The present methods using PSD to reconstruct road spectra can only be used to generate Gaussian road spectra. The lower tail thickness leads to Gaussian PSD curves are difficult to accurately describe those grim roads with severe road surface fluctuations. According to high-order moment characteristics of Weibull distribution, the method for calculating parameters of Weibull distribution possessing specified kurtosis was derived. Then, based on ZMNL method, a new method using Gaussian white noise to generate stochastic variables with symmetric Weibull distribution possessing specified PSD and kurtosis was proposed. With this method, several road spectra with varying severity were generated through specifying different kurtoses under the premise of keeping the same PSD function/curve. The correctness and validity of this new method were verified by applying it to reconstruct the road spectrum for a certain road whose reliability was tested. The results provided a new non-Gaussian road modeling method for road and vehicle riding simulation tests.

 

With the help of the time-varying feature of moving sound course’s position, according to the fact that sound speed profiles with spatio-temporal variation features can be modeled approximatively as empirical orthogonal functions whose coefficients evolve with time/distance under certain conditions, a method for jointly estimating moving sound source’s parameters and sound speed field’s parameters was proposed to solve the inversion problem of distance-dependent fast-changing sound speed fields in shallow sea environment. With this method, the extended Kalman filtering and the ensemble Kalman filtering algorithms were used to reconstruct a real sound speed field, track and position a moving sound source simultaneously. The effectiveness of the two algorithms was verified with comparing simulation results and test data. The two nonlinear algorithms were also compared. The results showed that the ensemble Kalman filtering algorithm has a better estimation ability; even under a limited condition that the number of receiving array elements is reduced, it can estimate the moving sound source position and sound speed parameters’ evolution trajectories in time/distance domain. This proposed method provided a reference for studying inversion of dynamic ocean parameters and laying observing systems under sea water.

 

It's an important operational performance of stealth aircrafts to realize embedded ejection and launch of air-to-air missiles under the condition of carriers’ large maneuvering flight. Carriers’ large maneuvering flight makes missile ejection separation parameters deviate design values to threat seriously the launch safety of stealth aircrafts. Based on the flexible multi-body Lagrange multiplier method, components modal tests and the condition of stealth aircrafts’ large maneuvering flight, a rigid-flexible-liquid coupled dynamic modeling method for stealth aircrafts’ embedded ejection under their large maneuvering flight was put forward. The corresponding launch dynamic characteristics were simulated. The influences of high overload centrifugal force produced due to carriers’ large maneuvering flight on the ejection separation parameters of air-to-air missiles were analyzed. The simulation results showed that carriers’ large maneuvering flight makes missiles’ ejection separation attitude angle decrease obviously to threat missiles’ launch safety. The results provided a theoretical basis for further studying stealth aircrafts’ launch safety under large maneuvering flight and initial trajectories of air-to-air missiles.

 

Discretizing a pile-soil system into many enough micro-element spheres, based on the multi-sphere planar strain model for complex stiffness transfer, the complex shear stiffness of the surrounding soil to the pile was derived. The vertical action of the surrounding soil on the adjacent pile micro-elements’ interface annular sections was simplified as a Voigt model, its spring and damper coefficients were derived. Then through Laplace transformation, combining the displacement continuity conditions and stress equilibrium ones on interfaces of adjacent pile micro-elements, the amended impedance function transfer method was deduced. Through solving dynamic equilibrium equations of pile micro-elements, combining the amended impedance function transfer method, the impedance function at the pile top was obtained. By comparing the solutions gained here with the published ones, the advantages of a tapered pile’s load-bearing ability were verified. Finally, a parametric analysis was conducted to study the interaction between the vertical action of surrounding soil and construction disturbance effect in low-frequency range. The results provided a guiding for aseismic design of pile foundations.

 

A damage detection method for a beam based on imaginary part of its frequency response function (FRF) was proposed. According to the beam’s modal shape curvatures, an index called CIFF to judge its damage was defined.  This index needs to use the beam random vibration response information after its damage to avoid the disadvantage of needing the modal information of the beam before its damage and consider the beam system error and noise disturbance to a certain extent. Through a dynamic test of a steel cantilever beam, the effectiveness using this method to judge the beam’s single-crack damage and multi-crack damage was verified. The test results indicated that the proposed method can not only be used to detect damage’s position, but also reflect its level. The results provided a reference for the damage detection of real beam structures.

