Applied Mechanics and Materials Vols. 66-68

Abstract: The refractive index of silicon material is very high, and antireflection coatings are widely used to improve conversion efficiencies of silicon solar cells. An ideal antireflection structure should lead to zero reflection loss on its surfaces over an extended solar spectral range for all angles of incidence. Based on optical thin film theory, a multilayer structure are adopted as initial stack, and with the aid of conjugate graduate optimized method, a broadband and wide-angle antireflection is designed for using on silicon solar cell. In our design, the incident angles of antireflection coating are considered from to , working wavelength ranges are considered from 400nm to 1200nm. Within these ranges, the design results show that it can reduce residual reflection evidently in theory.

Abstract: A high-absorption of thin film system used for solar energy photon-thermal conversion is designed. Which is composed of four function parts with metals and dielectric materials. The result of design show that it has a very high absorption over 95% with wide working wavelength range from 400nm to 1000nm and incident angle from 0^o to 60^o.

Abstract: Simulated annealing algorithm is a mathematic model, which imitates the physical process of annealing. And optical thin film is widely used in many industry, To perform the functions for which they were designed, the films must have proper thickness, roughness and other characteristics. In the paper, the simulated annealing algorithm is used to determine the film optical constant It uses the transmission data through thin film over a range of wavelengths to calculate the thickness. According to the experimental results, the solution found by simulated annealing algorithm is unique and correct.

Abstract: 2205 duplex stainless steel is often welded on the surface contact of the corrosive media in projects to prevent stress corrosion in petrochemical facilities. To explore the application scope and feasibility of the solution ,two welding processes (automatic welding and manual welding), three kinds of the common corrosion environment (saturated hydrogen sulfide, magnesium chloride, calcium chloride) are studied by constant load tensile and micro-fracture analysis methods. its stress corrosion is evaluated comprehensively and the mathematical model of stress–life is established based on the experimental results. The results indicate that constant tensile load threshold s_th automatic welding is the 0.45R_P0.2, manual welding is the 0.4R_{P0.2 in saturated H2}S environment, and the difference is 17%; all the samples remain intact after 96 hours in 0.9R_P0.2 stress test of the calcium chloride environment, which shows excellent resistance to chloride stress corrosion. But the material doesn’t work well in the environment of boiling magnesium chloride solution.

Abstract: The turbulent flow in stirred tank is highly complicated and anisotropic, especially when the macro-instability (MI) are involved. In this work, the numerical simulation method of the eccentric agitation was established based on the detached eddy simulation (DES) model to study the MI in an eccentric stirred tank. The turbulent flow in the eccentrically located Rushton turbine stirred tank was numerically investigated. The rotation of the impeller was simulated by the transient sliding mesh (SM) method. The effect of eccentricity, impeller Reynolds number and impeller-tank diameter ratio were studied in order to quantify the MI frequency. PIV experiments were performed to validate the DES results and frequency analyses were applied to the obtained time series of the velocity recordings. It was found that the flow field in eccentrically stirred tank are highly unsteady and is subject to MI with varying period less than 10 blade passage period. Good agreements have been found between the DES and PIV results, both indicate that the dominant frequency of MI increases linearly with the Reynolds number, increases with the impeller-tank diameter ratio and decreases with the eccentricity. According to the agreements between the experimental and simulation results, it can be concluded that the combination of DES and SM is suitable for the prediction of the MI phenomenon in stirred tanks.

Abstract: In order to study the nonlinear jamming problem in UCAV’s flight control system, a method of using observer to check the system’s jamming was designed, constructed robust dynamic inversion control law based on jamming observer. The simulation results show that the robust dynamic inversion control law based on jamming observer, make UCAV’s flight control system have good stability and robustness, it’s a great convenience analyzing the system stability.

Abstract: For the problem that power circulation and low efficiency easily occur in closed Continuously Variable Transmission (CVT), the input-coupled CVT drive system was taken as the object of study, the fundamental structure and working principle of the input-coupled CVT drive system were briefly introduced. In the circumstances of no energy loss, the sufficient condition for the input-coupled CVT drive system to realize power split was deduced in detail. Next, the meshing efficiency expression for the 2K-H type differential gear train was simplified under the sufficient condition. The condition for maximizing the meshing efficiency of the 2K-H type differential gear train was demonstrated. Finally, the conclusion was verified by example. The results show that the condition of maximum meshing efficiency ensures the highest meshing efficiency of the 2K-H type differential gear train from the design point of view.

Abstract: For researching the strong earthquake recurrence period of Kusai Lake and Xidatan fault segment in different sliding velocities, we apply the spring-block model (or BK model) controlled by the velocity and state depended frictional constitutive. Through numerically solving the one order differential equations picturing the block (or fault segment) motion, the parameter charactering the fault segment motion is achieved. Finally, we find the recurrence period of strong earthquake is shorter in fast sliding velocity than that in slow one. The 0.1 mm changing of fault segment sliding velocity per year will make the several hundreds years of variation in strong earthquake recurrence period.

Abstract: Test material of welded AA6061 Al alloy using ER5356 (Al-Mg-Si) filler metal was oxidized inflowing air gas for 40hrs at 600oC at a total pressure of approximately 1 atm. The morphology andmicrostructure of oxide formation on welded Al alloy was characterized using SEM and EDAX.Different oxide morphologies were observed on parent and fusion metal due to the differences of thealloying element. The oxidation mechanism represented a complex reaction where the morphology andphase formation of the oxide shows the protective oxide were developed on parent metal side, whilenon-protective oxide formed on fusion metal of the welded Al alloy.