INTERNATIONAL JOURNAL OF INDUSTRIAL ENGINEERING AND PRODUCTION MANAGEMENT (IJIE) (INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE) (PERSIAN)
Year:2006 | Volume:17 | Issue:3|Papers Count:16

In the present study the Al/SiCp composites were processed via Disintegrated Melt Deposition (DMD) technique. For preparing the Al-SiC slurry, the oxidized SiC particles were. introduced to the Al-356 alloy in the semisolid condition and stirred via a graphite impeller. The slurry was then reheated to above the liquidus temperature of the alloy and transferred to a preheated bottom pouring crucible positioned on the top of a gas atomizer. By removing the stopper, the melt stream was disintegrated by impingement of nitrogen gas streams and deposited onto a rotating copper-made substrate positioned at specified distances under the atomizer. It was shown that the increased atomizing gas pressure resulted in an increased porosity whit in the deposits as well as the more refined matrix microstructure in which the SiC particles/were distributed more uniformly. The increased flight distance resulted in a more refined matrix microstructure, but had no effect on the SiC particle distribution. It was also shown that by increasing the flight distance, the porosity was initially reduced to a certain amount and then increased for longer flight distances.

Contradicted results have been reported on sensitivity of low alloy Cr-Mo steels to fracture toughness, so it seems further investigations is required in order to establish the reasons for this contradiction. This study rationalized the causes of contradiction and established the reason of variation in the observed changes in fracture toughness which is related strongly to chemical compositions of these type of steels.For investigating the embrittlement sensitivity in this research, J- factor was used. The higher the J-Factor in steel, the more sensitive it would be to temper embrittleing. Two types of low alloy Cr-Mo steels having different compositions and J-Factors (i.e. equivalent to 107 and 224) were used in this research. For induction of temper embrittlment on these alloys, a Step-Cooling operation from high temperature to room temperature for a period of 234 hours was employed. Then the mechanical properties of the treated and untreated alloys were established and compared. The results show that in spite of the small effect of Step-Cooling operation on tensile and hardness properties of the steels, resistance to impact of both alloys was affected by temper embrittlement. Changes in temper embrittlemel1tof the two alloys used in this research are justified in this article.

Length of natural gas flame with stochiometric air to fuel ratio and also with 5 percent excess air for 15 MW burners which are used in large furnaces has been characterized by empirical equations reported in the literatures. In these investigations it was shown that the axial component of radiationis neglected, since it is relatively small compared to the radial component. This model has been employed to study the influence of firing rate and also examines the preheating air on the characteristics of flame.A one-dimensional model was used to predict the axial temperature profiles of the flame. Results indicate that the temperature at the nozzle of burner is small, but increases sharply along the axes of the flame. The effect of various speaces in the flame up to 1500k was found to be negligible and usually ignored in practice. The higher the temperature of the flame the more incomplete will be the combustion in the flame and so reduces the flame temperature.

So far a large number of algorithms have been developed for optimisation of ultimate pit limits, most of which follow deterministic rules. In this paper a new algorithm is introduced, which follows a probabilistic logic using Markov chains. The algorithm is implemented on a transition matrix that correspond the 2D conventional economic block model of the orebody. Probability of mining a block is proportional to the profit it may produce. Applying this algorithm, probability of mining each block is obtained and finally the optimum pit is defined as the pit, which provides with the highest probability of mining. A 2D analysis of the problem is discussed in this paper; however, it is not difficult to expand the problem to 3D cases.

In this paper the study and layout of an assembly of Wind turbines in a Wind Farm is presented. The arrangement of two wind farms as an example in Manjil/Iran and Austria reviewed and due to complexity of the problem, referring to experimental methods, using WAsP or WindPro Computer Codes available from RISOE National Research Laboratories of Denmark and www.emd.dk is advised.

One of the most critical and complicated steps in mine design is to select an appropriate extraction method. Since there are many factors involved for the selection of mining method, which is decision-making process, the problem is very difficult to solve. Especially many factors are opposite together and to increase the value of one factor often results to decrease the value of other factors. Therefore many different methods have been developed to assist the problem. One of the most powerful and flexible method of decision-making means for this problem is Analytical Hierarchy Process (ARP). In this paper, with the use of this technique and using different quantitative and qualitative factors, a suitable mining method for the Ghale-zari copper deposit in Birjand has been determined. The studies show that the appropriate mining technique for this deposit with regard to the present situation is shrinkage method.

By immersing initially nitrided steel into low temperature salt bath with ferrochromium powder additive, a hard and wear resistant chromium carbonitride coating will be produced, known as the Thermo-Reactive Diffusion and Deposition (TRD) method. The aim of this project is to evaluate the effect of different coating parameters on producing of chromium carbonitride coating on DIN 1.2210 steel using low temperature TRD method. Results indicate that the structure of the coating consist of chromium carbonitride. Increasing ferrochromium content in the bath along with the use of finer ferrochromium powder and increasing time in conjunction with the higher temperature results in increased surface-thickness and hardness.

In this study, the effect of abrasive particle size on wear behaviors of brake pad has been investigated.Five sets of samples containing different sizes of quartz particles with mesh size in the range, of 40-120 were synthesized. The wear test was carried out based on the National Iran Standard No. 586. In all the cases investigated only the samples containing quartz particles with the size is 80 showed a temperature in depended wear rate behavior. The details of the study will be presented in this paper.