 

Wing lift simulation during full scale carrier-based aircraft drop tests is to impose a dynamic load on an aircraft’s wing under indoor environment, so as to completely simulate the real wing load-bearing of the aircraft under landing condition. Whether or not applying wing lift is reasonable is the key of successful full scale carrier-based aircraft drop tests. Here, the simulation criterion of wing lift for full scale carrier-based aircraft drop tests was given, a simulating wing lift loading method for full scale carrier-based aircraft drop tests was proposed. According to the proposed method, the design principles of a wing lift loading device were presented, the mechanical performances of the wing lift simulator were tested. The method and the device were applied in the full scale aircraft drop tests of a certain aircraft. This method was verified and evaluated from four aspects including applied wing lift values, effect of aircraft attitude, effect of going down speed and landing energy absorption. The test results showed that the proposed method satisfies the simulation criterion of wing lift for full scale carrier-based aircraft drop tests; it can be used to simulate wing lift loading for such tests.

 

 

To study frame-masonry horizontal mixed structures appearing in rural areas of Fujian province in recent years, taking a real folk house as the prototype, shaking table tests for its 1/2 scale model were conducted, its dynamic characteristics, test phenomena and dynamic responses under different earthquakes were measured. Meanwhile, the structure’s finite element (FE) model was established with the software ANSYS. Then the elastoplastic response time-history analysis for the FE model under earthquakes was performed. The FE analysis results were compared with the shaking table test results. It was shown that the FE computing results agree well with the test ones, the effectiveness of the FE model was verified; destruction patterns of masonry part of this type structure are similar to those of brick-concrete structures; stress concentration occurs at the top node of frame part’s RC columns; the structure’s rigidity center and mass center do not coincide, the lateral stiffness of the second floor is obviously larger than that of the first one; under the action of earthquakes, the first floor has bigger displacements and torsion effects; due to poorer construction quality, there is a larger hidden danger in this type structures under earthquakes.

 

Chatter is caused due to the poor rigidity of thin-walled parts during their milling process, so it is difficult to ensure their machining quality and efficiency. Here, a novel rotary passive damper possessing variable stiffness was designed with its natural frequency changed through rotating the damper orientation. The design sizes were determined based on the vibration reduction theory and the finite element (FE) simulation. The modal tests for thin-walled parts were performed, then the damper’s optimal installation angle for chatter suppression of thin-walled parts milling was determined for milling processing frequency to avoid parts’ modal frequencies. Finally, the chatter suppression effect was verified with milling tests. It was shown that when the damper orientation is 80°, the amplitude of the system’s FRF drops to 9.8% of that without the damper; the optimal chatter suppression reaches when the damper orientation is 20°, the amplitude of the system’s FRF reduces to 13.6% of that when the damper orientation is 80°, the critical stable cutting depth of thin walled parts with no chatter increases by 1.8 times.

 

 

Shaking table tests were conducted to investigate the aseismic behavior and dynamic response features of an immersed tunnel model and its joints. In order to contrastively study influences of wave passage effect on soil, immersed tunnel and its joints, the uniform longitudinal seismic excitation and the longitudinal seismic excitation with wave passage effect at different apparent wave velocities were considered in tests. The results showed that under the uniform longitudinal seismic excitation, the tunnel and soil body keep a synchronous motion; when the wave passage effect is considered, the tunnel and soil body have a relative sliding; the longitudinal wave passage effect and its input direction have a larger influence on axial force, bending moment and deformation of joints; the wave passage effect makes joints’ responses tend to non-uniform distribution, so the wave passage effect should be considered in aseismic design of an immersed tunnel and its joints.

 

 

The regularization technique is often employed to deal with the ill-posed problem of load identification. However, regularization parameters obtained with the traditional regularization technique are constant. Here, a novel approach of load identification in time domain based on Gibbs sampling method was proposed to assume unknown loads and measurement noise to be stochastic variables. The hierarchical Bayesian model of load identification was built. Gibbs sampling was adopted to obtain the posterior probability density distributions of the identified loads. Numerical simulations were performed to demonstrate the effectiveness of the proposed method by comparing the simulated results using this method with those using Tikhonov regularization method based on L-curve and GCV criterion.

