Applied Mechanics and Materials Vols. 184-185

Abstract: Hot compression tests of AZ91D magnesium alloy were performed on Gleeble1500 ranging from 0.001 to 1 s-1 and deformation temperature ranging from 200 to 400°C. The results show that flow stress is dependent on deformation temperature and strain rates．When strain rate is a constant, flow stress decreases with the increasing deformation temperature. Meanwhile, as deformation temperature is a constant, flow stress increases with the increase of strain rate, which can be demonstrated by a Zener-hollomon parameter in the hyperbolic-sine-type equation during hot compression deformation. The hot deformation activation energy is 176.01kJ/mol and the stress exponent is 7.85 during hot compression deformation of AZ91D magnesium alloy.

Abstract: Through the thermal mechanical simulation experiment，combined with the metallographic analysis and microhardness test on the Nb-Ti micro-alloyed steel for the austenitic continuous cooling process. The results shows that: with the increasing of the cooling rate, the phase transformation starting and ending temperature decrease and the ferrite content was decreased at room temperature. In less than 5°C/s low cooling speed region, with the increasing of the cooling rate, the grain size of tested steel obviously increases; In more than 17°C/s high cooling speed region, the grain size and vickers hardness of tested steel change and tends to be smoothly.

Abstract: The reactions were carried out by decomposing acetylene at 1000 °C in a two-stage furnace system for 10 min. In the first furnace no catalyst was placed and an AAO template with the average diameter about 50 nm was placed in the second furnace whose temperature was designed to be 500 °C, 600 °C and 700 °C. The samples were characterized by scanning electron microscopy and high resolution transmission electron microscopy. The results show that carbon spheres with average diameter about 50 nm on the AAO template surface were obtained when the temperature of the second furnace was designed to be 700 °C. These carbon spheres are composed of unclosed graphene layers with an interlayer distance of 0.33–0.35 nm between the layers.

Abstract: The behavior on artificial weathering of the S320GD+Z prepainted steel sheet for construction was studied by neutral salt spray test, accelerated UV aging test. Their corrosion performance after accelerated UV aging test was investigated by electrochemical impedance spectroscope technique and atomic force microscopy. The results showed that the resistance to neutral salt spray and the resistance to accelerated UV radiation of the tested samples can meet the demands of domestic and overseas standards. After 2000 h accelerated UV radiation test, the corrosion resistance of prepainted steel sheet declined with the increase of roughness and decrease of electrochemical impedance of the coating surface.

Abstract: Polyethylene/montmorillonite (PE/MMT) nanocomposites were prepared by in situ polymerization. The crystallization behavior of PE/MMT nanocomposites at different MMT concentrations (from 0.1 to 1.2 wt %) were investigated by differential scanning calorimetry (DSC). The equilibrium melting points increase by the addition of MMT. The crystallization rates of PE/MMT nanocomposites are faster than those of pure PE. The addition of MMT facilitated the crystallization of PE, with the MMT functioning as a heterogeneous nucleating agent at lower content; at higher concentrations, however, the physical hindrance of the MMT layers to the motion of PE chains retarded the crystallization process.

Abstract: The microcellular foamed plastics (MCPs) have high material strength, a relatively small cell size, and a high cell density in comparison with conventional foamed plastics. In particular, the small size of cell in MCPs makes many applications possible in a range of fields. Its high reflectivity enables its application as a reflector that is a part of the back light unit in the LED industry. Thanks to its low density and high strength, MCPs can be used as diaphragm in speakers. They also have many other uses. MCPs show a noise suppression property which allows them to be used in the building industry. A soundproofing plate made of MCPs exhibits a better soundproofing property in comparison with a soundproofing plate made of ordinary plastic. In this study, the author manufactured a soundproofing plate using microcellular foamed polypropylene (PP) and assessed the properties of the absorbing and proofing sound. As a result, the findings showed the possibility of using MCPs as a soundproofing plate in the building industry.

Abstract: In the present paper, controlled cooling in different ways was performed using a laboratory hot rolling mill in ultra-high strength hot rolled ferrite-bainite dual phase (DP) steel. The results have shown that the final microstructures of DP steel comprise ferrite, bainite and a small amount of retained austenite and martensite. DP steel has a tensile strength ranging from 1010 to 1130MPa and yet retains considerable total elongation in the range of 14–17%. The addition of Mn and Nb to DP steel leads to the maximum ultimate tensile strength, yield strength and the product of ultimate tensile strength and total elongation due to the formation of retained austenite and granular bainite structure. Laminar flow cooling after hot rolling results in a significant increase in the quantity of ferrite and bainite due to the suppression of pearlite transformation, and as a result, the present steel possesses high strengths and good toughness.

Abstract: For a clear and comprehensive opinion on segregated SIMPLE algorithm in the area of computational fluid dynamics (CFD) during liquid processing of materials, the most significant developments on the SIMPLE algorithm and its variants are briefly reviewed. Subsequently, some important advances during last 30 years serving as increasing numerical accuracy, enhancing robustness and improving efficiency for Navier–Stokes (N-S) equations of incompressible fluid flow are summarized. And then a so-called Direct-SIMPLE scheme proposed by the authors of present paper introduced, which is different from SIMPLE-like schemes, no iterative computations are needed to achieve the final pressure and velocity corrections. Based on the facts cited in present paper, it conclude that the SIMPLE algorithm and its variants will continue to evolve aimed at convergence and accuracy of solution by improving and combining various methods with different grid techniques, and all the algorithms mentioned above will enjoy widespread use in the future.

Abstract: Fe, V and Ti of vanadic titanomagnetite in Panxi region in China have been extracted in traditional BF process so far, but the comprehensive utilization level of the ore is lower. To solve the problem, the research on direct reduction of the ore have been carried out continuely. Because of the restriction of equipment, technology and other factors, there is not a new technology can achieve mass industrial production. It is found by analysis that the BF process hold a leading position and direct reduction process can only be a supplement of utilization of vanadic titanomagnetite at presnt and days to come.

Abstract: In this paper, dyeability of Shengma fiber knitted fabric is investigated with reactive dyes in one bath process. Orthogonal analysis method is used to optimize and find the optimal dyeing process, and then reach the optimal dyeing effect.