The paper is aimed at studying vibro-acoustic responses of a coupled pump-jet-shafting-suboff system under unsteady hydrodynamic excitations from the pump-jet running in the wake of the suboff model.The excitations of the pump-jet in the rear of the a suboff model were analysed by the computational fluid dynamics (CFD) with a shear stress transfer(SST) k-ω model and the vibro-acoustic responses were predicted by the coupled finite element method(FEM).A mapping method based on radial basis function was established between CFD/structural meshes to obtain the distributed pulsation force on the structural wet surface.The radiated sound was studied by the boundary element method(BEM).Modal shapes, transmitted forces, sound radiation power and radiation directivity pattern were reported to illustrate the characteristics of vibro-acoustic responses.It is shown that the contribution of the rotor is dominant; among three directions components, the longitudinal distributed forces contribute most to responses over the second harmonics of shaft frequency; the responses exhibit peaks at multiple blade passing frequencies and characteristic structural modes, which include the longitudinal mode of hull, the in-phase mode(breathing mode) of propeller as well as the longitudinal mode of propeller-shaft; the vibro-acoustic responses under the distributed pressure on the stator and duct will produce peaks at blade passing frequency(BPF) and 2BPF, which are of the same level as those produced by the distributed pressure on the rotor, however, the magnitude of the vibro-acoustic response will not increase if they are applied simultaneously due to the phase difference and cancellation between them.The conclusions will shed some light on the design and controlling of vibro-acoustic responses of the coupled pump-jet-shafting-suboff-system.

To explore the influence of drug viscosity on injection performances and the dispersion pattern of microjet, glycerol-water solutions of different concentrations were used for injection experiments.The high-speed photography technique was employed to observe the propagation progress and atomization of the jets.The impact pressures of the jets were measured with a dynamic sensor.Then, the dispersion patterns of different viscous liquid jets’penetration into homogeneous gelatin were investigated.The results demonstrate that with the increase of viscosity, the spray angle and atomization degree decrease.The liquid viscosity has little effect on the duration of injection and the time of fluctuation, whereas the steady pressure increases with the increase of viscosity.In gelatin injections experience, the aspect ratio of the diffusion shape of the liquid with viscosity of 18 MPa•s is smaller than that of other viscous liquids.Therefore, the jet injection with a liquid viscosity of 18 MPa•s is likely to spread better in the lateral direction compared with those of other viscosity, bringing a satisfactory injection experience.

In order to obtain the effective design method for an ultrasonic tooth grinding longitudinal bending resonance system, based on the local resonance theory, the vibration system composed of a large-load forming grinding wheel disc in the grinding system was proposed and designed.According to the continuous conditions and boundary conditions between the vibration units, the theoretical model and frequency equation of the longitudinal bending resonance system were established according to the integrated design idea.Based on the theoretical model, the analysis softwares MATLAB and ANSYS were used to design and optimize the size parameters of each part of the system, and the finite element modal analysis, impedance analysis experiment and ultrasonic resonance test were carried out.The simulation and test results show that the system resonance effect and mode shape curves observed are relatively stable, the amplitude value is consistent with the expected result of the theoretical simulation, and the errors between the measured resonance frequency, the design frequency and the simulation frequency of the system maintain within 5%, which is of good design accuracy.Therefore, the feasibility and accuracy of the design method for the longitudinal bending resonance system of the grinding wheel disk based on the local resonance design theory are effectively verified.

Aiming at the difficulty to diagnose the early unbalance fault on the exciting force of a linear vibrating screen, a fault diagnosis method based on variational mode decomposition(VMD) and recurrence quantitative analysis(RQA) was proposed.Firstly, the vibration signal was decomposed by VMD, the fundamental frequency signal of the linear vibrating screen was separated, and the submerged high frequency components were obtained.Then, the dynamic characteristic recurrence plots of different signal components were drawn, and the quantitative indexes of the recurrence plots were calculated to constitute a nonlinear and nonstationary evaluation feature vector of the fault signal.Finally, the high-dimensional eigenvectors were input into a machine learning classifier for diagnosis, and its results were compared with those of traditional feature extraction methods.The results show that, the characteristic parameters extracted by the method has the highest recognition accuracy in the excitation force unbalance fault experiment, and the comprehensive recognition rate is 99.13%.In addition, applying the method to the fault diagnosis of   rotating machinery bearings, the comprehensive recognition rate reaches 99.38%, indicating that the method has certain reliability and engineering application value.

