Ali A. Al-Kayiem
Volume 1, Issue 2 , December 2008, Pages 35-55
Abstract
يتناول البحث دراسة نظرية لسلوك المعادن أثناء انجمادها في قوالب السباكة الدائمية. تم اختيار معدن الفولاذ حيث إن درجة حرارة الانصهار له [C°1520].كذلك تم دراسة عدة أحجام للقوالب ...
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يتناول البحث دراسة نظرية لسلوك المعادن أثناء انجمادها في قوالب السباكة الدائمية. تم اختيار معدن الفولاذ حيث إن درجة حرارة الانصهار له [C°1520].كذلك تم دراسة عدة أحجام للقوالب الدائمية حيث كان التغيير في طول القالب (من 30 mm إلى mm 100) وارتفاع القالب (منmm 10إلى mm 30) وبذلك حصلنا على تسعة أنواع من القوالب المختلفة. أما فيما يخص معالجة الموضوع رياضيا فقد تم اشتقاق المعادلة الحاكمة للحالة من خلال موازنة الطاقة لشريحة معينة من المعدن، حيث كانت المعادلة الحاكمة هي معادلة انتقال الحرارة ببعدين وغير مستقرة. وقد تم حل هذه المعادلة عدديا بطريقة الفروق المحددة، وكانت الشروط الحدودية والابتدائية تخص حالة السباكة. وقد تم بناء برنامج حاسوبي بلغة البيسك السريع يحاكي الحالة ويعطي توزيع درجات الحرارة للمعادن في القوالب خلال عملية السباكة.وقد تم اختيار أزمان مختلفة (2sec، 10sec، 50sec و 100sec) بحيث نصل إلى حالة انجماد المعدن
Ali I.Al-Mosawi
Volume 1, Issue 2 , December 2008, Pages 56-66
Abstract
The objective of this research is to study the effect of changed the reinforcement percentage by fibers on Mechanical properties for composite material consist of phenol formaldehyde resin reinforced by biaxial kevlar fibers (0o-90o))with (485g/cm3) density which included impact strength , tensile strength ...
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The objective of this research is to study the effect of changed the reinforcement percentage by fibers on Mechanical properties for composite material consist of phenol formaldehyde resin reinforced by biaxial kevlar fibers (0o-90o))with (485g/cm3) density which included impact strength , tensile strength , and hardness where we extracted the Mechanical properties for phenol formaldehyde resin before reinforced by fibers, then we reinforced the resin by different weight percentage from Kevlar Fibers(20%,40%,60%) and studied its effect on the above Mechanical Properties as illustrated in the diagrams .
Keywords:-Composite Material , Mechanical Properties, Phenol Formaldehyde Resin , Kevlar Fibers .
Abbas A. S. Al- Jeebori
Volume 1, Issue 2 , December 2008, Pages 133-143
Abstract
Tube banks are widely used in crossflow heat exchangers. Usually, the methods for its design are the NTU or LMTD methods, while in this research the Entropy Generation Method is used. By assuming constant tube wall temperature, a general dimensionless expression for the entropy generation rate is obtained ...
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Tube banks are widely used in crossflow heat exchangers. Usually, the methods for its design are the NTU or LMTD methods, while in this research the Entropy Generation Method is used. By assuming constant tube wall temperature, a general dimensionless expression for the entropy generation rate is obtained by considering a control volume around a tube bank and applying the conservation equations for mass and energy with the entropy balance. A comparison of the design is accomplished for a tube banks of different stream velocity, lengths and diameters. The heat transferred rate, ambient and tube wall temperatures are 20kW, 300K, and 365K, respectively. From the comparison of the design with the entropy generation rates, the optimal design is obtained. A single objective function is used which is the dimensionless entropy generation rate Ns subjected to the constraints of diameters and pitch ratio. This method of optimization can be applied for any constraints on the system which is the Lagrange optimization method. The effects of tube diameter, tube length, dimensionless pitch ratios, front cross-sectional area of the tube bank, and heat load are examined with respect to its role in influencing optimum design conditions and the overall performance of the tube banks. It is demonstrated that the performance is better for higher air velocities and larger dimensionless pitch ratios. Compact tube banks perform better performance for smaller tube diameters.
Munaf A. Abdulkadhem; Sadjad A. Hemzah
Volume 1, Issue 2 , December 2008, Pages 144-157
Abstract
A free vibration analysis of a curved plate cellular structure is presented. The flexibility matrices of both curved and straight members were used in the analysis; also a lumped mass matrix having the same number of equations as the consistent mass matrix was adopted herein. Jacobi’s iterative method ...
