A novel vibration isolation method using a plane grid structure is presented to meet the special demand of high-performance vibration isolation of microvibration in spacecraft. The vibration of the coupled system, which consists of the vibration source, the grid structure and the flexible support, is modeled and analyzed. The out-plane vibration equation of the grid structure in the frequency domain is obtained by using the substructure mobility synthesis principle. Based on the assumption that the coupling between the string and the beam is unidirecional, a complete description of the vibration of the beam is achieved by decomposing the dynamic tension force of the string in the vertical and horizontal directions. The vibration transmission characteristics are analyzed in terms of the synthesized model and an experimental platform is set up to verify the isolaion performance of the grid structure. The results have shown that the grid-structure is effective in vibration isolation and more than 20dB attenuation in transmission can be achieved.

On the basic of impact tests, we analysed the Load-Deflection information of the molded pulp products in the impact height of 30cm, 50cm, 80cm and under the relative humidity of 50%,65%,80%,90%. Meanwhile the nominal stress-strains curves and the energy absorption curves were established. The experimental results show that: under a certain impact height, with the increase of relative humidity, the nominal stress-strain curves move to the downward, the elasticity modulus and buckling critical stress decrease, and the best energy absorption point offset to the lower left. When the RH increase from 50% to 65%, 80% and 90%, the average second buckling critical stress is 14%,24% and 42% decreased respectively. Under a certain RH, with the increase of impact height, the nominal stress-strain curves move to the upward, the elasticity modulus and buckling critical stress decrease, and the best energy absorption point offset to the upper right, and this effect significantly enhanced with the increase of RH. Under impact load, the molded products occur two obvious buckling.

A kind of pendulous high-g micro-machined accelerometer is designed. Cruciform torsion beam is applied to reduce cross-axis sensitivity, and comb structure is used as stop and damper. The micro-structure parallels 6 sensing units to improve initial capacitance. Based on finite analysis, the micro-structure’s natural frequency is about 56 kHz with modal separation ratio more than 4. It could resist 1E5 g shock acceleration and the micro-structure’s sensitivity is 8.94E-6pF/g. The accelerometer’s fabricated by SOG technology, and its single-side initial capacitance is about 3.6pF. Measurement bandwidth of ring diode capacitance detection circuit is analyzed and high g accelerometer’s detection circuit is designed. Calibrated by Hopkinson bar, the accelerometer’s nonlinearity is 2% of 2E4 g range, and scale factor is about 24.5μV/g with 5V supply.

In-line and cross-flow vortex-induced vibration(VIV) of a circular cylinder is simulated using CFX software, including mass ratio of 7 and 3.24. The lock-in, beat and phase switch phenomena were caught and effects of mass ratio on VIV were discussed. The results show that fluid-structure interaction(FSI) should be considered in the analysis of VIV of a cylinder. The range of lock-in, the maximum transverse amplitude and the velocity to achieve lock-in in the mass ratio of 3.24 are larger than that in the mass ratio of 7.The frequency of in-line VIV is always twice of that of cross-flow VIV when the mass ratio is 7. However, when the mass ratio is 3.24, the frequency of in-line VIV is twice of that of cross-flow VIV in the lower velocity reduction (Ur≤4). And there are two values in the higher velocity reduction, one is twice of frequency of cross-flow VIV, the other is close to that of cross-flow VIV.

Capturing the target successfully is the key to accomplish the on-orbit service task such as space station assembling, satellite maintenance and refueling in the future. The end effector based on the wire rope has the properties of big tolerance and soft capturing, so it has a definite advantage to capture the spacecraft which is of large inertia and high speed. In this paper, we build the dynamics model of the rope using the 6 dimension spring flexible connection based on the discretization method, introduce the contact force between the rope and the target to obtain the capturing dynamic model of the end effector. This model fully considers the process of contact-impact between the wire rope and the target. Because having the ability to predict and prevent the impact brought by the capturing process, it is not only a meaningful explore in designing of mechanism and controller, but also an effective supplement for the physical experiment to solve the problem that it is difficult to do the ground test of the space large target capturing task for China in the future.

Load identification method is applied to force measurements in impulse combustion facilities. The dynamic model of the testing system is derived using substructure synthesis method. Then, the differential equations are discretized to establish the linear relationship between the outputs of balance and the dynamic forces history acting on the aircraft model. A hybrid regularization method which combines the Tikhonov regularization and subspace projection methods is proposed to solve the load identification problem. The hybrid method converts the ill-conditioned large scale problem into a well-posed small scale problem which can be solved easily. A new method is proposed to determine the size of the projection subspace. The L-curve criteria is employed to search the optimal regularization parameter of the dimensional-reduced problem. The accuracy of the structural dynamic modeling method and the effective and stability of the load deification method are validated by a numerical example.

