Advanced Materials Research Vols. 622-623

Abstract: Additive manufacturing (AM) of metal parts by using Selective Laser Melting (SLM) has become a powerful tool mostly in the area of automotive, aerospace engineering and others. Especially in the field of dentistry, jewelry and related branches that require individualized or even one-of-a-kind products, the direct digital manufacturing process opens up new ways of design and manufacturing. In these fields, mostly small and medium sized businesses (SME) are operating which do not have sufficient human and economic resources to invest in this technology. But to stay competitive, the application of AM can be regarded as a necessity. In this situation a new desktop machine (Realizer SLM 50) was introduced that cost about 1/3 of a shop floor SLM machine and promises small quality parts. To find out whether the machine really is an alternative for SMEs the University of Applied Science, Aachen, Germany, designed, build and optimized typical parts from the dentistry and the jewelry branches using CoCr and silver material, the latter being new with this application. The paper describes the SLM procedure and how to find and optimize the most important parameters. The test is accompanied by digital simulation in order to verify the build parameters and to plan future builds. The procedure is shown as well as the resulting parts made from CoCr and silver material.

Abstract: Widening is always accompanied with longitudinal rolling of strip varying thickness which is used for parabolic leaf springs production. The amount of this phenomenon at strip ends is highest which should be eliminated from end product. In this article a method for gradual elimination of widening during rolling passes is proposed. Idle rollers are used for elimination of rolled strip widening caused by rolling. A method is presented to determine tensile stress in the case of rolled strip drawing by idle rollers. Variation of ratio depending on reduction in width is studied.

Abstract: The aims of this study are to measure the defect rate and analyze the problems of production of ready concrete mixture plant by using Six Sigma methodology which is a business strategy for operations improvement depending basically on the application of its sub-methodology DMAIC improvement cycle and the basic statistical tools where the process sigma level of concrete production in the case study was 2.41 σ.

Abstract: The article examines the relationship of the kinematics of the deformable surface points with the stresses in the contact zone of deformation and strength rolling clip elastic and plastic surfaces. There is shown the features of deformation of two cylindrical bodies with identical elastic properties of solids and elastic plastic deformation. The features of deformation of the workpiece surface during rolling on the roller surface of the elastic-plastic are determined. A scheme for determining the kinematics of the points of the deformable surface rolling on the cylindrical surface of the roller without slippage are specified. The dependences of the radial and tangential stresses on the front surface of the roller which is resulting voltage changes depending on the half-width of the contact zone at the front of the video shows the main features of the process of elastic-plastic deformation. We present the variation of the efforts of the deformation of the radius and the radius of the roller parts for different values of the depth of penetration and changes in the deformation force on the depth of the introduction of video for different values of the radius of the workpiece.

Abstract: The aims of this research are to establish the forming limit curve (FLC) of tubular material low carbon steels commonly used in Thai industry, verify these FLCs with real part forming experiments and compare these experimentally obtained FLCs against analytical ones available in FEA software database. A self-designed bulge forming apparatus of fixed bulge length and a hydraulic test machine with axial feeding are used to carry out the bulge tests. Loading paths resulting to linear strain paths at the apex of the bulging tube are determined by FE simulations in conjunction with a self-compiled subroutine. These loading paths are used to control the internal pressure and axial feeding punch of the test machine. In this work a common low carbon steel tubing grade STKM 11A, with 28.6 mm outer diameter and 1.2 mm thick is studied. Circular grids are electro chemically etched onto the surface of tube samples. Subsequently, the tube samples are bulge-formed. The forming process is stopped when a burst is observed on the forming sample. After conducting the bulge tests, major and minor strains of the grids located beside the bursting line on the tube surface are measured to construct the forming limit curve (FLC) of the tubes. The forming limit curves determined for these tubular materials are put to test in formability evaluations of test parts forming in real experiment. It was found that the tool geometry can keep the strain ratio constant is not dependent on the thickness but only on OD of the tube, as in equations L=OD and r_d=(15xOD)/25.4. The experimen-tal FLDs have predicted failures in forming process consistently with the real experiments. The ex-perimentally obtained forming limit curves (determined following STKM 11A) differ from empiri-cal one (from FEA software) and analytical one by about 0.02339 and 0.15736 true strain respec-tively at FLD0, the corresponding plane strain values.

