Applied Mechanics and Materials Vols. 668-669

Abstract: The original method of electrochemical sedimentation of ultra-dispersed graphitefrom the colloid mixture on the polystalline copper cathode is designed.An interfacetransition region of several microns thickness is formed. Formation of electric potentialbetween the copper substrate and the graphite layer is observed. A mechanism of this effect is studied using the computer quantum mechanics simulation. A high level of precision cannot be maintained over large areas, so that large-area devices are currently difficult to fabricate. By contrast, we have noted that the dielectric elastomer actuators themselves set the gap, so that the gap can be formed in only a single step, film deposition on a flat surface. By using monolithic polymer substrates, one should be able to make large-area arrays of dielectric elastomer actuators.

Abstract: The thermal reaction kinetics of fly ash cement pastes were studied by Differential Scanning Calorimetry (DSC) and Thermal Gravity Analysis-Differential Thermal Gravity (TG-DTG) method, the kinetics parameters such as apparent activation energy was calculated by the Kissinger method, and the physical parameters were obtained. The result show that the fly ash cement pastes performance three endothermic reaction stages at different heating rates, peak temperatures of each stage at the range of 91.85~121.08°C, 453.93~496.48°C, and 680.21~751.62°C. TG-DTG show there were three thermal decomposition stages, thermal dehydration reaction apparent activation energy of fly ash cement pastes in each stage were 47.23kJ/mol, 128.84kJ/mol, and 134.07kJ/mol.

Abstract: Mg_xZn_1-xO films with hexagonal structure are prepared by radio frequency (rf) magnetron sputtering on Si substrate. The refractive indices and absorption coefficients of these films in the wavelength range from 300 to 800nm are determined by using ellipsometry at room temperature. The results show that the refractive index increases as the wavelength decreases in the transparent region (400-800nm). It reaches its maximum value around 340nm and 331nm, which is close to the fundamental absorption edge. Then the refractive index decreases as the wavelength gets shorter. The value of the refractive index is also a function of the Mg content. The higher the Mg content is in the film, the smaller the refractive index of the film is in the wavelength range from 330nm to 850nm. The band gap energy of the Mg_xZn_1-xO film is obtained by analyzing its absorption spectrum. An increase in the Mg content causes the fundamental absorption edge to shift toward shorter wavelength. In addition, UV and strong blue emission have been observed when the Mg_xZn_1-xO film is excited with light wave of 260nm at room temperature, and the emission mechanism is discussed.

Abstract: In this paper, metallographic examination, visual examination and scanning electron microscopy were used to analyze the perforation failure of the differential pressure transmitter impulse pipe. Macrostructure and microstructure of the hole, corrosion characteristics, and corrosion products were studied. Combined with the service conditions of natural gas pipe, relationship between the pipe material quality and the formation process of the perforation failure was determined utilizing fracture mechanics and corrosion analysis. The perforation failure may be caused by the defects and stress corrosion.

Abstract: The choice of materials and the design of device structure of the quantum dot light emitting diodes were investigated. The electron blocking layer or the hole injection layer was added into the fundamental structure. The results of theoretical analyses showed that the improved device structure can regulate the potential barrier height and the injection efficiency of the holes and electrons. In this way, the concentration of the holes and electrons can reach to a certain balance in the quantum dots layer, which consequently decreases the influence of the Auger quenching process and the luminous efficiency will be improved.

Abstract: Bolt load in a bolted connection directly influence the safety of a design in regard to both static and fatigue loading as well as in the prevention of separation in the connection. When the separating force is applied off the bolt center, although the materials for the bolted joint remain in the linear elastic range, the interface contact area between the clamped plates is sensitive to both the magnitude and the location of the separating force. This often causes nonlinear variation of the bolt load, the deformation etc. An analytical model is proposed to obtain the expression for the nonlinear bolt load under a separating service load. Finite element modeling is used for evaluating the accuracy of the proposed model.

Abstract: For the internodal absolute permeabilities of flow in heterogeneous porous media, the most popular method is harmonic means, but it has been known that the harmonic mean method underestimate the flux of the single phase steady flow, especially for the strong heterogeneities. Based on the power-law behaviour of pressure, a finite analytic numerical method is proposed for two phase incompressible flow in 2D heterogeneous porous media. Numerical example shows that the finite can obtain more accurate value than traditional numerical methods such as the harmonic average method and so on, for different permeability distributions, only with or subdivisions can provide rather accurate solutions while traditional numerical methods need very small scale grids.

Abstract: This paper discusses an optimal algorithm for distributing tyre force by an analytical multiplier penalty function method with which the maneuverability and stability of the four-wheel independent driving vehicles can be improved. Based on hierarchical method, the controller is divided into the upper level and lower level one. In the upper level controller, the yaw moment is calculated by sliding control to track the desired yaw rate. In the lower level controller, the analytical multiplier penalty method is utilized to distribute the yaw moment to tyre forces according with equality constraints of yaw and longitudinal acceleration. Simulation was conducted with Matlab/Simulink and Carsim. Simulation results show that the proposed method is effective.

Abstract: To obtain a prediction model of the equivalent parameters of cylindrical fixed joint, a model based on the micro-element cylinder method was proposed. Although the model based on the micro-element plane method could achieve the goal we wanted to some extent, there was a limitation to the characterization of vector direction and microscopic angle of cylindrical fixed joint; the prediction model of equivalent rotating contact stiffness and equivalent axial contact stiffness based on the micro-element cylinder method was more consistent with the actual contact state of cylindrical fixed joint, consequently, it made up for the shortage of the micro-element plane method; finally, the prediction model was successfully applied in the project, and the feasibility was verified. A new effective way for solving the similar problem is opened up by the model and it also lays a theoretical foundation for the following study of dynamic characteristics.

Abstract: According to the special technology requirement of conjugate cam beating-up mechanism, this paper introduce the motion law which acceleration curve is a combination of trigonometric functions and linear. Detailed analysis and study on this motion law property are given in this paper with the help of computer software programming.