Tikrit Journal of Engineering Sciences

Adoption of powder metallurgy technique used aluminum as the metal matrix with 99.7% purity and ≥03μm particle size reinforced with alumina (Al2O3) 99.7% purity with 53 μm in size and Silicon Carbide (SiC) 99.7% purity with ≥95μm in size to prepare the (Al - 10wt% Al2O3– 20wt%SiC) composite, these composites were cold pressed through uniaxial pressing at different pressure of (500,600,700,800,900)MPa and sintered at 550oC for one hour. The composite products were treated thermally using both rapid isothermal heating and traditional heating at temperature 400oC for 15min and then cooled in steady air. The research aims to study the effect of pressing pressure, heat treatments on the properties of the samples since it was found that the physical properties (density, porosity and thermal conductivity) increases with increasing pressing pressure and increase significantly after heat treatment (rapid isothermal heating and traditional heating) was accompanied by an increase in the mechanical properties (hardness, compressive strength ).

The concrete structures are often exposed to damage as a result of several factors including, environment, design, and other factors, and because of the high cost and long time needed for reconstruction of the damaged buildings, it become necessary to consider methods for rehabilitation of the damaged structural member in the building. Several methods for repairing the damaged beams are considered in the present work. The technologies of ferrocement, steel plate, fiber carbon reinforced polymer (FCRP), and the technology of the developed nano cement mortar are used in the present work. Twelve reinforced concrete beams (2200x200x150)mm were cast and tested under point load at mid-span to limit the failure. The ultimate strength of rehabilitated concrete beams using the techniques of injecting nano materials in the cracks or having a jacket made from reinforced nano cement mortar exceeds 80% of the ultimate strength of the beam before rehabilitation and exceeds 99% of ultimate strength of the beam before rehabilitation of rehabilitation by fiber carbon reinforced polymer (FCRP) with low cost compared to other techniques that used in research.

The present work deals with the influence of geometry and direction on energy efficiency for the envelopment of a dwelling building in Kirkuk government from existing models frequently used in the design of houses with a construction area 135.2 m 2 irregularly shaped four investigate cases of aspect ratio (1: 1, 1: 1.25, 1: 1.5 ,.1: 2) and put dimension by designed assistant program calculator by Visual Basic program for each cases at same format for the building envelopment, and then used building energy simulation program (Ecotect ) to compute the annual HVAC load ,peak cooling load and peak heating load during the preparation and import the hourly annual Weather data of Kirkuk region and examined the effect of orientation for building facade in the eight directions (north, northeast, east, southeast, south, southwest, west, north-west) for each aspect ratio separately and then find the amounts of savings in annual HVAC load, has been reached that the square geometry of building have aspect ratio (1: 1) achieve greatest energy efficiency by saving 10% of the annual air conditioning load compared with the longest rectangular shape have aspect ratio’s (1:2), as well as been reachedto the highest savings at the best direction of a square geometry of building at rate 1.43% of the annual air-conditioning load

In this research the suspended sediment load effect on efficiency of central Tikrit water supply station was studied. Samples were taken from four locations include raw water, water outside from deposition and filtration basins and treated water. The study continued five months starting in December 2015 until April 2016. This study includes eleven variables (pH, temperature, electrical conductivity, residual chlorine, turbidity, total hardness, calcium, magnesium, total dissolved solids (TDS), total suspended solids (TSS) and suspended sediment Concentration). Results were compared with the Iraqi standard 417 for drinking water. This study showed that the raw water and drinking water samples rising in turbidity where exceeded 516 NTU, the results appear maximum value for TDS was 780mg/L for raw water and the minimum value was 196mg/L for drinking water, whereas the maximum value for TSS was 420mg/L for raw water and zero for drinking water. The results showed that the removal efficiency of deposition basins are ranged between (22-97)%, and found that the removal efficiency of the filtration basins ranged between (5-41)%, while the total removal efficiency fall between (70-99)%.

An experimental study was investigated to show the effect of heat exchangers of capillary tube with suction line on compression refrigeration system performance which work on R-134a as refrigerant. Three types of heat exchangers (Coil, Concentric, Lateral) with capillary tube where made to use in refrigeration system. The experimental setup is measured for various volumetric flow rates for refrigerant, different air speeds for evaporator. So iterative method to find the actual process in capillary tube - suction line heat exchanger. The experimental results showed that at low refrigerant flow rate 15kg/hr, the maximum coefficient of performance for lateral heat exchanger which was 2.992 and minimum coefficient of performance for coil heat exchanger which was 2.876. While in case of high refrigerant flow rate 22.5kg/hr, the maximum COP for coil heat exchanger was 3.6, which was the highest value for all heat exchangers using in the system.

