N.A. Raji | Lagos State University, Lagos, Nigeria (original) (raw)

Papers by N.A. Raji

Engineering and Technology Research Journal, 2018

Majority of farmers who grow corn cannot afford the high cost of purchasing most of the available... more Majority of farmers who grow corn cannot afford the high cost of purchasing most of the available imported Shelling machine. Such farmers switch to manual hand shelling method which gives low efficiency, high level of wastage and high labour. This machine was fabricated from locally available material and to shell maize and separate the cob from the grain, at same time, blow the particle. Its cost is very low compared to the imported threshers. The machine was tested to establish the influence of moisture content levels, and the efficiency so as to reduce breakage and wastage during shelling operation. The machine has a power rating of 2.237KW and shelling capacity of 0.8 ton/hr with the shelling drum screw rotates at 60 revolutions per minute. This fabricated machine is capable of shelling maize efficiently and economically.

A process capability study is performed for the turning process on a general purpose center lathe... more A process capability study is performed for the turning process on a general purpose center lathe in order to verify the process performance and machine ability to perform within specified tolerance limit. The process and machine capability indices were measured to determine the process and machine adequacy for industrial application. The tolerance limits were obtained from the given nominal size of the shaft, using the basic hole system and 90 sample shafts were turned on the lathe machine to specification for varying spindle speed and feed rate of the lathe. Three (3) samples were randomly selected for the turning process of a combination of the spindle speed and feed rate as a subgroup size for a total subgroup of thirty (30). The diameters (representing the quality characteristics) were used to generate control charts and capability histogram for the process. The process is within statistical control but found incapable of meeting up to specification because the capability index (Cp) measured was less than 1 and the machine capability for industrial application is not adequate.

The paper deals with the modeling and sensitivity analysis of a swing roller follower system desi... more The paper deals with the modeling and sensitivity analysis of a swing roller follower system designed for the operation of the beat-up mechanism of a narrow loom weaving machine. The translation and torsion models were developed for the system using the Newton's second law of motion. The models were simulated in a MATLAB application. The performance and dynamics of the cam system are analyzed using the SIMULINK technique. The data obtained from the simulation is used for a partial sensitivity analysis of the system's model. The sensitivity calculations were performed so that the deviation in the desired outputs of the system due to variation in the systems inertia parameters is minimized. The parameters chosen with respect to the sensitivity analysis are the mass inertia, spring stiffness and the damping coefficients. The spring stiffness and damping coefficients were kept constant while the mass inertia of the cam plate, follower link and beater link were varied to obtain a robust sensitivity of the system. The analysis is used to characterize the mass of necessary materials required for the manufacture of the cam system's plate, follower and beater links for optimum system operation.

The design analysis of a conveyor mechanism for an automatic car park is discussed. A prototype o... more The design analysis of a conveyor mechanism for an automatic car park is discussed. A prototype of the conveyor mechanism is fabricated to demonstrate the automation involved in the design and construction of an automatic car park system for local application. The conveyor assembly is made up of three units; the rack-pinion unit, the cable drive unit and the cantilever. The rack-pinion unit converts the rotational motion of a stepper motor to a linear forward and backward motion of the conveyor. The cable drive converts the rotational motion of another stepper motor to upward and downward motion of the cantilever to lift and lower the car at will. The cantilever is responsible for positioning the vehicle in the stack unit. The parameter for the cantilever is estimated to avoid excess deflection that could result from impact loading of a vehicle on the lift mechanism. The pinion-rack design for strength and rigidity is considered for the load required to be translated by the conveyor. The prototype was interfaced with a computer for operation using parallel port.

The aim of this study was to develop an efficient and realistic response surface optimization tec... more The aim of this study was to develop an efficient and realistic response surface optimization technique for the design of V-belt drive for optimum power output of the drive in machinery design. Optimization mathematical model of the V-belt drive was constructed. The power output of the belt drive was modeled and optimized by the Response Surface Methodology (RSM). Analysis of variance was used to evaluate the extent of influence of each independent variables on the power output response of the belt drive. A RSM optimization process was proposed to calculate optimal power output for V-belt drive given a set of pulley diameter for the drive employed in a tilling machine. The analysis showed that optimum power output of the drive for workshop light operation machinery could be obtained at driving and driven pulley radius range of 550-900 mm and 250-500 mm. An optimum power output of 1418.76 kW was obtained at driving and driven pulley radius of 846 and 486 mm respectively for a farm tilling machine.