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A free vibration analysis of a curved plate cellular structure is presented. The flexibility matrices of both curved and straight members were used in the analysis; also a lumped mass matrix having the same number of equations as the consistent mass matrix was adopted herein. Jacobi’s iterative method was used to solve the Eigenvalue problems. The general purpose finite element program (MSC/NASTRAN) was used in the comparisons of the vibration analysis. The maximum deference in the results compared with (MSC/NASTRAN) are about (15%) for the fifth Eigenvalue and it decrease until (1%) for the first Eigenvalue
Muhammed Faleh Hassan
Volume 1, Issue 2 , December 2008, Pages 158-171
Abstract
Chirped fiber Bragg grating is a promising approach for dispersion compensation in optical fiber communication systems, since it’s passive optical component, fiber compatible and has low insertion losses and low costs. Unapodized CFBG is fail to achieve the expected performance due to high ripples ...
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Chirped fiber Bragg grating is a promising approach for dispersion compensation in optical fiber communication systems, since it’s passive optical component, fiber compatible and has low insertion losses and low costs. Unapodized CFBG is fail to achieve the expected performance due to high ripples in time delay response. Many apodization profiles are suggested to optimize grating performance. Among them, hyperbolic tangent (tanh) apodization profile result in overall superior performance. In this work, the reflection spectrum of CFBG is solved by numerical solution of Reccati differential equation. Results show that, the characteristics of the tanh apodized CFBG can varied systematically according to an angular tanh apodization profile parameter called truncation parameter (atr). By using this parameter the characteristics of the grating is assist in term of limitations of full-wave half maximum reflection bandwidth and minimizing average time-delay ripples for different truncation parameter values. Results show that for a given chirped parameter value CFBG approach optimal performance at truncation parameter of 4. In optical communication bandwidth of 0.5nm CFBG can compensate linear dispersion of 100 km of standard optical fiber length, the required grating length is 10 cm. According to these results, the truncation parameter must be chosen carefully in performance optimization of the hyperbolic tanh apodized chirped fiber Bragg grating.
Mushtaq Taleb Albdiry; Saad Hameed Alshafaie
Volume 1, Issue 2 , December 2008, Pages 172-179
Abstract
Aluminum matrix composites AMCS with 10 wt % Al2O3 particles with average size (3.86 µm) were fabricated by stir casting method, then the composite produced coated with Antimony Trioxide (Sb2O3) by hot dipping coating process. Thermal conductivity of composite materials with and without coating was ...
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Aluminum matrix composites AMCS with 10 wt % Al2O3 particles with average size (3.86 µm) were fabricated by stir casting method, then the composite produced coated with Antimony Trioxide (Sb2O3) by hot dipping coating process. Thermal conductivity of composite materials with and without coating was estimated by applying Fourier equation to investigate its behavior under different temperature conditions. Results revealed that coating with antimony trioxide decreased the thermal conductivity (k) of composite material. The thermal conductivity of the master composite material was (207 W/mC) at (80 C) and (182 W/mC) of the coated composite material at same temperature.
Hayder Aziz Neema
Volume 1, Issue 2 , December 2008, Pages 180-187
Abstract
The ability of the panel methods in solving the potential flow problem around 2-D lifting airfoils is tested in this study. The approximate solutions for potential flow pasts thick, thin, symmetrical, and non-symmetrical airfoils have been calculated by using panel methods and then compared with either ...
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The ability of the panel methods in solving the potential flow problem around 2-D lifting airfoils is tested in this study. The approximate solutions for potential flow pasts thick, thin, symmetrical, and non-symmetrical airfoils have been calculated by using panel methods and then compared with either the exact analytical solution or the numerical solution obtained by using a perturbation method. As a results, the linear-varying strength vortex method is seemed to be the better one in precision in solving the all four problems.
Riadh .A.Abass
Volume 1, Issue 2 , December 2008, Pages 188-195
Abstract
This research is directed to evaluate the relation ship between sub base resilient modulus (Mr) with uniform dry density during testing; only the deformation in the central portion of the specimen is measured. It is noticed that the divided layer of sub base sample is affected by the period of soaking ...
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This research is directed to evaluate the relation ship between sub base resilient modulus (Mr) with uniform dry density during testing; only the deformation in the central portion of the specimen is measured. It is noticed that the divided layer of sub base sample is affected by the period of soaking and reflects this effect on the ( Mr ) of the material .In this research ,the samples from the Nibaee quarry were took. These samples were representing the lower limit of gradation of the specification. The specimens were classified into two groups. The first one is soaked for a period of two days and the second group was soaked for four days.
