Al-Qadisiyah Journal for Engineering Sciences

In this research we made a composite material consist of the matrix which is epoxy resin type (Thortex) with the reinforcing of chopped carbon fibers with volume fraction of 20%. Some mechanical properties were studied of prepared composite specimen after subjected different environments included (air, distilled water, KOH, HNO3) The normality for all these chemical solutions is )1(. Several mechanical tests are carried out on these samples, and these are: Bending test, Impact Strength test, Brinell Hardness test, every 14 days for 60 days.

A simplified computational procedure for shear buckling problems of rectangular thin plates with constant and variable thickness is presented. The discretization of the problem is carried out by means of finite differences. Geometric and material non-linearity are neglected. The effect of boundary conditions, aspect ratios, and tapering ratios on the shear buckling behavior are considered. The plate was analyzed with different tapering ratios (ta/to) (1.0, 1.25, 1.5, 1.75, and 2.0). It is concluded that the shear buckling behavior of thin plate is very sensitive to the magnitude of tapering ratio.

This study describes a three-dimensional material nonlinear finite element model suitable for the analysis of high strength reinforced concrete slabs under different states of loading. The twenty-node isoparametric brick element has been used to model the concrete while reinforcing steel bars have been idealized as axial members embedded within the brick elements. The behavior of concrete in compression is simulated by an elasto-plastic work hardening model followed by a perfectly plastic response, which is terminated at the onset of crushing. In tension, a smeared crack model with fixed orthogonal cracks has been used with the inclusion of models for the retained post-cracking tensile stress and for the reduced shear modulus. Three high strength reinforced concrete slabs and one normal strength concrete slab have been analyzed in the present study with different boundary conditions and loading arrangements. Parametric studies have been carried out to investigate the effect of some important finite element and material parameters. These parameters include the compressive strength of concrete, amount of reinforcement and slab thickness. The finite element analysis indicated that when the concrete compressive strength of the slab is increased from (35 MPa) to (80 MPa) an increase in the ultimate capacity of about (60%) has been achieved. In general good agreement between the finite element solutions and the available experimental results have been obtained

The investigation includes the effect of freezing and thawing cycles on stress-strain relationships of polymer modified concrete (PMC). Cycles of freezing and thawing contains 12 hours at 100°C and 12 hours at -4°C. The process of cycles of freezing and thawing Simple experimental technique is used to obtain the complete stress-strain curves up to strain of 0.006 (Both ascending and descending portions) sample subjected to freezing and thawing cycles (FTC), then subjected also to stress-strain tests.

In this study, a mathematical model have been prepared for al – Kut water supply project depending upon the numerical methods such as Newton - Raphson method and Gaussian elimination method to solve non – linear simultaneous equations with known boundary condition and by using the characteristic method, the partial differential equations are transformed to ordinary differential equations. In this mathematical model, the values of the generated pressures were calculated when using control devices or without, also, to find the influence of this devices on, the pressure values was found. In addition to, the suitable number of control devices required for each pipeline was found to keep the pressure values within a tolerable limits. This model was applied on a published case study and the results were quite satisfactory.

تم اجراء دراسه نظريه لمنظومة تسخين المياه باستخدام الطاقه الشمسيه في مدينة البصره. اعتمدت التحليلات النظريه في هذه االدراسة على مبدأ السيفون الحراري كوسيله لتدوير المياه في المنظومة. تتكون هذه المنظومة من مجمع شمسي مستوي مائل بزاويه مع الافق يتصل بخزان ماء معزول حراريا عن طريق مجموعة من االانابيب المتوازيه. أجريت جميع الحسابات بالاستناد الى الظروف المناخيه السائده في مدينة البصره في يوم 21 كانون الثاني. أظهرت النتائج ان اداء منظومة السخان الشمسي تعتمد على موقع المجمع الشمسي من الشمس وزاوية ميله عن الافق ومساحته بألاضافه الى خط العرض والوقت. في مدينة البصره حيث تبلغ اقصى زاوية ارتفاع الشمس في كانون الثاني حوالي 40 درجه تكون زاوية ميل المجمع الشمسي المثلى عن الافق حوالي 50 درجة.وجد أن درجة حرارة الماء في الخزان تقع بين 65و95 درجة مئوية وهي كافيه للاستخدام المنزلي في مدينة البصرة

Experimental work were carried out in gas- solid CFBs to investigate the steady state heat transfer between gas and solid and the surface immersed in the bed. The bed column was 76 mm in inside diameter and 1500 mm in height fitted with a horizontal heating tube with outer diameter 28 mm heated electrically with different power supplies (105 W). The fluidizing medium was air at different velocities ( 4.97, 5.56 and 6 m/s). Three different size of sand particle were employed (i.e 194, 295 and 356 μm). The initial bed height used experimentally with different values ( 15, 25 and 35 cm). The column of heat exchange provide with return line which content of the cyclone to separated the sand with type is High efficiency cyclone connected to standpipe to transport the separated sand to riser mixing region inside the riser. Heat transfer coefficients are found to increase with fluidized air velocity and, through clear, with heat flux, but, they show an inverse dependence on particle size, and direct proportional with initial bed height which representation the bed density.

This paper presents a unification of kinematic and torque balance methods for the analysis of two-input epicyclic-type transmission trains. A method for the derivation of the velocity ratio of an epicyclic gear train in a symbolic form is developed. A single kinematic equation is derived to study the kinematic characteristics of fundamental gear entities. The method relies on previous work on graph theory. It improves on existing techniques used for automatic transmission mechanisms in its ability to accurately solve the kinematics of geared mechanisms and estimating their velocity ratios and arranging them in a descending order in a simpler manner. The results are then used for assignment of the various links of a given two-input epicyclic gear mechanism. This study contributes to the development of a systematic methodology for the torque and power flow analyses of two-input epicyclic gear mechanisms with a reaction link, based upon the concept of fundamental circuit. Specifically, this study presents for the first time a complete design and analysis of two-input velocity changer to be used as a power coupling in a new generation of tandem bicycles. Two new designs are demonstrated.

An analytical solution for local pressure drop due to obstructions in horizontal air-water twophase flow was presented. Various obstruction shapes with size were investigated. An analysis based on the momentum conservation through obstruction region. The relationship between twophase multiplier and local (normalized) pressure drop with the gas superficial velocity were investigated. The results showed, a higher pressure drops pointed for larger obstructions. The present results was verified with experimental investigations.

Heat transfer behavior for non-Newtonian power law fluids flow in circular duct with laminar flow, fully developed, constant heat flux. And constant wall temperature was studied. A mathematical model which is capable of accurately predicting temperature and velocity profiles and heat transfer rates for power law non-Newtonian fluids was obtained. The theoretical Nussult number was compared with previously published works where good agreement was noticed, which can be easily evaluated using theoretical model as a function of power law index only for constant heat flux and as a function of power law index and Graets number for constant wall temperature. It was found find that Nussult Number decreases when values of power index increases.