176 research outputs found
NUMERICAL SIMULATION OF OUTER DIE ANGLE OF EQUAL CHANNEL ANGULAR EXTRUSION PROCESS
The study of the simulation of effect of outer die angle in Equal Channel Angular
Extrusion (ECAE) process was investigated. The simulation was carried out on 6063
aluminium alloy with a view to achieve ultra-fine grain structures. ADINA user
interphase Version 8.6 (900 modes) was used for the simulation. The unextruded
parameters of the 6063 aluminium alloy were used as input codes and some basic
assumptions were made in designing the model on 2-Dimensional scale. The billet was
meshed by dividing the vertical and horizontal geometry into 30 and 4 elements
respectively. The die angle was varied from 0o
to 90o
and the simulation results were
displayed. The results showed that the force of 27.5X106 N, 27.5X106 N, 27.6X106 N
and 31.2 X106 N was required to deform when the outer die angle was 0o
, 22.5o
, 45o
and 90o
respectively. Also, the strains achieved were 0.61, 0.62, 0.66 and 0.69
respectively. Thus, highest force is required at 90o
and the strain achieved at 0o
is the
lowest. Based on the results, it was recommended that it is more economical to
extrude at an outer angle between 22.5o
and 45o
as a relatively higher effective strain
will be induced
Microstructural Characterization and Some Mechanical Behaviour of Low Manganese Austempered Ferritic Ductile Iron
This work studied the microstructural characterization and
mechanical behavior of low manganese Austempered Ductile
Iron (ADI), with a view to improve the properties of iron and
to increase the areas of applications. Three sets of ductile iron
of specified composition were machined from Y-blocks to
tensile and hardness pieces. The samples were preheated at
350 0C for 1hr and austenitised at 900 0C for 1hr in salt bath
furnace. The three sets of samples were immediately
austempered in the austempering salt bath furnace at uniform
austempering temperatures of 300 0C, 350 0C and 400 0C for
90, 120 and 150 minutes; each sample for each temperature
window. All sets were prepared for metallographic
examination; tensile and hardness tests were carried out. The
results showed that maximum hardness, tensile and yield
strength were obtained at austempering temperature of 350 0C
and at 150 minutes. At 300 0C and 350 0C, it was noticed that
the hardness and strength increase with austempering time.
The optimum tensile strength was 1300 MPa at 350 0C after
austempering for 150 minutes. In conclusion the austempering
operation has a significant effect on the mechanical and
microstructural properties of ADI
MECHANICAL AND MICROSTRUCTURAL CHARACTERIZATION OF DUCTILE IRON PRODUCED FROM FUEL - FIRED ROTARY FURNACE
The work compared the mechanical and microstructural properties of ductile iron produced in a locally manufactured fuel- fired rotary furnace with ASTM A 536 65-45-12, with a view to standardizing the produced ductile iron. Sets of low alloyed ductile iron were produced in form of keel Y-block inside green sand mould, using a rotary furnace of 100 kg capacity. The base alloy was treated with 5.5 wt. % Mg-Fe-Si alloy for spheroidisation followed by post inoculation with 75 wt. % Fe-Si. The samples of the as-cast were machined to mechanical test samples of tensile, yield and hardness. The microstructural and mechanical characterizations of the samples were carried out using computerized Instron Electromechanical Testing Machine (Model 3369), Mansato Tensometer (Model W) and Nikon Eclipse metallurgical microscope, Scanning Electron Microscope (SEM) and X-ray diffraction (XRD) method. The results showed that the yield and tensile strength of the produced ductile iron were 367 and 540 MPa respectively with the hardness value of 185 BHN. The results obtained were compared with standard ASTM A 536 65-45-12 to confirm the suitability of the manufactured fuel-fired rotary furnace for the production of ductile iron
Equal Channel Angular Extrusion Characteristics on Mechanical Behavior of Aluminum Alloy
Materials strengthened by conventional methods such as strain hardening, solute additions, precipitation and grain size refinement are often adopted in industrial processes.