Mechanical properties of metal are strongly affected by the metal's microstructure. The microstru... more Mechanical properties of metal are strongly affected by the metal's microstructure. The microstructure evolution of the deformed grains strongly depends on the deformation path applied. This paper investigated the influence of the degree of drawing process on the evolving microstructure of low carbon steel wires used for the manufacture of nails. In order to investigate the structural changes, optical microscopy was used. The micrographs were obtained for the different degrees of the drawing process (20, 25, 40 and 55% deformation). Tensile properties were determined by the tensile test of the drawn wire and values of the ductility and resilience at the various degrees of drawing were detailed. The associated microstructures were also obtained using optical microscope (OM) to study the effect of the degree of deformation on the microstructure evolution of the nails. The result showed that increase in cold drawn deformation generally increased the strength of the wire while its ductility reduces.

This work studied the effect of grain size evolution of cold drawn 0.12wt% C steel subjected to p... more This work studied the effect of grain size evolution of cold drawn 0.12wt% C steel subjected to process annealing on tensile behavior. 20%, 25%, 40% and 55% cold drawn 0.12wt% C steel were subjected to annealing comprising of slow heating-up to various temperature ranging from 500oC to 700oC at interval of 50oC followed by soaking treatment for 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes under each of the temperature in a muffle furnace. These samples were submitted tooptical microscopy analysis and to tensile test. After annealing at 650oC and soaked for 10 minutes, the dislocation defects were annihilated in the 25% cold drawn samples. Grain coarsening is observed for the annealed steel at soaking time of 20 minutes to 30 minutes after which grain growth commenced at annealing temperature above 650oC at soaking time of 40 minutes for the 25%, 40% and 55% cold drawn samples. Fine grains of the microstructure were observed for all the annealed samples between the temperature range 500 o C-650 o C.The yield strength of the annealed samples increases compared to the non-treated samples thus improving the ductility of the steel. A better improvement of the yield strength is observed for the annealing temperature of 500 o C and 550 o C at soaking time of 10 minutes and 30 minutes for all the cold drawn samples except for the annealed 25% cold drawn steel whose yield strength is below the yield strength of the non-treated samples.

The importance of recrystallization kinetics in metal process cannot be over emphasized in provid... more The importance of recrystallization kinetics in metal process cannot be over emphasized in providing information as to the control of microstructure of materials for purpose of improving or impacting desired mechanical properties in processed materials. In this study, 0.12wt% C steel cold drawn between 20% -55% were graduallyheateduptoatemperatureof900°C followed bysoakingtreatment between 600 seconds and 3600 seconds in a Gallenkomp® mufflefurnace model SVL-1009 with voltage regulation of 220 V, 50 Hz of temperature range 300°C -1000°C. The influence of the annealing process on the strength and impact toughness properties of the annealed steel were evaluated from tensile and charpy-impact testsconductedontheannealedsteel.A phase field method is used to describe the recrystallization kinetics of the annealed cold drawn 0.12wt%C steel for the different degrees of cold drawn deformation.The experimental data obtained from the tensile and charpy-impact test were used as input data for the phase field simulation of the recrystallization process. The results show that the yield strength of the annealed cold drawn 0.12wt% C steel increases with increasing soaking time within the range of 600 sec.-3600 sec. for the 20% cold drawn steel, between 600 sec.-2400 sec. for the 25% and between 600 sec.-1800 sec. for the 40% and 55% cold drawn steel. The treatment increased the impact toughness of the steel for the 20%-40% cold drawn deformation but loses its toughness for the 55% cold drawn steel. The tensile strength however reduces for all the cold drawn steel irrespective of the degree of deformation.The simulation results show that reformation of grains in cold drawn 0.12wt%C steel depends on the degree of cold drawn deformation and the soaking time of annealing. The response of the mechanical properties of the annealed cold drawn 0.12wt% C steel therefore depends on the degree of cold deformation and soaking time of annealing.

In an attempt to reduce sound radiated from a portable generator, a sound proof enclosure has bee... more In an attempt to reduce sound radiated from a portable generator, a sound proof enclosure has been developed to absorb effectively the generator noise. This sound proof enclosure is designed and fabricated with locally available materials from the opinion of an idea which aims at easing the pains and stress of receiving the noise radiating from a portable electric generating set. The walls of the enclosure is fabricated by combining panels of foam, composite sawdust and grinded glass and an outer plywood with air trapped in-between the composite and plywood. A reverberation room method is used to measure the noise absorption efficiency of the enclosure using a 950 watts/220 volts rated generator to ascertain the enclosure performance average at 76.40% noise absorption.