 

Nowadays, spacecraft industry develops quickly to directions of large-scale, complicate and precision. Considering the rigid-flexible coupled effect of an axially moving flexible beam attached and a spacecraft’s main body is very necessary to improve service life, operation precision and working efficiency of the spacecraft. Here, based on Euler-Bernoulli beam theory and the rigid-flexible coupled modeling method in the flexible multi-body dynamics, the dynamic model for a rigid-flexible coupled system including an axially moving flexible beam and a spacecraft was established. The dynamic equations of the system were derived by using Hamilton principle. The dynamic equations of the system were solved with the separation variable method and the mode-superposition method. Several examples were numerically computed with the fourth order Runge-Kutta method. Finally, the effects of radius and mass density of spacecraft main body and axial velocity of flexible beam on the transverse vibration of the axially moving flexible beam and the attitude angle of the spacecraft were analyzed using the above several examples.

 

 

 

Combining the information fusion technique and the application background of damage detection of civil engineering structures, a new evidence theory combination method was proposed. By introducing the concept of evidence ullage, the combining rule of the evidence theory was extended and improved, the calculation formulas for two important parameters including ullage function and tendency factor were built. The new combining rule was not only capable of covering Dempster combining method, but also capable of solving problems of evidence conflict and evidence compatible brought by the multi-source uncertain information. Therefore, compared with the traditional evidence combination method, the new combining rule was more suitable for engineering application. A single-span 3-story spatial truss structure model was used to conduct damage detecting tests under various operation conditions. The test results indicated that the proposed damage detection method based on the improved evidence theory can make full use of the multi-source uncertain information, effectively suppress the damage false positive rate, and improve the correctness and reliability of the damage detection results.

 

Offshore wind turbines are often supported on large diameter monopole foundation suffering various complex external loadings, especially, wind and wave loads. These long-term cyclic loadings cause the monopile foundation to have accumulated deformation and changes in its lateral stiffness, they have important effects on offshore wind turbines’ safety. For considering the effects of long-term cyclic loadings on offshore monopole foundation, the current deign code is to use the p-y curve method adopted in the American Petroleum Institute Standards. The p-y curve is obtained from field tests with less than 200 cycles loads and piles’ diameter range up to 0.6 meters, and may not be applicable to monopile with large diameter and subjected to much more cycles loading. Here, an overall 3-D FE model was built to study displacements of an offshore wind turbine on a monopile in a sandy seabed under long-term cyclic lateral loading. A simplified model to account for the influence of long-term cyclic loading on the soil surrounding the pile was adopted based on the model test results in the literature. A real wind turbine on a monpile foundation was taken as a study object, the effects of long-term cyclic loading on the foundation’s natural frequencies and the pile’s deformation characteristics were analyzed in detail. The results provided a reference for the design of offshore wind turbine’s monopole foundation.

 

Based on the principles of the statistical energy analysis (SEA), a whole-body model for a vehicle was constructed here. From the model, a side-body model was built and simplified to analyze the flow of acoustic power from excitation sources to the acoustic cavity inside the car’s passenger compartment. According to the analysis results including main excitations, major leaking positions and main paths of acoustic power flow, three different arrangements of cavity fillers were made. Cavity fillers were put into the whole-body model, the noise attenuation effects of cavity fillers in three arrangements were predicted, respectively. Through comparing three results, the optimal arrangement was obtained. The study results showed that the optimal arrangement with less cavity fillers has a better denoising effect than the original arrangement does.

 

Liquid sloshing makes force-bearing state of a tank truck be complicated, so liquid sloshing has important influences on dynamic responses of the tank truck’s front wheel shimmy system. Here, a two-axle tank truck was taken as an example, the liquid-solid interaction mechanism in liquid sloshing process was analyzed. Combining the dynamic modeling analysis of a steering mechanism, a 10-DOF dynamic model for the tank truck shimmy system was established considering the effect of clearance in the motion pair of the tank truck’s steering linkage mechanism. Using numerical analysis, the effects of liquid sloshing, vehicle speed and clearance on the vehicle shimmy response were investigated. The analysis showed that with increase in vehicle speed, the influence of liquid sloshing on the shimmy response firstly is inhibitory, then anabatic, and inhibitory again. Finally, some measures to reduce the tank truck’s shimmy were proposed according to the corresponding conclusions.

