Showing papers in "Engineering and Technology Journal in 2007"

A Finite Element Analysis of Orthogonal Machining Using Different Tool Edge Geometries

Abstract: This paper summarizes the effects of edge preparation of the cutting tool in orthogonal cutting on the following variables: stress distributions at the tool rake face, cutting forces and tool-chip contact length. The Finite Element Method (FEM) is selected using the ANSYS /V4.5 code. Six models of cutting tools have been suggested having edge radii of (0.01, 0.05, 0.1, 0.15, 0.2, and 0.25) mm. The results obtained provide a fundamental understanding of the process mechanics for cutting with realistic cutting tool edge radius in order to assist in the optimization of tool edge design. The results show that the optimum edge radius from the six simulated models is (0.05) mm; this edge radius gives minimum value of effective stress. The results show also that the optimum edge radius that shows minimum tangential cutting and feed forces is (0.01) mm. The results investigated that the tool-chip contact length is increased, until reaching maximum value of (2.4) mm at (r=0.15mm), and minimum value of (0.75) mm at (r=0.01mm). The maximum relative difference between simulated results of this work and other previous paper results is (2% - 17%) for the tool effective stresses, (5%) for the tangential force, and (11%) for the feed force.

The Effect of Cutting Tool Vibration on Surface Roughness of Workpiece in Dry Turning Operation

Abstract: This study is to find a correlation between surface roughness and cutting tool vibration in turning. The ranges of process cutting parameters in the present study are limited: cutting speed (34, 70, 130 m/min), depth of cut (0.1, 0.2mm), feed rate (0.07, 0.13, 0.17mm/rev) and tool overhanging (25, 30, 35, 40mm). The data are generated by lathe dry turning of medium carbon steel samples at different levels of the mentioned above parameters. Dry cutting tests (without using cutting fluid) are conducted to simulate a good turning, the dry turning provided a clean environment to obtain undisturbed clear cutting vibration, which results in more accurate and clear correlation between cutting vibrations and roughness. The analysis of variance reveale in this study is that the best surface roughness condition is achieved at a low (feed rate less and equal 0.13mm/rev), and with smaller tool overhang less and equal 30mm). The results also show that the cutting speed has small effect on surface roughness than feed rate and tool overhang. The depth of cut has not a significant effect on surface roughness in this study. Above results can be obtained when there is no built up edge and no damage of the tool tip. Finally experimental results have shown good correlation between the cutting tool vibration and surface roughness which can be used to control the finish surface of the workpieces during the mass production.

Dopping Effect On Optical Constants of Polymethylmethacrylate (PMMA)

Abstract: The optical constants (refractive index (n) , extinction coefficient (k) , real and imaginary parts of dielectric constant(e1&e2)) of polymethyl methacrylate (PMMA) doped with methylene blue (mb) and methyl red (mr) with thickness in the range (0.1-0.2) mm were measured in the wavelength range (200-900) nm. Refractive index (n) and extinction coefficient (k) showed irregular changes with increasing (mb) dopant concentrations, while (n) and (k) of PMMA doped with (mr) declared a systematic increase with increasing dopant concentrations. The data showed that (n) values of PMMA doped with (mr) are lower than the values of samples doped with (mb) which is atteributed to the progressive increase of absorbance in the wavelength range (400-550) nm with increasing (mr) concentration .

Improvement of Marshall Properties of the Asphalt Concrete Mixtures Using the Polyethylene as Additive

Abstract: In order to increase the durability of highway pavement specific requirements are needed to control the quality of pavement materials. Therefore, the aim of this study is to make and test laboratory specimens in order to characterize asphalt-polymer and aggregate mixtures by using results from conventional test procedures. The research work covers six percentages of polymer content those are (2%, 4%, 6%, 8%, 10%, and 12%) percent by weight of asphalt content. The polymer modified mixes were designed in accordance with Marshall method and the engineering properties of these mixes were determined. The engineering properties of the control and polymer modified mixes (stability, flow, bulk density, percent of voids in total mix, and percent of voids filled with asphalt) were evaluated by conventional test (Marshall test).The test results show that the engineering properties of polymer modified mixes meet the requirements of the S.O.R.B. specification for the asphalt mix used in the construction of surface course. The Marshall stability for modified mixes is higher than of control mixes.

