber bellows with the height of RLAS,  and the nonlinear effect of mechanical performance brought by the complex piston contour, taking the inner cone angle of straight line segment contour and the radius of the arc segment contour as two key design parameters, a unified model of nonlinear structural parameters of RLAS with complex contour is established. The influence laws of two key design parameters on structural parameters and spring stiffness are further revealed. The results show that the maximum relative error between structural parameters predicted by the unified model and testing results is 10.98%, the relative error of static stiffness under different internal pressure is less than 7%, and the maximum relative error of load capacity is less than 9%, which all proves the effectiveness of the unified model of nonlinear structural parameters. The research results provide theoretical guidance for the fine design of piston contour and the prediction and optimization of the stiffness and load capacity of RLAS.

The surrounding rock damage caused by tunnel blasting excavation has an important impact on the safe construction and support cost of tunnel. In order to study the effect of millisecond delay blasting on the surrounding rock damage of the tunnel, taking Chongqing North Avenue Tunnel as the research background, three-dimensional numerical calculation model of 34 surrounding holes of the tunnel is established through Hypermesh, the surrounding rock damage of different blasting parameters is calculated by Ls-Dyna, and the relationship between blasting damage and inter-hole delay time, charge and surrounding rock lithology is analyzed and studied. The results show that the value of inter-hole delay time has great influence on the damage range. Within a certain range, the damage range decreases with the increase of the delay time. When the inter-hole delay time continues to increase, the damage range tends to stable value. The damage range increases with the increase of the charge. When the delay time between holes increases, the difference of the damage range of different charge gradually decreases. The damage range of the peripheral hole blasting of granite is smaller than that of sandstone. Under different delay time initiation of peripheral holes, the difference of damage range of granite peripheral holes is small, while that of sandstone is large. According to the numerical calculation results, the blasting parameters of the peripheral holes on the site are determined. The tunnel contour is formed smoothly, and the damage of the surrounding rock is controlled well.

The prediction of the Remaining Useful Life (RUL) of rotating machinery is of great significance to the prediction and health management of industrial equipment. This paper addresses the problems of harrowing extraction of degradation information and poor prediction of the RUL of rotating machinery due to redundant data from multiple sensors. This paper proposes a Kernel Principal Component Analysis-Long Short Term Memory (KPCA-LSTM)based method for predicting the RUL of rotating machines. Firstly, the multi-dimensional degradation data of rotating machinery is analyzed, and the data that can characterize the degradation of rotating machinery is selected. Secondly, KPCA fusion and feature extraction were carried out on the degraded data, and the features of dimensionality reduction fusion were used as the input of the prediction model. Then, the health indicators of rotating machinery were constructed, and KPCA-LSTM model was established to predict the remaining useful life of rotating machinery by dividing the different health states of rotating machinery by multi-order differentiation. Finally, the proposed method is also tested by the mine reducer platform organized by our laboratory. Experimental results show that compared with LSTM and particle swarm optimization LSTM, the proposed method has a better prediction effect than the other two models, and reduces the complexity of model training and the time of prediction.

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.

A single-stage spur gear pair is considered, and the Poincaré mapping is constructed. The coexisting attractors of the system and their evolutions are calculated and traced by applying initial value cell mapping method, continuation shooting method and numerical simulation. The eigenvalues of Jacobi matrix are calculated, and the stability and the type of bifurcation are determined by means of the Floquet theory. The basins of attraction are calculated by using cell mapping method. The bifurcation characteristics of coexisting attractors are studied, and the attractors existing in the minimum interval of system parameters, which are not easy to be found, are revealed as well as discontinuous bifurcation behaviors including saddle-node type of grazing bifurcation and chaos crisis. There are a large number of coexistence phenomena of multiple attractors and period-doubling and saddle-node bifurcations in the single-stage spur gear pair under certain parameter conditions. Due to the influence of non-smooth factor, the grazing-induced saddle-node bifurcation leads to the jump and hysteresis of final-state response of the system. The results can provide guidance for the evaluation of dynamic behavior of spur gear pair and the design and optimization of system parameters.

