Advanced Materials Research Vols. 295-297

Abstract: According to the loading characteristics of engine blades, a vibration bending fatigue system by using the ultrasonic fatigue test technique has been developed and the specimen is designed by finite element method, fatigue tests of TC17 between 10⁶ and 10⁹ cycles have been completed in this paper. The results show that the fatigue life of specimen increases over 10⁷ cycles and the initiation of fatigue cracks transfers from only in the surface of specimen to both in the surface and the sub-surface with loading decreasing.

Abstract: By using laser cladding technology, a nano-Y₂O₃/Co-based composite coating was prepared in the Ni-based alloys substrate with Nano-Y₂O₃ and cobalt based alloys powder. The microstructure, micro-hardness wear resistance of the composite coating were researched by scanning electron microscopy (SEM) and other testing methods. The results show that the micro-hardness of laser cladding is HV868, and the welded surfacing layer is only HV512. Wearing values are decreased by 25.6 mg of the surfacing layer to 0.5 mg of the laser cladding layer in the wear testing of 40 minutes. The wear resistance of laser cladding layer is 51 times of the the wear resistance of the surfacing layer using the Co-28Cr-4W-1C electrode. The microstructure of laser cladding layer consists of the fusion zone, the fine equiaxed dendrite zone and the coarse crystalline zone.

Abstract: The formation energy and electronic structures of Fluorine-doped ZnO have been calculated by the first principles. The calculated results show that F_i, which is easier to form under O-rich conditions, is helpful to achieve p-type ZnO. The main contribution of accept level are the hybridization between F(2p)，O (2p) and Zn(3d) states which are near the top of the valence band.

Abstract: We have performed a study on La heavily doped ZnO, based on the first principles. The calculated results show that with the increase of concentration of La, the lattice parameter is expanded. It is found that the top of valence band maximum is determined by the O-p states and the conduction band minimum is depended on the La-f and La-d states. The band gap of doping system is broadened as the increase of concentration of La, because the valence band moves towards lower energy more than the conduction band does. Furthermore, it is found that heavily doping of La with low concentration can enhance the conductivity of ZnO. The results are helpful to gain a systematic understanding of electrical properties of La-doped ZnO.

Abstract: Reliability optimization design of the gear box is proposed. It includes an objective function, 30 design variables and 52 constraints. It is important to note that material properties, geometry parameters and applied loads of the structure are assumed to be normal random variables. Reliability calculation adopts the HL-RF method. The comparison of design parameters demonstrates the proposed method.

Abstract: Micro V-groove is an important optical component in the packaging of optoelectronic devices, which holds the position of the optical fibers. The micro V-groove can be fabricated by three main techniques on different materials: wet etching, ultra precision machining and molding press. The main parameters, which determine the micro V-groove quality, include core pitch, surface roughness and cured adhesive height. In this paper, three fabrication techniques are discussed to address the future needs of the next-generation optical fiber communication technology. The advantages and disadvantages of each fabrication technique are discussed with the quality issues. The findings can be served as guides for the materials and fabrication in micro V-groove in optoelectronic packaging.

Abstract: This essay is the subject of national eleventh five support schemes: The analysis of key technology on emission reduction and comprehension utilization of solid waste from large iron ore mine (Number:2008BAB32B14). The purpose of this test is to replace natural sand with the same amount of iron tailings and find a new technology method to utilize solid waste, iron tailings, efficiently and valuably. Pre-determined cement, fly ash and cellulose ether are reasonable, which guaranteed the expected results of iron tailings instead of natural sand test .The proportion of iron tailings to replace natural sand is 0, 30%, 50%, 80%, 100%. Proportion design of M5, M7.5, M10, M15, M20 iron tailings dry mortar is determined by preliminary test. Respectively test water consumption, consistency and folding strength and compressive strength in 3d, 7d and 28d. Experiment results showed that the cementing material, PO42.5 cement made in Heng-sheng-ran Building Material Technology Co., Ltd. Beijing, has a good effect on smaller solid particles of iron tailings. After analyzing test data result, according to the provisions of “Specification for mix proportion design of masonry mortar” (JGJ 98-2000), In accordance with the principles of maximum using iron tailings and higher strength in 28d, recommended proportion of M5, M7.5, M10, M15, M20 iron tailings dry mortar has been determined. The test result will be used by actual production test.

Abstract: Aiming at the stress state in the hot-extrusion process of Mo powder, the paper has studied the 3D stress characteristics provided by the hot-extrusion of the canning. The material model is established by the finite element software DEFORM-3D. Via calculating, the load-stroke curve, temperature, relative density, the equivalent stress and the equivalent strain distribution characteristics were obtained. The results show that canned powder after hot-extrusion technology can improve its density greatly. The press load grows fleetly at early, and then slowly grows at the stable stage. Only reach last stage the press load drops quickly of the hot-extrusion. The maximum temperature and maximum equivalent strain appear below the die entrance. The maximum equivalent stress appears in the die entrance. Therefore ,the die entrance angle and the surface geometric parameters of the die have significant effects on the equivalent stress.

Abstract: In the present investigation, the in-situ powder metallurgy (IPM) method was utilized to synthesis aluminum alloy matrix composite powders containing SiC nanoparticles. Specified amounts of SiC particles (with a size in the range of 250-600 µm) together with SiC nanoparticles (average size of 60 nm) were preheated and added to aluminum melt. This mixture was stirred via an impeller at a certain temperature for a predetermined time. The kinetic energy of the impeller was transferred to the melt via the non-wetting SiC particles and resulted in melt disintegration. The liquid droplets created by this process were then solidified upon cooling the blend resulting in a mixture of Al powders and SiC particles. This blend was passed through a 250 µm sized sieve and a mixture of Al powders and SiC nanoparticles was produced which could be subsequently used as a feedstock for preparation of Al-SiC nano-composites via the standard powder metallurgy methods. The results confirmed that the surface condition (oxidized vs. as-received), amount and different proportions of the added nano-sized and micron sized SiC particles as well as the chemistry of the metallic charge (CP aluminum or Al-1wt.%Mg) affect the size distribution and yield of the resultant sub-250 µm sized powders. The scanning electron microscopy (SEM) studies revealed that Al/SiC composite powders containing nano-sized SiC particles could be produced by using Al-1 wt.% Mg as the matrix alloy.

Abstract: In order to solve the active vibration control of piezoelectric smart structures, focus problems on the structural analysis of the dynamic characteristics. To piezoelectric smart structure for the research object, finite element modal analysis, solving the natural frequency and response characteristics. Firstly, analyzed the problems of structural eigenvalues ​​and eigenvectors problems, then prepared dynamic response analysis program of FEM based on MATLAB, and complete the theoretical model calculations. At the same time, using ANSYS software to simulate and analyze, theresults show that, ANSYS simulation result is consistent with the theoretical value, so as to study the piezoelectric active vibration control of smart structures and lay a good foundation.