Annular seals are the key component of turbomachines to reduce the fluid leakage.The fluid-induced vibration characteristics of the annular seal are extremely crucial to the system stability.Based on the computational fluid dynamics method and a multiple frequencies whirling model, the fluid-induced vibration characteristics of an anti-stagnant labyrinth seal were investigated.The effect of anti-stagnant nozzles’geometry parameters and its position on the dynamic and static characteristics was studied.The fluid-induced vibration suppression mechanism of the anti-stagnant nozzles was examined.The results show that the anti-stagnant flow can significantly suppress the circumferential flow, and improve the pressure distribution on seal cavities and the system stability.Compared with the traditional labyrinth seal, the anti-stagnant labyrinth seal possesses a smaller cross-coupled stiffness coefficient k, a larger direct damping coefficient C and an effective damping coefficient Ceff.The suppression effect on the unstable vibration is especially remarkable at low frequencies.There exists an optimal radial position for the anti-stagnant nozzle with identical geometric parameters.When the centroid height hc is 1.65 mm, the effective damping Ceff is the largest.Increasing the nozzle inlet height hin and decreasing the ratio of outlet/inlet height hout/hin can both improve the system stability.The anti-stagnant labyrinth seal with hin=1.00 mm, hout/hin=0.25, hc=1.65 mm, is the optimal structure for the current calculation conditions, while the leakage flowrate increases slightly.

Based on the basic principle of structural noise transmission path analysis, the CAE model of a vehicle for NVH performance simulation under the excitation of wheel center acceleration was established, and the method for optimizing the vehicle interior peak noise by matching the transfer function was discussed.Taking a certain SUV type of vehicle as a research object, the interior noise and wheel center acceleration of the vehicle at 60 km/h speed were measured at the Xiangyang test site.The wheel center acceleration was used as the boundary condition in the vehicle structural road noise analysis, and the noise near driver right ear was obtained by simulation.The simulation value of the vehicle interior noise is basically consistent with the experimental data, and there are obvious noise peaks at 56 Hz and 112 Hz.The largest contribution path of the peak noise at 112 Hz was determined by the transmission path analysis, and the vibration-vibration transfer function (VTF) of the suspension side in the path was analyzed.Then it was adjusted and optimized to match the noise-vibration transfer function (NTF) of the body-side.The result shows the peak noise at 112 Hz is reduced by 8.45 dB (A).

Based on Eringen’s nonlocal linear elastic theory and n-th order generalized beam theory (GBT), the coupled vibration and buckling characteristics of functionally graded material (FGM) nanobeams subjected to thermal-mechanical loads were investigated by using a modified generalized differential quadrature (MGDQ) method.The material properties were temperature-dependent according to the Voigt mixture power-law model and various types of temperature distributions were assumed to be steady along the thickness direction of the structure.The governing differential equations for the coupled vibration and buckling of the system were derived unifiedly in accordance with the Hamilton’s principle.By introducing control parameters for three different kinds of boundary conditions, the MGDQ method was  used to solve the coupled vibration response of the structure with the MATLAB procedure.A loop subprogram was also written to obtain the static responses based on the duality between the vibration and buckling responses of FGM nanobeams.The MGDQ method presented was validated to be available and highly efficient by comparison with those of available results in the literature.Finally, the effects of various beam theories, boundary conditions, nonlocal scale parameters, initial axial mechanical loads, various types of temperature distributions, temperature rises, thermal-mechanical loads, material graded index and slenderness ratios on the vibration and buckling characteristics of FGM nanobeams were studied.

The rotor/stator rubbing fault has a serious impact on the safety and reliability of a gas turbine, and the uncertainty of the nonlinear rubbing response is an important constraint for its evaluation, prevention, and control.Therefore, considering the uncertain effects of the rotor/stator clearance, rotor unbalance and contact stiffness, the uncertain dynamic model of a gas turbine dual-disk single-axis rotor with fixed-point rubbing faults was established to study the rubbing induced vibration response characteristics and its influential parameters.For the non-smooth/uncertainty rubbing dynamic equations, the combination of the harmonic balance method and the alternating frequency-time scheme (HB-AFT) was adopted to obtain the periodic solution of the rotor system, and the non-intrusive Chebyshev interval method was used to estimate the upper/lower bounds of the nonlinear vibration response.The influence of each interval variable on the response uncertainty could be quickly quantified.Finally, the effectiveness and computational advantages of the proposed method were verified by comparing with the traditional Monte Carlo simulation.The numerical results show that the uncertainty of the parameter interval has a significant effect on the global amplitude-frequency responses of the rubbing rotor, which can lead to differences in the occurrence conditions and severity of rotor/stator rubbing fault.The research results provide a guidance for more accurate diagnosis and prevention of gas turbine rotor rubbing faults.