In wire drawing process, the yield strength, tensile strength and impact toughness play major rol... more In wire drawing process, the yield strength, tensile strength and impact toughness play major role in the structural reliability of the drawn wire. Low carbon steel wiresof 0.12wt% C are used for the manufacture of plain nails. Improved yield strength and impact toughness of the nails are often desire to avoid fracture failure andbuckling. In this study, polynomial modeling coupled with Response Surface Methodology was used to study the behavior of the tensile properties and impact toughness of cold drawn low carbon steel when annealed at various temperatures and soaking time. The Response Surface Methodology (RSM) was used to investigate the individual and interaction effect of annealing temperature and soaking time as independent variables on the yield strength, tensile strength and impact toughness properties of annealed cold drawn low carbon steel. The steel wire cold-drawn to 20% was annealed at various temperatures between 500oC-650oC for soaking time of between 10 minutes-60 minutes. The influence of the annealing temperature and soaking time on the yield strength, tensile strength and impact toughness were investigated by modeling the relationship using second order quadratic polynomials to develop the response surface plots and their respective contour plots. The RSM proposes models describing the influence of the annealing heat treatment parameters on the properties of the heat treated cold drawn wires. The model was able to account for the curvature of the response and the interaction of the independent variables in the response surface. The response surface methodology (RSM) was applied to optimize the annealing process parameters to attain the optimal values of the properties.The optimized values for the yield strength, tensile strength and impact toughness for the heat treated cold drawn wire were obtained as 678.90 MPa, 779.15 MPa and 42.65 J respectively. The optimization was achieved within the 95% confidence interval.

The study considers the impulse-momentum method for the analysis of the narrow loom with impulsiv... more The study considers the impulse-momentum method for the analysis of the narrow loom with
impulsive force and discontinuous velocities. The system equation of motion is analyzed to determine the main
body velocities used for the system variables without introducing rotational coordinates or the turning effect
of the system follower on the beater. Discontinuities in the velocity are observed when an impact force results
from the beat-up action of the beater on the weft-yarn. Formulation between the velocity jump and displacement
is presented for the system response. The impact phenomenon is characterized by the rise in the system velocity
resulting from the vibration propagation through the system. The velocity is observed to increase as the system
displacement response increases. This is typical of a high speed mechanism of this type mostly used in the
textile industry if not controlled

Drawn low carbon steel is characterized by brittle fracture. These defects are associated with th... more Drawn low carbon steel is characterized by brittle fracture. These defects are associated with the poor ductility and high strain hardening due to the cold work. There is a need therefore to determine optimum heat treatment parameters that could ensure improved toughness and ductility. Determining the optimum annealing parameters ensures valued recrys-tallization and also minimizes grain growth that could be detrimental to the resulting product. 40% and 55% cold drawn steels were annealed at temperatures 500°C to 650°C at intervals of 50°C and soaked for 10 to 60 minutes at interval of 10 minutes to identify the temperature range and soaking time where optimum combination of properties could be ob-tained. Tensile test and impact toughness experiments were done to determine the required properties of the steel. Po-lynomial regression analysis was used to fit the properties relationship with soaking time and temperatures and the clas-sical optimization technique was used to determine the minimum soaking time and temperature required for improved properties of the steel. Annealing treatment at 588°C for 11 minutes at grain size of 44.7 m can be considered to be the optimum annealing treatment for the 40% cold drawn 0.12 wt% C steel and 539°C for 17 minutes at grain size of 19.5 m for the 55% cold drawn 0.12 wt% C steel.

Low carbon steel metal is used for the manufacture of nails. Steel wire with <0.3% C content is c... more Low carbon steel metal is used for the manufacture of nails. Steel wire with <0.3% C content is cold-drawn through a series of drawing dies to reduce the diameter of the wire to the required diameter of the nails. A 0.12%w C steel wire cold drawn progressively by 20%, 25%, 40% and 50% was investigated. The influence of the degree of cold drawing on the mechanical properties of the carbon steel material were studied using the tensile test, impact test and hardness test experiments in order to replicate the service condition of the nails. The tensile test was done on a Montanso® tensome- ter to investigate the yield strength and the tensile strength of the material as the degree of deformation increases. An Izod test was used to determine the impact toughness of the steel using the Hounsfield impact machine and the hardness numbers were obtained for the different degrees of drawn deformation of the steel on the Brinnel tester. The study used the stress-strain relationship of the tensile test experiment to study the effect of the degree of cold-drawing deformation on the yield strength and tensile strength properties of the low carbon steel. The yield strength of the material was ob- served to reduce with increasing degree of cold-drawing, an indication of reduction in the ductility and the tensile strength of the material reduced with increasing degree of cold-drawn deformation. The ability of the material to resist impact loads when nails are hammered reduced with increasing degree of drawn deformation as a result of strain hardening of the material after the drawing operation. However the resilience of the material to further cold drawn deformation increased with increasing degree of deformation as evident in the Brinnel hardness number which in- creases with the degree of drawing deformation. This is an indication of the material’s approach to brittleness as the degree of drawn deformation increases.