In this research, the strain hardening behavior of dual phase steel containing 0.11% C 1.30% Mn is studied, using the tensile tests. The empirical relationshipa=k(e°+e)n , which has been suggested by several investigators for strain hardening behavior, is conformed. It is also shown that dual phase steels with up to 50% martensite have two stages of strain hardening and by increasing martensite over than 50% there is only one stage of this process. Finally it was observed that increasing martensite volume fraction results in decreasing strain hardening exponent (n) and increasing strain hardening coefficient (k).

The impurity of phosphor in hypo-eutectic Al-Si alloys and its interaction with strontium or other modifiers impairs the morphology of silicon in the microstructure, although its effect can be nearly nullified by the increase in the modifier concentration. The phosphor-strontium interactions and their effects on the silicon microstructure and mechanical properties of A356 alloy has been studied systematically. The results show that it is very difficult or even unlikely to have a fully modified structure if the phosphor concentration is high. Also in a high phosphor containing alloy although the increased Sr-content raises the modification rate, this increase will not lead to higher-mechanical properties since it also increases the casting porosity content.

After determining the optimum composition of plating solutions, samples of Cr18Ni9Ti steel were coated by Ni-P and Ni-Cu-P coatings, using electroless technique. An oxford 7059 EDX and a Siemens D500 diffract meter have been used to study the microstructure of coatings and crystallizing behavior of Cu and P, respectively. Corrosion study of coatings has been made in different solutions as: 5 vol% HCl, 0.5 molar H2S04, 10 vol% NaCl, and 50 vol% NaOH. The results showed that Cu on the contrary to P behaved as crystallizing element in Ni-P coatings, the results also showed that Ni-P base coating were resistant in dilute H2SO4, NaCl and NaOH containing solutions. This was not the case in solutions including HCl.

With increasing the competitions in the tile markets and increasing the production cost, new full automated production procecess such as single fire and fast firing cycles were introduced to the wall tile production industries. The main reasons for the large using of this kind of tiles, is the shorter firing cycles (shorter than 50 Min.), low energy consumption, defects detecting at short times and high levels of production. Also this provide more controlling on tile dimensions specially for the porouse single fired tiles. The goals of this research project are the study and production of the body and glaze of monoporosa tiles. On these bases several experimental tests were examined to determination of several properties green, dried and fired body strength, water absorbtion and shrinkage percent, microstructural and phase analysis by X-ray and electron microscopy techniques for all fired and green samples. The results showed the adoption of tested body and glazes with EN standards.

Owing to the nature of the coal reserves in Iranian collieries, and consequently impossibility of employing mechanized mining system in most of these districts, the mining activity at such areas is of the type of labour intensive.In order to accommodate more miners to achieve acceptable productivity, establishment of more than one stope in one panel is practiced in some coal mines such as Tazareh in Shahrood.Roof behavior at this colliery was studied using two methods namely: empirical method and numerical method. Empirical method showed the semistable category for the roof rock and numerical approach using FLAC software showed that in the case of presence of two working areas in one panel the interaction will start at distances about 10 meters between the stopes. Also it was shown that in the case of simultaneous activity of the stopes in one direction, in other words both retreat or both advance, the interaction is less tangible than the case where they are in the opposite directions. The results yet to be validated by other means can be used to allow a minimum width of 10 meters between the stopes as pillars, provided that it is confirmed by anlytical assessment of strata weighting on the pillar in each case depending on the roof geometry.

In this research, the effect of substrate surface roughness on the tribological behaviour of hard chromium coatings deposited on heat-treated steel substrate (DIN 1.6959) has been investigated. The coatings were plated on substrates with surface roughness of Ra=0.01, 0.03, 0.05, 0.3 and 2.2mm produced by mechanical method and Ra=0.07 and 0.14  mm produced by electropolishing. The wear and frictional behaviour of the coatings were investigated by a ball-ondisk test machine in dry sliding condition through the use of ruby ball under different loads. The results indicated that the surface roughness and hardness of the coatings were affected by their own substrate surface roughness. The results of wear experiments under a load of 2 kgf showed that the coating with substrate surface roughness of Ra=0.05 mm had the lowest hardness and the highest wear rate. For coatings plated on substrates with- surface roughness of above and below this value the hardness and wear resistance increased. The best wear resistance was obtained by the coating with substrate surface roughness of Ra=0.07mm produced by electropolishing with pulse current. In this case, the dominant wear mechanism in short sliding distance is abrasion and in long sliding distance is spalling of the coating (i.e. fatigue mechanism).

Matte smelting is the most important way for extraction of copper of sulfide ores. Reverberatory furnace is the oldest furnace in copper smelting. These types of furnaces with some modification and changes are still in service in Iran and some other places in the world. Using of oxyfuel burners causes to increase the matte production efficiency.useing of oxygen in the oxyfuel burners causes to increase of oxygen potential in the furnace atmosphere. Increasing oxygen potential in the furnace enhances formation of magnetite (Fe3O4) in furnace, which is an undesirable compound.Therefore with controlling of combustion condition, burner type, oxygen potential, temperature and the rate of addition of the converter slag, performance of furnace can be modified. two first items are more important than the others.In this project, calculation were done according to the complete combustion and the equilibrium conditions (with the use of the FACT software). The volume, composition and partial pressures of gases were calculated and compared in two conditions namely: with use of oxyfuel and heavy fuel burners. Moreover the data for input and output of two types of furnaces (oxyfuel & heavy fuel burners) of Sarcheshmeh copper complex were compared with each other for 90 days. Finally the chemical composition of output gases of the furnace was analyzed. Investigation also showed that the available excess air in this furnace is around 2-3 times needed air. This huge amount of excess air causes to be similar the condition of combustion in two type of Sarcheshmeh reverberatory furnaces, also to decrease in partial pressure of SOz and increase oxygen partial pressure in outlet gases.