On January 8, 2022, an MS 6.9 earthquake occurred at Menyuan, Qinghai. Under the conditions of the same epicenter and similar path, the ground motions observed by nearby stations with a distance of 5.5 km were quite different. To explain this phenomenon, we used Nakamura method (Horizontal-to-vertical Spectra Ratio, HVSR) and Borcherdt method (Standard Spectra Ratio, SSR) respectively to analyse the influence of site effect and topography effect on ground motion based on the records of mainshock and aftershocks. A method was proposed to determine the dominant contributing frequency band of the peak ground acceleration (PGA) by moving the high-frequency cutoff frequency of bandpass filter. The reasons for the large discrepancy of PGA are preliminarily analyzed in different frequency bands by considering site effect and topography effect.

Fuzzy entropy is not only a nonlinear dynamic analysis method to measure the complexity of time series, but also an effective tool to extract the nonlinear fault features of gearbox. However, the fuzzy entropy only measures the complexity for a single time series and the coupling characteristics between two sequences are ignored. To fully utilize the rich information between vibration signals, the cross-entropy theory, which can effectively measure the synchronization, similarity and mutual prediction of two time series, is introduced into the planetary gearbox fault diagnosis. Aiming at the problem that the entropy value of a single scale can not fully reflect the pattern similarity between sequences, this paper makes a multi-scale analysis of time series by means of composite coarsening, and a composite multi-scale cross fuzzy entropy method to measure the similarity and mutual prediction of two channel time series is proposed. Based on that, a new fault diagnosis method based on composite multi-scale cross fuzzy entropy and firefly algorithm optimization support vector machine is proposed for planetary gearbox. Finally, the proposed fault diagnosis method is applied to the test data analysis of planetary gearbox by comparing with the existing methods. The analysis results indicate that the proposed method can effectively extract the nonlinear fault features of gearbox and has a higher recognition rate in fault type identification than the compared methods.

In the development of heavy-duty and motorization of multi-axle special vehicles，power transmission performance is the guarantee of their rapid maneuvering combat ability and a manifestation of wartime survivability. The internal resistance loss of the transmission system will reduce the power transmission efficiency and directly affect the power performance, among which the mechanical friction resistance loss is the main loss of the transmission system. Focusing on the mechanical friction resistance loss characteristics and transmission efficiency research methods of the transmission system, this paper firstly analyzes the structural particularity of the multi-axle special vehicle transmission system and shows the importance of transmission efficiency to the transmission system performance. Secondly, the formation mechanism and main influencing factors of four main types of mechanical friction resistance loss are analyzed，namely gear meshing power loss, bearing friction power loss, oil seal power loss and transmission shaft power loss, which shows the relationship between transmission efficiency, structural parameters of components, and operating conditions, and provide an analytical basis for the characterization of transmission system performance. Then, the research core and difficulties of transmission system efficiency are summarized from three aspects: theoretical numerical study, simulation study and experimental demonstration study, which provides guidance for the optimal design and condition monitoring of transmission components, optimal matching and performance evaluation of transmission systems. Finally, the prospect of the current research depth of transmission efficiency characteristics is expounded, and it is considered that multi-factor coupling analysis, uncertainty analysis, dynamic characteristic analysis of power loss, and comprehensive transmission efficiency analysis based on vehicle driving conditions have more engineering application value.

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.

