Iraqi journal of mechanical and material engineering

The present research deals with study of the effect of applied casting pressure at constant pouring and die preheating temperatures on the microstructure and dry sliding wear behavior of the squeeze cast Al-12%Si alloy was investigated. A pin-on-disc tests were conducted at varying loads from 5 to 20 N and a sliding speed of 2.7m/sec for a constant sliding time of 20min. The results showed that a refinement in the microstructure with increasing the squeeze pressure. The results showed that the wear rates and coefficient of friction ( μ ) of the squeeze cast samples are lower than that of the gravity die cast sample. The results also showed that the density of the specimens decreased with application of a 7.5 MPa applied pressure, but it increased steadily for higher pressures up to 53 MPa. Increasing the squeeze pressure resulted in increasing the hardness and decreasing the wear rate. These results were explained based on the densification mechanism brought about by the application of pressure during solidification.

The growing concern about the fast depletion of hydrocarbon-based fuels and the environmental pollution caused by their combustion has been a compelling incentive to all researchers to study the effective parameters on the combustion processes. One of these parameters is the effect of spark plug location. Keeping this in mind, a mathematical model for the power cycle in a 4-stroke spark ignition engine was developed using quasi-dimensional cycle simulation. The model takes in to consideration mass and energy conservation in the engine cylinder. The model calculates instantaneous variation in gas thermodynamic states, gas properties, cylinder pressure, burnt temperature, turbulent flame speed, flame radius, and pollutants formation. Three spark plug location are used, namely,
1- The spark plug at the center.
2- The spark plug is at a distant ratio (0.4).
3- The spark plug is at a distant ratio (0.3).
It is found that the position of the spark plug have a strong effect on the pressure, temperature, flame speed, and pollutants concentration. Shifting the spark plug from central position towards the wall reduces all studied parameters.

This study deals with the effect of heat treatment and thermo-mechanical treatment on the corrosion behavior of (Al-2Cu-2Mg) alloy by using simple immersion in salt solution ((3% NaCl) by weight) and acidic solution((3% HCl) by volume) at room temperature. The weight change method and microscopic examination are used in this study. Alloy without treatment, solution heat treated at (500 C), artificial aged at (170 C) and thermo-mechanical treated (12%,24%)لare used to complete this study.
The result of effects of heat treatment on the corrosion behavior of alloy in salt solution showed different corrosion behavior for the same alloy under the same conditions but at different heat treatments. Solution heat-treated alloy has the lowest loss weight levels compared with the other states untreated and artificial aged alloys which showed convergence in corrosion rate at the final stages of the test .In other hand the results of effects of thermo-mechanical treatment on the corrosion behavior in salt solution showed that the lower cold working percent cause vibration in corrosion rate while high cold working percent cause in reducing weight and lower corrosion rate .
The result of effects of heat treatment on the corrosion behavior of alloy in acidic solution showed that the solution-treated alloy have the lowest weight losing compared with the untreated and artificial aged alloys where the last one show a mid state between the other states. In the other hand the results of effects of thermo-mechanical treatment on the corrosion behavior in acidic solution showed that the corrosion has been dropped with increase the cold work ratio and the results showed decreasing in weight loss with increasing the percent of cold working.

various vibration materials are available as structure use in equipment insulation. Rubber mounting type is a wide use as machine damping material in electrical generator . Rubber mounting characteristic are improved with thermoplastic addition. In the present paper an investigation of LDPE percentage on the different types of rubber matrix (IIR, SBR/Reclaim) to prepare the composite mounting and comparison these mountings with the prepared blend (SBR:NR)mountings. The works is achieved by using TM16 universal vibration apparatus with modifying the viscous damper into rubber damper and Wallace R-2 Dunlop Triposometer.
The results show, increasing the damping ratio () and logarithmic Decrement () with increasing of LDPE percentage of (0-10) (pphr.), and decreasing of decrement of trasmissiblly ratio( T) ,also show reducing of these criteria (,) above 10 (pphr),also can be concluded the best damping characteristics are founded in the SBR/Reclaim with 10% of LDPE type.

