INTERNATIONAL JOURNAL OF INDUSTRIAL ENGINEERING AND PRODUCTION MANAGEMENT (IJIE) (INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE) (PERSIAN)
Year:2006 | Volume:17 | Issue:1|Papers Count:9

A novel design for a low pressure chemical vapor deposition (LPCVD) system, used for the deposition of tin oxide thin films, is presented. The system is cost-effective and provides control on all the major parameters of the deposition process. A solution of SnCl4 in distilled water is used as a precursor. The precursor solution is located inside the low pressure chamber and the system has no input during the deposition process. The evaporation rate is controlled by the amount of precursor dropped on a temperature controlled hot plate. The substrate temperature can be varied from room temperature up to 600°C. The pressure of the chamber could be adjusted by the calibration of a multi-valve evacuation control unit installed between the chamber and the rotary pump employed. Deposition of uniform SnO2 thin films in the thickness range of 50-400 nm was achieved. The maximum surface conductivity of the undoped Sno2 layers was 10-3 moh. . Above 10-4 moh., conductance reproducibility of ±10% was achieved.

Adaptive arrays are used in a variety of applications including, radar, sonar, and communication systems. In large fully adaptive arrays, high computational load and low convergence speed are two severe problems. Hence, partially adaptive arrays with lower adaptive elements are used. SLC structure is used in large phased array radars as a partially adaptive technique. If desired signal has long time duration in comparison with the SLC adaptation time, signal components may be cancelled. In this paper, a new technique is introduced to modify the SLC structure. Several simulation results are presented for illustration and comparison of the performance of this modified SLC for a planar array. In these simulations, RLS adaptive algorithm is used.

Numerical simulation of ballistic impact of long rod penetrator into ceramic armors with semi-infinite backing targets is considered in this paper. An explicit, three-dimensional finite element code LS-DYNA is used in the analysis of the problem. The behavior of ceramic and backing materials are modeled as Elastic-Plastic Hydrodynamic with pressure cutoff and failure strain. Johnson-Cook material model has been used for the projectile. Mie-Gruneisen equation of state for the projectile and also linear polynomial equation of state for backing plate are used. The impact velocity range is from 610 to 1350 m/s. The results of investigation are in a good agreement with experimental data.

Residual stresses are self equilibrium stresses and a portion of the strength of a specimen is used to tolerate these stresses. The effect of residual stresses depends On the magnitude and the direction of them in comparison with the external stresses could be useful or dangerous. Central hole drilling is the only method for measuring the residual stresses which are mentioned in ASTM standard.In this research, the central hole drilling process for thin components is simulated. This process has not been simulated by finite element method yet. Therefore, the model presented in this study can be used instead of the experimental methods. Two and three dimensional simulations are performed. After applying the load as the residual stresses, the elements in the region of the hole are removed. Then the strains in the locations of the strain gages are extracted and averaged. The comparison of the results obtained by this model and the ASTM standard method shows an error less than 3%.In three dimensional modeling, three plates with different thicknesses are modeled. The average strains for all elements in the region of the strain gages and the elements in the first layer of the model are calculated. The results of the simulation show a good agreement with the results of experimental standard method.

Forged and heat treated low alloy steels containing Ni, Cr, Mo, V have a wide applications in industry. In such steels, the amounts of Mn and Cu have a great influence on the mechanical properties. The effects of Cu and Mn on the mechanical properties of a low alloy steel containing Ni, Cr, Mo, V have been investigated in the present research. The specimens with different amounts of Cu, Mn in the range of, 0.15, .0.45, 0.23-0.85 were used, respectively. The specimens were austenitized and quenched after forging. Tension test, impact test and hardness measurements were carried out to investigate the effects of Cu and Mn on the mechanical properties. Fractography and microstructural evaluation have been carried out by optical microscopy and SEM. The results showed that increasing the amount of Cu, improve the hardness, as well as the yield and ultimate tensile strengths and reduce the ductility. The impact energy showed a maximum value at %0.25 Cu. However, by increasing the amount of Cu to %0.45, the impact energy is reduced. Increasing the amount of Mn from %0.35 to %0.85, leads to improvement in hardness, as well as yield and ultimate tensile strengths. The impact energy showed a maximum value with %0.35 Mn, but with increasing the amount of Mn to %0.85, the impact energy is reduced due to increase in MnS inclusions.A significant change is not observed by increasing the amount of Cu and Mn. According to the results of mechanical properties, the best combination of strength and toughness are found with the amount of %0.25 Cu in steel containing Cu and %0.35 Mn in steel containing Mn.

Diffusion bonding is used for joining the powder metallurgy components together or to wrought parts. The key element of the joining process is based on the variation of dimensional changes between counterparts during sintering cycle. These dimensional changes may be optimized by proper chemical composition and/or density of the green compacts. It is also known that the strength of the bond is influenced by several factors such as the particle size of powder, fit size of the assembling, sintering atmosphere and lubrication method. This article presents the effect of the iron particle size of iron powder on the bond strength of sintered bonded P/M Fe-5%Cu to low carbon wrought steels. To study the quality of the bonding zone, shear strength, metallography and microhardness tests were performed. It is found that the maximum bond strength is obtained when the particle size ranges from 75 to 100μm.

The determination of a value for e that is considered as a non-Archimedean infinitesimal in the concept of Data Envelopment Analysis (DEA) is an important subject. A procedure for determining the overall assurance interval for e in DEA models has been presented by Mehrabian, et al (1998). Although choosing e in the presented overall assurance interval guarantees the feasibility and boundedness of the models but we show that may lead to incorrect recognition of efficiency and inefficiency for some DMUs. We also propose a new e-free model that correctly recognizes the efficient from the inefficient DMUs.

Diffusion problems are nonlinear partial differential problems of parabolic type with diffusion coefficient as a function of fluid flow in a porous medium. Usually this coefficient is unknown. In this paper, the one phase flow of fluid in porous medium is modeled and the existence and uniqueness of porous medium problem is proved.