A pseudo-static model of the angular contact ball bearings in a high speed motorized spindle is built based on their high speed rotation, from which the impacts of the bearing radial force and the speed of motorized spindle on the contact angle and the contact force between the ball and the bearing race are discussed. According to the force equilibrium condition of the bearing and the ball, the impact of the bearing preload on the bearing stiffness is studied. Then, the finite element models of the bearing and the spindle are set up based on the Timoshenko beam theory, from which the influence of the bearing on the critical speed of the motorized spindle with different preloads is studied. The results show that the radial force and the speed of the motorized spindle may change the contact angle and the force between the ball and the bearing race, the bearing stiffness degradation will arise as the rotate speed is high and the preload is decreased, and the critical speed of the motorized spindle can also decrease. Moreover, to guarantee the safety of the motorized spindle, the effects of the bearing centrifugal force, the inner expansion, and the preload should be taken into account.
 

Using model test method combined with new digital laser dynamic caustics experimental system(DLDC), the dynamic behaviors of crack initiation at joints were compared in condition of different intervals between boreholes and joints, the effects of joints on blasting induced cracks propagation were studied. It showed that the failure forms of test specimens were various duo to mesoscopic differences of joint structure. There were two forms of crack initiation at joints according to different crack initiation time situations, Form 1: Crack at the joint did not initiate until the blasting induced crack reaching to the joint; in this form, the direct action of blasting induced cracks on joints was primary cause of crack initiation at joints, the offset distance of crack which initiated at the joint had little to do with the distance between borehole and joint in such form. Form 2: Crack at the joint had already initiated and propagated before the blasting induced crack reaching to the joint; in this form, the action of blasting stress waves on joints was primary cause. The overall scope of crack offset distance at the joint was determined by these two forms. Different failures of specimens showed various discrepancies and complexities in the aspect of crack stress characteristics.
 

Full-scale measurements have been conducted for a 270-m tall building in Hong Kong. Acceleration response data of the tall building has been collected during Typhoon Kammuri and 512 Wenchuanearthquake in 2008. Based on two sets of acceleration data, dynamic modal properties of the tall building were identified by two methods. One is the traditional method of empirical mode decomposition (EMD) combined with the Random decrement Technique (RDT), the other is the recently proposed Fast Bayesian method using the fast Fourier transform (FFT). The natural frequency of each mode identified by these two different methods is very close to each other. Noticeable differences are observed for damping ratio results associated with each mode. The identified results can also be compared between two excitation events. As expected, wind-induced acceleration data suggests almost the same frequency values compared to the results identified from the acceleration data due to the long-distance earthquake. However, the damping ratios corresponding to Wenchuan earthquake were found to be larger than the damping results of the tall building under typhoon excitation. The difference of two sets of damping ratio results might be attributed to the the role of aerodynamic damping, which could be estimated from the two sets of damping ratio.  
 

To suppress the vibration localization and improve the vibration control system of mistuned space-borne antenna structure, a single rib multi-freedom lumped parameter model of radial rib antenna was established in this paper. Firstly, a mode localization factor for measuring the overall quality of structural vibration mode was proposed. Secondly, the influence of the certain mistuned ribs arrangements of the antenna on the overall structural vibration mode was studied. Finally, the problem of optimal design of the mistuned ribs arrangement was investigated by the genetic algorithm (GA), and the effect of optimization of the mistuned ribs arrangement on enhancing the performance of vibration control system was assessed. The results show that: for a group of certain random mistuned ribs, the optimal or approximate optimal mistuned ribs arrangement can be quickly and accurately obtained by the genetic algorithm and mode localization factor proposed in this paper, and the optimal mistuned ribs arrangement can not only greatly improve overall quality of structural vibration mode, reducing the structural vibration response, but also improve the efficiency of the vibration control system of the antenna.
 

In order to study the effect of gaseous explosion suppressant on gasoline⁃air mixture explosion, an experiment system of gasoline⁃air mixture explosion suppression in long-narrow confined space was set up. Carbon dioxide and heptafluoropropane(FM200) were chosen as explosion suppressant. The gasoline⁃air mixture explosion suppression experiment was systematically conducted and was compared with experiment under no explosion suppressant condition. The changes of overpressure, rate of pressure rise, flame propagation velocity, flame intensity and explosive products were analyzed. Experiment results indicate that when carbon dioxide and FM200 were chosen as explosion suppressant, the maximum overpressure declined by 28.85% and 42.54%; The maximum rate of pressure rise decreased by 11.62% and 16.04%. The flame propagation velocity declined by 60.69% and 89.23% respectively. Meanwhile, flame duration was shortened and flame intensity was weakened. When all other conditions remained stable, the explosion suppression effect of FM200 was better than that of carbon dioxide.
 

