Advanced Materials Research Vols. 217-218

Abstract: FPGA has been used in CNC system, it can achieve the impulse, the count, arithmetical operation, I/O interface and so on, and therefore it can greatly simplify the design of control circuit. In this special structure mechanism, the processing and monitoring of CNC system based on FPGA instead of traditional MCU is implemented. The overall structure of reconfigurable CNC system is described, meanwhile, the DDA accurate interpolation and the control circuit of stepper motor is emphatically solved through Using the FPGA. With the result of several experiments, the performance of the CNC system is improved, reconfiguration is strengthened, besides, the peripheral interface devices and cost is greatly reduced.

Abstract: Based on technology of multi-resolution wavelet analysis, a simulating method for velocity signals of blasting seismic waves was put forward. The simulation signals not only represent main characteristic parameters of blasting seismic waves, but also consider action of several dominant frequencies of sub-bands with large energy proportion. It is indicated by comparing structural dynamic response to simulation signals and measured signals that the method for simulating blasting seismic signals based on technology of wavelet analysis has great practical value and feasibility.

Abstract: polycarbonate (PC), polyethersulfone (PES) and a multi-block random copolymer of PES and PC were blended. It was found that the interfacial adhesion was enhanced, the size of the dispersed phase was reduced and PES and PC formed an interlocking structure with the copolymer, which suggest the addition of the compatibizer may improved the miscibility between PES and PC, and result in the improvement of the mechanical properties of the blends. The compatibility behavior of PES with PC was examined using differential scanning calorimeter (DSC), scanning electron microscope (SEM) and SAXS.

Abstract: A series of random polysulfone/polyethersulfone (PSF/PES) copolymers were synthesized by the polycondensation of 4, 4'-isopropylidendiphenol, 4, 4΄-dihyolroxy diphenyl sulfone and 4, 4'-dichlorodiphenyl sulfone in the presence of K2CO3. We obtained a series of copolymers by changing the molar ratio of 4, 4΄-dihyolroxy diphenyl sulfone and 4, 4'-isopropylidendiphenol (it was marked as the ratio of S:A). The copolymers have the similar solubility with polyethersulfone. They also have high glass transition temperatures (Tg: 199°C~229°C) and 5% weight loss temperatures (4, 4'-isopropylidendiphenol: 4, 4΄-dihyolroxy diphenyl sulfone=1:1, Td5=497°C). At the same time the elongation at break is much higher than that of PES, while the tensile strength is a little lower than that of PES.

Abstract: The blends of Polyethersulfone (PES) and MCM-22，49，56 were prepared by melt mixing in a Brabender-like apparatus. The specimens for measurements were made by compression molding under pressure and then were water-quenched at room temperature. The miscibility behavior of PES and MCM-22，49，56 was examined using differential scanning calorimeter (DSC), scanning electron microscope (SEM), and density.

Abstract: The purpose of this paper is to study the methodology on structural optimization of inertially stabilized platform (ISP). It is difficult for the ISP structure design since lots of objects are required and many of them are conflicted each other, hence structural optimization should be carried out to seek a compromise between theses contradictions, such as high stiffness and light weight, high ratio of payload to mass and small size, etc. In this paper, first of all, an optimal configuration of 3-axis gimbals assembly is determined on the basis of analysis on the operating environment; and then, an approving structure is eventually obtained with the help of 3D CAD modeling and FEA. The structure is compact as well as lightweight. FEA results show that its strength and stiffness are both satisfied with the requirements.

Abstract: The ground-state lattice constants, bulk modulus and six independent elastic constants of β-Si3N4 have been calculated through the framework of density functional theory within the plane-wave pseudopotential method. The quasi-harmonic Debye model, by means of total energy versus volume calculations obtained with the plane-wave pseudo-potential method, is applied to the study of the thermal, elastic and vibrational effects. In the temperature interval 0--1800K, the calculated results agree reasonably with numerous experimental and theoretical data. Other thermal outcomes gained from this method provide overall predictions accurately for the temperature and pressure dependence of different quantities such as the thermal expansion, heat capacity and Debye temperature. The variations of Debye temperature ӨD with temperature are analysed, which show the temperature has hardly any effect on ӨD. Therefore, the present study indicates that first-principles combined with quasi-harmonic Debye model is an effective way to stimulate the behaviors of solids at simultaneously high temperature and pressure.

Abstract: Microstructure observation by optical microscope and numerical simulation by MSC software were performed to study the reason of ring crack at the bottom of the extruded magnesium alloy tube. On this basis, the effective protective measures were proposed by numerical simulation analysis. The result shows that: there is a significant difference between the direction of backward extrusion metal flow and the direction of the original metal flow direction. Therefore, the plastic deformation is difficult, and then the crack initiates owing to severe stress concentration. Through simulation analysis, it is found that both increasing the bottom thickness and changing the bottom position could effectively prevent the crack.

Abstract: The experiment of laser alloying on the surface of P20 steel was made. Tungsten carbide (WC) powder was used as alloying material. The microstructure and property of laser alloying layer and nitriding layer are studied. The research showed that laser alloying layer had better properties such as minute crystals, deeper layer, higher hardness and good metallurgical bonding with base metal. The average hardness of alloying zone was 600HV0.2. The average hardness of phase-change hard zone was 450HV0.2. P20 steel was widely used in the field of plastic mold manufacture, especially mold core and cavity. Abrasion, corrosion and pressure resulted in change of mold size and shape which could greatly affect molding precision. Using laser alloying, the good wear layer would be made on the surface of p20 steel and would greatly increase the mold useful life.

Abstract: This paper was focus on the technical parameters matching model of laser direct metal deposition（DMD）forming. Based on a series of DMD forming experiments, the energy balance equation of laser power, beam radius, powder feeding velocity and scanning velocity was established which could provide a theoretical principle for parameter selection and optimizing.