Calculation of Energy Band gap of Porous Silicon Based On The Carrier Transport Mechanisms

Abstract: The energy bandgap of photoluminesc ence porous silicon is calculated based on the analysis of the current-voltage characteristics and the measurements of the thermal activation energy of the zero bias and reverse bias currents of PS/n-Si porous silicon diodes at different temperatures. The 2.1 eV bandgap resulting from these electrical measurements agrees well with 2 eV measured in PL spectra.

Study of Tensile Strength and Hardness Property for Epoxy Reinforced With Glass Fiber Layers

Abstract: Tensile strength and hardness property were studied in an epoxy (DGEBA) resin as a matrix reinforced with glass fibers for different volume fraction as layers. A comparison was done between woven roven samples, random layers samples and sandwich composite samples which consists of (woven roven and random). Finally the results show that the sandwich composite gives higher tensile strength, while the composite reinforced with woven roven fiber has maximum hardness values.

Phase Transformations of Hadfield Manganese Steels

Abstract: In the present work, the effect of different silicon percentages that were added to Hadfield manganese steel on the microstructure, phases and hardness are investigated. The results show that silicon has the crucial role in changing the hardness and Fe3C phase morphology from acicular to chunky through different stages. X-ray diffraction line profile analysis shows that two phases are presented in the matrix of Hadfield manganese steels; these phases are austenite and Fe3C.

Nonlinear Finite Element Analysis of Reinforced Concrete Beams with Large Opening under Flexure

Abstract: This paper describes a three- dimensional nonlinear finite element model suitable for the analysis of reinforced concrete Beams with Large Opening under Flexure. The 20-node isoparametric brick elements have been used to model the concrete. The nonlinear equations of equilibrium have been solved using an incremental-i terative technique operating under load control. The solution algorithm used was the modified Newton-Raphson method. The numerical integration has been conducted using the 27-point Gaussian type rule. The reinforcing bars are idealized as axial members embedded within the concrete element and perfect bond between the concrete and the reinforcement has been assumed to occur. The behavior of concrete in compression is modeled using an elasto-plasti c 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 the reduced shear modulus. Different types of reinforced concrete beams with large rectangular transverse openings have been analyzed and the finite element solutions are compared with the experimental data. Generally, good agreement has been obtained between the numerical and experimental load-deflection curves and ultimate load. Numerical studies including some material parameters such as concrete compressive strength, amount of longitudinal tensile reinforcement and opening size on the load-deflection response have been carried out to study their effect on the over all behavior of reinforced concrete beams with Large opening under Flexure.The finite element solution revealed that the ultimate load and post-cracking stiffness increase with the increases of concrete compressive strength, increases with the increase of the bottom steel reinforcement amount and decreases with the increase of length or depth of opening.

Influence of Heat Treatment Conditions on Microstructure of Ti- 6Al-7Nb Alloy As Used Surgical Implant Materials