Mahdi S. Essa Al-Saegh
Volume 1, Issue 2 , December 2008, Pages 196-210
Abstract
The present study aims aimed to investigate factors affecting the soundness of Portland cement (in terms of autoclave expansion test). These factors are C3S, C2S, C3A, C4AF, fineness (in terms of specific surface measured by Blaine method), the minor oxides MgO, free CaO, SO3, and the variables obtained ...
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The present study aims aimed to investigate factors affecting the soundness of Portland cement (in terms of autoclave expansion test). These factors are C3S, C2S, C3A, C4AF, fineness (in terms of specific surface measured by Blaine method), the minor oxides MgO, free CaO, SO3, and the variables obtained from the chemical analysis of cement like silica modulus (SM), alumina ratio (AR), loss on ignition (LOI), insoluble residue (IR), and lime saturation factor (LSF). The autoclave expansion prediction models were built by using multiple linear regression analysis and based on (40) different cement samples taken from (7) different Iraqi cement factories, Indian cement, and Kuwaiti cement. (29) of the samples were ordinary Portland cement while the other (11) samples were sulphate resisting Portland cement. It was found that the multiple linear regression is very suitable for predicting the autoclave expansion of Portland cement. It was also found that the increase of fineness of cement, LSF, and LOI decreases the autoclave expansion, while the increase in the other factors increases the autoclave expansion. The correlation coefficients of the proposed models were (0.71002 and 0.98338) for the first model, (0.84366 and 0.98789) for the second model, and (0.85593 and 0.98872) for the third model, with and without intercept respectively
Ali A. Jazie Al-Khaledy
Volume 1, Issue 2 , December 2008, Pages 211-224
Abstract
In the combustion of hydrocarbon fuel there was needing to lower the volume of unburned gases and pollutant emissions and increase combustion efficiency. The first to be oxidized are the hydrogen atoms when hydrocarbon fuel is combusted and in normal conditions some of the carbon will be only partially ...
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In the combustion of hydrocarbon fuel there was needing to lower the volume of unburned gases and pollutant emissions and increase combustion efficiency. The first to be oxidized are the hydrogen atoms when hydrocarbon fuel is combusted and in normal conditions some of the carbon will be only partially oxidized; this is responsible for the incomplete combustion. A magnetic field unit was manufactured for altering H atom in the hydrocarbon fuel from the stable state (parahydrogen) to the more reactive unstable state (orthohydrogen) so that transform the hydrocarbon molecule from its para state to the higher energized ortho state. In this research the pollutant emissions and combustion efficiency was studied for diesel fuel in an electrical generator (100KVA) for four weeks period with and without magnetic field unit.A Flue gas analyzer unit (IMR 1400) was used for testing and analyze the exhaust of the electrical generator.The output data for magnetized diesel fuel was compared with the output data of normal diesel fuel and showed significant decreasing in pollutant emissions and increasing of combustion efficiency using the magnetic field Unit.
Ali Sabah AL-Amili; Jasim Al-Khafaji; Sabih Z. Al-Sarraf
Volume 1, Issue 2 , December 2008, Pages 225-244
Abstract
In this study, a theoretical analysis is presented for estimating the in-plane large displacement elastic-plastic stability behavior of steel frames having prismatic and non-prismatic members with end gusseted plates subjected to increasing static loads. The analysis adopts the beam-column approach and ...
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In this study, a theoretical analysis is presented for estimating the in-plane large displacement elastic-plastic stability behavior of steel frames having prismatic and non-prismatic members with end gusseted plates subjected to increasing static loads. The analysis adopts the beam-column approach and models the structural members as beam-column elements. The formulation of the beam-column element is based on Eulerian approach allowing for the influence of the axial force on bending stiffness. In this study, the effect of gusseted plate is taken with the modified stability and bowing functions for gusseted plate with prismatic and non-prismatic members (Tapered and Non-linearly tapered).The post-buckling analysis is studied, and the incremental load control with different load increment strategies and the modified Newton-Raphson method with different iterative strategies are used to obtain the complete load-displacement curve. Furthermore, the determinant technique is used to detect the intersection of load limit points.As a result, the beam column approach can be used in the analysis of plane frames with and without gussets and with any varying section. The ultimate load capacity can be increased with gusset-plate members, and with tapering the prismatic members for the same weight, and then the displacement can decrease