 

To examine the effectiveness of Lode parameter dependent fracture criterion, Taylor impact tests of 6061-T6511H aluminum alloy cylinder rods with the diameter of 5.9 mm in the impact velocity range of 163.4 ~ 327.7 m/s were conducted with a one-stage light gas gun, two deformation and fracture modes including upsetting cracking and shear one were identified. Material performance tests under various stress states and temperatures were conducted in order to characterize the mechanical behavior of 6061-T6511H aluminum alloy. Based on test results and the corresponding FE numerical computing ones, the modified Johnson-Cook constitutive model, the modified Johnson-Cook fracture criterion and a newly developed Lode parameter dependent fracture criterion were calibrated. Then, 3D finite element models were built in ABAQUS/Explicit, Lode parameter dependent fracture criterion calibrated and other parameter independent fracture criterions calibrated were adopted, respectively to numerically simulate Taylor impact tests. Results showed that Lode parameter dependent fracture criterion can reasonably predict fracture behaviors of Taylor rods made with 6061-T6511H aluminum alloy, while Lode parameter independent fracture criterions over-estate the material ductility and can’t predict the relevant fracture behaviors.

 

The energy-capturing performance of a directly driven floater type wave energy converter (WEC) with linear power-take-off (PTO) mechanism and nonlinear one was studied. Based on the linear potential theory, considering heaving oscillation of the WEC, the motion equations for the floater-PTO coupled system was established and numerically solved using the 4th order Runge-Kutta method. The influences of the stable equilibrium position of the PTO mechanism on energy-capturing were parametrically studied, the difference among power captures of WECs with linear/nonlinear PTO mechanisms was analyzed. The results showed that a WEC with nonlinear PTO mechanism can capture more energy in low-frequency range through selecting a proper stable equilibrium position than a WEC with linear PTO mechanism can, and have a wider bandwidth of the captured energy spectrum; so the former is more applicable for capturing wave energy in actual ocean.  

 

Based on the saturated porous medium theory, vertical vibration of a large diameter pile with transversal inertia effect in homogeneous saturated soil was studied. Firstly, the complex stiffness of surrounding soil was obtained with Novak’s thin layer theory and the saturated porous medium theory. According to the continuous contact condition between the pile and surrounding soil, considering the pile’s transversal inertia effect, the large diameter pile was equivalent to a Rayleigh-Love rod, the coupled dynamic equations of the large diameter pile and soil were established. The analytical solutions to the impedance function and admittance function at the top of the pile were derived by solving the coupled dynamic equations of the large diameter pile and soil with Laplace transformation. Then, the semi analytical solution to the velocity response at the top of the pile in time domain was deduced with the convolution theorem and the inverse Fourier transformation. Finally, the influences of relevant parameters of the pile and saturated soil on the response function in frequency domain and that in time domain at the top of the pile were analyzed, and the influences of relevant parameters on the complex stiffness at the top of the pile within a lower frequency range were also analyzed. The results provided a new theoretical basis for dynamic detecting of piles in saturated soil.

 

Based on the equivalent reducted-scale principle, a 1:8 equivalent reducted-scale model was designed for a typical ship cabin. The double-point inner explosion test was conducted on the model. The inner explosion effect features with double-point charge and single-point charge were contrastively analyzed. The damage effect of the reducted-scale cabin model was studied. The results showed that when the double-point charge simultaneously explodes, shock waves mutually overlapped on the charge central surface, the momentum effect of shock waves is much larger than that when the single-point charge explodes, so the double-point charge simultaneous inner explosion can effectively increase damages to such a ship’s cabins.

 

 

In order to improve the correctness of vibration intensity prediction in a tunnel’s field near blasting, a calculation model for the vibration velocity of the field was established based on the assumption of the linear superposition theory. Based on the measured vibration data in Beijing’s Xing-yan highway tunnel within the mileage range of YK28 + 190 to YK28 + 354, the feasibility of the calculation model was verified, the vibration law of the tunnel’s field near blasting was studied. The results showed that (1) the blasting vibration prediction model based on the waveform superposition is suitable for the near field vibration prediction; (2) in the direction of the tunnel cross-section parallel to the tunnel face, with increase in a single-hole charge, the energy density of each tunnel cross-section increases, the intensity of vibration velocity contours increases; the vibration velocity growing rate of the central measuring line is larger than those of both sides, this phenomenon is specially obvious in blasting near area; on the measuring line perpendicular to the tunnel face, the vibration velocity attenuation speed decreases gradually with increase in the distance from blasting source; (3)with increase in the number of cutholes, the vibration velocity contours shift outwards and become flat gradually; in the direction of the tunnel cross-section parallel to the tunnel face, the vibration velocity growing rate decreases gradually.