Abstract: The study involves mechanical deformation and heat treatment effect on the microstructure of the Ti-6Al-7Nb alloy which is used as surgical implanted materials. The observed properties of (alpha-beta) Ti-based alloy are strongly dependent on their microstructures. These alloys are heat treated by solution treatment and aging (STA) as an effective strengthening method for (alphabeta) titanium alloys. Ti-6Al-7Nb alloy is hot rolled in the (alpha-beta) field and subjected to solution treatment above and below its beta transformation temperature. The solution treatments are applied at three different temperatures (850 o C, 930 o C and 950 o C) for one hour to these treatments. The solution treatment specimens are water quenched (WQ), normalizing [air cooled (AC) and annealed,[ furnace cooled(FC)] and subsequently aged the quenched and normalized specimens at 550 o C for 4 hours. Changes in the microstructure were observed from heat treatment action using optical microscopy, Atomic Absorption Spectroscopy (AAS) and phases analysis by X-ray diffraction (XRD). The microstructure examination results for as received alloy indicate alpha grains within a β- transformed matrix. The results also indicate that the grain size and percent of α /β for the heat treated specimens depend on heat treatment type and cooling media. The microstructure of specimens heat treated at 950 o C with air cooled shows fine duplex ( α / β) structures which have excellent properties for surgical implanted field applications. Keyword: Titanium heat treatment, titanium alloy, implant material, heat treatment ,surgical materials.

Experimental Study of Flexural Strength of Laminate Composite Material

Abstract: The effect of fiber volume fraction on the flexural properties of the laminated composite test specimens constructed of two layers, one of them reinforced with glass fiber and the other layer reinforced with Kevlar fiber has been investigated experimentally. The results illustrate that tension stress decreases with the increase in fiber volume fraction of glass fiber of the lower layer while it increases with the increase of Kevlar volume fraction of the upper layer. As for compression stress, it increases with the increase in volume fraction of glass fiber of the lower layer while it decreases with the increase of volume fraction of Kevlar fiber of the upper layer. The results also show the maximum value of tension stress (= 25.3 MPa.) at Vf of Glass fiber (= 15 %) and Vf of Kevlar fiber (= 60 %), while the maximum value of compression stress (= -17.1 MPa.) at Vf of Glass fiber (= 60 %) and Vf of Kevlar fiber (= 15 %).

Improvement of Thermal Properties for Binary Systems PVF- Ph, PVF-B by Addition of Silicon Carbide

Abstract: Two binary systems of (PVF-Ph and PVF-B) were prepared at specific conditions, and then thermal properties were improved by addition of a ceramic material (SiC). A different mixing ratio of ceramic material (SiC) powder was added to a prepared binaries (PVF-Ph, PVF-B) at (polyvinyl formal-phenol, and polyvinyl formal-bitumen) with a range (0.1-1)gm varied with (1-0.1)gm addition from both phenol (Ph) and bitumen ( B ). The thermal properties (thermal conductivity, stability) were measured for both improved binary systems (PVF-Ph, and PVF-B), and the results proved that: All thermal properties of two binaries (PVF-Ph, PVF-B) are modified with excellent properties of bitumen that will be raised from (50˚C to 250˚C) and other system (PVF-Ph) improved from (120˚C to 200˚C). Also the thermal conductivity

Numerical Simulation Of Two Dimensional Transient Natural Convection Heat Transfer From Isothermal Horizontal Cylindrical Annuli

Abstract: Numerical solutions are presented for the transient natural convection heat transfer problem in horizontal isothermal cylindrical annuli, enclosed in heated inner and cooled outer cylinders. Solutions for laminar case were obtained within Grashof number based on the inner diameter which varied from 1x10 2 to 1x10 5 in air. Both vorticity and energy equations were solved using alternating direction implicit (ADI) method and stream function equation by successive over relaxation (SOR) method. The structure of fluid flow such as a velocity vector and temperature distribution as well as Nusselt number were obtained and the effect of diameter ratio on them was examined. In addition, the Grashof number was changed with the influence of variation in Prandtle number and diameter ratio. Our numerical calculation are summarized by Nussult number vs. Grashof number curves with diameter ratios and Prandtl as a parameter, which serves as a guide to natural convection heat transfer calculated from annulus. Good agreement with previous data is obtained.