In order to study the influence of blasting excavation on the stability of surrounding rock in the tunnel with a small clear distance, taking the Yidong high-speed Fangjun tunnel project in Zhejiang province as the engineering background, the calculation formula of surrounding rock vibration velocity during blasting construction was derived according to the law of energy attenuation. The finite element software MIDAS GTS NX was used to simulate the change law of surrounding rock vibration velocity and stress under different clear distance conditions. The numerical results of vibration velocity in surrounding rock are compared with the theoretical values to verify the accuracy of the formula. According to the relation between vibration velocity and stress, the threshold value of vibration velocity is proposed to ensure the safe construction of tunnels. The results show that: (1) The maximum relative error between the theoretical value and the simulated value is 5.9%, and the maximum relative error between the theoretical value and the field monitoring data is 7 %, which verifies the accuracy of the theoretical formula. (2) There is a negative correlation between the peak vibration velocity of the rear tunnel and the distance between the blasting center of the first tunnel, and the peak vibration velocity of the monitoring point on the blasting side of the surrounding rock is greater than that on the back explosion side. 2D is the minimum safe clear distance of the anti-military tunnel during blasting construction (D is the clear distance of the tunnel), at this time, the maximum peak vibration velocity of the excavation of the upper step is about 1.20 times that of the lower step. (3) After blasting excavation, the peak stress and vibration velocity of the surrounding rock are mainly concentrated near the arch waist and arch foot. With the increase in the clear distance, the influence of the advance tunnel on the rear tunnel gradually weakens and is eventually ignored. (4) Under the action of blasting, there is a certain linear relationship between the peak stress of surrounding rock and the peak vibration velocity, and the vibration velocity control threshold to ensure the safe construction of tunnel blasting is 1.9 cm∙s-1. The research results can provide a reference for the blasting construction of similar small clear-distance tunnel projects in the future.

In order to solve the problems of different operating conditions, less effective data, no labels, and low prediction accuracy, a life prediction model of transfer learning bearing based on an improved time convolution network is proposed. The life prediction knowledge learned by the model from the source domain is transferred to the target domain, and the transfer model can be trained with small samples of unlabeled data. Firstly, the efficient channel attention network is adopted to recalibrate the data features of the source domain; Secondly, the temporal convolutional network (TCN) is used to learn the feature information and train the optimal source domain model; Finally, the migration model is trained by source domain data, source domain model and target domain data. The transfer model can predict the remaining life of signals from different equipment and different working conditions. Comparative experiments were carried out on the IEEE PHM Challenge 2012 bearing life data set and the XJTU-SY rolling bearing accelerated life data set. The results show that this method can better mine the internal degradation trend of bearings, and effectively improve the prediction accuracy of remaining useful life. Compared with the existing popular prediction methods, the prediction error has been reduced by 40.1%~77.8%. This method is proven to be effective and feasible in predicting the residual life of different equipment and different working conditions.

This paper proposes a simulation method for the dynamic response of the compressed 102-type coupler and draft gear based on test data, and then studies the dynamic performance of the heavy-haul locomotive and its 102-type coupler and draft gear for the 10,000-ton heavy-haul train with double locomotive traction marshalling. Firstly, based on the structural characteristics and compressed stability mechanism of 102-type coupler and draft gear, the weighted discrete method is used to simplify the draft gear into multiple impedance force elements with the same hysteresis characteristics, and the shear stiffness is introduced to consider the shear effect between these impedance force elements. By this way, the dynamic model of 102-type coupler and draft gear is established to simulate the one-side compressed characteristics of the coupler shoulder and draft gear accurately. And then the model of 10,000-ton train with the marshalling of “master locomotive + re-connected locomotive + freight vehicle + dummy freight train” is developed by using the substructure method; Then the shear stiffness between the discrete impedance force elements is confirmed and this train dynamic model is also verified by comparing the simulation results with test data. Finally, the influences of track conditions, structural parameters and locomotive electrical braking forces on the train dynamics response and running safety are calculated. The results indicate that the large locomotive electric braking forces on small radius curves are very dangerous for the train running safety; With the increases of the coupler free angle and the lateral stiffness of locomotive secondary suspension, the coupler rotation angle and locomotive running safety index increase gradually, but too large lateral stiffness may strength the wheel-rail lateral interaction.