It shows that determination of damping matrix in the dynamic time-history analysis method strongly affects the seismic response of complex engineering structures, and the safety related structures of nuclear power plant in dynamic analysis usually adopts the dynamic time-history analysis method. To study the effect of determination of damping matrix on the seismic response of nuclear power plant structure, we consider the proportional damping fitting accuracy of nuclear power plant structure, and the influence of different shape of structure based on structural damping, to set up a more precise model, an equivalent proportional damping model. Furthermore, a corresponding method of the seismic response analysis of the nuclear power plant structure is proposed by taking consideration of structural vibration characteristics, which is, determining the proportional damping coefficient by weighted least square fitting method. The application and analysis show that the method is more consistent with the exact solution than the method with traditional damping coefficient, and it is suitable for the seismic response of nuclear power plant structure.

Under Bi-directional horizontal seismic load, coupling seismic response of structure would seriously weaken the cylinder deformation capacity and ductility of structure damage, intensified the structure damage. This paper introduces seismic incidence angle to simulate the more objective, effective horizontal seismic excitation that structure may encounter, based on the traditional IDA method, using the Latin hypercube sampling method to consider the common influence of seismic intensity and seismic incidence angle on the structure, the Multi-component Incremental Dynamic Analysis (MIDA)method was introduced. Based on the MIDA method, dynamic time history analysis was carried out on the reinforced concrete core walls according the finite element analysis software Perform-3D, the MIDA curves were obtained to reflect the structural seismic performance. The four limit state points of structure were defined according to the MIDA curves based on the performance, Corresponding seismic fragility curves of reinforced concrete core walls was obtained, and vulnerability performance of the structure can be analyzed and evaluated.

An application of generalized harmonic wavelet in the response determination of nonlinear stochastic dynamic system is developed in this paper. Specifically, first, based on the wavelet expansion of the nonlinear differential equation and the newly developed wavelet connection coefficients, the dynamic differential equation is converted into a set of nonlinear algebra equations. Next, the Newton’s method is utilized to solve algebra equations. Finally, according to the relationship between the time-varying Power Spectrum Density (PSD) and the wavelet coefficients, response PSD is therefore obtained. Pertinent numerical simulations demonstrate the reliability of the proposed technique.

In this paper, a nonlocal viscoelastic sandwich-beam model is developed to investigate the dynamic stability of a pulsating-fluid-conveying carbon nanotube (CNT) embedding in linear viscoelastic mediums. The classical Euler-Bernoulli beam model is modified by considering the effects of surface elasticity and surface residual stress induced by thin surface layers presented on the inner and outer tube surfaces and nonlocal effect. The governing equation is solved via the averaging method and the stability regions are obtained. Numerical examples are presented to reveal the complicated influences of tube thickness, viscoelasticity, surface effects and two medium parameters on the dynamic stability of the CNT. The conclusions drawn in the present paper are thought to be helpful for the structural design and vibration analysis of nanofluidic devices.

In terms of the non-stationary systems existed in engineering systems, cointegration model can be established only when the system variables are integrated of first order. The cointegration coefficients matrix is proposed as the characteristic parameter of non-stationary system fault diagnosis. System variables have to be verified integrated of first order through unit root test, then use Johansen method to estimate the cointegration coefficients matrix, which can be used as the diagnosis characteristic parameter. The classification algorithm of supporting vector machine (SVM) is used to train the model and test the accuracy of classification. Thus, a new approach applied in non-stationary system is established towards finding a new characteristic parameter of fault. This new approach is applied to the fault diagnosis of a simulated hydraulic flap servo system, 5 system variables including input orders, flap angle, etc. are used as the cointegration variables. The test results indicate that the cointegration coefficients matrix model has great fault diagnosis ability in a typical non-stationary system.

The need suppress aerodynamic noise in open cavities represents an important problem in aeronautical applications. Acoustic field of the standard cavity model is simulated by using the non-linear disturbance equations and synthetic reconstruction of turbulence based on the RANS equation. The reliability of the method is validated by comparing the result with the experimental data. Based on this, the impact of passive control measures of baffles on cavity turbulent kinetic energy, velocity profile, sound source distribution, pulsating pressure distribution and spectrum characters are also analyzed. The analysis indicates that, the strength of the sound source cannot be reduced only by altering the direction or intensity of the shear layer, the maintaining of the stability of the shear layer is also required to influence the distribution and strength of turbulent kinetic energy and sound source, so as to reduce the flow oscillation effects. The results show that the passive control measures can effectively decrease the cavity aerodynamic noise , which have a certain value in engineering applications.

