Journal of Engineering

1

DAMAGING EFFECT OF MOVING TANK LOADS ON FLEXIBLE PAVEMENT

Saud Abdulaziz Sultan

Pages: 5283-5299 English

Abstract

This article presents a study on the damaging effects of moving tank loads on flexible pavements. The research develops an equivalent load based on a mechanistic-empirical approach. It was found that the damaging effect of tank loads ranges from 0.898 to 2.356 times the damaging effect of the standard 18 kips (80 kN) axle load. Additionally, tank braking forces were found to have a damaging effect 2.375 times greater than the tank weight alone in terms of tensile strain (fatigue cracking), and tank turning maneuvers were found to have a damaging effect 1.216 times greater than the tank weight alone. These loads also have severe damaging effects on the functional serviceability of the asphalt layer surface.

Keywords

Tank Loads Flexible Pavement Mechanistic-Empirical Approach Equivalent Load Braking Forces Turning Maneuver Tensile Strain Fatigue Cracking AASHTO Equivalency Factors Functional Serviceability

2

INVESTIGATION ON THE USE OF MICROPILES FOR SUBSTITUTION OF DEFECTED PILES BY THE FINITE ELEMENT METHOD

Dr. Mohammed Y. Fattah, Dr. Yousif J. Al-Shakarchi, Yasser M. Kadhim

Pages: 5300-5314 English

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Abstract

This article investigates the use of micropiles as a substitution for defected piles using the finite element method (FEM). Micropiles are small diameter, cast-in-place or grouted piles with steel pipes ranging from 50 to 300 mm in diameter, driven by a boring machine. Despite their small wall thickness, micropiles provide high bearing capacity, offering both axial and pullout resistance. The study uses the OpenSees program, an open-source software based on Tcl (Tool Command Language), to analyze the behavior of micropiles under static and dynamic loading conditions. A model for groups of laterally loaded pipe piles in sand was adopted to study the effect of defects on their lateral performance. The results indicate that inserting steel micropiles beside the defected pile at two opposite directions decreases the deflection of laterally loaded piles. The increase in group deflection is greater when the defected pile is modeled in the front row.

Keywords

Micropiles Defected Piles Finite Element Method (FEM) Static and Dynamic Loading OpenSees Program Steel Pipes Axial and Pullout Resistance Lateral Performance Eight Node Brick Elements Sand

3

FINITE ELEMENT ANALYSIS OF A FRICTION PENDULUM BEARING BASE ISOLATION SYSTEM FOR EARTHQUAKE LOADS

Asst. Lect. Zuhair Abd Hacheem, Asst. Lect. Israa Khudhair AL-Shimmari

Pages: 5315-5336 English

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Abstract

This article presents a finite element analysis of a friction pendulum bearing base isolation system subjected to earthquake loads. The study focuses on a multi-story building model with and without base isolation, subjected to two real earthquake events: El Centro and Loma Prieta. The analysis was conducted using the ETABS Nonlinear version 9.5 engineering program. The results demonstrate that the base isolation system significantly reduces the base shear and improves the dynamic response of the structure. A parametric study was performed to investigate the effects of the coefficient of friction and the radius of the concave surface on the base shear and displacement of the friction pendulum system. The findings highlight the effectiveness of the friction pendulum bearing in enhancing structural reliability during seismic events.

Keywords

Base Isolation Systems Friction Pendulum Bearing Finite Element Analysis Earthquake Loads Seismic Isolation Structural Reliability ETABS Nonlinear Version 9.5 El Centro & Loma Prieta Earthquakes Base Shear Dynamic Response Parametric Study

4

SEISMIC DESIGN OF SINGLE SPAN STEEL GIRDER BRIDGES AND BRIDGES IN SEISMIC PERFORMANCE CATEGORY A

Asst. Prof. Dr. Abdul Muttalib I. Said, Esraa Mubder Edaan

Pages: 5337-5351 English

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Abstract

This article investigates the validity and accuracy of the seismic design force recommended by AASHTO for single span steel girder bridges and bridges in Seismic Performance Category A. A parametric study is presented, including the effects of span length, elastomeric bearing stiffness, and lateral bracing (cross-frame) stiffness. The results of the simplified AASHTO method are compared with response spectrum and time history analysis. The study concludes that the AASHTO simplified analysis method underestimates the seismically induced forces at supports. A proposed seismic design force of
2.5
×
acceleration coefficient
×
tributary weight
is recommended for single span bridges in seismic zones 3 and 4 and for soil type II. Additionally, the seismic design force for two-span continuous bridges in performance category A is found to be a safe and conservative method to predict shear forces transferred by connection elements to the substructures.