To understand the flutter and vortex-induced vibration(VIV) performance of the bridge deck with double-slots and to propose feasible control measures, a sectional wind tunnel test was carried out based on a steel-box suspension bridge which was been planned. Afterwards, 2d-3DOF method and CFD simulation were introduced respectively to understand flutter and VIV mechanisms. The results show that, double-slotting is an effective method to improve the flutter performance of a steel-box deck. According to this section, the type of railings, with or without pedestal, influences the critical wind speed significantly. Besides, central stabilizer, as a conventional control alternative, also has a positive impact on bridge’s stability. In a certain range of height, the section with a higher plate will perform better. As is shown by 2d-3DOF method, both central stabilizer and optimized railing can slow down the increasing of aerodynamic damping with wind speed. Since VIV often occurs with a slotting deck, various measures have been taken into account in the test, while the equidistant grating is proved to be more efficacious. By CFD simulation, the essential  mechanism is that grating changes the flow field notably, avoiding large-scale vortex shedding.
 

In view of the poor working environment of the thin walled structure under the thermal-acoustic loading conditions that extremely easy to occur buckling and acoustic fatigue which can affect the stability and service life of the component. The object is C/SiC composite laminated structure with clamping. Utilizes the finite element method to calculate the nonlinear random response of thin composite laminated structure at various combinations of sound pressure levels and temperatures and obtains the typical thermal-acoustic motion. Though analyzed the response characteristics of laminated structure under the buckling and post buckling and summarized the typical nonlinear vibration response characteristics. Finally based on the high specific strength and special structure fatigue damage mechanism of composite laminated, improved rain flow method to count the stress response of laminated plates under the condition of high temperature and loud noise, combination the data on test of the performance of the material symmetry cycle and fitting the equivalent life formula which considered the mean stress effect and Palmgren-Miner linear cumulative damage criterion to estimate the fatigue life of composite laminated.

 

Generalized inverse beamforming is an effective sound source locating method. But its calculation robustness is sensitive to random noises. For the sake of improving the robustness of generalized inverse beamforming, a modified algorithm based on high-order matrix function is proposed. The regularization matrix is defined based on generalized inverse beamforming and used in iteratively resolving beamforming output. At the same time, the high-order matrix function is incorporated into the cross spectra of beamforming output to optimize the effect of sound source localization. Moreover, to find the optimum range of matrix function order, the numerical simulation is implemented and the influence of sound source frequency on value selection of matrix function order is analyzed correspondingly. Finally, the identifications of both monopole and coherent sound sources are realized numerically and experimentally. The results show that the proposed modified algorithm can identify the source position with higher space resolution and less side-lobe. 
 

In view of the low reusability of monitoring data, the influencing of complex working condition and failure of trained model, Transfer Component Analysis (TCA) is introduced to solve the problem of equipment fault diagnosis in variable working conditions. TCA methoddecreases the distribution difference of train sample and test sample, by utilizing kernel function to map the feature of two samples to latent space. Besides, the effect of four different kernel functions is compared in TCA algorithm and transfer degree index KL divergence (Kullback-leibler divergence) is introduced to measure the distribution difference degree of train samples and test sample. According to the simulation analysis and experiment verification, compared with traditional machine learning methods, TCA performs better in reduction the distribution difference of two samples and improving gearbox diagnose accuracy, especially the Gaussian kernel function. 
 

Transfer function method is applied to the flutter of aircraft wings carrying an external store. Firstly, the flutter differential equation of a clean wing is established by combining the bend-twist vibration equations of the wing and the Therdorson’ unsteady aerodynamics model. Then, the external store hung below the wing by a pitch spring is regarded as a rigid body owning a certain mass and rotary inertia. The influence of the external store on the wing flutter is introduced through the deformation harmony and internal force balance conditions. Further, using the transfer function method, the control equations are formulated in a state-space form by defining a state vector. Both the flutter velocity and flutter frequency are obtained by solving a complex eigenvalue problem. The results are good agreement with the literature solutions and the finite element method solutions, which indicates that the present method is accurate and efficient. Finally, the effects of the mass, rotary inertia, position and pitch stiffness of the pylons are investigated.      

