Abstract: A special grinding device is designed to solve the problems of the shape precision, surface quality and grinding efficiency. The device is based on the sine generator and triaxial speed to achieve the ideal Grinding trajectory. The accuracy of grinding in spherical valve core & surface quality is assured and improved by three-dimensional elastic support, pressurized floating contact and auto centering device in core and lapping tools. The grinding efficiency is highly enhanced by using the lateral and vertical speeding workpiece installration and the automatic control. The device is worth widely being applied to achieve a good large diameter hemispherical workpiece grinding.
Abstract: The steady temperature distributions in a ceramic / metal composite FGM plate with temperature-dependent material properties during heating process were investigated by the NFEM. From numerical calculation, when T0=300K, Ta=650K and Tb=1 700K, the temperature distributions in the composite FGM plate were obtained. The results are as follows. With the increase of the FGM gradient layer thickness and when M=1, the temperature distributions in the composite plate are more reasonable. With the increase of porosity, the variations of the temperature curve become big obviously, and there is an abrupt change for the temperature at =0.5, its value is about 917K, but the temperature curve is gentle and smooth at the bonding interfaces of the three-layered composite FGM plate. Compared with the nongraded two-layered ceramic/metal composite plate, the temperature of the ZrO2/FGM/Ti-6Al-4V composite plate is very gentle. When the temperature dependency of the material properties was considered, the temperature in graded three-layered composite FGM plate becomes small obviously. The results provide the foundations of theoretical calculation and the further analysis of thermal stress for the design and application of the composite plate.
Abstract: Activated carbons were prepared through chemical activation of waste particle board (WPB) precursor using potassium hydroxide as the chemical agent. The effects of different parameters, such as chemical/WPB ratio, activation time and activation temperature on yield and the methylene blue adsorption capacity of activated carbon were investigated. Experimental results indicated that the optimum conditions were as follow: activation temperature 850°C, KOH(50% concentration)/ WPB 4.0, activation time 50 min. Amount of methylene blue adsorption, Iodine number and the yield of activated carbon prepared under optimum conditions were 15.0 mL/0.lg, 1213mg/g and 36.9%, respectively. Therefore, great potential exists for developing activated carbon products from waste wood, which will have the positive effects of reducing our landfill problem and gain attractive products.
Abstract: Pyramid shaped pyrolysis flame is a new method for carbon nanofibes (CNFs) synthesis. Oxy-acetylene flame outside the frustum of pyramid shaped reactor provides the necessary high temperature environment, while CO is used as the source of carbon, iron pentacarbonyl (Fe(CO)5) as the source of catalyst precursor in reactor. Inside, the mixture of CO, H2, and Fe(CO)5 will burn incompletely after initial reaction under high temperature. Inserting a sampling substrate into the incomplete burning flame can gain CNFs. Field emission scanning electron microscope (FE-SEM) was used to illustrate the results of experimental. By adjusting the distance between the oxy-acetylene flame jet and the synthesis zone, studied the effects of pyrolysis and synthesis temperature. The preferable pyrolysis temperature in experimental is about 693°C while the synthesis temperature is about 595°C, and preferable synthesis temperature is about 535°C while pyrolysis temperature is about 1000°C. It can be also concluded that when the synthesis temperature is high (595°C, comparing with 535°C), preferable pyrolysis temperature is low (693°C, comparing with 1000°C), vice versa. Effects of sampling substrate were also studied. Using 304 stainless steel wire as sampling substrate can not gain CNFs, while 201 stainless steel plate can gain straight and uniform, and silicon chip can gain curly ones.
Abstract: The aim: quantitatively evaluate the response of climate change upon the sustainability of the agricultural production. The method: the paper selected two regions (Hubei and shan’xi province) which represented different climate environment, utilized modern statistic data, Principal Component Analysis and multivariate linear regression to quantitatively evaluate the influence of climate change upon agricultural production through isolating climate environment from arable area, land utilization and management and landform and so on. The conclusion: The study indicated that when environmental condition turned good to agriculture, the function of environmental condition to agriculture relatively decreased; the capability of agricultural society and production decreased too, and people could select the land to cultivate, where agricultural productivity is higher. And that when environmental condition turned bad to agriculture, the function of environmental condition to agriculture relatively increased; the capability of agricultural society and production increased, too; people could not put emphasis on the land where agricultural productivity is higher, whereas focused on productivity per capita.