Keywords

Seismic Design Steel Girder Bridges Single Span Bridges Seismic Performance Category A Elastomeric Bearing Cross Frame Response Spectrum Analysis Time History Analysis Seismic Zone Tributary Weight Soil Type II

5

EFFECT OF MINERAL FILLER TYPE AND CONTENT ON PROPERTIES OF ASPHALT CONCRETE MIXES

Eng. Noor M. Asmael

Pages: 5352-5362 English

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Abstract

This article investigates the influence of different types and contents of mineral fillers on the properties of asphalt concrete mixes. The study was motivated by the premature failures observed in newly constructed highway pavements in Iraq, primarily due to rutting and cracking. A detailed laboratory study was conducted using aggregates from Al-Taji quarry, (40-50) grade asphalt from Dourah refinery, and three types of fillers: Portland cement, silica fume, and fly ash. Marshall mix design was performed using various filler types and ratios to evaluate their performance in the asphalt mixture. The mechanical properties of the mixes were assessed through indirect tensile strength, creep, and Marshall tests at different temperatures (15°C, 30°C, and 45°C). The results indicate that replacing Portland cement with 9.8% silica fume improves resistance to rutting and cracking, while fly ash is not suitable as a mineral filler in hot mix asphalt paving applications.

Keywords

Mineral Filler Asphalt Concrete Mixes Portland Cement Silica Fume Fly Ash Rutting Cracking Indirect Tensile Strength Creep Marshall Test Temperature Susceptibility

6

FREQUENCY DOMAIN EQUALIZATION TECHNIQUES FOR MULTICODE DS-CDMA IN FREQUENCY SELECTIVE RAYLEIGH FADING CHANNEL

Eng. Noor M. Asmael

Pages: 5363-5376 English

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Abstract

This article investigates the application of frequency domain equalization (FDE) techniques to improve the performance of orthogonal multicode direct sequence code division multiple access (DS-CDMA) in frequency selective Rayleigh fading channels. The study evaluates two FDE methods: one based on fast Fourier transform (FFT) and the other on circulant matrices. Additionally, a channel interleaving method called chip interleaving is employed to enhance the system's performance. The results demonstrate that FDE techniques effectively restore code orthogonality and significantly improve the bit error rate (BER) performance of the multicode DS-CDMA system. The findings highlight the potential of FDE in enhancing broadband wireless communication systems.

Keywords

Mineral Filler Asphalt Concrete Mixes Portland Cement Silica Fume Fly Ash Rutting Cracking Indirect Tensile Strength Creep Marshall Test Temperature Susceptibility

7

MODELING AND SIMULATION OF A BUCK CONVERTER CONTROLLED A SENSORLESS DC SERIES MOTOR

Bassim M. H. Jassim, Tagreed M. Ali

Pages: 5377-5391 English

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Abstract

This article presents the modeling and simulation of a speed sensorless control for a DC series motor driven by a buck converter. The system model computes the motor speed from the converter output voltage and current, considering the nonlinearity of the series motor magnetization characteristics, including the variation of field inductance with motor current. The control system is designed using digital techniques and evaluated through simulations in the Simulink toolbox of Matlab. The results demonstrate the effectiveness of the proposed sensorless speed control method, which reduces the cost and weight of the drive system by eliminating the need for speed sensors.

Keywords

Buck Converter Sensorless Control DC Series Motor Speed Control Digital Simulation Simulink Matlab Duty Ratio Power Switching Device High Frequency Output Voltage Ripple

8

DERIVATION OF THE LORENTZ-EINSTEIN TRANSFORMATION VIA ONE OBSERVER

O.M. AL-Kazalchi, Faiz T. Omara

Pages: 5392-5397 English

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Abstract

This article presents a novel derivation of the Lorentz-Einstein transformation using a single observer, which is not commonly found in the literature. Traditionally, the transformation is derived using two observers in relative motion within Galilean reference frames1. This study proposes a method that employs local coordinates of two Galilean systems with relative motion, following the track of a spherical pulse of light. The derivation is based on the principles of special relativity and demonstrates the invariance of physical laws in all reference frames1. The approach provides a fresh perspective on understanding the Lorentz-Einstein transformation and its applications in theoretical physics.