Stainless steel is widely used in the engineering industry for its suitable engineering properties such as corrosion resistance, high flexibility, hardness and durability to static and dynamic loads. It is very suitable for home uses, automotive parts and many engineering applications. In this study, a sample of 304 stainless steel was selected, where a heat treatment (Normalizing) was performed. This process was performed at (1050, 1100 and 1150) °C respectively and according to (ASTM 304 S30400). And Tempering at 350 °C to remove the internal stresses and prevent the deposition of carbides, which occurs at the degree of (450-800) °C for stainless steel. Mechanical tests were conducted, the tensile and Brinell hardness tests. In addition to the test of the fatigue, wear and Izod impact tests. X-ray diffraction (XRD) analysis was used to distinguish the phase (s) that formed The results showed in general that the heat treatments lead to the improvement of mechanical properties except the impact test, the best cases has been at 1100 °C temperature.

This research studied, theoretically, the performance of a tilted pad journal bearing. This bearing consists three inclined pads. These pads are distributed circumferentially around the journal. These pads can be adjusted in two ways: by changing the tilt angle of each pad _and by changing the circumferential position of the pads around the journal, relative to the external load direction, in order to obtain the following goals: (1) Maximum external load, (2) Maximum oil flow rate in order to carry out as much heat as possible, (3) Minimum power consumption, and (4) Control the attitude angle magnitude in order to control the stiffness and damping coefficients then improve bearing stability. The thickness of the oil film between the pads and the shaft surface had been obtained using an equation that was derived specially for this purpose. Then the pressure of each point on the three pads surfaces were also calculated using Reynolds equation which solved numerically using a computer program. The results showed that there is a certain direction for the external load (a specific value for ????), that gives a maximum value for the external load (W), and the attitude angle (Ф), while the oil flow rate (Q) reaches its minimum value at this angle. And this value for ???? increases as the pads tilt angle (α) increases. Also there is another value for ????, that gives a maximum value for the oil flow rate (Q). And also this value of ???? increases as α increases.

In this study, three laboratory units were constructed and operated in order to investigate the effect of pre-aeration on removal efficiency of ammonia and organic materials for solid waste leachate from Quashi landfill in Duhok city. The effect of aeration times and pH values on the removal efficiencies were also investigated in this study. Each unit consists of a glass reactor with an effective volume of ten liters supplied by the air pumps and plastic tubes that were used to distribute the air-flow evenly throughout the unit. All units were designed to work in parallel at the same operational conditions. The study program was divided into three stages. In the first stage, the aeration times between (6 to 72) hours were used and the pH value for the leachate was on its original level. Whereas in the second and third stages, the same aeration times where used while the pH values of leachate were adjusted to be 10 and 11. The results of the study showed that; the aeration improves the removal of organic matter and ammonia and the removal efficiencies increase with increasing aeration time. In addition, there is no significant difference in the removal efficiencies of ammonia at pH values equal to 10 and 11.

This research deals with optimum design of parabolic solar collector with exergy analysis, a mathematical model built to reach the optimum design for the parabolic trough solar collector by three main parts. The first part concentrated on optimal design depends on the measured values of the solar intensity radiation fell on the city of Kirkuk and to obtain solar absorbed radiation, while the second part revolves on energy analysis of parabolic solar collector, and the final part was carried out exergy analysis of parabolic trough solar collector. The exergy efficiency took as a measurement to found the optimum operation condition (inlet water temperature and mass flow rate) and design parameter (concentration ratio, length solar collector and width solar collector). The design depended on the climatic conditions of the city of Kirkuk after it measured, also it show’s the importance of using exergy analysis in the design by studying the impact of some of the basic transactions of the solar system.

Induction motors are the most widely used electrical machines and the most popularly in the industrial applications, aerospace, and electrical vehicles or hybrid electrical vehicles. This celebrity of these machines because of some of their benefits such as: relatively low manufacturing cost, robust construction, moderate power factor, ability to operate in hostile environments, good reliability, and ease of control especially in the recent years. In fact, induction motors are the main component of many of these applications and they are used in the most of these applications with their power electronic drivers in order to control their speeds, torques, or control their starting conditions. However, these motors and their drivers may encounter several faults due to operating conditions. In fact, these faults are either due to the motor itself or due to its power electronic driver circuit. Therefore, this paper presents the performance analysis and simulation of a Sinusoidal pulse width Modulation (SPWM) inverter-fed three-phase induction motor under some fault conditions. Two different types of faults are studied and analyzed in detail. These faults were: driver single switch short circuit fault, and driver single switch open circuit fault. The motor currents and voltages at pre-fault and post-fault conditions are presented and investigated. In the two fault cases, the motor phase currents are changed and increased, but in different ratios, under same load conditions. Also, decreasing and oscillating in both motor speed and its developed torque are occurred due to these faults. The simulation and analysis results show that the single switch short circuit fault has the sever effect on the motor performance, therefore especial care should be taken under this fault conditions.