Abstract: poly(N-isopropylacrylamide) (PNIPPAm) is a thermally sensitive polymeric material which exhibits large volume transition at temperatures around its lower critical solution temperature (LCST). To get a thermosensitive semi-Interpenetrating Polymer Networks(semi-IPNs), N- isopropylacrylamide (NIPPAm) was dispersed and synthesized with different crosslinking agent amount in thermoplastic polyurethane(TPU) solution. The resulting films were characterized in terms of swelling ration, surface contact angle, and scanning electron micrograph (SEM). The results showed that filming medium has great affect on the structure and swelling of PU/PNIPPAm composite film and the amount of crosslinking agent influents the miscibility of PU and PNIPPAm. Ethanol as filming medium makes the phase separation behavior of PNIPPAm insignificant in the films.
Abstract: Polishing is a manufacturing process for surface-smoothing. To minimize surface damage and defects, gentle polishing conditions are required. The main objective of this research is to determine the effect of polishing conditions by using Taguchi method , and to optimize the process parameters to obtain the best surface possible. The experimental results indicate that a set of optimal polishing conditions for producing work surface within the range of parameters evaluated, double oblique polishing path, relatively high speed and low feed rate are desirable for improve surface.
Abstract: In order to solve the existing problems such as the less-plump corners and wrinkle during the forming process of a double curvature thin-wall part. Material parameter formulas are calculated based on Hill 1948 anisotropic yield criterion and flow rule. The material mechanical property parameters of 2A12 are obtained using uniaxial tensile experiment. Single factor test method is used and LS-DYNA is applied to conduct finite element analysis. So the influence law of holding force, blank shape and blank size imposed on the finite element model are calculated in sequence. On the basis of these laws, that the blanking force, blank dimension and blank shape are decided. Stamping die for the experiment model is designed and made, deformation measurement technology of coordinate grid circle is used to carry out strain analysis. From the comparison result between experiment and simulated data, it can be seen that Hill 1948 yield criterion and flow law can better solve the formability of 2A12 sheet.
Abstract: Owing to setting viscosity of lubrication oil as a constant value will lead errors in hydrostatic bearing calculation, the influence of cavity depth on load capacity of heavy static bearing is analyzed in variable viscosity condition. Firstly, viscosity-temperature equations of oil film are established; secondly, viscosity-temperature curve is fitted by B-Spline; finally, using finite volume method, hydrostatic pressure field and dynamic pressure field of heavy hydrostatic bearing is calculated with different cavity depth at the same velocity, and influence of cavity depth on load capacity is revealed. The results show that, were the cavity depth shallow enough(≤2mm), hydrostatic pressure and dynamic pressure of cavity would decline rapidly with the cavity depth increasing; whereas, were cavity deep enough(≥2mm), hydrostatic pressure and dynamic pressure of cavity would change little with the cavity depth extending. This numerical simulation reflects real distribution of bearing pressure appropriately, and provides a theoretical basis for hydrostatic bearing design and lectotype.
Abstract: With the ESE module of FIRE software, this paper establishes the diesel engine model of 4100, and verifies the correctness with the test result. Based on this, the paper carries on a simulation on three high proportions of DME-diesel D65, D75 and D85, and makes a contract with diesel on the mean pressure, mean temperature, mass fraction, accumulated heat release, as well as the mass fraction of NOx and soot. The result shows that the higher proportional, the lower mean pressure in-cylinder. Also the result shows that NOx growth will come to a “freezing period” when it comes to a certain temperature, while soot growth is growing first and oxygenated later, and with the increase of DME proportion, NOx grows later and its mass fraction is lower. Besides, the mass fractions of soot of three kinds of mixed fuels are far below diesel’s, D85’s is the lowest.