Analysis of the instantaneous angular speed (IAS) has been proven to effectively detect bearing faults. To investigate the generation mechanism of IAS signal double-impulses phenomenon in ball bearings, a dynamic model is proposed in this paper based on the coupling characteristics between the normal, tangential forces and the time-varying impact excitation, in which the influences of the rolling resistance and the sharp edges of local defect on the dynamic behavior are considered. In this model, the elastic quarter-space method is adopted to calculate the additional deformation induced by the local spalled edges and its corresponding time-varying displacement excitation model is deduced. Additional contact forces and time-varying displacement excitations are considered when steel ball enter into and exit from the defect. The disturbances of normal and tangential forces in the bearing under sharp-edge excitations of local fault are studied, and the time-varying tangential force excitation model is also deduced. The nonlinear dynamic equation sets are solved using the Runge-Kutta numerical integration method. Comparisons between the simulation results and the actual measured results of outer race local fault bearings show the established dynamic model can effectively reveal the mechanism of double-impulses phenomenon based on IAS signals.

The intrinsic characteristics of all-composite honeycomb core sandwich panels (ACHCSP) were investigated using a combined approach of theory and experimentation. A theoretical model of the ACHCSP structure was established based on the high-order shear deformation theory and Gibson equivalent theory. The dynamic characteristics of this structure were determined using the Rayleigh-Ritz method and orthogonal polynomial approach. A relevant experimental platform was constructed to conduct tests on ACHCSP as the research subject, thereby confirming the accuracy of the theoretical model. The results indicate that this theoretical model can accurately predict the natural frequencies of ACHCSP plates. Based on the established model, the influence of fiber layer thickness, honeycomb cell wall thickness, and wall length on the natural frequencies of ACHCSP structures is discussed.

To study the influence of the vibration characteristics of ballastless track on bridge under the failed fasteners, this thesis adopts an existing scale model of ballastless track-box girder structure. Under the random loading, the influence of different invalid fasteners conditions on the vibration response change of the track-box girder structure is discussed. The results show that the peak value of acceleration admittance increases and the peak frequency of admittance moves forward when the fastener fails, it appears in each component of the mid-span section of track-box girder structure, especially appears in the rail and track plate. At the same time, it is found that when the distance between the failure fastener and the observed section is different, the vibration response effect of the rail-box girder components is also different. When the distance between the failure fastener and the observed section within one fastener spacing, the acceleration admittance of each component of the track-box girder increases significantly, with the peak value at the track plate increasing by 1.48 times. When the distance between the failure fastener and the observed section is more than three fastener spacings, the acceleration response increase of each component of the box beam is within 5%. In addition, it is found that the dynamic response of various components of the track-box girder structure is directly proportional to the number of failed fasteners. For example, the peak acceleration admittance of the three fasteners with continuous failure at the track plate is 1.9 times higher than that without failure of fasteners. The maximum increase of peak admittance at the top plate and wing plate is 131% and 82% respectively, while the increase of peak admittance at the web plate and bottom plate of the box girder is approximately less than 25%.

The command‑FxLMS algorithm for multi‑order noise modulation has unnecessarily high output gain when there is a phase error between the command signal and the disturbance signal. Aiming at this problem, a multi‑order active sound profiling system based on the modified differential phase scheduled command filtered‑x least mean square (DPSC‑FxLMS) algorithm is constructed. By adjusting the phase of the command signal to keep it in phase with the disturbance signal, the output level of the control signal is reduced while keeping the same control performance. Simulation analysis and comparison of engine steady‑state multi‑order noise modulation using the above algorithms are carried out, and the control effect of the algorithms is verified. For the in‑phase case, two algorithms share the identical performance and control effect, while for the out‑of‑phase case, the DPSC‑FxLMS algorithm requires less control effort than the command‑FxLMS to achieve the same control performance. The multi‑order noise modulation simulation of the above algorithm is carried out using the multi‑order noise signal collected from a real vehicle. The simulation results validate the feasibility of the proposed algorithm for practical in‑vehicle applications.

The non-uniform input of ground motion has a significant effect on the dynamic response of a concrete cut-off wall in deep overburden. In order to explore the response characteristics of the cut-off wall under non-uniform ground motion input at the overburden site, this study establishes the input method of P-wave three-dimensional oblique incident wave motion under any incident angle in space based on the wave field decomposition method and the viscoelastic artificial boundary method, and validates the input method. Nine non-uniform input conditions were designed to investigate the influence of different azimuthal and oblique incidence angles on the dynamic response of the cut-off wall under a combination of incidence. The results show that the maximum acceleration in the down-river direction of the cut-off wall at α=60° and γ=0° incidence is 3.89 times that of vertical incidence, and the maximum acceleration in the axial direction of the dam at α=60° and γ=90° incidence is 8.93 times that of vertical incidence. Non-uniform input causes a significant increase in the transverse riverward tensile stresses in the impermeable wall, up to 3.53 times that of the vertical incidence, with a significant change in the peak distribution region, and the vertical compressive stresses are significantly reduced at an oblique incidence angle of 90° incidence compared to the vertical incidence. The traditional vertical incidence method can ignore the expansion area of tensile stress of the cutoff wall under non-uniform input, so the non-uniformity of ground motion should be considered when analyzing the dynamic response of the cutoff wall in a deep overburden layer.