Keywords

Lorentz-Einstein Transformation Special Relativity Galilean Reference Frames Space-Time Manifold Spherical Pulse of Light Four-Dimensional Manifold Coordinate Frames

9

HYDRODYNAMIC STUDIES OF BED EXPANSION IN LIQUID SOLID FLUIDIZED BED

Sawsan A. M. Mohammed

Pages: 5398-5410 English

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Abstract

This article investigates the hydrodynamic behavior of bed expansion in a liquid-solid fluidized bed. The study utilizes the Richardson-Zaki correlation to model the relationship between the superficial velocity of the feed stream and the void fraction of the bed at moderate Reynolds numbers. Empirical parameters such as the effective diameter of the particles and an exponent for the velocity-voidage relationship are introduced. The research examines how the density ratio and diameter ratio influence bed expansion, noting the presence of an accelerating or dense regime at the bottom of the test section when the density ratio exceeds unity. The findings contribute to a better understanding of fluidization dynamics, which is essential for various industrial applications including fermentation, wastewater treatment, and ore reduction.

Keywords

Liquid-Solid Fluidized Bed Bed Expansion Richardson-Zaki Correlation Superficial Velocity Void Fraction Reynolds Number Particle Density Particle Size Surface Characteristics Fluidization

10

REMOVAL OF COPPER IONS FROM WASTE WATER BY ADSORPTION WITH MODIFIED AND UNMODIFIED SUNFLOWER STALKS

Besma Ismael Hussein

Pages: 5411-5421 English

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Abstract

This study explores the use of sunflower stalks, both modified and unmodified, as low-cost adsorbents for the removal of copper ions from wastewater. The sunflower stalks were activated using nitric acid to enhance their adsorption capacity. Experiments were conducted in both batch and fixed bed modes to evaluate the adsorption efficiency. The results showed that sunflower stalks, particularly when modified, effectively adsorbed copper ions, achieving up to 100% removal efficiency under optimal conditions. The adsorption process followed the Freundlich, Langmuir, and Freundlich-Langmuir isotherms, indicating the suitability of sunflower stalks as an alternative to expensive activated carbon for heavy metal removal from wastewater.

Keywords

Copper Ions Waste Water Adsorption Sunflower Stalks Modified Sunflower Stalks Nitric Acid Activation Batch Mode Fixed Bed Mode Freundlich Isotherm Langmuir Isotherm Freundlich-Langmuir Isotherm Adsorption Kinetics

11

REMOVAL OF KEROSENE FROM WASTE WATER USING IRAQI BENTONITE

Abbas H. Sulaymon, Ziad T. Abd Ali

Pages: 5422-5436 English

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Abstract

This research investigates the potential of Iraqi bentonite as an adsorbent for removing kerosene from wastewater. The study compares the adsorption capacity of bentonite with that of activated carbon. Batch experiments were conducted to evaluate the effect of various conditions, including initial kerosene concentrations (100-500 mg/L), agitation speeds (125-800 RPM), bentonite weights (0.05-1.1 g), particle sizes (0.5-0.6 mm), and temperature (303 K). The results indicate that the Freundlich isotherm model fits the equilibrium adsorption data well, while the Langmuir model is less suitable. The best results for kerosene removal using bentonite were achieved at an initial concentration of 500 mg/L and an agitation speed of 800 RPM. Although activated carbon showed higher activity, bentonite remains a cost-effective alternative for kerosene removal from wastewater.

Keywords

Bentonite Activated Carbon Kerosene Adsorption Langmuir Isotherm Freundlich Isotherm Batch Experiments Agitation Speed Initial Concentrations Particle Size Temperature

12

SIMULATION OF SULFUR DIOXIDE REMOVAL FROM A GAS STREAM IN A FLUIDIZED-BED REACTOR

Nibras M. Abdulrasol, Waleed M. S, Kadhem

Pages: 5438-5438 English

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Abstract

This article presents a model and simulation of a fluidized-bed desulfurization reactor using a two-phase bubbling-bed model proposed by Kunni and Levenspiel. The study focuses on the removal of sulfur dioxide (SO2) from flue gas using calcium oxide (CaO) as the fluidized solid. The reaction involves the exothermic conversion of SO2 to calcium sulfate (CaSO4) and heat. The effects of various parameters, such as solid feed rate, SO2 concentration, bed height, bed diameter, particle size, fluidizing velocity, and operating temperature, on the extent of conversion of both gas and solid were investigated. The results provide valuable insights into optimizing the desulfurization process in fluidized-bed reactors.

