Applied Mechanics and Materials Vol. 590

Abstract: A visualization method is proposed in order to characterize the dispersion process of dust cloud in Siwek 20-L explosion device. The visualization system consists of a transparent spherical vessel, a dust dispersion device, a high precision control valve and a high-speed camera. Experiment with wheat flour powder indicate that the non-uniformity of dust cloud in space and time can be clearly distinguished based on the frame pictures, as well as the evolution of particles settlement with time after dispersion. Moreover, qualitative analysis based on picture processing technique was carried out to obtain the transmission data of dust cloud from the frame pictures. Results show that the transmission changes rapidly with time and reaches to the minimum value at about 60 ms after dispersion, and with this time, the optimum ignition delay time can be determined for dust explosion test in Siwek 20-L device.

Abstract: Thermal diffussion (TD) is a method of coating steels to improve the service life of materials and tools. With this process, high hardness of vanadium carbide coating is formed on the surface of materialsso that its wear, bite, corrosion resistance can be greatly improved. Since thereare still several problems remaining to be solved, this technology is still not widely used in our country and that limit the popularity of the salt bath technology. In this paper, these problems and their causes are discussed based on experiments, and several solutions are presented to hopefully provide suggestions for industrial production.

Abstract: Use the electrochromic coating technology and the driving installation design could show various metallic color brilliance of the metallic material bracelet by this device. Experimental observations show that the green base color will transform to pink then blue and the pink base color transform to green then blue.

Abstract: Grind-hardening is a green efficient processing technology that focus on surface harden. The paper simulated the traverse cylindrical grinding with establishing a finite element model, which revealed the thermal gradient while processing in history. And the research confirmed the possibility of prediction of the harden layer, and summarized the properties of traverse cylindrical grind-hardening.

Abstract: This thesis is mainly about modifying PLA with PA6 as compatilizer and blending PLA with PA6. The alloying of PLA and PA6 can change the original fragility and mutability of PLA, and therefore improve its mechanical property. The blending of PLA into PA6 decreases the water absorbability and light resistance of PA6. Since PLA is of high cost, the blending of PA6 can lower the cost.

Abstract: To improve crash worthiness and fuel economy, the automotive industry is, increasingly, using Advanced High Strength Steel (AHSS). However, in recent years, stampers, particularly those serving the automotive industry, have begun to face new challenges related to the increased use of AHSS. Stamping AHSS can push the capability limits of some lubricants and often cause lubricant film break down and galling thereby increasing scrap rate and tool maintenance cost. This paper discusses the advantages of AHSS in auto metal stampings, highlights the new challenges faced by stampers, and delineates the exigency of draw lubricant in producing high quality auto stampings from AHSS.

Abstract: In this study, effect of machining parameters and wear mechanism in milling process of mold steel AISI-P20 and AISI-1050, using 10 mm twin flute type end mill diameter. The experimental results found that characteristics of milling surfaces and wear of the mill end were directly influenced by changes of parameters for all test conditions. As a result, the quality of milling surfaces also changed. However, mould steels which had the good quality surface is AISI-1050, with roughnesses of 2.120 μm. Quality milling surfaces were milled by using the most suitable parameter feed rate of 45 mm/min, a spindle speed of 637 rpm and a cut depth level of 3 mm, for both grades. Moreover, material removal rate and duration of the milling process, the milling end mills affect wear of the edge in every bite when the feed rate is low, high speed and level depth of cut at least. It was found that limited wear less will affect the surface roughness (Ra) represents the good quality surface.

Abstract: A three-dimensional model of micro-turning using the finite element method (FEM) is created in this paper to analyzed the formation mechanism and influencing factors of feed-direction burr in micro-turning. According to the simulation and analysis result, in micro-turning,the deformation of the workpiece feed direction end is the combined action of the plastic bending deformation and shear slip deformation, and plastic bending deformation influences burr height and shear slip deformation affects the burr root thickness. Meanwhile, due to the amount of material involved in different deformation actions is changed, compared with conventional scale cutting, the various influencing factors have significant differences effect on the size of burr.

Abstract: Welded structures which set up in outdoor in snow-and cold-prone areas are exposed to severe environment, in which liquids containing Cl-chloride ions from the sea breeze and snow melting agents undergo freeze-thaw cycles during the winter. Cl-solutions are known to produce pitting corrosion in austenitic stainless steel. However, the relationship between the freeze-thaw environment and pitting corrosion occurred in welded austenitic stainless steel has not yet been clarified. In the present study, the effect of the freeze-thaw environment on pitting corrosion in welded austenitic stainless steel submersed in Cl-solutions is investigated. AISI 304 (X5CrNi18-10 in ISO/TS 15510, SUS304 in JIS G 4305) samples with bead-on-plate welding are used as specimens. The thickness of the specimen is 4 mm. The specimens are fully immersed in FeCl₃ solution. The freeze-thaw environment is created by temperature cycling from 20°C to-20°C. In the meanwhile, residual stresses due to the welding process in stainless steel structures can significantly affect behavior of pitting corrosion as same as influence of sensitization. Authors carried out the welding simulation as the purpose of predicting the welding-heat history and residual stress near the welding bead. As a result, large-scale pitting corrosion occurs primarily in areas of high tensile residual stress and sensitive metallographic structures near weld beads in the freeze-thaw environment. Accelerated pitting corrosion is confirmed to have occurred as a result of concentration cell corrosion due to the local concentration of Cl-chlorine ion around a weld bead during freezing and thawing of the solution. Furthermore, based on your study it became clear that the center position of large-scale pitting corrosion is in agreement with the simulation result rather than the stress peak position by X rays measurement.

Abstract: The dry shrinkage deformation of polypropylene fiber mortar was analyzed by ANSYS software and compared with experiment value in this paper. The error of the calculated and experimental results in the 14 days and 28 days are 7.8% and 10.5%. It can be found that the calculated results are in good agreement with test results. The results indicate that the dry shrinkage value of polypropylene fiber mortar is lower than ordinary mortar. Adding polypropylene fibers can inhibit the process of cracking and improve the fracture toughness of cement-based materials.