The aim of this work is to study the development of mechanical properties of castings, obtained by melting and casting of worght Al-Cu alloy pipes, by using metallic mold different cooling rates of solidification. The castings are then subjected to asolution treatments at (515 oc) for (4 hrs) and then cooled at different rates to room temperature. Then the specimeus are naturally and artifivially aged at (175oc)for(1-3hrs).Hardness, tensile and fatigue test are conducted it is obtained after artificial aging ultimate tensile strength of (268.7 MPa), for the heat treated casting compared to (170.42 MPa) for the same casting without heat treatment. It is also noted the improvement of hardness and fatigue properties after artificial aging as its compared to natural aging. The phases developed by castings are identified by using x-ray diffraction. It is noted the existence of phase (α) which is responsible for the improvement in mechanical properties.

Design and fabrication of a die, in the case of sheet metal forming, is an experimentally iterative process. So, the hard sheet metal forming dies are generally dispensed with flexible dies. This paper presents a simple approach to control the motion of the die pins and estimation of blank working area. The proposed method is directed to control any free form shapes such as Bezier surfaces. The results of the study are simulated in suitable programming code (MATLAB and IronCAD) to show the effect of proposed method.

This study deals with the effect of temperature on the corrosion behavior of Al-2Cu-2Mg) alloy by using simple immersion in acidic solution((3% HCl) by volume) at (30,40,50,60,70,80C°). The weight change method and microscopic examination are used in this study. Alloy without treatment, Solution heat treated at (500C°), Artificial aged at (150C°) are used to complete this study. The result of effects of temperature on the corrosion behavior of alloy in acidic solution showed a continuous increasing in corrosion rate with increase the temperature of solution. The result showed that the solution-treated alloy have the lowest weight losing compared with the untreated and artificial aged alloys where the last one show a mid stat between the other states. In the other hand the results of Arrhenius equation and the Arrhenius plots showed the rate of corrosion of the solution heat treated alloy increase ( 12 ) time when increase the temperature from (30C°) to (80C°) , the rate of corrosion of the artificial alloy increase ( 24 ) time when increase temperature in the same range above , and the untreated alloy appears high increase in corrosion rate ; the rate of corrosion increase ( 180 ) time when increase the temperature from (30C°) to (80C°) . The solution heat treated alloy submit to the Arrhenius equation while the untreated alloy and the artificial alloy not submit to the Arrhenius equation.

The investigation envolved determination of the partial molar volumes oV at infinite dilution of the dibromo Acetic acid in the thiourea- water mixtures at five temperatures in the range 293.15-313.15 K and at five compositions in the range 5 to 30 percent by weight thiourea, the concentration of the acid in each solvent mixture covered the rang 10-3 to 0.4 mol dm-3.
Densities and viscosities of thiourea-water have been measured at each temperature for all thiourea-water mixtures as well as for solutions of dibromo acetic acid. The concentration dependence of densities of dibromo acetic acid solution have been used to estimate the partial molar volumes.
The volumetric behaviours of thiourea-water have been investigated in terms of excess molar volume. The variation of the relative excess molar volume of mixture was found to be due to a volume contraction (negative
V)on mixing the constituents of the mixture. The results were rationalized in terms of the two models for liquied water; one maximally hydrogen-bonded and voluminous the other non-hydrogen-bonded and dense.
The thermodynamic activation parameters () for the ion flow in thiourea-water could be estimated from the dependence of viscosity on temperature . the presence of dibromo acetic acid in thiourea-water mixture did not influence sigificanlty the values of these thermodynamic activation parameters.
SandHG,
The dependence of dynamic viscosities (ηr) values on the concentrations (c) of dibromo acetic acid in thiourea-water have been determined, electrolytic solutions of moderate concentration generally have relative dynamic viscosities (ηr) which obey the empirical equation of Jone and Dole.

This research deals with studying the effect of spindle speed on the drilling length and surface finish for producing deep holes. Where experiments are done by using twist drills having (9, 10, 11) mm diameters by using samples of stainless steel under dry cutting conditions.
The results show that increases of the spindle speed limits from producing drilling length and it has negative effect upon magnitude of drill deflection and its vibration , it keeping in mind the drill deflection and its vibration these have small diameter will be more for the drill that has big diameter . The speed and drill diameter have clear effect on flank wear land, in another word, with the increasing of speed and drill diameter, the flank wear land will increase. Also, there is a direct proportional relationship between the speed and drill diameter in one hand and the surface quality on the other hand, therefore; the roughness increase when the speed and drill diameter increases.

