Volume 25, Issue 4, Autumn 2018, Page 1-63

Application of Dynamic Cone Penetration Test to Gypseous Soils

Tikrit Journal of Engineering Sciences, 2018, Volume 25, Issue 4, Pages 1-5

Dynamic cone penetration test (DCPT) is a fast, economical and easy to conduct. It is widely used to assess the strength of natural and compacted soils. The device is introduced in the 1950s. However, it was newly introduced in Iraq. This study aims to evaluate the potentials of DCP in geotechnical explorations in the gypseous
soil since it covers a large area of the country and to obtain correlations with the California bearing ratios (CBR) and investigating the effect of gypsum on the CBRDCP relationship. Field and Laboratory tests were conducted on soil sample retrieved from six sites with different gypsum contents (28-41) %. Laboratory tests
include performing CBR and DCP tests in a cylindrical mold. A statistical analysis of the results shows that gypsum content is an affecting factor on DCP and good CBR-DCP correlations on gypsum content were obtained..

Optimum Building Wall Thickness under Actual Weather Conditions for Kirkuk City

Tikrit Journal of Engineering Sciences, 2018, Volume 25, Issue 4, Pages 11-15

The aim of the present study is to obtain the optimum wall thickness of the buildings from four different wall thickness sizes that which selected as 48, 32, 24, and 16 cm used for building room. The dimension of 6×4×3 m, built by a common brick insulated for all sides except south wall. For this purpose, an energy simulation has been conducted by preparing a computer programmer and was executed by Matlab software. The two days in different weather conditions on 2016, first on 30/12, and other 01/07 for a constant indoor temperature at 23oC. The results showed that the inner surface temperature was more stability against to the weather change for both climate conditions. In addition, the thick wall 48cm needs more
energy consumption than other three types of walls about twice that 16cm thickness in a cold climate. The wall thick was more active for energy saving in a hot climate, and obverse, where the thin wall has more energy saving in a cold climate. The energy analyzing for both climates showing that the optimum wall thickness about 30 cm and the rate of energy consumption were estimated about 500 W..

Effect of Fluidized Bed Particle Size on Heat Transfer Coefficient at Different Operating Conditions

Tikrit Journal of Engineering Sciences, 2018, Volume 25, Issue 4, Pages 24-29

The aim of this study is to investigate the effect of gas flow velocity, size of sand particles, and the distance between tubes immersed in a fluidized bed on heat transfer coefficient. Experimental tests were conducted on a bundle of copper tubes of (12.5 mm) diameter and (320 mm) length arranged in a matrix (17×9) and immersed in a fluidized bed inside a plastic container. One of the tubes was used as a hot tube with a capacity of (122 W). (25 kg) of sand with three different diameters of sand particles (0.15, 0.3 and 0.6 mm) was used in these tests at ten speeds for gas flow (from 0.16 m/s to 0.516 m/s). The results showed a significant inverse effect of fluidized bed particles diameter on the heat transfer coefficient. Accordingly, the heat transfer coefficient for (0.15mm) diameter sand was found to be higher than that of (0.3 mm) and (0.6 mm) sand by about (3.124) and (6.868) times respectively, in all tests. The results showed good agreement with results from other studies conducted under the same conditions but with different sand
particle size..

Flexural Behavior of Reinforced Concrete One-Way Slabs with Different Ratios of Lightweight Coarse Aggregate

Tikrit Journal of Engineering Sciences, 2018, Volume 25, Issue 4, Pages 37-45

The aim of the present research includes an experimental investigation of flexural behavior of lightweight reinforced concrete one-way slabs with different ratios of course aggregate. Nine lightweight reinforced concrete one- way slabs incorporated by two types of lightweight course aggregate were tested in these
investigation. Also the mechanical properties and workability test for concrete used in the study. There was chosen eight concrete mixes were casted by replacing the normal coarse aggregate by lightweight course aggregate; claystone (bonza) and thermostone. Different percentage of aggregate replaced were done (25, 50, 75 and
100) %, in addition to the reference mix of (0%) replacement ratio was casted. For each concrete mix: Three cylinders for compressive strength and density of saturated and dry surface concrete tests, three cylinders for splitting tensile strength test and three prisms for modulus of rupture test were prepared. Also for each mix was casted, prepare a one slab specimen for bending moment test for all mixes contain a light coarse aggregate and reference mix. The main results of mechanical properties are ((38.44-12.38), (3.969-2.172) and (10.467-3.194)) MPa, for compressive, splitting and flexural strength respectively with differences of (67.79, 45.12 and 69.48) % respectively compared with the reference mix. Also the flexural capacities of the lightweight concrete slabs that contained a different ratios of light coarse aggregate (0.028 and 0.026) MPa were recorded with (22.5 and 28.62) % compared with reference sample of 0.035 MPa. )035.0 )MPa.

