JOURNAL OF FACULTY OF ENGINEERING (UNIVERSITY OF TABRIZ)
Year:2007 | Volume:34 | Issue:2 (47) MECHANICAL ENGINEERING|Papers Count:9

Power source in explosive welding is explosive charge that provides enough energy for a flyer metal plate to reach extremely high velocity which on coinciding to another metal plate will be welded to it. Among the most important variables includes stand-off distance, explosive charge content and thickness of flayer tube. In this paper shear strength of explosive welds of aluminum to steel in various welding conditions is investigated. For this propose special tension specimens were prepared. Results indicates that the strength of weld interface improves by increasing the stand-off distance and explosive charge content and decrease of aluminum flayer tube thickness.

In this paper, the effects of die comer radius and punch comer radius on fonning energy, including deep drawing load and blankholder force, and also their effects on the geometry of product, including final shape and thinning of the product, in deep drawing process are studied. The material of study is annealed aluminum 1050 and the finite element simulation is used for the analysis. In order to make sure about the validity of the simulation, experiments have been performed and the obtained results have been compared with those from the simulation. It is illustrated that the results are in good agreement. ANSYS 6.1 package is used for the simulation. The results illustrated that the die comer radius has significant effect on the studied parameters in deep drawing process, but the punch comer radius has only affected the product geometry.

Subsequent to rails, sleepers are the most important elements of the railway superstructures, for which its role is to keep the geometry of the line, resist against vertical and lateral loads and transfer them to the layer of ballast. Contact point between sleeper and ballast play an important role in defecting of the railway tracks. For this reason; method of analysis, design and built of sleepers and also how they have been implemented in superstructures are of an important issue in the railway engineering researches. This paper presents investigation of contact stress distribution in lower surface of sleepers through some experiments on railway tracks. In this experiment one sleeper equipped with several load cells was installed on a railway track situated in Bahram station. After tamping, some load was passed over the sleeper and the exerted forces were measured and consequently were analyzed as an output. It should be stressed that passing trains with an identified axial load were passed over the installed sleeper before and after the stabilization. Results show the real contact stress distribution in lower surface of the sleeper in different status i.e. (after tamping, before and after stabilizing) and the effect and importance of required ballast compaction under the sleepers. With due consideration to the results achieved, it could be said that; right amount of ballast, sufficient compaction under the sleeper and performance of railway track's repair and maintenance machineries are of utmost importance and reduces non-uniformity of load distribution.

The effect of MgO and B2O3 on the formation, physical properties, phase analysis and microstructure of aluminum titanate was investigated. Density results showed the sample containing of 1wt% B2O3 and 2wt B2O3 MgO leads to the highest density while the lowest density was seen in samples containing 1wt% B2O3 compared to pure aluminum titanate. Regarding the phase analysis of samples MgO was found most effective additive on reaction sintering of aluminum titanate through the intermediate phases. Furthermore at the temperatures above 1350°c, B2O3 promote the formation reaction of aluminum titanate. Microstructural analysis showed the samples containing MgO are fine grain and homogeneous. Thermal expansion coefficient of samples with additives is greater than pure aluminum titanate. Pure aluminum titanate samples and one containing B2O3 additive decompose to Al2O3 and TiO2 after 5 hours heat treatmept at 1150°C while the samples containing 2wt%M0Go was stable even after 25 hours.

In this experimental work, pure elements, Te, Bi and Sb with 5N purity, were used to grow p-type thermoelectric crystals. Then in quartz capsules at 10-6 Torr pressure, (Bi2Te3)x(Sb2Te3)1-x solid solutions with 0.20£x£0.30 were prepared .The samples were crystallized by zone melting method with the velocity of 8 mm per an hour at 720°C and annealed at 370°C for 24 hours for heat stress relieving. Scanning electron microscopy (SEM) was used to characterize the quality of crystal growth. Electrical conductivitys, Seebeck coefficient a and thermal conductivity K, of the prepared samples were measured to obtain figure of merit from the Z=a2s/K formula. The optimum value for x=0.25 yielded the value of 2.654x10-3K-1 for Z.

Biological treatment is a common process in wastewater treatment systems. Volatile Organic Compounds (VOCs) are major environmental pollutants that are released from industrial wastewaters. In this research, Ethylbenzene (EB) was selected as a candidate of volatile organic compounds. Using a pilot scale aeration system effect of EB concentration on its transferring to air was examined. Sampling was carried out with standard method of Environmental Protection Agency (EPA) and samples analyzed with gas chromatography (GC). Results showed that, amount of mass transfer to air, depends to effluent EB concentration. Amount of exit concentration increases and reached to 11-27% of inside concentration because of changing of transfer mechanism from bubble to surface evaporation and deviation from Henry's Law. Comparing differences between theoretical and experimental results shows that assuming equality between total mass transfer resistances with resistance in liquid phase is acceptable.

On the test bed of the centrifugal pump, the centrifugal pump performance has been investigated using water and viscous oil as Newtonian fluids, whose kinematic viscosities are 9x10-7, 43x10-6 and 62x10-6 m2/s, respectively. Also, the finite volume method is used to model the three dimensional viscous fluids for different operating conditions. For these numerical simulations the SIMPLEC algorithm is used for solving governing equations of incompressible viscous/turbulent flows through the pump. The RNG k-e turbulence model is adopted to describe the turbulent flow process. These simulations have been made with a steady calculation and using the multiple reference frame (MRF) technique to take into account the impeller-volute interaction. Numerical results are compared with the experimental characteristic curve for each viscous fluid. After comparison the experimental and numerical results, the fluid flows are simulated for varies outlet angles for investigating the effect them in centrifugal oil pump. The obtained results show when the outlet angle increases, the wake decreases. This phenomenon leads the improvement of pump performance.

The aim of this project is to find a practical way to reduce soot by investigation in different waste gate opening in Diesel engine. Combustion in Diesel engines produce soot. Soot produces in diesel engine because of non-homogeneous mixture of air and fuel in combustion chamber. If combustion process prolong there is no chance to re-bum the soot in late combustion phase in Diesel engine. This causes to increase the soot emission in exhaust of engine. In this project different waste gate control operations are investigated. The OM314 turbocharged diesel engine is tested in ECE-R49 standard test in three Waste gate operations. The results show that, at W.G operation No.2 which controls the maximum inlet manifold pressure gage at 0.23bar, specific soot emission reduces 17% in comparison with the period of operation No.1, which controls the maximum inlet manifold gage pressure at 0.26bar, and reduce 21% of specific soot emission in comparison with the period of operation No.3, which control the inlet gage pressure at 0.52bar. This result shows that maximum inlet manifold pressure has a high sensitivity. This would be better to control by an ECU.

In this paper, a simulation algorithm for dynamic and nonlinear analysis of liquid propellant engines is presented. The application of this algorithm in a specific liquid propellant engine is developed, and the simulation results are presented. The nonlinear model of the engine is composed of a set of algebraic and a set of differential equations, and the set of equations are implicit. Until now, an algorithm for simulation of this type of model did not exist, and on the contrary to existing algorithms for simulation, the developed simulation algorithm does not depend on the type of the mathematical model of the engine. The simulation algorithm is composed of 6 primary steps. The comparison of the simulation results and that of the actual, at the nominal conditions, is presented. The software language is FORTRAN, and the simulation code is composed of approximately 250 subroutines, and most of the subroutines are composed of 10 lines.