Abstract: Development relevance to improve the operational parameters of the support units of machine tools in their design elements is introduced that increase the rigidity of the components, their carrying capacity, damp occurring vibrations in the process, the coefficient of performance (COP), smoothness of motion, positioning accuracy, reducing the wear of their working surfaces and maintain the original accuracy. A number of engineering development [1], [2], aimed at improving the above characteristics of the machine by changing and improving design of reference nodes used in these rails rolling bearings, aerostatic and hydrostatic guides, as well as the use of automatic control systems of its basic parameters, determine its quality. However, in some operating conditions in which errors occur, mainly due to the instability of oil-film thickness (gap) between the mobile and immobile elements of the hydrostatic bearing. For high accuracy requirements it will negatively affect the quality of machined parts and equipment performance. On this basis, it becomes apparent urgency of the problem of automatic stabilization of oil-film thickness (gap) in the IR. To ensure high precision equipment to improve power system hydrostatic bearing units of machine tools. This, in turn, creates the prerequisite for the development of stabilization systems of the gap in the hydrostatic bearing, with the help of which the thickness of oil layer in them would be kept constant even with significant dynamic load on the support.

Abstract: In this study, the main aim was to recovery the gold from iron tailings, and comprehensive recovery of iron by using combined separating technology. Experimental studies were carried out on the iron tailings in Dahongshan samples, which contain 0.5g/t of gold and 16.8% of iron. Through the experiment, the first is pre-discarding tailings by centrifuge, and then the gold is recovered by cyanidation leaching with using of H₂O₂ to increase the rate of gold dissolution. The gold’s leaching rate can reach 97.60%. The qualified iron concentrate can be got from leaching slag and gravity tailings by magnetic separation. Iron tailings get a comprehensive utilization, which has a better effect.

Abstract: The study attempts to produce iron concentrate from a high-purity pyrite concentrate using oxidizing roasting at industry scale. The effect of key parameters, i.e., roasting temperature, excess air coefficient and roasting intensity on the Fe and S content in the pyrite cinder was fully investigated. The results indicate that the roasting temperature plays a key role in decrease the S content in the pyrite cinder; an increase in the roasting temperature from 800°C to 950°C decreased the S content in the pyrite cinder remarkably from 0.43% to 0.18%. The optimum conditions for produce a high quality iron concentrate from the high-purity pyrite concentrate were identified as roasting temperature around 900 ~ 950°C, excess air coefficient at 1.20 and roasting intensity at 4.36 ~ 5.61 t / m2•day. Under such a condition, high-quality iron concentrate containing 65.11% Fe and 0.21% S was achieved from the pyrite concentrate.

Abstract: Both merits and demerits of existing recovery techniques of crystalline silicon scrap cutting fluid were analyzed and compared in this paper. In the thesis, a new separation process for separating and recovering SiC in crystalline silicon cutting fluid was presented. The performance index of recycled SiC powder is equal/familiar to the new one, and that can replace the use of new one completely.

Abstract: The study aims to remove copper from a pyrite cinders using chlorination roasting and optimizing the roasting parameters through response surface methodology (RSM). After a series of experiments, a quadratic model was suggested by RSM to correlate the variables to the copper volatilization ratio. The results indicate that the model is in good agreement with the experimental data and the dosage of chlorinating agent and roasting temperature play a key role in improving the volatilization ratio. The optimum conditions for remove copper from the cinders were identified as chlorinating agent dosage at 5%, roasting temperature at 1155.05 °C and roasting time of 10 minutes; under such a condition, an average copper volatilization ratio of 95.16% was achieved from the cinder.