Numerical Investigation intoVelocity and Temperature Fields Over Smooth and Rough Ducts for Several Types of Turbulators

Abstract: Numerical study on a laminar and turbulent fluid flow and temperature distribution in a rectangular duct with six types of vortex generators has been carried out. A modified version of ESCEAT threedimension code has been used to solve Navier-Stokes and energy equations. The effect of vortex generator type, geometrical configuration, and dimensions on flow and temperature in different planes has been presented. The purpose of the present investigation is to highlight the complex threedimensional interaction of the vortices generated by wings and other vortex generators to understand how such vortices configurations structure the velocity and temperature fields. Experiment in terms of velocities and temperatures vectors and contours were performed on 6 configurations, which experiments are (fin, fence, rib, wing-type, rectangular-type, and winglet-type) vortex generators The results show good agreement with published data.

Mathematical Model of Autoclave Curing of Epoxy Resin Based Composite Materials

Abstract: Polymer matrix composites using thermosetting resins as the matrix are increasingly finding use in several applications. Process modeling describing the governing curing has played an important role, in improving the fundamental understanding and development of composite fabrication techniques. In present work, the thermokinetic involved in the autoclave curing of fiber-reinfor ced epoxy has been studied by means of a computer program, using the transient heat conduction equation coupled with kinetic equation, and the initial and boundary conditions. In the analysis the cure assembly is assumed to consist of a tool plate, composite laminate. The temperature distribution and the degree of reaction are obtained as a function of position and time.

Surface Preparation of Aluminum for Plating by Zincating

Abstract: The objective of this work is to gain better understanding of the influence of zincate bath chemistry on zincating morphology of Aluminum bond pads to provide reference for zincating chemistry design and process control for wafer bumping applications.

Improving Oxidation Resistance of Stainless Steel (AISI 316L) by Pack Cementation

Abstract: The cyclic oxidation resistance of austenitic stainless steel (AISI 316L) can be improved by enriching the surface composition in Al and Si using pack cementation process. In this work, stainless steel is coated with two different types of coatings, the first one is Si-modified aluminide coating and the second is the Ce-doped silicon modified aluminide coating. Aluminum, silicon with and without cerium were simultaneously deposited by diffusion into St.St.316L substrate by the packcementation process, using a pack mixture containing (18%A1, 7%Si, 2%NH4C1 and 73%Al2O3) and 0.5% Ce (wt %) when required. Microstructure and chemical composition of the coated specimens were analyzed using electron microscopy (SEM) with energy dispersive spectroscopy (EDS). X-Ray diffraction (XRD) was used to identify phase formed in the surface layer of as-coated specimens. The coating time was changed, and it was found that diffusion coating time of 3h at 970C° produces coating thickness of 160-180μm and consist mainly of FeAl and (Cr4Si4Al13) phases. Also, the surface morphology for the coated samples after 3h coating time at 970C° are dense, smooth and homogeneous. Cyclic oxidation tests were conducted on the uncoated St.St.316L , Si-modified aluminide coating and on Ce-doped silicon modified aluminide coating at a temperature range between (700-900)C° in (air and H2O) for 120h at 10 h cycle. The oxidation kinetics for uncoated St.St.316L in air environment are found to be linear, while the oxidation kinetics at water vapor environment are found to be nearly parabolic. The linear rate constant (KL) and the parabolic rate constant (Kp) values obtained at 800C° in air and water vapor are –2.77*10(mg/cm)/s and 2.18*10(mg/cm)/s respectively. The phases present on the cyclic oxidation of uncoated St.St.316L surface under most test conditions as revealed by XRD analysis are chromium (III) oxide, NiFe2O4, NiCr2O4 and iron oxide. Oxide phases that were formed on coated systems during air and H2O oxidation exposure condition are FeAl2O4, Fe(Al,Cr)2O4 and Fe2O3. The oxidation kinetics for both coated systems in air and water vapor are found to be linear and parabolic respectively. يتيانتسولأا أدصلا مواقم ذلاوفلل ةدسكلأا ةمواقم نيسحت ) AISI 316L ( ةقيرطب ب ءلاطلا ةتنمسلا