The optimum design of the heat sink by using differential evolution (DE) method is discussed in the present paper. The DE strategy (DE/ best/ 1/exp) is used here because this strategy is best strategy for heat transfer applications [1]. The main procedures for the heat sink optimization is found the minimum thermal resistance (maximize the heat transfer per unit volume) of the heat sink in order to reduce the cost of heat sink by reducing the heat sink material. The main design parameters (the fin diameter, df, the fin length, Lf, number of fins, Nf, the approach velocity, Uapp, stream wise pitch, SL, span wise pitch, ST) assumed varied between lower and upper values during the present study to get the minimum thermal resistance. The overall dimension of the heat sink and the pressure drop across the heat sink are taken as deign constrains.
After applying the DE for the case study in the present paper, the optimum thermal
resistance for maximize the heat transfer from inline fin arrangement heat sink is
found (0.500467 ◌ْC/W) and for staggered fin arrangement heat sink is found (0.4021
◌ْC/W). The effect of the constant parameters (the thickness, dimensions and material
of the base plate) on the minimum thermal resistance is discussed.
Also, the effect and selections of the differential evolution parameters (crossover coefficient (CR) and scaling factor (F)) on the generation (iteration time) are examined. The optimum values of F & CR that minimize the generation for attaining the minimum thermal resistance are (F=0.9 & CR=0.8) . Also, the results of the DE are compared with Nelder Mead simplex method for same case study in order to check the accuracy and efficiency of the DE method. The DE was consumed less time than the simplex method for the same present case study.

In the present work, the effect of hydrogen addition on the performance of a diesel engine has been studied. A quasi-dimensional multizone combustion model to simulate a four-stroke cycle of a diesel engine fueled with hydrogen-diesel mixture is developed. It is found that the addition of (12)% by mass of hydrogen causes an increase in the maximum (pressure, zonal temperature, and rate of heat release). This is due to increase in the rate of fuel mass burning, therefore, the time required to complete the combustion is reduced. In general, the addition of (10)% of hydrogen by mass gives a maximum improvement in the power and efficiency and a maximum reduction in specific fuel consumption (60)%.

In this study has been compared the heat transfer performance of various commnoly fin geometries by studying the temprature and velocity distribution. Comparitive thermal tests have been carried out using aluminum heat sinks with extruded fins, staggered square pins, and staggered cylinderical pins in forced convection air flow environments. The extruded fin heat sink was designed to minimize the pressure losses across the heat sink by reducing the vortex effects to enhance the thermal performance by maintaining large exposed surfaces area available for heat transfer. Experimental and theoretical investigation were carried out.
The most electronic components operates in the range of temprature between (40)oc and (60)oc therfore in the experimental tests, air velocity was varied from (2) m/s to (6) m/s and the heat flux from (20) Watt to (40) Watt are used to obtain the range of temprature. The temprature of the solid structure was measured experimentally by using (15) thermocouple. They are distributed on the heat sinks uniformly.The velocity and temprature of the flow field in the test section was measured experimentally using portable anemometer.
A software packages (ANSYS 5.4) was used to carry out the theoretical study using adiabatic flow condition. This gives a good ability to calculate the velocity and pressure distributon and sketching the eddies wake behind the pins and fins in the core of the heat sink. By the aid of this software package a three-dimemsional model was built by putting horizontal orintation only. The model boundary condition can be easily varied through (ANSYS 5.4), including all ranges used in the present study. The flow was analyzed for three-dimensional steady, adiabatic, incompressible and viscous. Navir-stocks equations and continuity equation were solved. A two-equation K- model (turbulence model) was also solved by this program.
The straight fin experienced the lowest amount of flow by-pass over the heat sink. For this particular application, where the heat source is localized at the bottom of the heat sink base plate, the overall thermal resistance of the straight fin was lower than the other two designs mainly due to fins have large area of convection. The relative thermal resistance for cylinderical pin-fin heat sink was higher than the other two designs. This is due to the improve distribution of air flow around the circular pin.The results show that when the heat sinks have the same area of convection, the cylinderical pin-fin heat sink was the best choice while when the heat sinks have the same area of conduction the straight fin was the best choice because it give large exposed surface (large area of convection).