Vanishing moments and approximation orders of basis functions are both the significant important properties in wavelets. The traditional customized multiwavelet construction methods could only change either vanishing moments or approximation orders. Meanwhile, the time-frequency characteristics and waveform difference among the new multiple basis functions are quite small, leading to the difficulty for efficiently adaptive extraction and identification of complex dynamic faults. Thus, the customized multiwavelets by the hybrid method combining two-scale similarity transform with lifting transform are proposed. Using the linear and nonlinear combination of multiple scaling wavelet functions to extend the construction space, the method could both obtain the multiple scaling functions with the high approximation orders and the multiple wavelet functions covering the multiple vanishing moments, which enhance the regularity, smoothness and the capabilities for signal approximation and local position, and improve the signal analysis precision. It provides the adaptive basis functions with super properties and a promising tool for the weak and compound fault feature extraction and identification. For the customized selection of adaptive basis functions, the improved local spectral entropy minimization rules are proposed, classified into the typical shaft, gear and rolling bearing faults, which simplify the fault modes. The engineering applications showed that the method could effectively identify the bearing weak inner-race damage disturbing by the complex background noise, and successfully diagnosis the impact and rubbing compound faults with multiple features from the thrust splint of gearbox. 
 

The magneto-elastic resonance of axially moving current-carrying beams in magnetic field was investigated. With the geometric nonlinearity and the interaction in force, motion, electric and magnetic considered, the expressions of kinetic energy, strain energy and electro-magnetic force was derived. Then the Hamilton princile was applied to the vibration equation of the axially moving current-carrying beam in magnetic field. According to the simply supported boundary condition and assuming the third-order modal shape function, the magneto-elastic vibration differential equation of beams was obtained through the application of Galerkin integral method. Based on the method of multiple-scale, the principal resonance amplitude-frequency response equation of external excitation and applied current interaction system were gained. Influence of the magnetic field strength, the applied current, axial velocity, external motivation on the amplitude of system resonance was analyzed. The results show that in the curve of amplitude-intensity of magnetic field, with the increase of tuning parameters resonance, the curve gradually retracted and its upper final closed, the critical separation point "shifted" to the right by the applied current in this process. 

 

Large-scale high-rise reinforced concrete cooling tower belongs to typical wind-sensitive structure. In recent years, study on dynamic response under extreme external actions, such as earthquake, jet-crash, blasting et. al gets extensive concern in engineering field. Research on earthquake response influence for projects like dams, bridges and so on taking into account soil structure dynamic interaction is relatively abundant, however it is seldom involved in cooling tower. Based on elastic wave motion theory combined with finite element method, 3D viscous-spring artificial boundary model and formula were set up and deduced while considering soil structure dynamic interaction, and verify the accuracy of the earthquake input method through half space free field model. A large cooling tower in coal-fired power plant in domestic engineering project as the research background, based on general program ANSYS platform, cooling tower rigid foundation model, massless foundation model and viscoelastic artificial boundary model were modeled respectively. Modal analysis and elastic time history analysis were performed in order to study dynamic characteristics and changes of internal force, influence law of soil structure dynamic interaction for the different model was discussed. Research results show that the cooling tower structure system natural vibration frequency distribution is very dense, and the vast majority of vibration modes are local coupling vibration mode in ring and meridian directions. The natural vibration frequencies are reduced due to considering elastic foundation, and the whole vibration mode appear earlier. Through time history analysis it can be seen that by using the viscous-spring artificial boundary model, considering the infinite foundation radiation damping effect, compared with the rigid foundation model, the maximum absolute acceleration of tower reduces to 43.4%. Moment and axial force in meridian direction reduces 50%, and in ring direction increases significantly. Internal force amplitude value for X columns reduces about 20%~50%. Therefore, when performed the earthquake response analysis of cooling tower, it cannot be neglected influence of soil structure interaction.