 

In order to achieve active flutter suppression of a two-dimensional airfoil, an improved state-dependent Riccati equation (SDRE) nonlinear robust control law is proposed based on Lyapunov stability theory. The model of a two-dimensional airfoil with leading- and trailing-edge control surfaces are described in state space, and then this model is transformed into a form which input matrix   is full row rank matrix. The problem that SDRE nonlinear control method can’t be directly applied to active flutter suppression is solved. The simulation results are presented, which show the closed-loop system reaches to stability quickly under the impact of wind gust even if there is a hard constraint on the control input and flutter suppression is accomplished effectively. In addition, adjusting the weighting parameters   and  can decrease control inputs. 
 

Aiming at the optimization of sensors’ number and locations in active control of structural response, an existing optimization selection method was improved. The method can effectively reduce the number of sensors and find their relevant optimization locations, at the same time the effect of vibration reduction maintains almost the same as before, and the control scale of hardware can be reduced distinctly. The optimization procedure was resolved with the genetic algorithm. In order to eliminate the coupling between multi-channel in active control, FxLMS algorithm was used. Four hydraulic actuators were placed between the floating raft and the hull structure, and the error signals were used as feedback signals for each actuator simultaneously, while using the improved integer coding genetic algorithm, the experimental research of active vibration isolation of multiple excitation frequencies was studied. Experimental results show that the effect of vibration reduction of 4 error signals maintains almost the same as that of 22 error signals, sound pressure of the 10 monitoring microphones were effectively suppressed.
 

 

An optimal design method of the vibration control of self-standing high-rise steel structures is presented in this paper. Firstly, a ring shape Tuned Liquid Column Damper (TLCD) is designed according to the characteristics of the self-standing high-rise steel structure, also its mechanical model is presented, and then the dynamic equation of the high-rise structures with the ring shape TLCD is derived. Secondly, a composite satisfactory function, which can be used in the designation of structural control devices, is constructed using Sigmoid function and linear superposition methods, and a multi-objective optimal design method is established based on the satisfactory degree principle and pattern search method. Lastly, focusing on the designation of the wind-induced vibration control for a self-standing high-rise steel structure, a numerical case study is conducted by programming the method. In this study, the design variables are the geographic parameters of the ring shape TLCD, and the objective is the composite satisfactory function composed of the items related to the top displacement, mass ratio and windward area ratio. The study shows that the method can efficiently obtain a set of design parameters which can satisfy project requirements and the coefficients of variation of both the optimal parameters and the related objectives are all less than 0.1. Therefore, this is a method with high robustness, and the difficulty of choosing weight coefficients in multi-objective optimization is reduced.
 

A new modeling method combining wavelet singular entropy andSelf Organizing Feature Map(SOFM) neural network is proposed to identify the motor bearing faults.The end position of the faulty bearing can be identifiedby computing and comparing the wavelet singular entropies of the fault vibration signals collected at the drive and fan ends of the motor firstly.Then the SOFM neural networkmodel using the bottom node energies of the fault signals decomposed by wavelet packet as input feature vectorsis built to identify the pitting corrosiondamage locationin the faulty bearing.The faulty bearing end positionand its internal pitting corrosion location can be identified jointly by the combination of wavelet singular entropy and SOFM neural network.Through the modeling and identification to the bearings damaged by pitting corrosionatinner,outer raceway and rolling element respectively,the results show that this model can identify the faulty bearing end position and its internal pitting corrosiondamage locationeffectively;this model has a more accurate identification ability and is more robust than that of the traditional support vector machine and the BP neural networkidentification model,and is more suitable for fault identification of such a multi classifica-tion problem.
 

In order to solve the problem of random vibration acceleration response of a high resolution space camera, the main support structure of the space camera has been optimal designed. First, the mathematical model is established based on random vibration response, and random vibration root-mean-square response expression is deduced. Then, the camera supporting structure is designed based on the principle of the three point location principle and bipod flexible structure. Adopting the method of size optimization, which directed by objective function of acceleration response RMS and in the meanwhile restricted by the natural frequency. The position of the flexible link is optimized. Using MSC.Patran & Nastran to analysis the support structure, the result show that the camera installation point random response RMS value less than 19.6grms. Finally, the camera support structure is tested with the random vibration test. Obtained results show that the maximum relative error of the Random vibration response between analysis result and test result is 8.2%.The performance parameters of the main support structure meet the requirements of space camera well, which has verified the feasibility of the optimization method.