 

The friction sliding feature of laminated rubber bearings and the mechanical performance of stoppers have significant influences on the transverse aseismic ability evaluation of medium-small span bridges. A cyclic loading test was conducted to investigate the friction sliding feature and the mechanical performance of laminated rubber bearings after sliding, the effects of relevant parameters, such as, vertical compressive stress, loading rate and rubber material were considered. The FE model of a three-span prestressed concrete continuous beam bridge was built and its transverse seismic responses were studied with the incremental dynamic analysis method considering performance degradation of bearings and stoppers. The results showed that laminated rubber bearings have a certain damage due to friction and sliding under the action of horizontal cyclic loads; their damage levels are different under different affecting factors, but their friction sliding feature can tend to a stable state gradually; friction sliding damage of bearings and stoppers’ performance degradation have significant influences on the transverse seismic responses of bridges, they interact each other, so the performance degradation of bearings and stoppers should be considered in aseismic analysis of medium-small span bridges.

 

In order to simulate effectively a non-stationary non-Gaussian stochastic process possessing a given time-varying power spectrum and probability density function, a nonlinear translation relationship to achieve mutual conversion between non-Gaussian and Gaussian random processes was established, the conversion relationship between power spectrum or correlation function of a non-Gaussian stochastic process and that of a Gaussian stochastic process was also established. Then, a non-stationary non-Gaussian stochastic process was converted through these relationships into a non-stationary Gaussian stochastic process to be simulated. A non-stationary Gaussian stochastic process was effectively simulated with the spectral representation. In order to verify the effectiveness of this method, the simulation of a fluctuating wind velocity possessing target non-stationary non-Gaussian characteristics was performed. The simulation results showed that the simulated fluctuating wind speed sample’s power spectrum has time-varying characteristics, meanwhile its instantaneous power spectrum and correlation function match those of the target; the probability density function (PDF) of the fluctuating wind velocity sample at any time matches the target’s PDF possessing non-Gaussian characteristics; therefore, the simulated random samples not only have the non-stationary features of target time-varying power spectrum, but also have the non-Gaussian features of target probability density function, the effectiveness of the proposed method to simulate a non-stationary non-Gaussian random process is verified.

 

As an underwater imaging sonar, the multi-beam echo sounding sonar (MBES) becomes one of the major oceanographic surveying tools in ocean activities, such as, marine scientific research, seabed resource development, ocean engineering construction and so on. The multi-beam synthetic aperture sonar (MBSAS) was proposed here, it was a combination of conventional synthetic aperture sonar and multi-beam echo sounding sonar to better meet the demands of underwater topography detection. Based on the MBSAS theory, the model of MBSAS was established to conduct verification tests. In tests, two hollow balls with the diameter of 13 cm were put into water at the single side of the basic matrix to transmit LFM signals with the center frequency of 180 kHz, the impulse width of 1ms and the bandwidth of 8 kHz. The targets were illuminated by sound sources with no directivity at different sampling positions along the course. Multi-beam synthetic aperture sonar images with high precision were obtained through the synthetic aperture processing. After comparing the imaging results of MBSAS with those of MBES and the side-scan synthetic aperture sonar (SSSAS), the MBSAS imaging theory’s effectiveness and correctness were verified. Advantages and disadvantages of MBSAS were analyzed, the results provided a reference for the future study. 

 

Low-loss gears are designed and applied in high-speed-ratio planetary gear transmission to improve its efficiency. Here, a multi-DOF pure torsional system dynamic model for a high-speed-ratio planetary gear transmission with low-loss gears was established using the lumped-parameter method. Natural frequencies and corresponding modal shape vectors of the system were gained by solving the system’s eigen-problem, so the natural characteristics of the high-speed-ratio planetary gear transmission system were obtained. Through studying the relationship between the system’s resonance rotating speeds and natural frequencies, the correctness of the pure torsional dynamic model was verified. Finally, the effects of low-loss gears on the dynamic characteristics of this transmission system were analyzed. Results showed that when the overlap ratio of low-loss gear pairs is designed within a certain range, the transmission system has a higher efficiency and a smaller vibration.