Space manipulator will face collision problems when performing operational tasks, such as active capture or passive collision, which will cause sudden change of instantaneous momentum of the manipulator, increase of elastic vibration of the manipulator rod, decrease of trajectory tracking accuracy, and even lead to instability of the space manipulator system. Space manipulator is a complex system with nonlinear and strong coupling, especially for collision process, it is difficult to accurately model the system. In order to suppress the vibration of space manipulator during collision, fuzzy-Model-free adaptive control (Fuzzy-MAFC) algorithm was proposed by combining Fuzzy strategy with model-free adaptive control. Based on the vibration displacement and velocity error of the manipulator, a fuzzy strategy was designed to self-adjust the step factor and weight factor of the model-free adaptive control, which solved the limitation of the traditional model-free adaptive control to the initial value of parameters, and realized the vibration adaptive control of space manipulator in the collision process.  Simulation results show that the vibration suppression efficiency of fuzzy-model-free adaptive control is about 30% higher than that of traditional model-free adaptive control, which verifies the effectiveness of the algorithm.

In the process of deepwater drilling, the riser and blowout preventer system are an essential part of the entire operation process. Due to many risks involved in the operation process, therefore, establishing an accurate mechanical analysis model of the coupling system between riser and BOPs, accurately analyzing its mechanical behavior and performance, is of great significance for guiding the safety of drilling operations. At present, most people only focus on independent modeling of the riser and ignore the potential impact of the blowout preventer group, which will lead to differences between the established model and the actual situation, and making it difficult to accurately analyze the mechanical properties of the riser system. This paper puts forward the rigid-flexible coupling concept of riser and BOPs, derives the kinetic energy and potential energy of the coupling system, establishes the theoretical model by Lagrange method, and uses Newmark- β Perform numerical calculations on the dynamic model using the direct integration method. A simulation modeling was established using ADAMS software to conduct comparative analysis of dynamic response under different operating conditions. The results indicate that the lateral displacement envelope and bending moment envelope of the riser obtained from the theoretical model in this paper, as well as the lateral displacement time history curve and bottom bending moment time history curve of the middle node of the riser, are in good agreement with the ADAMS simulation results, indicating the importance of the theoretical model in this paper, which can provide reference and support for the design and analysis of risers in China.

To study the extreme wind pressure distribution in semi-closed stations, the wind pressures induced by high-speed trains passing through railway stations are simulated. The accuracy of the numerical model is also verified against the field-measured data. Based on this validated numerical model, the extreme wind pressure distribution at the train head and tail is analyzed for the two typical station regions (near platform Region I and far from platform Region II) under the traveling train speed of 250km/h, 300km/h and 350km/h, respectively. The corresponding empirical equations are established. The results show that there is a nonlinear relationship between extreme wind pressures and train speeds. At the same train speed, the extreme wind pressures in Region I and Region II decrease exponentially with the horizontal distance, whereas the decrease rate is inversely proportional to the vertical distance. When the horizontal distance is less than 15m, the positive extreme wind pressures due to train head in Region I are always larger than those in Region II at the same vertical distance, while the absolute values of the negative extreme wind pressures due to train head in Region I are always smaller than those in Region II. When the horizontal distance exceeds 15m, the extreme wind pressures gradually tend to be steady, and the corresponding steady values in Region I are larger than those in Region II. The empirical equations developed in this paper can accurately describe the extreme wind pressure distribution in the semi-closed station. The research results can provide reference for the structural design of semi-closed stations.

The multi-dimensionality, class imbalance and concurrency of industrial fault data bring three major challenges to industrial fault diagnosis: first, the extraction of fault features from multi-dimensional sensor data is excessively dependent on expert knowledge; second, the extreme class imbalance between different types of fault samples seriously limits the performance of the classifier; third, multiple types of faults may occur at the same time to increase the complexity of fault diagnosis. In order to meet these challenges, a multi-label fault diagnosis model based on the improved Transformer of multiple self-attention is proposed. Combined with adaptive synthetic sampling (ADASYN) and Borderline-SMOTE1 oversampling methods, making full use of the advantages of Transformer encoder-decoder structure and attention mechanism, features can be automatically extracted from multi-dimensional sensor data, the complex mapping relationship between multi-dimensional sensor data and multiple fault labels can be fully mined. The results show that this method can still diagnose multiple faults occurred at the same time in the extreme imbalanced industrial fault data for the PHM2015 Plant data set.