Tensile Strength, Micro-hardness and Microstructure of Friction-Stir-Welding AA6061-T4 Joints

Tikrit Journal of Engineering Sciences, 2018, Volume 25, Issue 4, Pages 51-56

Welding of aluminum alloys by traditional welding methods creates some defects such as hot cracks, porosity, and void that led to decreasing of mechanical properties. Friction Stir Welding (FSW) gives good mechanical properties of aluminum alloy welds. In this paper, FSW worked in 4 mm thick plate of 6061-T4 aluminum alloy, with two welding parameters are used (tool rotational speed and feed rate) was investigated, were analyzed the microstructure and mechanical properties by carried out microstructural, microhardness, and tensile strength tests. From results are found defect-free of welds at a wide range of parameters. Stir zone shows a fine-equiaxed grain and high hardness, not significantly change between heat affected zone and base metal in size grain. Tensile strength of welds was lower than base metal and fracture location was occurred at a low hardness region for the welds.لحام سبائك االلمنيوم بالطرق التقليدية يخلق بعض العيوب مثل الشقوق الحارة والمسامية والفراغات التي تعمل على خفض الخواص الميكانيكية للملحومات، لحام الخلط االحتكاكي يعطي خواص ميكانيكية جيدة لملحومات سبائك االلمنيوم. في هذا البحث دراسة للحام سبائك االلمنيوم (T4-AA6061) بسمك (4mm) بوساطة لحام الخلط االحتكاكي تحت متغيرات) السرعة الدورانية ومعدل التغذية(، وحللت الخواص الميكانيكية والبنية المجهرية من خالل اجراء فحوصات البنية المجهرية والصالدة المجهرية ومقاومة الشد. من خالل النتائج وجد ان البنية المجهرية لمنطقة الخلط ذات حجم حبيبي ناعم-ومتساوية المحاور وذات صالدة عالية وليس هناك اختالف مميز في الحجم الحبيبي بين منطقة المعدن األساس والمنطقة المتأثرة بالحرارة، مقاومة الشد للملحومات أدنى من مقاومة الشد للمعدن األساس وموقع الكسر للملحومات حدث في منطقة
الصالدة المنخفضة.

The Effect of Pads Number and Their Tilt Angles on the Bearing Stiffness

Tikrit Journal of Engineering Sciences, 2018, Volume 25, Issue 4, Pages 6-10

In this work a plain (conventional) and a tilted bad bearings are analyzed and studied (both have the same dimensions and work conditions). Three, four and five pads models are studied. The pads are fixed circumferentially in a manner each two close pads are separated with an angle that is the same for all the close pads.
Each pad is pivoted in its trailing edge and is facilitated to be tilted around this pivot with small angles. This study was achieved for three values of tilting angles. These angles are, 0.01o, 0.011o and 0.012o. Two dimensions' form of Reynolds equation is used and solved numerically then the stiffness coefficients had been calculated. A comparison had been done between the stiffness coefficients values for the two models (tilted pads and conventional bearings). The results of this comparison was found that (for n = 0.4), are, +28%, +275%, +270 % and -100% for Ksr, Krr, Kss and Krs respectively. It was noticed that the values of the principal coefficients Krr and Kss are increased significantly while the cross coupling coefficient, (Krs) is decreased significantly and (Ksr) is increased slightly. And this is a positive sign for stability improvement. Also it was found that increasing the tilt angle (delta) cause an increase of the stiffness coefficients values. These increases (for n = 0.4 and changing the tilt angle from 0.010 to 0.011 then to 0.012 respectively) are, Krr=+50%, +47%, Kss = +40%, +32%, Ksr = +33%, +42%, and Krs = +15%, +20%. And since increasing the values of the cross coupling coefficients make the bearing stability worse, so increasing the tilt angle is not a
preferable method for improving stability. Changing the number of pads is a better solution and it was found that three pads bearing is the best among them..