Features of Spot-Matrix Surface Hardening of Low-Carbon Steel Using Pulsed Laser

Abstract: In this work, results of spot hardening in low-carbon steel by using a pulsed Nd:YAG laser are presented. These results include determination of hardening depth, diameter of hardened spot, aspect ratio and heat-affected zone width with varying laser energy density. In order to determine the effect of irradiation profile on the overall achievable hardness, the profiles of overlapping, adjacent and separated hardened spots are compared and the percent coverage of the workpiece as a function of the laser-hardened spot dimensions.

On-Line Current-Based Condition Monitoring and Fault Diagnosis of Three-Phase Induction Motor

Abstract: A stator current measurement has an important role in condition monitoring and fault diagnosis of induction motors. For instance, the eccentricity, rotor bars and end ring breaks, shorted stator windings can be detected by analyses based on stator current measurement. This paper addresses the application of stator current spectral analysis technique for the detection and localization of abnormal electrical and mechanical conditions that indicate, or may lead to, a failure of the induction motors. The effects of stator current spectrum are described and the related frequencies are determined. In the present investigation, the frequency signatures of some asymmetrical motor faults are well-identified using signal processing techniques, such as Welch method for spectral density estimation. In fact, experimental results clearly illustrate that stator current spectral analysis using Welch method is a very good tool to detect faults in induction motors. These faults are shaft speed oscillation, eccentricity, broken rotor bar, and end ring cracked.

Organic Vapors Sensor Based on Dangling Bonds of Porous Silicon

Abstract: In this paper, a porous silicon (PS) layer is investigated as a sensing material to detect the organic vapors with low concentration. The structure of the prepared sensor consists of thin Au /PS/n-Si/Au thick where the PS is etched photo -chemically. The current response of the sensor is governed by the partial depletion of silicon located between two adjacent (porous regions).This depletion is due to the charges trapped on dangling bonds associated with the silicon – porous silicon interface .

A Content-Based Authentication Using Digital Speech Data

Abstract: A watermarking technique for speech content and speaker authentication scheme, which is based on using abstracts of speech features relevant to semantic meaning and combined with an ID for the speaker is proposed in this paper. The ID which, represents the watermark for the speaker, is embedded using spread spectrum technique. While the extracted abstracts of speech features are used to represents the watermark for the speech, is embedded in the original speech file using secret key. The abstracts speech feature is implemented using B-spline curve interpolation. The paper provides a background knowledge for the concept of speaker watermarking and content-fragile watermarking based on digital speech data. Then, the suggested feature based authentication scheme is develop and the results from the evaluation are presented. It shows that the suggested scheme is successful for combining speech and speaker watermark authentication.

Effect of Ethanol Concentrations in Internal Coagulant on the Morphology and Separation Performance of Polyethersulfone (PES) Hollow Fiber UF Membranes Prepared by PES/Ethanol/NMP Solution

Abstract: Polyethersulfone (PES) hollow fiber UF membranes were fabricated using ethanol (non-solvent) as additive and N-methyl-2-pyrrolidone (NMP) as a solvent. Asymmetric hollow fiber UF membranes were spun by wet phase inversion method from 18 wt.% solids of 18:10:72 (weight ratio) PES/Nonsolvent/NMP solutions. Effect of ethanol concentrations in internal coagulant on morphology and separation performance of PES hollow fiber UF membranes were investigated. UF membranes were characterized in terms of scanning electron microscope (SEM) while UF experiments were conducted using polyethylene glycol (PEG10,000 and 20,000 M W), PVP 40,000MW, and PVA 78,000MW as a solute. It was found that with an increase of ethanol concentration from 30 to 50 wt.% in the internal coagulant, membrane internal surfaces were dense and smooth, While the cracks phenomenon was appear on the internal surfaces of PES hollow fiber membrane with increase of ethanol concentration up to 100 wt.% (pure ethanol). The external surfaces for all of the PES membranes are smooth and dense because water is used as external coagulant; moreover, there is no change observed in the cross-section of PES hollow fiber with increase of ethanol concentration in the internal coagulant. Pure water permeation fluxes were decreased from 39 to 23.3 (L/m 2 hbar) and solutes rejection increased within less than 50 wt.% ethanol concentration in internal coagulant and then pure water permeation fluxes increased up to 65.4 (L/m 2 hbar) and solutes rejection decreased with an

