Any domain can be discretized with a mesh of arbitrary n-sided ( ) Polygon Scaled Boundary Finite Elements （PSBFE） through Delaunay triangulation automatically. Compared with previous literatures based on SBFEM, PSBFE retains the characteristics of SBFEM in accurately representing orders of singularities at the crack tips yet is more general and flexible in modeling complicated structures and its crack propagation. In this paper, PSBFE is for the first time, applied to the dynamic interactions between the crack and inclusions in composite material. The numerical result of stationary cracks under dynamic load is found consistent with available data in literature. Next, a local remeshing scheme is employed to simulate the dynamic crack propagation. The numerical results demonstrate the shielding and amplification effects of stiff and soft inclusion respectively. It is found that the sizes and positions of inclusions will also affect the dynamic stress intensity factor. The larger and close the inclusion is, the more effect it will has.

 

A methodology is developed for eliminating the transducer mass loading effects (TMLE) from time-domain response in this paper. By utilizing the measured free vibration response, the modal parameters including the effects of transducer mass loading are firstly identified by the eigensystem realization algorithm. Then, the initial finite element model of the target structure with the transducer mass loading effects is updated with the experimental modal parameters, and the changes of modal parameters with and without transducer mass are predicted with the updated finite element model by removing the transducer mass. After that, a set of identification equations for eliminating the TMLE are set up based on the modal superposition method, and the TMLE are eliminated from the original measured time-domain response with the previously predicted changes of modal parameters. Finally, the proposed methodology is verified through the dynamic test carried out for a laboratory beam with clamped-clamped boundary conditions.

 

In order to meet the practical needs of damage assessment of the steel-concrete composite beams (i.e. the composite beams in short) subjected to blast loading, tests of carrying load capacity of the composite beams were conducted compared with reinforced concrete beams. The carrying load capacities and failure features of the two kinds of beams were studied, and the experimental resistance curves and bending deformation limits as well as the resistance functions of them were obtained. Based on the equivalent single-degree-of-freedom motion equation of the composite beams, the pressure-impulse (i.e. P-I in short ) isodamage curves for assessing the damage status of them were got by means of the numerical simulation method. The research results show that the carrying load capacity, deformation limits, critical overpressure and critical impulse of the composite beams are higher than those of reinforced concrete beams, indicating that the former beams have better blast resistance.

 

The second-order directional cyclostationary is defined based on the second-order cyclic statistics.This method extend the second-order cyclic statistics which is restricted to analyze the real-valued signal to process the constructed complex-valued signal obtained from the journal bearing supported rotor system operating with oil film instability by defining Directional cyclic autocorrelation(DCR) and Directional cyclic spectral correlation density(DSCD).To verify this method, the rotation test bench was used to simulate rotating machinery fault.The analysis of the experimental data showed that the periodic vibration characteristics and rotation direction within the plane of interest can be easily discovered. Besides the slice of DSCD at the  specified frequency can show more frequency coupling information of rotor,which verified the effectiveness of the method.
 

In order to solve the mesh distorted problem, which is caused by large deformation, in simulation of linear shaped charge jet by traditional mesh based method, the self code of SPH method is applied to simulate the formation process of linear shaped charge jet and its subsequent penetration process of metal plate. The SPH method implemented in this paper can be taken as an alternative method for numerical study of linear shaped charge jet. Firstly, the numerical model of linear shaped charge jet based on experiment has been constructed and simulated by SPH method. The jet formation process of linear shaped charge has been simulated successfully by SPH method. Comparing numerical result with experiment data, the error of jet head velocity is less than 10%. Then, the jet formation processes of linear shaped charge with different liner but the same of charge mass, liner mass and width of charge cross section have been studied by numerical simulation. The penetration of metal plate by linear shaped charge jet has also been simulated. Through the numerical analysis, the forming characteristics of linear shaped charge jet, the time history of cutting width and penetrated depth of metal plate are obtained. The regularity of the formation and subsequent penetration process of linear shaped charge jet with different liner obtained in this paper can provide references for the design of linear shaped charge jet.

 