Effects of Rice Husk Ash–Magnesium Oxide Addition on Wear Behavior of Aluminum Alloy Matrix Hybrid Composites

Tikrit Journal of Engineering Sciences, 2018, Volume 25, Issue 4, Pages 16-23

A336.0 aluminum alloy used to fabricate hybrid composites using rice husk ash (RHA) and MgO particles as reinforcement. The influence of the particles on the wear behavior of A336.0 aluminum alloy as a matrix that reinforced with MgO and RHA was investigated. Firstly, the rice husk burned at 700°C and then heat treated at 1100°C for 2 hrs. The ash characterized by X-ray florescence and X-ray diffraction. Less than 53 and 125 micron are the particle sizes of MgO and RHA respectively. The hybrid composites manufactured using stir casting method in two steps. A336.0 aluminum alloy reinforced with 4:0, 3:1, 2:2, 1:3 and 0:4 of RHA: MgO with 10 wt% total reinforcement phase. Optical microscope and X-ray diffraction were used to characterize the prepared hybrid composites. Dry sliding
wear, hardness, apparent density, percentage of porosity and coefficient of friction were examined. Results indicated that porosity, apparent density and hardness enhanced with increasing MgO, while increasing wt% of RHA decreased the apparent density. Results indicated that with inceasing the applied load the wear
rate of the composites was enhanced. Coefficient of friction varies inversely with applied load and wt% of RHA. Hardness increased with increasing RHA while the friction coefficient and the wear rate decreased. The minimum wear rates were at 10% RHA and Al-alloy-(RHA-MgO) [3:1] composites, while the minimum friction coefficients were at 10% RHA composites. 10%RHA.

Effecting of Steel Fibers and Fly Ash on the Properties of Concrete

Tikrit Journal of Engineering Sciences, 2018, Volume 25, Issue 4, Pages 30-36

In this research, the effect of the addition of fly ash particles with different weight ratios of 15%, 20%, and 25% as well as the addition steel fibers with different volume fractions of 0.25%, 0.75%, and 1.25% on the mechanical properties of concrete (compressive strength and modulus of rupture) was studied. To carry out this research, ten concrete mixes were prepared, one of which is the reference normal concrete (without any additives), the others contain steel fibers and fly ash as additives with the mentioned volumetric and weight proportions. For each type of concrete mix, three standard 150×300 mm cylinders and three standard prisms
100×100×500 mm were casted, water to cementing material ratio was fixed for all concrete mixes (W/cm = 0.435) and the superplasticizer was used with ratio of 0.98%-1.22% by weight of the cementitious material in mixtures that contain steel fibers and fly ash particles as a partial replacement of cement weight. The results showed that the addition of fly ash particles had little effect on the mechanical properties of normal concrete, while the steel fibers had the greatest effect. The highest increase in compressive strength and flexural strength compared with reference concrete was 61.60% and 78.84%, respectively in the volume fractions 1.25% of steel fiber..

Effect of Colored Filters on PV Panels Temperature and Performance under Baghdad Meteorological Condition

Tikrit Journal of Engineering Sciences, 2018, Volume 25, Issue 4, Pages 46-50

In this work, the influence of colors of filters upon the photovoltaic panels rising temperature and electrical performance was studied under Baghdad Meteorological Condition. Basing on the energy analysis of a photovoltaic solar system and by using the photonic theory, the available energy on the PV plane system has been evaluated. Seven colored filters each with (85W) PV modules were used in this case study, to reveal the impact of colored filters upon the electrical productivity of PV panel with the variation in the temperature caused by these filters. There is the
main issue of this work is to show how the performance of PV module by imposing colored filter and hence how and to how much improve it by reducing the cell temperature in hot climate. Outcomes showed that the PV technology is affected by the color filters. In other words, red filter gives light have least photons energy, and violet filter gives light have the most photons energy and green is between the two. So, red colors filter gives highest PV panel temperature comparative with others filters, while violet color filter was the lowest. PV module with the lowest temperature colored filter gives the best electrical performance than others..

Control Techniques of Torque Ripple Minimization for Induction Motor

Tikrit Journal of Engineering Sciences, 2018, Volume 25, Issue 4, Pages 57-63

A Matlab-Simulink environment used to build a model of an Induction Motor (IM) to study and explore methods for minimizing the torque ripple. Various control strategies were reviewed and simulation studies were carried out for the following control methods: Direct Torque control, Direct Torque control with harmonic elimination, and Direct Torque control with Matrix convertor were the obtained results analyzed, evaluated, and compared to each other. The simulation results confirmed that Using Direct Torque Control with Harmonic elimination method was significantly minimized the torque ripple as the harmonics of the output voltage were canceled; discussions and conclusions were presented in this study..