Iraqi journal of mechanical and material engineering

A numerical investigation has been implemented to elucidate the effect of vertical and horizontal vibration at normal gravity on natural convection in a square enclosure filled with air at Rayleigh number 7×107 and 4× 108. The enclosure was comprised of two vertical and opposed surfaces (the right hot and the left cold) while the two other surfaces are adiabatic. The two-dimensional, low-Reynolds number k − ???? turbulence model is applied to enable it to cope with low Reynolds number flows. By transforming the equation of (continuity, Navier-Stokes and energy) using finite volume method from differential forms to algebraic forms using SIMPLE algorithm with hybrid scheme dealing with the time term are adopted to solve the governing equations. A computer program in Fortran 90 was built to carry on the numerical solution. Three cases were studied in this work, case I(reaches to steady state and then begins the effect of vibration at each frequency), caseII and caseIII(begin the effect of vibration from the transient at ascending and descending frequencies respectively).After the validity of the present code by comparing results with these of previous study for similar conditions, solutions have been obtained for Prandtle number of 0.7, aspect ratio (A=1). In the high Rayleih number case (Ra=4×108), the gravitional thermal convection dominates, and the vibration motion does not enhances the heat transfer remarkably. In contrast, in low Rayleigh (Ra=7×107), the vibration thermal convection is dominant, and the vibration enhaces the heat transfer rate significantly. The effect of vertical directional vibration is more powerful in caseII(ascending frequency), when the horizontal directional vibration more effective in case III(descending frequency).

In this work, surfaces of Al 6061 alloy were coated using anodizing and micro–arc oxidation ( MAO) duplex processes. MAO electrolyte was modified using ( 2-6 g/l )Al2O3 additives . X-ray diffraction (XRD), scanning electron microscopy (SEM), Vickers indenter, atomic force microscopy (AFM), and Microprocessor coating thickness meter ,were employed for characterization of the deposited coatings .Results showed that the coatings contained porous oxide γ-alumina with morphologies characterized by different levels of porosity non-uniform distribution, and their thickness and hardness increased by the increasing of Al2O3 additives. The research demonstrates that a relatively hard (421-490Hv), thick (43-65μm) and uniform coatings, can successfully be deposited on preanodized Al alloy (12-15 μm with hardness of 190Hv) using Al2O3 additives containing MAO electrolytes as a new method for more future research on surface improvements of Al alloys

The current study deals with fabricating a hybrid nanocomposite. Pure aluminum as the base matrix and Fe2O3 and Al2O3. A reinforcements Fe2O3 weight percentage (wt%) is varied (1.5, 2.5 and 5 % wt%) and Al2O3 is held constant (2 wt%). The new designed nanocomposite was produced using Powder Metallurgy (P/M) method. The experimental results revealed that the microstructure images of nanocomposites showed uniformly distributed of Fe2O3 and Al2O3 in aluminum matrix. Dry tribological behavior (wear rate and coefficient of friction) was studied and for varying hybrid reinforcement content. The results observed that the wear resistance of hybrid nanocomposites improved with the increasing of Fe2O3 + Al2O3 reinforced material but the better wear resistance was recorded with the (1.5% Fe2O3 + 2% Al2O3) wt% than the base metal and other nanocomposites. It is evident that the maximum reduction of wear rate and COF were 4.87 × 10-8 g/m and 0.59 respectively for the (1.5% Fe2O3 + 2% Al2O3) nanocomposite. The hysteresis curve of nanocomposites showed that the magnetic properties which indicated that the better response of magnetic properties was found with the nanocomposite of (1.5% Fe2O3 + 2% Al2O3) content.

This research study the properties of two different crude oils . Two samples of crude oil were used, which were ( Al – Dora and Al - Ahdab )crude oil. Atmospheric distillation used to separate these two crude oils into their fractions according to boiling point. This research introduced most important characteristics and information's about these samples of crude oils and their products. ASTM distillation was converted to TPB distillation curve. It was found that the preliminary boiling point is lower than the cease point is higher than ASTM distillation for the two crude oils. Most important properties of the products of the two crude oils were calculated. These properties are API, gravity, Watson characterization factor (k), viscosity, molecular weight and refractive index. It was found that the API gravity for Al-Dora crude oil cuts is less than that of the Al-Ahdab crude oil cuts. Also , Al-Dora and Al-Ahdab crude oils cuts having more naphthenic or aromatic components since the characterization factor is less than 12.5. it was concluded that the characterization factor (K) for Al-Ahdab crude oil is less than Al-Dora crude oil for gasoline only. While the opposite happens with Kerosene and gas oil. Finally , It was conclude that the viscosity, molecular weight and refractive index of Al-Dora crude oil products were higher than that of the products of Al-Ahdab crude oil. It was found also that the viscosity of cuts for Al-Dora and Al- Ahdab crude is increase because kerosene is more viscous (heavy cut) than gasoline. Also gas oil is more viscous than gasoline and kerosene. Finally , it was concluded that the viscosity of gasoline, kerosene and gas oil for Al-Dora crude is higher than gasoline, kerosene and gas oil for Al-Ahdab crude oil. It was concluded that the molecular weights of gasoline, kerosene for Al-Dora crude is higher than gasoline, kerosene for Al-Ahdab crude oil but the gas oil is on the contrary. It was concluded that the refractive index for Al-Dora crude is higher than Al-Ahdab crude oil.

The present research investigated multi-zone single-cylinder four-stroke direct-injection model. The model simulates closed cycle processes and describes the combustion behavior by employing thermodynamic equations of a penetration spray theories. The model has been coded on the base of the programming tools of Matlab software. In this simulation model, the combustion events is divided into five zones, in order to determine the amount of fuel, access air, and amount of products in each zone. The simulation model, produced in this work, provides a more accurate framework for zero dimensional model by introducing physical zones within the model that correspond to the combustion structures in the engine. Comparison the results of the simulation model with other methods in the published researches shows that the behavior of engine parameters with theoretical and experimental earlier works has a good agreement. From the simulation model results can be concluded that, there is a change in the limits of the combustion zones with changing engine speed, amount of injected fuel, intake air pressure, and temperature, especially in the rich premixed burn zone.

The shape memory alloys (SMAs), that consist of Cu-Al-Ni, have been established and developed for the applications used at higher temperature values due to their capability to return to its original shape when heating close to its transformation temperature. Cu-Al-Ni alloy has high value of transformation temperature and show small hysteresis as compared to the other types of SMAs. This work present a general review about how SMAs have developed by adding several metals such as, Ti, Be, B, Mn, and Zr or by changing its content (Ni or Al) by either decreasing or increasing. That might show a significant impact on the phase transition and enhancing the corrosion behavior and mechanical properties of the presented alloys. However, the transformation of the martensite phase is the critical factor that might change the properties of Cu-Al-Ni SMAs. This phase is largely affected by addition of the alloying element mentioned above. A review about effect of addition some alloying elements for enhancing the corrosion characteristics of the alloy and phase transition is presented.