But there is limitation to the amount of deformation that these conventional methods can impact to a material. This study focused on the review of major mechanical properties
of aluminum alloys in the presence of an ultrafine grain size into polycrystalline materials by subjecting the metal to an intense plastic straining through simple shear without
any corresponding change in the cross-sectional dimensions of the sample. The effect of the heavy strain rate on the microstructure of aluminum alloys was in refinement of the
coarse grains into ultrafine grain size by introducing a high density of dislocations and subsequently re-arranging the dislocations to form an array of grain boundaries. Hence, this investigation is aimed at gathering contributions on the influence of equal channel
angular extrusion toward improving the mechanical properties of the aluminum alloys through intense plastic strain
NUMERICAL SIMULATION OF OUTER DIE ANGLE OF EQUAL CHANNEL ANGULAR EXTRUSION PROCESS
The study of the simulation of effect of outer die angle in Equal Channel Angular Extrusion (ECAE) process was investigated. The simulation was carried out on 6063 aluminium alloy with a view to achieve ultra-fine grain structures. ADINA user interphase Version 8.6 (900 modes) was used for the simulation. The unextruded parameters of the 6063 aluminium alloy were used as input codes and some basic assumptions were made in designing the model on 2-Dimensional scale. The billet was meshed by dividing the vertical and horizontal geometry into 30 and 4 elements
respectively. The die angle was varied from 0o to 90o and the simulation results were displayed. The results showed that the force of 27.5X106 N, 27.5X106 N, 27.6X106 N and 31.2 X106 N was required to deform when the outer die angle was 0o, 22.5o, 45o and 90o respectively. Also, the strains achieved were 0.61, 0.62, 0.66 and 0.69 respectively. Thus, highest force is required at 90o and the strain achieved at 0o is the lowest. Based on the results, it was recommended that it is more economical to extrude at an outer angle between 22.5o and 45o as a relatively higher effective strain will be induced
Mechanical Behaviour and Microstructural Characterization of Carbon Steel Samples from Three Selected Steel Rolling Plants
The research investigated the mechanical behavior of samples of steel rods obtained from three selected Steel Rolling Companies in South Western part of Nigeria. This was done by carrying out some mechanical tests such as tensile, impact and hardness as well as microstructural examination.Four sets of 16 mm steel rod samples were collected from Tiger steel industries, Phoenix steel and Oxil steel Industies, all located in South West Nigeria, The chemical composition was carried out using a Spectrometer (EDX3600B). Afterwards, different samples were prepared, cut and machined according to ASTM standards dimensions of tensile and impact tests as well as hardness test from which their Ultimate tensile Strength, Yield strength, Percentage elongation, Impact strength and Brinell hardness number were obtained and compared to three standards (ASTM A706, BS 4449 and Nst 65-Mn). Their microstructures were also examined and analyzed.The results showed that the Ultimate tensile strength for the samples from Oxil steel, Phoenix Steel and Tiger steel were 661 N/(mm)2, 653 N/(mm)2 and 631 N/(mm)2 respectively while their hardness values were 150 BHN, 178 BHN, 214 BHN respectively. The sample from Tiger steel and Oxil Steel had the finest and most coarse microstructure respectively. In conclusion, it was observed that the results of the sample analysis from the three selected Steel Rolling Companies conformed to most of the standards except the sample from Tiger steel which had a high hardness value compared to the standard
Material Selection for Fuel Fired Crucible Furnace Using GRANTA
The study investigated the material selection for the fuel fired crucible furnace using bubble charts. The results were generated using GRANTA software. Different properties were considered during the selection of the materials for the furnace. The appropriate engineering materials were sought locally for the design and construction of the fuel fired crucible furnace. Among several parameters taken into consideration are strength/weight ratio, formability, cost and ability to fulfill specific service functions. All these were taken into consideration during the material selection process for the fuel-fired crucible furnace. These properties were plotted against each other in bubble chart and the selection of the appropriate candidate material was done on the bubble chart. The software plotted the properties of each unit of the furnace in form of bubbles and the candidate material where selected from the bulk of materials suggested by the software. The functions, objectives and constraints of the parts or the units to be designed were adequately specified and the material properties to be selected were determined based on these fundamental parameters