When the critical wind speed for the vortex induced resonance is close to that for the  quasi steady galloping, a kind of coupled wind-induced vibration is easy to occur on a rectangular bar, which is different from the conventional vortex-induced vibration and divergent galloping.It is a kind of “soft galloping” phenomenon that the response amplitude increases linearly with the increase of wind speed.The mass and damping are the key parameters that affect the coupling degree and the amplitude response estimation.Based on a set of models with 1.2 width-height-ratio rectangular section member, by adjusting the equivalent stiffness, the equivalent mass and the damping of the model system, contrast experiments on the wind-induced vibration responses were carried out in the following cases: the same mass with different damping , the same damping with different mass and the same Scruton number with different mass and damping combination under the condition of uniform Reynolds number.The results show that in the coupling state, the influences of mass and damping parameters on the amplitude responses of “soft galloping” are independent and the weights are the same; for the “soft galloping” amplitude response, there is a Scruton number “locked interval (12.4-30.6)”.In the “locked interval”, the linear slope of the dimensionless wind speed amplitude response curve does not change with the Scruton number.Moreover, a “transition interval (26.8-30.6)” for the Scruton number coexists, where the coupled wind-induced vibration state is transferred to uncoupled state; the empirical formula for “soft galloping” response amplitude estimation is modified, which can be used to predict the amplitude within the designed wind speed range of similar engineering members.

On the basis of generating the stationary Gaussian bridge deck irregularity by the inverse fourier transform method, the relationship between the phase angle and the high-order central moment of the random excitation process was established, and then the non-Gaussian characteristics of the bridge deck irregularity were changed by continuously adjusting the phase angle, the random excitation of non-Gaussian bridge deck irregularity with given power spectral density, skewness and kurtosis was generated by iteration.At the same time, based on the measured data of deck roughness, the stochastic process of deck roughness was reconstructed by phase modulation method.Numerical examples and reconstruction results of measured bridge deck irregularities show that the non-Gaussian bridge deck irregularities generated by phase modulation can meet the requirements of given target power spectral density, kurtosis and skewness, and the simulation accuracy is high.The area of amplitude distribution and the maximum value of amplitude increase with the increase of kurtosis, and the amplitude distribution area of the positive or negative deviation of the deck irregularity increases with the increase of the skewness.The engineering application results show that the vehicle-bridge vibration response excited by super-Gaussian bridge deck irregularity is the largest, followed by Gaussian bridge deck irregularity, and the vehicle-bridge vibration response excited by sub-Gaussian bridge deck irregularity is relatively small.The sensitivity of vehicle vibration to non-Gaussian bridge deck irregularity excitation is greater than that of bridge vibration.

Resonance demodulation is one of the most advantageous methods in rolling bearing diagnosis, but the determination of demodulation frequency band is always a huge challenge.In order to solve the problem that the traditional kurtogram based methods can’t identify the optimal resonant frequency band to perform the envelope analysis under the condition of complex interference, a new adaptive resonant demodulation method based on autocorrelation spectrum kurtogram was proposed.The kurtosis of autocorrelation spectrum of the squared envelope of a filtered signal was used as an index to generate a new kurtogram.The validity and superiority of the method under complex working conditions were verified by the experimental signals of a high-speed railway bearing under three different working conditions of no-load, static load and dynamic load and also by a railway truck bearing experimental signal.The proposed method performs a high engineering application value.

The way for accurately describing the vehicle vibration response affected by the track was studied by fully considering the influence of track circuit.Through analysing the constraint relation of the track and the topological structure of the driving system, a complete dynamic model of the tracked vehicle was established.The track circuit model was established based on the assumption of continuous elastic track, and its inherent vibration characteristics were analysed by the eigenvalue method.The power spectrum method was used to compare the results by the dynamic models of flexible track and rigid track and to verify the effect of track on the vehicle vibration.Real vehicle tests were carried out to verify the accuracy of the model.The results show that the effect of track on the vehicle vibration mainly includes the inherent vibration of the track circuit and the high frequency vibration related to the track pitch.The track vibration energy holds ten to twenty-five percent of total vehicle vibration energy in general condition.

