Computational Methods in Engineering

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Application of gravity and magnetic separation methods to upgrade low grade Manganese ores from Venaj Mine has been reported elsewhere. This paper discusses the results of flotation tests, as well as combination of flotation and magnetic method to concentrate fine particles (less than 150 microns) of manganese ore. Results obtained from various direct and reverse flotation tests, using different types of reagents, indicated that manganese fines cannot easily be concentrated by flotation. In this investigation, combination of direct flotation and magnetic separation for fine particles (finer than 150 microns) with 8.36% Mn, 34.11% SiO2, 23.05% Fe2O3 yielded a manganese concentrate with 26.78% Mn, 11.64% SiO2, 20.37% Fe2O3 and 56% recovery. Desliming 10-15 micron particles prior to flotation tests improved product quality and the recovery. Keywords: Mineral Processing, Flotation, Manganese, Vanarj Mine

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Recently, image processing technique and robotic vision are widely applied in fault detection of industrial products as well as document reading. In order to compare the captured images from the target, it is necessary to prepare a perfect image, then matching should be applied. A preprocessing must therefore, be done to correct the samples’ and or camera’s movement which can occur during the capturing of images. The Radon Transform technique is applied in this study which is inherently invariant to any movement, such as dislocation and rotation which leads to scale changing. According to this technique, simple methods are proposed to determine the degree of movement. Results of computer simulation show the priority of the proposed method to other techniques. The accuracy of the proposed algorithm is less than 0.1 degree and is applicable to different segments such as texts, tables, drawings, …, which are prepared in different writing languages by different devices such as digital camera, scanner, fax, and printer. Keywords: Image processing, Image matching, Radon Transform, Skew detection documents, Computer application in industry.

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In hot forming process, the workpiece undergoes plastic deformation at high temperature and the microstructure of the workpiece changes according to the plastic deformation. These changes affect the mechanical properties of workpiece. In order to optimize this process, both the plastic deformation of workpiece and its microstructural changes should be taken into consideration. Since material behaviors at elevated temperatures are usually rate-sensitive, the analysis of the hot forming processes requires a thermo-viscoplastic model. In this paper, by coupling the flow stress prediction model developed with finite element analysis of thermo-viscoplastic of the hot upsetting process, temperature, strain rate, flow stress distributions and geometry of the workpiece at each time step can be calculated. At each time step, the strain rate and temperature at each element are obtained. From these values and the history of deformation, the changes in microstructure and flow stress can be determined. Keywords: Hot forming, Process, Finite element analysis, Flow stress, Microstructure, Hot upsetting process

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The purpose of this work was to production of ceramic thin films by using of Sol-Gel process. For this purpose deposition of SiO2 on substrates of soda-lime glasses has been carried out. Coating treatments on prepared specimen were conducted in a Sol solution by means of dipping at various times. After drying and performing appropriate heat treatment on each sample, the thickness of coated layer was measured by means of roughness method. Some of the specimens were also exposed to heat and chemical environment to evaluate the coating resistance in such media. SEM examination and EDAX and XRD analysis of coating layers was also conducted on some samples. The results indicated that by Sol-Gel method, it is easily possible to achieve thin layers in the scale of one hundredth micron meter. Any change of the thickness layer on the surface is negligible and the quality of the coating is excellent. Also, experiments indicated that deposited coatings by Sol-Gel process, are stable and give enough durability in various environments.

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Among the titanium alloys, Ti-6Al-4V is the most widely used. In the present work, the uniaxial hot compressive behavior of Ti-6Al-4V has been investigated under constant strain rates. A series of dilatometery experiments were carried out to determine the transformation temperatures at different cooling rates. Specimens were homogenized at 1050 °C for 10 minutes followed by fast cooling to different straining temperatures from 1050 to 850°C. The cooling rate was chosen fast enough to prevent high temperature transformation during cooling. A series of isothermal compression tests were conducted at different temperatures of 850, 900, 950, 1000, 1050°C at constant true strain rates of 0.1, 0.01 and 0.001 s-1, respectively. Samples were uniaxialy compressed to a true strain of 0.55 followed by water quenching to room temperature. The apparent activation energy for compression in two phase regions was calculated at 840 KJmol-1. The partial globularization of a-phase was observed in the specimens deformed at low strain rates and at temperatures near the transformation zone followed by annealing.

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Flame bending process is one of the forming processes of steel plates. During this process, plate is formed with heating by gas torch flame followed by controlled cooling along specified paths. Considering simple tools used in the process, it is a popular and economical forming method. At present, this process is manually done on the basis of skilled technician’s experience. Experimental and non-automated procedures decrease productivity of the process. In this paper, a method is proposed for simulation of material deformation. Regarding the physics of the process, large deformation thermoelastic-plastic analysis has been applied. In the simulations, a new analytical solution is used for thermal analysis of plate. The analytical solution along with finite element analysis of the deformation in ANSYS program is able to interpret experimental observations. The simulations show reasonable results, compared with the analytical results by other researchers and with experimental data. The method and simulation results can be used to study the process automation

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This research proposes a vigorous methodology based on the fuzzy set theory to improve the facility layout process. Using natural language, the fuzzy set theory is an appropriate tool for controlling complex systems such as facility planning. The closeness rating between departments in a plant depends on qualitative and quantitative factors. Some of these factors may have a greater effect on the closeness rating. Thus, analytical hierarchy process (AHP) is used to find the weight of these factors. In this paper, a computer program, called FDARC, is developed to generate quantitative activity relationship charts. These charts are used by FLAYOUT to develop the layouts. The procedure is compared with two other recent methods. Computational results are used to demonstrate the effectiveness and efficiency of the method proposed.

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Scheduling in production environments is used as a competitive tool to improve efficiency and respond to customer requests. In this paper, a scheduling problem is investigated in a three-stage flexible flowshop environment with the consideration of blocking and batch processing. This problem has been inspired by the charging and packaging line of a large battery manufacturer. In this environment, the first and third stages involve a single processor machine, and the second one consists of m identical parallel batch processing machines. The objective is to minimize the total weighted tardiness of the received orders.Given the lack of consideration of this problem in the literature, first, a mathematical programming model is presented for the problem. Also, due to the NP-hardness of the problem, a variable neighborhood search algorithm and a memetic algorithm are developed to solve it. The computational results show that the variable neighborhood search algorithm can solve instances up to 1200 orders and 15 machines with an average deviation of about 1.9%, relative to the best solution of the two algorithms, and the memetic algorithm can solve instances up to 1200 orders and 15 machines with an average deviation of about 7.8%, as compared e to the best solution of the two algorithms. In general, computational results show the better performance of the variable neighborhood search algorithm in comparison to the memetic algorithm.