Based on the dynamic analysis theory of rolling bearing , a mathematical model of deep groove ball bearing considering the effects of bearing working surfaces waviness is established. Taking a type of low-noise deep groove ball bearing as example, the bearing vibration characteristics are analyzed theoretically at various bearing structural parameters, working conditions and working surface waviness. The results show that: the bearing basic vibration value can be reduced by selecting reasonable primary parameters, for instance, bearing radial clearance, inner and outer raceway groove curvature radius coefficients, pocket clearance of cage, and so on; the bearing width larger, the bearing vibration value smaller; the bearing vibration value will decrease effectively when the bearing applied axial loads at a certain range; there is a reasonable speed range which can limit the vibration value effectively; the severe vibration occurs when the inner and outer raceway surface waviness orders is integral times to the numbers of balls; the waviness orders exciting frequency of outer raceway equal   and the inner raceway is  ; the even waviness orders of ball working surface make an exciting effect on the vibration value; the vibration produced by rotating ring is more severe than fixed ring; the vibration value will increase greatly when the bearing radial loads or rotating speed increased instantly.

 

Using cellular structure impact resistance, improving its poor stiffness shortcomings at the same time, this paper designed two types of ship vibration isolation shock honeycomb base with positive Poisson’s ratio effect and negative Poisson’s ratio effect. By adjusting the stiffness of base’s upper and lower panels, inside and outside closure plates, we can adjust the base natural frequencies and vibration isolation performance. By keeping the weight of honeycomb core, studied the effect of the thickness and layers of cellular unit on base isolation performance and impact resistance. The varying curves of isolator stress, natural frequency, vibration level, vibration level difference versus cell wall thickness were obtained and proved that cellular base has good impact resistance isolation and negative Poisson’s ratio has better performance.
 

The aim of this paper is to address the study of the natural frequency of a cantilever beam with dry friction using an equivalent method. The motion equation of the studied model and the equivalent model (a cantilever beam) is established using the Newton’s second law and the second kind of the Lagrange equation, respectively. Then the relationship between excitation force and frequency of the two models can be obtained, base on the idea of inputting same energy, thus the equivalent method can be carried out to obtain an analytical expression for the first order natural frequency of the studied model. The numerical method for the first order natural frequency is used to verify the effectiveness of this equivalent method. The results show that the first order natural frequencies obtained by numerical and analytical method are better unanimous under different dry friction, that is, the equivalent natural frequencies decrease as increasing dry friction. Furthermore, the analytical expression of the equivalent natural frequency can directly reflect a relationship between the frequency and dry friction. 

 

In order to model the dynamic attachment characteristics of a rolling tire’s tread, a dynamic model of tread in the longitudinal direction is proposed. Considering the dynamic characteristics of the friction in the tread’s contract area, a dynamic friction model, the LuGre distributed model, is employed to describe the attachment of wheel tread in this model. Then a series of numerical simulations under various conditions are implemented using Matlab/Simulink. The model is verified and the influences of factors such as speed, tire pressure are discussed. Furthermore, the distribution pattern of friction and displacement in the tread’s contract area is analyzed, which provides a theory basis for the research of rolling tire’s longitudinal vibration.
 

To study the mechanism on the vortex resonance characteristics and countermeasures of the central- slotted box girders, the large-scale sectional model vibration measurement, pressure measurement as well as CFD are employed. This paper takes a long-span cable-stayed bridge over the Yangtze River as an example to conduct the wind tunnel tests of large-scale sectional model. The test results indicate that it is the inside maintenance rails located in the aerodynamic susceptible sites that cause the vortex-induced vibration of the bridge. CFD numerical simulation results show that the upwind flow passing through the curved soffit plate will be hindered by the inside maintenance rails, resulting in an increased width of dead water region forming in the wake of upwind box (and an enlarged drag coefficient), where a periodic and intense vortex shedding phenomenon occurs due to velocity gradient, giving rise to the VIV of bridge in the end. Accordingly, the inside maintenance rails are proposed to be moved towards the center line by a certain distance, which will not yet be an obstacle to the high-speed upwind flow. Thus the flow will separate in the location far away from knuckle line and diminish the size of dead water region forming in the upwind box wake as well as prevent the periodic vortex shedding. The static pressure test results show that when shifting the inside maintenance rails, the negative mean pressure at the soffit plate knuckle line will not change dramatically ,the fluctuating pressures on the upwind and downwind inclined panels can be reduced, and the fluctuating energy will be dispersed without a consistent predominant frequency. Wind tunnel test in case of modified section are conducted and the results show that the VIV of the bridge can be suppressed completely.