 

To extract the weak fault feature of gear, aFractional Fourier Transform(FRFT) filter method based on frequency tracking (FFFT) is proposed to peel the feature components that including fault information by tracking frequency and closely to curve feature of frequency under transient condition. Firstly, the linear multi-scale segmentation method is researched to divide the curve frequency signal into some segments whose frequency are similar to linear; Then, the method to ascertain the filtering parameters by matching the frequency is researched to calculate the FRFT filtering parameters of each segmental signal, and the signal in every segmentation is filtered by FRFT filter using these parameters to complete the FFFT method. The vibration signal of gearbox’s acceleration and deceleration process is analyzed by FFFT and the filtered signal is demodulated, the experimental results show that : linear multi-scale segmentation method is able to divide any curve frequency signal into almost least segments whose frequency are similar to linear; the method to ascertain the filtering parameters by matching the frequency is able to accurately ascertain the FRFT filter parameters of each segmental signals without the influence of the vibration source and the quantity of multi-components; the feature component including fault information of gearbox’s transient condition is accurately extracted by this filter method, the other components and noise are peeled at the same time. The early fault of gear is exactly extracted by the demodulation of extracted feature component, which is difficult to be identified by the traditional method.
 

The controlled stroke based active-passive tuned mass dampers (APTMD), referred herein to as the CS-APTMD, have been proposed in this paper. More specifically, an added viscous damping device between the structure and smaller mass block in the APTMD was introduced, then forming the CS-APTMD. In order to study the optimum performance of the CS-APTMD, an optimum criterion is defined. Employing this defined criterion, the influences of the mass ratio have been scrutinized on the optimum parameters and effectiveness as well as the stroke of the CS-APTMD. Furthermore, for the purpose of comparison, this study simultaneously investigates the optimum performance of the APTMD. It is found in terms of numerical results that the CS-APTMD remarkably outperforms the APTMD.
 

Aiming at the problem that large elastic deformation of Gatling gun tripod during the shooting process is an important factor affecting the firing accuracy, mesh morphing and approximate model technique are comprehensively applied to the multi-objective optimization of gun tripod for improving its rigidity. Rigid-flexible coupling virtual prototype model of Gatling gun is built and the shooting process of the gun is dynamically simulated. The feasible of the model is verified through the comparison between the simulation data and the test data. Virtual prototype model with optimized gun tripod using mesh morphing technique is established, and the shooting dynamic characteristics of the optimized model and the original model are compared. The vibrant angular displacement and speed of muzzle in perpendicular direction are significantly reduced, and a 12.16% quantity of the radius of 70% dispersion circle is achieved. The results indicate that the optimized tripod can effectively suppress the vibration of gun system in the perpendicular direction, and improve the density of dispersion.
 

For fluid-structure interaction problems of centrifugal pump cavitation, centrifugal pump cavitation was simulated numerically based on the full cavitation and gas-liquid two-phase model, and the deformation of the rotor system was simulated under different cavitation conditions using one-way coupling. Cavitation bubbles on the impeller, static pressure, relative liquid velocity distribution of centrifugal pump and pressure pulsation in volute, impeller radial force characteristics were analyzed, the effect on the internal flow field and rotor system deformations were studied. The results show that the vapor volume fraction and area on blade suction surface are larger than blade pressure surface, impeller static pressure distribution is more uneven with cavitation development. The bubbles on the impeller will plug flow channel under serious cavitation, results in flow separation phenomenon, then vortex is generated. Cavitation lead to the increase of pressure fluctuation in volute and  irregular distribution of radial force. Cavitation has an effect on the deformation of centrifugal pump rotor system, impeller appears non-axisymmetric deformation caused by vortex under cavitation condition.
 

 

In order to study the dynamic responses and failure modes of long span concrete cable-stayed bridges under blast loads, finite element models for the whole bridge and local segment of midspan of the stiffening girder were established to perform dynamic analysis of cables under different TNT weights and different detonation locations. The results show that stayed cables under blast loading are strong enough to resist breaking except for the case of eccentrical blast loading under which the cables close to the detonation may have high risk of break. Local damage modes for concrete girder may be greatly influenced by TNT equivalent weights and its corresponding location. As TNT equivalent weight increase,the damage mode will change from flexural failure to direct shear failure. The stiffening ribs may improve the blast-resistance for concrete girder under the small and medium-blast loading by enlarging its lateral rigidity and inhibiting the expansion of damage areas. More serious damage occurs in the box girder under the blast loads due to confinement effect on shock wave from inner chamber of the girder after its top slab being penetrated.