Based on the selected codes for seismic design in China and foreign countries, the difference on the classification of the site soil was compared. Considering the factors such as the return period of the earthquake and the importance coefficients of the structures, the acceleration platform and the curves of the response spectrum on different earthquake levels, namely the frequently occurred earthquake(FOE), designed fortification earthquake(DE) and the rarely occurred earthquake(ROE) for the main seismic design codes in China compared with the Code for Seismic Design of Railway Engineering (GB50111-2006, 2009 Version). It was shown that the design earthquake action at the level of FOE for the long-span bridges in high-speed rail were conservatively higher than those of other seismic design codes. The seismic actions at the level of the DE were similar to those of the seismic design codes in China, while for the ROE, the seismic actions were relatively lower. Comparison analysis on the seismic actions for long-span bridges in high-speed rail between the code (GB50111-2006, 2009 Version) and the Eurocode 8 showed that the FOE actions in China(50 years return period) were lower than those from the Eurocode 8(90 years return period), and so far as the DE action(both 475 years of return period). Results from the comparison analysis on the seismic actions coded in AASHTO and Caltrans with the code (GB50111-2006, 2009 Version) showed that the FOE actions(50 years of return period) in China were much higher than those from AASHTO and Caltrans, due to the adoption of 1.5 as the importance coefficient of structures; the maximum acceleration values of the response spectra for the DE level in China(475 years of return period) were slightly lower than those Caltrans(975 years return period), but slightly higher than those in AASHTO(1000 years return period); The curves of the response spectrum in China were similar to the curves in Caltrans, but a little higher than those in AASHTO; For the ROE(2475 years return period), the values of seismic actions in AASHTO were between the values of those from the design acceleration 0.1g and 0.2g. In summary, the design earthquake actions for the long-span bridges in high-speed rail in China were relatively conservative.
 

For investigating pull in and pull-in instability of the microstructure under the electrostatical force, a typical single-freedom electrostatically actuated MEMS sensor is considered. The delayed position feedback is applied on DC bias voltage of the system. The conditions of system parameters for reducing pull-in instability of the microstructure are discussed. And the mechanism of the delayed feedback to improve pull-in stability is investigated in detail. The threshold of AC voltage amplitude for pull-in instability in the delayed controlled system is obtained by the Melnikov method. Basing on the evolution of safe basin of the controlled system with control parameters, the effect of delayed feedback on suppressing pull-in instability is verified quantitatively. It follows from the numerical results and the theoretical analysis that the delayed feedback can be effective in reducing pull-in instability of the electrostatically actuated MEMS structure under a positive feedback gain and a short delay.
 

To precisely simulate the dynamical response of seated human body and simplify the mathematical model, a six degree-of-freedom biodynamical model is developed by combining analytic mechanics with the actual situation of each segment of human body. Equations of motion and formulas of dynamical response are presented and parameters of the model are derived from measured data of apparent mass, vertical and rotational vibration transmissibilities to the head of five individuals by curve fitting. Results shows that the model can precisely fitting the dynamical response of seated human body. Comparing to classical lumped model（a model recommended by ISO 5982（2001））and a complex biodynamical model (Tae-Hyeong Kim’s model), the model can fitting dynamical response more precisely and can present relatively intact information with simple structure. It can be used to simulate the dynamical response of seated human body.
 

This paper proposes a rolling bearing fault diagnosis method based on multivariate empirical mode decomposition-based noise assisted multivariate empirical mode decomposition (NAMEMD) and mathematical morphology. NAMEMD, as a noise assisted data analysis-based method, could effectively avoid such shortcomings of ensemble empirical mode decomposition as mode mixing and heavy computation, thus being superior to traditional noise assisted data analysis-based method to a certain extent. This paper uses NAMEMD with multiscale morphology for rolling bearing fault diagnosis. As for the method proposed, NAMEMD is used to adaptively decompose multi-component FM and AM fault signal into a series of IMF components, of which the high-energy ones are subjected to summation & reconstruction; then, a multiscale morphological difference filter is employed to extract the fault characteristic frequency of signal. In order to verify the correctness of theory, simulation experiment and bearing fault experiment were performed to compare with EEMD and envelope demodulation-based methods; according to the result, the present technique could further alleviate mode mixing effect, significantly improve the computation speed, bring about higher detection accuracy for the faults in outer race, inner race and roller in rolling bearing, and clearly extract the frequency characteristics of fault signal.
 

Based on a numerical method calculating electromagnetic force between conductors, a finite element to determine the electromagnetic force during galloping simulation of twin bundle conductor lines is incorporated into ABAQUS software by means of the user-defined subroutine. The numerical method, which is verified with a numerical example, is employed to simulate galloping of twin bundle conductor lines with different span lengths and analyze the effect of electromagnetic force on their galloping characteristics. It is reflected by the numerical results that the effect of electromagnetic force on galloping of shorter span line is very small, however, the effect on that of longer span line increases with the electric current intensity. Therefore, it is necessary to take into account the effect of electromagnetic force while investigating galloping of bundle conductor transmission lines with longer span.
 

The controllable rocking reinforced concrete frame (CR-RCF) with column-end-hinge Joints is a new type seismic-reducing structural system with special design for the column-beam joints and the application of structural control theory and technology. Based on the comparative shaking table tests of a 1/3 scale 3-story-3-span CR-RCF with column-end-hinge Joints and a same size conventional reinforced concrete frame, the dynamic characteristics, acceleration reponse and displacement response of the model structures under different earthquake levels are discussed to validate the seismic performance of CR-RCF with column-end-hinge Joints. Test results indicate that the CR-RCF with column-end-hinge Joints has a definite centralized energy dissipation mechanism, excellent self-centering capability during earthquake and it is a damage-free structural system with the main bearing component remaining intact under major earthquake.