Based on the study of the existing equivalent single particle mechanical model of a multi-particle damper (M-PD), an equivalent single particle model with an inerter (EISM) was established to consider the rolling effect of particles on the damping performance of the M-PD.The motion state of a single-degree-of-freedom structure with the M-PD under harmonic and seismic excitation was investigated by the use of the Runge-Kutta algorithm.Shaking table tests of a single-layer steel frame with the M-PD was designed and conducted.The influence of filling rate on the displacement frequency response curve of the top of the structure was explored.The principle for determining the EISM’s parameters in non stacking state was proposed, and then the experimental and theoretical verification on the EISM were carried out based on the above testing results and the analysis results by the existing equivalent single particle model.On this basis, the damping effect and energy change of the M-PD were analysed based on the EISM under different excitation, such as free vibration, harmonic and seismic excitation.The results show that the EISM can further reflect the complex damping effect and damping mechanism of M-PD, and the proposed parameter evaluation principle is more suitable for the numerical simulation of the M-PD in non stacking state.The M-PD has better damping effect under different excitation conditions, but the existing equivalent single particle model may overestimate the damping effect of M-PD with the optimal impact distance.

A superconvergent patch recovery method was presented for superconvergent solutions of the vibration mode of each order in the finite element (FE) post-processing stage of moderately thick circular cylindrical shells, and the adaptive mesh refinement analysis for free vibration based on the superconvergent solution was implemented.On a given finite element mesh, the FE solutions of frequency and mode of the moderately thick circular cylindrical shell were obtained by the conventional finite element method (FEM).Then the superconvergent patch recovery displacement method and high-order shape function interpolation technique were introduced to obtain the superconvergent solution of mode (displacement), while the superconvergent solution of frequency was obtained by Rayleigh quotient computation.Finally, the superconvergent solution of mode was used to estimate the errors of FE solutions in energy norm, furthermore, the mesh was subdivided to generate a new mesh in accordance with the errors.The above procedure was repeated until the optimized mesh was derived and the accuracy of FE solutions met the preset error tolerance.The numerical examples show that the proposed algorithm is suitable for solving the continuous orders of frequencies and modes under different kinds of boundary conditions, different circumferential wave number and different thickness to length ratio of moderately thick circular cylindrical shells.The computation procedure is reliable and effective and can provide accurate solutions.

Aiming at solving nonlinear boundary value problems(NBVPs) with variable fractional order, a novel single Bernstein sequence (SBS) where a parameter was attached to each item was proposed.The specific process for solving the problems was as follows: firstly, the SBS was constructed with the single parameter, and the variable fraction order term was transformed into a polynomial expression based on SBS.The integral in the objective function of the nonlinear boundary value problems was approximated into an analytical expression by the Gauss-Legendre integral method.Then, considering the phenomenon of multiple solutions existing in nonlinear optimization procedure, a genetic algorithm was introduced to obtain all the sub-optimal solutions at the same time.Finally, the sub-optimal solutions were taken as the initial values and the optimal solutions were obtained by using the MATLAB optimization module.Two simulation examples were provided.The results indicate that the accuracy of the method is consistent with those of Hassani, and is higher than that by using a Bernstein polynomial with the same number of terms.

The semi-active suspension with adjustable damping in the cab of a commercial vehicle can make the vehicle get better ride comfort under various driving conditions.In previous studies, the control strategy of the cab suspension was studied, taking the cab as an individual isolated body, and the control accuracy was at lower level.A ten degree-of-freedom vibration model of the whole vehicle was established by integrating all the parts of the vehicle into a whole model.Based on this, the control algorithm of the cab semi-active suspension system was explored.Considering the hysteretic characteristics of the system and the algorithm characteristics, two algorithms, the Smith-proportional integral derivative（PID）and the fuzzy adaptive PID, were proposed.The results show that the controllers based on the two algorithms can effectively restrain the vibration responses of the cab.Between them, the fuzzy adaptive PID is superior to the Smith-PID in the control of cab vibration response, the control force curve is smoother, and the peak suppression effect on its PSD curve is more obvious.All of the above results have been verified by road test.