Keywords

Sulfur Dioxide Removal Fluidized-Bed Reactor Bubbling-Bed Model Calcium Oxide Flue Gas Desulfurization Reaction Kinetics Continuous Flow Conversion Data Operating Temperature

13

PREDICTION OF NATURAL CONVECTION HEAT TRANSFER IN COMPLEX PARTITIONS CAVITY

Sattar J. Habbeb, Israa Y. Daoud

Pages: 5459-5482 English

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Abstract

This article presents a numerical investigation into the effects of insulated baffles on natural convection heat transfer within a complex cavity, representing an industrial building. The cavity is characterized by an adiabatic horizontal bottom, inclined upper walls, and vertical isothermal walls1. The study employs flow-energy equations in terms of stream-vorticity formulation in curvilinear coordinates. Two cases are considered: Case 1 with the insulated baffle attached to the horizontal bottom wall, and Case 2 with the baffle attached to the upper inclined wall1. A parametric study is conducted using Rayleigh numbers ranging from
10
3
to
10
6
and Prandtl numbers of 0.7 and 10. The results indicate that the flow strength generally increases with higher Rayleigh numbers, greater baffle heights, and lower Prandtl numbers1. Additionally, the configuration in Case 2 leads to a higher heat transfer rate compared to Case 1.

Keywords

Natural Convection Heat Transfer Complex Partitions Cavity Baffle Flow Pattern Rayleigh Number Prandtl Number Baffle Height Baffle Location

14

DYNAMIC BEHAVIOR OF NON - RETURN VALVES OPERATING AT SMALL OPENING

Ali A.M. Al-Asadi, Hameed D. Lafta, Ali W. Abbas

Pages: 5481-5501 English

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Abstract

This article presents a comprehensive study on the dynamic behavior of non-return valves subjected to jet flow when operating at small openings. The research involves developing differential equations of valve motion and discharge in non-dimensional form using suitable dimensionless variables and parameters of the valve system. These equations are coupled nonlinear differential equations, which were solved using a computer program developed in MATLAB. The study identifies three types of valve responses based on the overall hydrostatic pressure difference. It was found that the valve can vibrate at a constant limit cycle, potentially leading to system failure. Additionally, the limit cycle frequency decreases with increasing stiffness parameter and inertia factor, while the losses factor has a negligible effect on valve vibration and discharge.

Keywords

Non-Return Valves Dynamic Behavior Jet Flow Nonlinear Equations Dimensionless Variables Limit Cycle Hydrostatic Pressure Stiffness Parameter Inertia Factor Valve Vibration

15

SEPARATION OF OIL FROM O/W EMULSION BYELECTROFLOTATION TECHNIQUE

Ahmed A. Mohammed, Ali Jassim Mohammed Al-Gurany

Pages: 5503-5515 English

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Abstract

This article investigates the removal of dilute emulsified oil in water (50-500 ppm) using the electroflotation technique. The study examines the effects of various parameters such as current density, initial pH, sodium chloride concentration, electrode material, gap distance, temperature, electrode surface area, and treatment time on the removal efficiency. Experiments were conducted in both batch and continuous modes. The results indicate that the highest removal efficiency (99%) was achieved at a pH of 7.5 using aluminum electrodes, while iron electrodes achieved a similar efficiency at pH 8. The removal efficiency increased with higher current density and shorter electrode gaps. The optimal temperature was found to be 60°C, and the best sodium chloride concentration was 400 ppm for an oil concentration of 500 ppm. The study demonstrates the effectiveness of electroflotation in treating oily wastewater, offering a potential alternative to conventional methods.

Keywords

Electroflotation Oil-Water Emulsion Current Density pH Sodium Chloride Concentration Electrodes Material Treatment Time Batch Mode Continuous Mode Removal Efficiency

16

VERTICAL VIBRATIONS OF BASE ISOLATED MACHINEFOUNDATIONS

Thmir K. Mahmood, Salim Y. Awad

Pages: 5516-5535 English

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Abstract

This article investigates the vertical vibrations of base-isolated machine foundations using the Scaled Boundary Finite Element Method (SBFEM) and the cone model method. The study determines the dynamic stiffness of soil supporting rigid massless foundations, which is represented by complex values. The real part of the stiffness indicates the reflected energy of restoring and inertial forces, while the imaginary part represents the energy dissipated within the soil as geometric damping. The effects of geometric and material properties of the soil on the dynamic stiffness are analyzed and presented in dimensionless charts for the relevant frequency range. Results show that increasing the embedment ratio significantly affects the dynamic stiffness, and the use of soft isolators reduces the dynamic response of the foundation and soil reaction.