Mathematical Modeling Of Multi Component Batch Extractive Distillation

Abstract: A dynamic model has been developed to study the dynamic behavior of multi component batch extractive distillation column. The set of equations governing (material bvalance, heat balance, summation of mole and equilibrium equations) which represent the dynamic model are solved to give the temperature and composition profile. Eigenvalue method was used to integrate the stiff ordinary differential equations. Matrix method was used to solve many equations simultaeously to redefine the column parameters during program run. Newtons algorithm was used to calculate the plate temperatures on each tray. The calculations and simulations in this paper were obtained by using MATLAB environment, version 6. The result of the proposed model are compared with experimental result taken under the same operating conditions. This model shows good agreement with experimental results and explains features of the batch extractive distillation process.

Effect Of Solid Catalyst On Bubble Rise Velocity And Gas- Drift Flux In Three-Phase-Columns

Abstract: The bubble rise velocity and drift flux were measured in 0.051 m i.d glass column with ethanol as the liquid phase, cobalt catalyst as the solid phase in concentration varying from (1.0 to 0.4) vol % in three phase column. Gas superficial velocity (Ug) was varied from (0.02 to 0.1) m/s. Experimental results show that the gas-holdup and gas flux decreases with the increasing of catalyst concentration but increasing bubble rise velocity.

Load-Slip Relationship in Modified Push-Out Test (Experimental Work)

Abstract: In this work, a modified push-out test is proposed to study the load-slip relationship in steel-concret e-steel sandwich beams. This relation is one of the most important factors that are required in the analysis and design of steelconcrete-steel sandwich beams with partial interaction. The diameter of the connector is assumed to be variable while the other parameters are kept constants. The modification in this test in comparison with the standard test concentrated on the use of steel tube- concrete slab- steel tube instead of concrete slab- steel (I-Section)- concrete slab (in Standard Test) in order to be more compatible than the standard test in modelling the steel-concrete-steel sandwich or double-skin beams. The stud is suggested to be threaded along the whole length, connected to the tube by a nut (the separation between the layers is eliminated and only interlayer slip is assumed to exist) and the connector passes to the other tube through the concrete slab (thus the connector is subjected to double shear force). These cases maximize the function of this stud. Five dial gages are used; one at the base, and two at each side in order to measure the slip at each stud. An experimental relationship of load-slip is carried out to simulate the behaviour of this type of connection in steel-concrete-steel sandwich construction.

Finite Element Analysis of the Rake Angle Effects on Residual Stresses in a Machined Layer

Abstract: In this paper, a plane strain Finite Element Method is developed and applied to model and simulate the orthogonal metal cutting of (AISI 1045 St) with continuous chip formation. Seven sets of simulation results for cutting with rake angles (-15 o , -10 o , -5 o , 0 o , 5 o , 10 o and 15 o ), are summarized and compared to analyze their effects in the cutting process in steady state condition. Simulation results of the residual stresses below the machined layer are presented and compared with other papers in the literature and showed good agreement. Simulation results offer an insight into residual stresses through different values of rake angles. Based on simulation results, characteristics of residual stress distribution can be controlled by optimizing the rake angle. The simulated results show that for positive rake angles and position, the zero of maximum effective stress is found to be at (0.04) mm beneath the work piece surface, while for negative rake angles, the position of maximum effective stress is changed to be directly on the workpiece surface.