The simulation and optimization method for an internal combustion engine was proposed, which was used to evaluate the interior noise change before and after the engine noise optimization. The finite element models of the engine and dash panel were constructed and validated by modal analysis technology. The flexible multi-body dynamic method was employed to calculate the engine vibration response with which the structural radiated noise was obtained via boundary element codes. Then, optimal design of the block was implemented to improve its stiffness and separate global modal frequencies and excitation peak frequencies, which aimed to decline the structural response and radiated noise. The acoustic coupled model of the engine and dash panel was constructed to calculate the acoustic power transmitted from the engine surface through the dash panel before and after the block optimization. The results show that the optimal scheme for the block substantially lower the structural radiated noise, as well as that for the engine. The acoustic transfer path between the engine and interior noise finds that the interior noise is distinctly reduced, which proves the feasibility and effectiveness of the optimal design.

An approach is presented to study dynamical buckling of stiffened plates. The stiffened plate is divided into one plate and some stiffeners, with the plate analyzed based on the classical thin plate theory, and the stiffeners taken as Euler beams. Assuming the displacements of the stiffened plate, the Hamilton principle and modal superposition method are used to derive the eigenvalue equations of the stiffened plate according to energy of the system. Finally, numerical examples of simply supported stiffened plates are presented to study the critical loads with the initial geometrical imperfection considered. Detailed discussion on how the initial geometrical imperfection, the number and the flexural rigidity of stiffeners influence the critical load is carried out. The results show the 1st mode shape of the initial geometrical imperfection has a great effect on the critical load, and the increase of the number and the flexural rigidity of stiffeners can strengthen the dynamical buckling capacity. These conclusions can also provide references for engineering design.

Based on a φ100-mm-diameter split Hopkinson pressure bar with confining pressure apparatus, cyclical impacting with confining pressure of 4 MPa and 20 MPa for sandstone specimens were performed as well as uniaxial impact tests. Meanwhile, the ultrasonic longitudinal wave test was executed before and after each impact. The stress-strain properties of sandstone under cyclical impact were analyzed, whose relationship with longitudinal wave velocity (Vp) in sandstone was analyzed based on impact damage defined by Vp as well. The yield-elastic-ratio was defined to analyze the elastic-plastic characteristics of sandstones under confining pressure. The results show that, the stress-strain curves under confining pressure present a typical elastic-plastic feature. With the increase of cyclical impact times, yield stress and peak stress of sandstone sample reduce while yield strain and peak strain increase. The accumulative damage under lower confining pressure is apparently higher than that under higher confining pressure. The cyclical impact damage of sandstone shows an obvious confining pressure effect. Results of this paper have a guiding significance to the underground construction and protection.

Based on hopkinson bar (SHPB) experiments, for some aviation organic glass materials and fragile projectile composite materials by the mixture of metal and sulfur, getting two materials dynamic mechanics parameters under different strain rate. According to the experimental data fitting, getting the Johnson - cook intensity model materi-als parameters of fragile projectile and aviation organic glass, And verifying the parameters with the use of numerical simulation. On this basis, on the use of AUTODYN - 3d finite element program, the whole process of the fragile projec-tile with different warhead forms impacting aviation organic glass is numerically simulated. Through comparing crush-ing effect of the projectile and the damage effect of aviation organic glass, analyzing and summarizing some laws. The results show that: the composite material has good effect of fragile; the crushing effect of empty pointed fragile projectile is better than that of ordinary fragile projectile, and the damage effect of aviation organic glass by the former is less than that by the latter, the empty pointed fragile projectile is more in line with the actual application than the other.

According to the configurationally characteristics, a bearing-gear coupling non-linear dynamics model of two-stage split herringbone gear trains used on special equipment will be presented, and this model includes bearing stiffness, mesh stiffness，mesh errors and gear backlash. Then the Runge-Kutta step-by-step integration method will be used to solve the non-linear differential equations of motion of a two-stage split herringbone gear train, and the time travel curve and frequency spectrum of the dynamic meshing force and dynamic bearing force can be obtained involving random mesh stiffness and mesh error excitations, and further, the statistical characteristic of them can also be obtained by Monte Carlo simulation to analyze the influences of the discrete degree of random mesh stiffness and mesh errors on dynamic mesh force and dynamic bearing force. The research results lay a foundation for the dynamic optimization and dynamic reliability optimization of two-stage split herringbone gear trains.