Keywords

Base Isolated Machine Foundations Vertical Vibrations Scaled Boundary Finite Element Method (SBFEM) Cone Model Method Dynamic Stiffness Soil-Structure Interaction Geometric Damping Embedment Ratio Stiffness Ratio

17

EXPERIMENTAL STUDY ON THE PRESENCE OF OPEN CAVITY EFFECTS ON INTERNAL FLOW AND CONVECTIONHEAT TRANSFER CHARACTERISTICS

Ikhlas M. Fayed, Moayed R. Hasan, Anees A. Al-Fakhri

Pages: 5536-5547 English

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Abstract

This article presents an experimental study investigating the effects of an open cavity on the internal flow and convection heat transfer characteristics. The study examines the velocity profile, temperature distribution, heat transfer coefficient, and Nusselt number at various Reynolds numbers (1.910^4 to 2.710^4) for both smooth surfaces and surfaces with an open cavity (with and without excitation). The results indicate that the presence of the cavity alters the downstream velocity profile and the skin friction coefficient between the upper and lower surfaces by approximately 64% at a distance of 20.5 times the cavity length. Consequently, the heat transfer coefficient and Nusselt number increased downstream of the cavity by around 30%. The effect of cavity excitation with different sound levels and frequencies was found to be relatively minor compared to the cavity itself.

Keywords

Internal Flow Convection Heat Transfer Open Cavity Velocity Profile Temperature Distribution Heat Transfer Coefficient Nusselt Number Reynolds Number Skin Friction Coefficient Cavity Excitation

18

DAMAGE DETECTION IN ROTATING BLADE BY VIBRATIONAL ANALYSIS USING FINITE ELEMENT METHOD

Nabil H. H. Shwan, A. Z. Shwan

Pages: 5548-5568 English

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Abstract

This article explores the development of monitoring systems for rotating blades to reduce maintenance costs and improve safety and reliability. The study employs four different coordinate systems to describe blade motion and formulates element stiffness and mass matrices using Hamilton's principle and the finite element method. Each element is described by seven degrees of freedom. The method is demonstrated analytically on a finite element model to estimate modal parameters under rotating and non-rotating conditions in a vacuum to eliminate aerodynamic effects and damping coefficients. Damage is simulated by reducing the stiffness of assumed elements and introducing cracks. The study investigates damage severity, location, and the effect of rotation speed on these methods, providing a statistical assessment to suggest the most effective approach. The Residual Error Method was found to be the best among the evaluated methods.

Keywords

Damage Detection Rotating Blade Finite Element Method (FEM) Vibration Analysis Modal Parameters Hamilton's Principle Degrees of Freedom Centrifugal Effect Stiffness Reduction Crack Simulation

19

ANALYSIS OF CONCRETE FLEXURAL MEMBERS REINFORCED WITH FIBRE POLYMER

Nazar K. Oukaili, Ahlam Ali Al-Asadi

Pages: 5569-5587 English

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Abstract

This article presents an analytical model to predict the load-carrying capacity of structural concrete members reinforced with fibre polymer (FRP) under flexural and normal forces. The model is based on the principles of equilibrium and compatibility of strain in concrete and FRP. The cross-section of the member is discretized into a mesh with the smallest cells to determine stress or strain in each cell. These values are then integrated to define the elements of the stiffness matrix. Nonlinear equations are linearized using iteration methods with a fixed secant modulus of elasticity in each cycle. The FORTRAN computer program language is used to compute force and strain vectors. The analytical results are compared with experimental data from other researchers, showing reasonable agreement. This model provides a valuable tool for predicting the behavior of concrete flexural members reinforced with FRP.

Keywords

Flexural Member Fibre Reinforced Polymer (FRP) Ultimate Moment Capacity Moment-Curvature Diagram Stress-Strain Diagram Equilibrium Compatibility of Strain Stiffness Matrix Nonlinear Equations FORTRAN

20

DESIGN OF A SLIDING MODE CONTROLLER FOR A TORA SYSTEM

Waladin Khairi Sa\'id, Shibly Ahmed Hameed

Pages: 5588-5605 English

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Abstract

This article presents the design of a sliding mode controller for an uncertain model of a TORA system (Translational Oscillations with a Rotational Actuator) as a two-degree-of-freedom underactuated mechanical system. The switching function is selected to make the TORA system an asymptotically stable mass-spring system with a nonlinear damping effect when the sliding mode controller constrains the state to the sliding manifold. This sliding mode controller is derived according to a new formula consisting of continuous and discontinuous parts. The main obstacle in the controller design is the uncertainty in the switching function, which appears in the controller formula. The sliding controller is found effective in bringing the system state to the neighborhood of the equilibrium point despite the uncertainty in the switching function. Additionally, the chattering problem is solved using the approximate signum function.

