JOURNAL OF FACULTY OF ENGINEERING (UNIVERSITY OF TABRIZ)
Year:2000 | Volume:- | Issue:25|Papers Count:7

Among the most important parameters involved in solidification and structure of the cast ductile iron are: the composition, melt temperature, cooling rate, kind and amount of inoculant, and the nucleation procedure. The effect of graphite nodules per unit area on the mechanical properties of the ductile iron has been the subject of intensive research in recent years. In this paper, the effect of nucleation on the percentage of graphite nodules and the structure of cast material has been investigated. In addition, various methods of nucleation have been investigated. The effect of the inoculant size distribution on the microstructure and hardness of ductile iron with respect to thickness of cast material has been studied. It was shown that, it is even possible to produce ductile iron with nodular graphite in sections as thin as 2-3 mm.

New methods for determination of the diffusion coefficients in granular and fine grained soils using the laboratory models were presented in this paper. Repeatable test results proved the accuracy of the obtained diffusion coefficients under applied boundary conditions. For simulation of the hydrogelogic conditions' consisting of two layered soils (fine grained soil over a granular soil) a laboratory model was designed and the model behavior was accurately predicted using the predetermined diffusion coefficients and the PIPING model. The contaminant transport mechanisms in these tests were advection and diffusion and the observations showed that due to low seepage velocity under applied boundary conditions, diffusion is the dominant mechanism.

In this paper, three new schemes based on normalized variable diagram (NVD) to calculate convection term of conservative equations are developed. The solution technique is of the finite volume type utilizing a co-located arrangement for storage of variables and a uniform mesh. The working variables are velocity and pressure which makes the schemes applicable to both compressible and in compressible flows. The interpolation of these schemes has been done with smooth functions and this point improves the convergence and accuracy of the solution. These methods are applied to the computation of steady transonic over bump in channel geometry as well as to the transient shock-tube problem. The results are compared with other computations published in the literature.

Today gas turbine power plants play an important role in power generation. Different methods have been proposed to improve the performance of this plant. One attractive method is to produce steam and then inject it into combustion chamber. In this paper the effect of different parameters like turbine inlet temperature, compressor pressure ratio, pinch point temperature difference, ... on performance parameters of the steam injected cycle is investigated. The attempt has been made to model the actual behavior of this system. It has been observed that the efficiency and power output of steam injected cycle is always higher than corresponding simple cycle. For example, at turbine inlet temperature of 1400K, the efficiency and work output is higher about 10-38% and 49-90% respectively depending on cycle pressure ratio.

In this research, web stability of plate girders with diagonal stiffeners has been studied. For theorical study of stability of plate girders with diagonal stiffeners same rules have been employed which are implied in studying the web stability of plate girders with vertical stiffeners. For obtaining the buckling factor k, Lusas software has been used. With regard to obtained formulas and tests results, it has been found that where diagonal stiffeners are used, the shear post-buckling strength of web which in turn is a result of the existing tension field action is higher than the case where vertical stiffeners are used. Thus by using diagonal stiffeners, the thickness of plate girder's web can be reduced which will cause economy. It should be noted that in this case, the force in diagonal stiffeners will be higher than that of vertical stiffeners, but the increase in weight of stiffeners is less than decrease of the weight of web plate due to employment of diagonal stiffeners.

Radar altimeters were designed to collect height data over surfaces where there are few sodden changes in elevation to send the instrument off-lock. One third of the earth's land area is arid. Information of the surface topography of this region is difficult to obtain with methods. Operating conditions some of these areas are very different when it comes to surveying and photogrammetric methods to provide digital elevation maps and it is very time consuming. It is therefore tempting to consider the use of radar altimeters to try to obtain the height of data points without it being necessary to come into direct with the surface. The purpose of an altimeter to make accurate and precise measurements of surface height. Height refers to the distance of the surface above a reference, and is computed from satellite altitude and altimeter range.

In this paper the variation of aerodynamic properties of a thin airfoil in ground effect is investigated. First, a formulation is developed to calculate the induced drag in ground effect, which correlates the experimental data better than the present standard methods. Then the single vortex method and the distributed vortex method are extended to include the ground effect. The results of the two methods are compared with the available exact solution results. Due to the better correspondence between the distributed vortex and the exact solution methods, in comparison to the single vortex method, the first was used to determine the effects of angle of attack, flap and camber in ground proximity. According to the results, ground effect could lead to and increase or decrease in the lift coefficient depending on the combined effects of the ground clearance, angle of attack and camber.