JOURNAL OF FACULTY OF ENGINEERING (UNIVERSITY OF TABRIZ)
Year:2006 | Volume:33 | Issue:2 (44 MECHANICAL ENG.)|Papers Count:9

Fatigue properties of a unsymmetrical sandwich composites with glass/carbon faces and PVC foam core has been investigated. To determine fatigue properties of the sandwich laminate, first of all, the static strength tests must be conducted. On the other hand the sample test geometry must be designed such that the failure occurs in gauge zone for both case of static and fatigue tests. Two different type of foam/solid laminate interface geometry are considered. Based on static analysis of the two FEM models, critical points in the specimens causing static failure were explained. FEA and experiments results both give improvement of failure zone and strength values for oblique type design of gauge interface. The angle of the oblique design is 45 in degree. With such an efficient design fatigue tests were conducted. Fatigue properties of the laminate were determined and discussed. The pulverization observed within normal crack in the foam indicates that the main part of the laminate fatigue is spent in this type of damage.

The size of computational domain has been a major factor in the numerical solution of fluid flows. In this paper a characteristic based model for the solution of external, inviscid compressible flows is presented. In this model, the asymptotic expansions of Riemann variables along with enhanced characteristic method have been used. Applying this .model enabled us to obtain accurate results for the flow over an airfoil. The numerical solutions are compared to that of other investigators, in which a good agreement would exist. The main importance of the far-field model is the computational domain reduction, while conserving the solution accuracy. Consequently, the number of grid points is reduced considerably, leading to a reduction in competing time –and memory specially in implicit schemes.

Melamine is industrially produced from urea. Therefore the kinetic inspection of the relevant reaction seems to be important to the end of accessing a suitable model and design of the catalyzed bed reactor for synthesizing Melamine. The kinetics of the mentioned reaction has not been found in the literature review. A fixed bed reactor with injection solid urea was constructed to inspect the relevant reaction kinetics. Urea is changed into Melamine, CO2 & NH3 at the presence of silica gel catalyst and the temperature of 400°C. The designed experiments were performed at the temperatures 370, 380 & 390°C based on the catalyst weight varying with the molar flow rate of the entering urea [W/FA0 (kgcat/ (grmole/hr)] An equation pointing out the variance of the vv MJ conversion factor according to the ratio W/FA° was reported which followed the patent: XA=a (W/ FA°)b. Based on the mentioned equations above, at each temperature, the reaction rate conforming the concentration of the outlet urea was reported r¢A =k ( CA). The mean reaction order at these three temperatures equaled to n=0.4.The functionality of k conforming T turned out to be an Arrhenius function (k = k0e – E/RT). The activation Kcal energy and the frequency content are 2.212  kcal/grmol and 75.4 respectively.

Recovery of precious metals from spent catalysts is justified due to mainly environmental regulations, concerns of sustained development and economic added value. In this work recovery of Molybdenum and Cobalt from spent refinery catalysts are studied. Various methods of recovery of these metals from spent catalysts have been reviewed and compared. Experimental methods have been used to find the practical methods and optimum conditions for recovery. It has been found that one can recover about 93% of the initial Co by solving the catalyst in boiling water and about 97% of the initial Mo by leaching with NaCl and 85% by leaching with Na2CO3 solution in presence of H2 O2 of spent Hydrotreating catalyst.

The experience has shown that the reaction of cardan joint in different angles of axis installation is different. Cardan joint fails more due to yoke bending and the failure of cross trunnion is more in the form of galling of end surfaces, the spalling and brinelling of trunnion. In this research we have tried to study the effect of different angles of input flange yoke (the angle of output axle of transmission), output flange yoke (the angle of input axle of differential) and cardan shaft axle subject to the forces of cardan connective parts. Considering all analysis we conclude that reducing the installation angle of driveshaft, will cause in reducing of number of cycles 'of forces developed in cardan elements. Comparison of the results between two models (in the first model, the cross element and the input flange yoke have the same angle of setting that in the second model, the setting angle of cross element is the same as that of output flange yoke) shows that the curves of forces in the second model are more uniform with less fluctuations.

Lithopon Pigment is mixture of zinc sulphide and barium sulphate that covering power is higher than white pigments such as zinc oxide and lead oxide. In order to synthesis of lithopon, first various portions of barium sulphate and active carbon were pressed in pellets forms and in final stage barium sulphate was pressed and reduced at 1150-1300°C in carbon bed for 2h. According to reaction formula of lithopon formation solutions of zinc sulphate and barium solphide were prepared. Reactor temperature was controlled in range of 70-90°C and soaked for 10-300 min. Investigation of phases was used by X-Ray defftactometry, element analysis by XRF and wet chemical analysis. Also the physical properties of pigment such as partical size distribution, specific surface area and powder density were measured by laser particle sizer, nitrogen gas absorption (BET method) and gas picnometry. In the final stage, optimized parameters of synthesis were investigated by technical raw materials.

Because of the motion transferring role of connecting rod from piston to crankshaft, an accurate design of this part is of vital important. In this research the stress distribution in small-end during combustion stroke is obtained. 3-D finite element method (FEM) is employed to model the interaction of piston pin, connecting rod small-end and piston bosses in combustion stroke. Contact sections of the mentioned parts are modeled by employing enhanced contact elements. Non-linear analysis is performed to solve the governing equations. The results were compared with semi-empirical relations of other investigators in which good agreement would exist, besides it is shown that semi-empirical method cannot properly predict the critical stress distribution in combustion stroke.