Keywords

Sliding Mode Controller TORA System Underactuated Mechanical System Asymptotic Stability Nonlinear Damping Switching Function Uncertainty Approximate Signum Function Chattering Problem

21

INVESTIGATION AND MODIFICATION OF AERODYNAMIC CHARACTERISTICS OF SUPERSONIC AIRCRAFT

Jafar M. Hassan, Laith K. Abbass, Laith W. Ismail

Pages: 5606-5619 English

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Abstract

This article explores the enhancement of aerodynamic efficiency and supermaneuverability for a selected supersonic aircraft (F-16A). The study estimates aerodynamic characteristics, surface pressure distribution, and maximum lift for the baseline configuration at different Mach numbers and angles of attack in subsonic and supersonic potential flow using a low-order three-dimensional panel method supported by semi-empirical formulas of Datcom. The research also evaluates the total nose-up and nose-down pitching moments about the center of gravity of the aircraft under various flight conditions. A modern program suggests a two-dimensional thrust vectoring technique (pitch vectoring up and down) controlled by an advanced aerodynamic and control surface design (foreplane or canard). The results show that the canard, as a control surface, with thrust vectoring produces enough nose-down moment to support the stabilator at high maneuvers, while achieving a 5-6% increase in aerodynamic efficiency (lift-to-drag ratio) for both subsonic and supersonic flight.

Keywords

Supersonic Aircraft Aerodynamic Efficiency Supermaneuverability Surface Pressure Distribution Pitching Moments Mach Number Angle of Attack Potential Flow Thrust Vectoring Canard Control Surface

22

FLASH EVAPORATION ENHANCEMENT BY ELECTROLYSIS OF SATURATED WATER FLOWING UPWARDS IN VERTICAL PIPE

Akram W. Izzat, Radwan Muhammad Addaiy

Pages: 5620-5632 English

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Abstract

This article presents an experimental system designed to enhance flash evaporation of saturated water flowing upwards in a vertical pipe. The system uses water electrolysis to inject hydrogen bubbles into the two-phase mixture flow within the test section. These bubbles act as an exciter for steam generation inside the saturated water. The study found that using a 12 V ionization current of 7 A increased the steam quality at the test section outlet by 33% compared to the results obtained without electrolysis. Additionally, a reduction of 42% in the non-equilibrium temperature difference was achieved using the same ionization settings. The experimental results were compared to theoretical results obtained by solving mass, momentum, and energy equations for two-phase flow, assuming a separated flow model. The findings demonstrate the potential of electrolysis to enhance flash evaporation processes.

Keywords

Flash Evaporation Electrolysis Bubbles Injection Steam Quality Non-Equilibrium Temperature Difference Two-Phase Flow Mass Balance Heat Balance Separated Flow Model

23

USE OF AVAILABILITY SIMULATION TO FIND OPTIMUM PERIOD OF TIME BETWEEN SCHEDULE MAINTENANCE

Dr. Z. I. Al-Daoud, Hussain A. M. Al-Bawi

Pages: 5633-5643 English

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Abstract

This article investigates the optimal period between scheduled maintenance using availability simulation techniques. The study focuses on an old water tube boiler with double identical drums, aiming to maximize boiler availability by determining the best maintenance intervals. The Monte Carlo simulation method is employed to model system reliability and predict failures based on historical data. By analyzing the expected number of failures, maintenance actions, and mean time to repair, the study identifies the optimal maintenance period that minimizes downtime and ensures maximum system availability. The findings suggest that adjusting the maintenance schedule based on simulation results can significantly improve operational efficiency and reliability.

Keywords

Availability Simulation Maintenance Optimization Reliability Monte Carlo Simulation System Availability Maintenance Planning Failure Analysis Mean Time to Repair (MTTR) Downtime Minimization

24

DEVELOPING LAMINAR MIXED CONVECTION HEAT TRANSFER THROUGH CONCENTRIC ANNULI

Ihsan Y. Hussain, Mohammed Abdul Raouf, Nima Al-Safi

Pages: 5644-5662 English

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Abstract

This article presents both theoretical and experimental investigations on developing laminar mixed convection heat transfer in concentric annuli for both aiding and opposing flows. The theoretical part involves solving the energy equation using the Alternating Direction Implicit (ADI) method, while the momentum equations and continuity equation are solved using the SIMPLE algorithm. The study covers a range of Rayleigh numbers from
4.55
×
10
4
to
5.649
×
10
7
and Reynolds numbers from 300 to 1000, with a radius ratio of 0.555 and Prandtl number of 0.72. The experimental setup consists of an annulus with a uniformly heated inner cylinder and an adiabatic outer cylinder, subjected to ambient conditions. The results reveal that the secondary flow created by natural convection significantly affects the heat transfer process, with an increase in the Nusselt number as the Rayleigh number increases. The experimental results show that the local Nusselt number values for aiding flow are higher than those for opposing flow at the same Reynolds number and heat flux.