As a component widely used in various industries, the noise problem of fans has always attracted people’s attention. In equipment with relatively low noise energy levels, abnormal noise, such as whistling, or rattlesing, from fans are key factors that lead to user complaints. Taking laptop fans with various abnormal noises as an example, the correlation between the severity of fan abnormal noise and the main psychoacoustic parameters of sound quality was studied, and a linear regression model between the subjective score of abnormal noise and the objective parameters was established. The results show that loudness, sharpness, prominence ratio, and the frequency corresponding to the maximum value of pitch affect the subjective feeling of abnormal noise. The multivariate linear model including loudness and sharpness can better evaluate the subjective score of the severity of abnormal sound.

To overcome the shortcomings of traditional base isolation technology, such as non-adjustable isolation parameters, limited low-frequency isolation effect, and inability to achieve vertical isolation, magnetic levitation technology is introduced to design a magnetic levitation vibration isolation bearing. The relationships between the levitation force of the electromagnet and the coil current and levitation gap are analyzed. The nonlinear model of the magnetic levitation vibration isolation bearing is established. Combining the advantages of terminal sliding mode and super-twisting algorithm and introducing an adaptive law to adjust the coefficients in the super-twisting algorithm, an adaptive super-twisting terminal sliding mode control strategy is proposed. Through experimental verification, the proposed control scheme can suppress the chattering phenomenon in the traditional sliding mode control, with high control accuracy and good steady-state and dynamic performance. The magnetic levitation vibration isolation bearing has excellent stability and disturbance-resisting performance.

In order to obtain the main influencing factors of buffeting response calculation of Π‑shaped main girder cable‑stayed bridge, taking Qingzhou Minjiang River Bridge as the engineering background, the buffeting response characteristics of main girder displacement were analyzed by using three‑dimensional multi‑modal coupling buffeting calculation method on the basis of wind tunnel test. The significance of nine factors in buffeting response was tested by uniform experimental design and regression analysis method. The results show that the aerodynamic admittance, fluctuating wind correlation coefficient, vertical wind spectrum, average wind profile index, surface roughness height and air density have significant influence on the buffeting response of cable‑stayed bridge in the common range of values. The influence of structural mass and damping ratio is not significant, and its value deviation can be ignored in buffeting calculation. The horizontal wind spectrum only has a significant effect on the lateral buffeting response.

Ride comfort evaluation of high‑speed trains has vital importance for continuously improving the structural design and passengers’ ride satisfaction. This paper tries to evaluate the long‑term and momentary ride comfort of high‑speed trains in China in the light of the European standard EN 12299：2009, and discuss the applicability of the standard. Objective vibration test and subjective comfort evaluation were carried out in a comprehensive inspection train. Average comfort index and discrete events comfort index recommended by the EN 12299：2009 standard were briefly introduced, and the two indexes were selected for long‑term comfort evaluation and momentary comfort evaluation respectively. For the three kinds of track sections with different subjective feelings, based on the measured vibration acceleration data, the long‑time and momentary comfort evaluation indexes were calculated respectively, the comfort of high‑speed train and track quality were analyzed. Combined with the subjective evaluation results, the applicability of the corresponding indexes was analyzed, and attempts were made to put forward suggestions for improvement. according to which the comfort of high‑speed rail ride and the quality of the track into the standard is analyzed. The applicability of these indices was analyzed by referring to the subjective evaluation, and certain suggestion was proposed to modify the indexes.

Seismic experience has shown that underground shaft structures are subjected to seismic threats and severe examples of damage have occurred. In order to obtain the seismic response of the shaft, the ‘beam-spring’ model was used to establish a system analysis model for the dynamic interaction between the large-diameter shaft and the soil based on the Pasternak foundation and the Timoshenko beam theory. On the basis of considering the normal earth pressure of site soil layer and shaft structure, the tangential shear force of site soil layer and shaft structure is further considered. The analytical solution of seismic response of large diameter shaft under horizontal earthquake was studied. The peak seismic response of the shaft along the depth direction is analyzed from the aspects of the ratio of the length to diameter of the shaft, the ratio of the inner and outer diameters, the ratio of the elastic modulus of the shaft to the site and the boundary conditions at the bottom of the shaft. The results show that the decrease of the ratio of the length to diameter of the shaft will lead to the increase of the peak response of the internal force of the shaft along the depth direction. The increase of the inner and outer diameter ratio of the shaft will reduce the peak internal force response of the shaft along the depth direction. With the increase of the ratio of the elastic modulus of the shaft to the site, the peak response of the internal force of the shaft along the depth direction will gradually increase. The displacement response of the shaft under the elastic soil foundation is larger than that of the rock-socketed foundation. The shear response under the rock-socketed foundation along the depth direction of the shaft is significantly larger than that of the elastic soil foundation, and the bending moment peak response of the rock-socketed shaft at the bottom position is larger.