Modeling heat flow across fuel-fired crucible furnace using ADINA
-The study simulated the heat flow across a fuel-fired crucible furnace using ADINA Software. Appropriate engineering materials were selected for the design and construction of the fuel fired crucible furnace. Among several parameters taken into consideration were strength/weight ratio, formability, cost and ability to fulfill specific service functions. Heat dissipation to the outside was minimal and this was clearly shown in the temperature gradient. Heat dissipation was uniform within the flame gap and inside the crucible pot. The Kaolin refractory material used showed very good insulation capacity significantly reduced heat losses. The modeled temperature distribution profile, heat flux and the temperature gradient were all in agreement with the validated results
Impact of Heat Treatment on HSS Cutting Tool (ASTM A600) and Its Behaviour during Machining Of Mild Steel (ASTM A36)
Carburization is one the best heat treatment that responded well to hardening with Palm Kernel Shell giving the
best hardness value. This work studied the influence of carburization on HSStool(ASTM A600) and its behaviour during
machining of mild steel (ASTM A36). Composition of the samples (12 pieces of 180 x 12 x12 mm) HSS tools were
checked using UV-VIS spectrometer and the tools were carburized with PKS at holding temperatures and time of 800,
850, 900,950 oC and 60,90 120 minutes using muffle furnance. The micro structural analysis, surface and core hardnessof
the treated samples gave better results than the untreated samples when checked withsoft driven and optical microscope.
It wasalso observed that increase in the feed rate and depth for length of cut of 50 mm significantly reduces the wear
progression and thereby gave best machining time at maximum carburizing temperature and time(950 oC / 120 minutes)
when it was used to cut mild steelon the lathe machine
ADOPTION OF COMPUTER ASSISTED LANGUAGE LEARNING SOFTWARE AMONG NIGERIAN SECONDARY SCHOOLS’ STUDENTS
Covenant University (NIGERIA)
Learning a language can be a daunting task especially if a learner has acquired his/her first language. In second or foreign
language learning (L2 or FL), an effective learning strategy can contribute very much to one’s success. Hence, computer
assisted language learning (CALL) materials could be used in teaching to facilitate the language learning process. CALL
encompasses broad range of information and communication technology applications and approaches. CALL materials are
useful for two reasons; they are focused on learning rather than instruction or teaching and student-centered which enables
a learner to learn at his/her pace. The four skills covered by CALL are listening, speaking, reading and writing. There are evidences in the literature that CALL has performed well in promoting three skills; listening, speaking and reading while
substantial gains have not been made in writing skill. CALL, like other educational software that is computer software has
the potential to facilitate, accelerate, motivate and deepen skills in language learning. This study therefore examined the
level of adoption of CALL among secondary students in Nigeria. The study covered two geopolitical zones (North-central
and South-west) in Nigeria. Four states were randomly selected; two from each zone. The states are Kogi and kwara from
North-central, Lagos and Ogun from South west. Eight secondary schools from each of the states participated in this study.
A total of thirty two secondary schools were selected. Twenty students were selected from each of the thirty-two schools
(371 girls (58%), 269 boys (42%)). The ages of the participants range from 12-18years with mean age of 14.63years and
standard deviation of 2.08. All the participants had English language as one of their subjects while 23% had French
language in addition. CALL Adoption Questionnaire (CAQ) was designed and used to measure adoption. Four research
questions were raised and answered. The findings revealed that only 147 students representing 23% adopt CALL
applications in their language learning activities. The factors that promote the adoption of CALL include; educational
qualification of fathers, type of school, peer influence and class of students. The study concluded that the adoption of CALL
is low among secondary school students and recommended that parents, government and proprietors of private schools
should procure and enforce the use of CALL in our secondary schools to reduce abysmal failure rate in English and French
languages
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