 

The traditional harmonic oscillation force model can’tpredict the narrowband random characteristics of themeasuredvibration velocities of direct air coolingfanbridge.Consequently, a random oscillation force model based on the carrier theoryis proposed totake the slowly varying amplitudes and phases of the tested velocities into account.Combined with the analysesin time and frequency domains,the model parametersare identified withthe power spectrumofvelocitiesas the target.The results show that the standard differential of the random oscillation force model increases with the increasing rotation speeds of the fans.
 

Faced on driveline torsion vibration of EV, electromechanical coupling simulation method considering the dynamic characteristics of the control motor and driveline clearance/flexible was proposed. Firstly, driveline lumped mass vibration model was established considering the influence of electromagnetic stiffness, modal characteristics were grasped and verified by test; then lumped-distributed mass model was constructed considering backlash and flexible axle, dynamic response simulation and experimental verification were conducted; finally set up the control motor model and the electromechanical coupling model, driveline torsion vibration response has been obtained under the influence of torque ripple. Results show that the proposed electromechanical coupling simulation method can provide abundant dynamical phenomena, helps to further reveal the driveline torsion vibration characteristic of EV. 
 

With the high rotating speed of blades, it is more difficult to identify the operational modal parameters of the offshore wind turbine structure accurately because the structural modal information of responses usually buried in the period components induced by the strong recurring harmonic excitation. In order to solve the problem of structural operational modal identification, a method, combined the modified eigensystem realization algorithm (ERA) with probability density function (PDF), was implemented in this paper. Subsequently, the interference resulted from the rotating frequencies and frequency multiplication was eliminated and the effective identification on the multi-operational modal parameters of one offshore wind turbine experimental prototype was also achieved based on the measured signals under different operational conditions. This approach can not only avoids the strong harmonic interference so as to obtain the real structural operational modes effectively, but also has a better engineering applicability on the online real-time monitoring and evaluation of the structural operational security for the offshore wind turbine structure. 
 

Based on classical elastic thin shell theory, the structure modal shape were expressed by beam modal function with the same boundary, and the dynamic response calculation methods of cylindrical shell with spherical dome under internal blast load were proposed. The simplified calculation method for dynamic response was obtained by analyzing the influence of slenderness ratio on cylindrical shell vibration. Though calculation examples, the calculated results of the presented method were compared with those of the existing methods. The rationality of the proposed method was validated, and the influences of dome on structure vibration were analyzed. The conclusions are as follows, by using the calculation model of cylindrical shell with equivalent concentrated mass of spherical dome, the computing error of shell radial displacement on higher order modes, which caused by elastic hinge stiffness coefficient obtained under cylindrical shell internal static pressure, can be reduced effectively. The calculation results of cylindrical shell vibration frequency and roof radial displacement are smaller than those of existing method. The influences of spherical dome on the cylindrical shell vibration decrease with the increase of the slenderness ratio of structure.

 

The low-g shock standard device based on rigid body collision for shock acceleration calibration was investigated and established, with the half-sine squared acceleration shape range from 20m/s2 to 10000 m/s2 and pulse duration from 0.5 ms to 10 ms. The expanded calibration uncertainty of sensitivity of shock accelerometers by laser interferometry is 1%, k=2. The structure of the device and key technology involved were described．The pulse generation materials were explained．The calibration results and uncertainty evaluation were provided．This low-g shock standard device is used for piloting international shock comparison APMP.AUV.V-P1.
 

Based on the perturbation theory, two interval analysis methods named first-order interval parameter perturbation method (FIPPM) and high-order interval parameter perturbation method (HIPPM) were proposed for the coupled structural-acoustic system prediction with interval uncertainties in both system parameters and external loads. The structural-acoustic discrete equilibrium equation was established based on the finite element method. Interval variables are used to quantitatively describe the uncertain parameters with limited information. According to the first-order Taylor series and first-order perturbation theory, the response interval could be quickly evaluated by FIPPM. On the contrary, HIPPM introduced modified Taylor series to approximate the non-linear interval matrix and vector. Higher order terms of the Neumann expansion were retained to calculate the interval matrix inverse. By comparing the results with traditional Monte Carlo simulation, a 3D cuboid model was given to demonstrate the feasibility and effectiveness of the proposed methods to predict the sound pressure ranges of the coupled structural-acoustic systems.