Keywords

Laminar Flow Mixed Convection Heat Transfer Concentric Annuli Aiding Flow Opposing Flow Nusselt Number Reynolds Number Rayleigh Number Boundary Layers

25

FLOW SEPARATION OF AXIAL COMPRESSOR CASCADE BLADES

Arkan Kh. Al-Taie, Sabah Faleh Habeeb

Pages: 5663-5682 English

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Abstract

This article presents an experimental and theoretical investigation of the effect of flow separation on the performance of a cascade NACA 65_(12)10 axial compressor blade. The experimental work includes the fabrication of three blades from wood, each having a chord of 100mm, with one blade having a span of 90mm for smoke tunnel testing and the other two blades having a span of 380mm for wind tunnel testing. The cascade was tested in an open-type low-speed subsonic wind tunnel (Mach number 0.117) for a Reynolds number of 239605 based on maximum velocity (35 m/s) and airfoil chord length. The total and static pressures were measured at stagger angles of 4°, 0°, -4°, -8°, and -12° using a multi-tube manometer and a pitot-static tube. The small blade (90mm span) was tested in the smoke tunnel to visualize the real behavior of flow separation. The theoretical work involved using the software FLUENT (V6.2) to simulate the flow between the two blades. The study shows that flow separation begins at a stagger angle of 4° on the suction side of the lower blade and increases with increased stagger angle in the clockwise direction. This separation affects the compressor's performance, decreasing the static pressure ratio as the separation zone gets bigger. The results were validated by smoke tunnel tests and showed good agreement with theoretical results.

Keywords

Axial Compressor Cascade Flow Separation Viscous Flow Wind Tunnel Testing Smoke Tunnel Visualization Stagger Angle Static Pressure Ratio FLUENT Simulation Blade-to-Blade Configuration Nozzle-Diffuser Effect

26

MATHEMATICAL MODEL TO INVESTIGATE THE TEMPERATURE AND HARDNESS DISTRIBUTIONS DURING THE ANNEALING AND NORMALIZING TREATMENT

B. Shaheen, Bachy Mechanical Department, College of Engineering, Baghdad University

Pages: 5683-5698 English

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Abstract

This article presents a mathematical model to simulate the annealing and normalizing heat treatment processes for steel and its alloys. The model accounts for variations in physical material properties and heat transfer coefficients on the metal surface. A numerical scheme based on the control finite volume method is employed, and a computer program written in C++ is used to solve the numerical equations. The model estimates temperature distributions and hardness values at various points of the workpiece. The results show good agreement with experimental data published previously. This model provides a valuable tool for predicting the outcomes of annealing and normalizing treatments, helping to optimize these processes in industrial applications.

Keywords

Annealing Treatment Normalizing Treatment Heat Treatment Temperature Distribution Hardness Distribution Finite Volume Method Numerical Simulation Material Properties Heat Transfer Coefficient

27

THREE-DIMENSIONAL FINITE ELEMENT ANALYSES OF A SINGLE PILE IN AN ELASTOPLASTIC CLAYEY SOIL

Omar F. S. Al-Damluji, Usama Saeed Al-Anbaki

Pages: 5699-5724 English

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Abstract

This article presents a three-dimensional finite element analysis algorithm to predict the behavior of single piles in clayey soil. The analysis uses 20-noded brick elements, with each node carrying four degrees of freedom: three for displacements in the three perpendicular space dimensions and one for pore water pressure. The pile material is modeled using a linear elastic constitutive relationship, while the soil behavior is represented by the Modified Cam-Clay model extended to three-dimensional characteristics1. The algorithm was applied to three documented field studies, showing good agreement with observed load-displacement results and pore fluid pressure build-up and dissipation. This study provides valuable insights into the behavior of piles in clayey soils and can be used to improve design and construction practices.

Keywords

Finite Element Analysis Elasto-Plastic Clayey Soil Single Pile Load-Settlement Behavior Pore-Water Pressure Modified Cam-Clay Model 20-Noded Brick Elements Field Studies Numerical Simulation

28

PCCC MC-CDMA COMBINATION PERFORMANCE OVER MULTIPATH RAYLEIGH FADING CHANNEL

Husam Abduldaem Mohammed

Pages: 5724-5735 English

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Abstract

This article presents a simulation study of a Parallel Concatenation Convolution Coding (PCCC) with Multi-Carrier Code Division Multiple Access (MC-CDMA) system over multipath Rayleigh fading channels. The study compares the performance of PCCC with uncoded data and Serial Concatenation Convolution Coding (SCCC). Iterative decoding techniques were used to achieve maximum efficiency with six iterations. Modulation schemes such as Phase Shift Keying (BPSK, QPSK, and 16 PSK) and Orthogonal Frequency Division Multiplexing (OFDM) were employed. The channel models followed the Third Generation Partnership Project (3GPP) Technical Specification TS 25.101 v2.10 with a channel bandwidth of 5 MHz. The results indicated that PCCC significantly improved the Signal to Noise Ratio (SNR) compared to SCCC and uncoded data. However, with 8 and 16 PSK modulation schemes, the Bit Error Rate (BER) remained around 10^-2 and did not converge to 10^-4.

Keywords

16 PSK) Serial Concatenation Convolution Coding (SCCC) Parallel Concatenation Convolution Coding (PCCC) Multi-Carrier Code Division Multiple Access (MC-CDMA) Multipath Fading Channel Signal to Noise Ratio (SNR) Bit Error Rate (BER) Orthogonal Frequency Division Multiplexing (OFDM) Third Generation Partnership Project (3GPP) Phase Shift Keying (BPSK QPSK

29

VOLTAGE STABILITY ENHANCEMENT AND LOSS REDUCTION VIA OPTIMUM LOCATION OF A SERIES CAPACITOR

Firas Mohammed Tuaimah

Pages: 5736-5752 English

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Abstract

This article explores the strategic placement of series capacitors to enhance voltage stability and reduce losses in power systems. The study focuses on an 11-bus power system and employs the Newton-Raphson method for load flow analysis, implemented using MATLAB. The proposed method identifies the optimal location and compensation percentage of a series capacitor to improve the voltage profile and minimize power losses. The results demonstrate significant improvements in voltage stability and efficiency, offering a practical solution for power system optimization.

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Voltage Stability Loss Reduction Series Capacitor Load Flow Analysis Newton-Raphson Method MATLAB Simulation Power System Optimization Reactive Power Compensation

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STRENGTHENING OF CRACKED REINFORCED CONCRETE T-BEAM BY JACKETING

Adnan Sadiq Al-Kuaity

Pages: 5753-5771 English

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Abstract

This article presents an extensive experimental study on the behavior and strength of reinforced concrete T-beams before and after strengthening using reinforced concrete jacketing. Four full-scale beams were loaded to various levels of ultimate capacity (0%, 60%, 77%, and 100% of failure load). After cracks or failure occurred, the beams were repaired using the jacketing method and tested again up to failure. The study aimed to restore the full ultimate capacity of beams failed by flexure and to investigate the effect of loading conditions on the ultimate capacity after repair. Extensive measurements of deformations, cracking, and strength were made before and after repair throughout all stages of loading. Test results showed that repairing by reinforced jacketing could effectively restore more than 150% of the full flexural capacity of the original beam and increase the ultimate capacity of cracked T-beams after repair up to 250%. The use of reinforced jacketing significantly improved serviceability, deformation behavior, cracking behavior, and ductility of T-beams compared to the original beams. The ultimate flexural strength of T-beams failed by flexure and repaired by reinforced concrete jacketing can be accurately predicted using conventional ultimate strength methods of reinforced concrete.

Keywords

Cracked Beam Reinforced Concrete Jacketing Flexural Capacity Repair Ultimate Strength Deformation Serviceability Ductility

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COPPER ETCHING IN AIR REGENERATED CUPRIC CHLORIDE SOLUTION

Baseem H. Fadhil

Pages: 5771-5777 English

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Abstract

This article investigates the copper etching process using an air-regenerated cupric chloride solution, which is widely used in printed circuit board (PCB) manufacturing due to its low cost, environmental benefits, and simple regeneration techniques. The study evaluates the etching rates as a function of time, specific gravity of the etchant, free acid concentration, and temperature. Continuous air injection in the etching cell enhances mixing and solution regeneration. The optimal operating conditions for maximum etching rate were found to be at temperatures between 45-55°C, specific gravity of 1.3-1.4, and free acid concentration of 1.3-1.4 M. The findings provide valuable insights for improving the efficiency and effectiveness of the copper etching process in PCB fabrication.

Keywords

Copper Etching Cupric Chloride Solution Air Regeneration Printed Circuit Board (PCB) Etching Rate Specific Gravity Free Acid Concentration Temperature

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