The objective of this study is to investigate the influence of service situation on the mechanica... more The objective of this study is to investigate the influence of service situation on the mechanical
properties of plain nails manufactured from low carbon steel. The influence of the degree of cold drawing on
the mechanical properties and strain hardening of the material is investigated by tensile test experimentation.
The stress-strain relationships of the cold-drawn low carbon steel were investigated over the 20, 25, 40 and 55%
degree of drawn deformation for the manufacture of 4, 3, 2½ and 2 inches nails, respectively. The true stressstrain
curves were analyzed to obtain the yield strength and tensile strength of the cold drawn steel. It is shown
that the yield strength, tensile strength, hardness and toughness of the low carbon steel reduce with increasing
degree of cold-drawn deformation. The micrographs of the deformed samples obtained using optical
microscope shows that the grain structure elongates in the direction of the drawing operation and misorientation
of the grains set in at 40 and 55% degree of deformation. The difference in yield strength was attributed to the
strain hardening, resulting from the different degrees of drawn deformation.

The recrystallization behavior of cold-drawn 0.12 wt% C steel during annealing at temperatures 60... more The recrystallization behavior of cold-drawn 0.12 wt% C steel during annealing at temperatures 600°C and 650°C was
investigated. Hardness tests were used to characterize the recrystallization kinetics. The micrographs of the steel were
obtained using optical microscopy (OM) to characterize the grain microstructure of the non-treated and the annealed
steel samples. Annihilation of dislocation defects occur within the soaking time of 5 - 10 minutes for all the deformed
steel after annealing at 650°C. Specifically at 5 minutes soaking time the grains elongation is still observed indicating
that reformation of grains is not taking place but recovery of the deformed grains. At the 10 minutes annealing time,
new grains are observed to begin and full recrystallization is achieved at 15 minutes annealing time. At annealing time
between 20 - 25 minutes, grains coarsening are observed indicating the onset of grain growth. The hardness of the material
reduces with increasing annealing temperature for all the degree of cold drawn deformation. On the basis of the
experimentally obtained hardness values, recrystallization increases with increasing degree of cold drawn deformation
for the annealed steel. Recovery process was found to prolong in the 20% cold drawn steel as compared to the 55% cold
drawn steel. The prolong recovery process is due to reduction in the driving force. Full recrystallization of the annealed
steel is achieved at different soaking time depending on the degree of the cold drawn steel.

The paper presents the results of investigation on the effect of soaking time on the yield streng... more The paper presents the results of investigation on the effect of soaking time on the yield strength, ductility and hardness properties of annealed cold-drawn low carbon steel. The low carbon steel cold-drawn at 40% deformation was annealed at 900 deg Celsius for soaking times of 10, 20, 30, 40, 50 and 60 minutes. Tensile, charpy and Brinnel hardness tests were conducted to determine the yield strengths, tensile strengths, impact strengths, ductility and hardness of the an- nealed steel with increasing soaking time. The yield strength, tensile strength, hardness and impact strength of the steel showed a continuous drop in value with increasing soaking time up to 60 minutes with a steep drop between 30 and 40 minutes. Ductility values followed the same decreasing trend up to 40 minutes soaking time after which the values started increasing again till 60 minutes soaking time. There was a linear relationship between the tensile strength and hardness of the material for different soaking times. This linear relationship was also observed for yield strength and hardness of the material.

The aim of this work is to determine the mechanical properties of cold drawn low carbon steel sub... more The aim of this work is to determine the mechanical
properties of cold drawn low carbon steel subjected
to full annealing. The specimens were slowly heated
up to a temperature of 900°C followed by soaking
treatment of 60 minutes under this temperature in a
muffle furnace. Tensile, charpy and Brinnel
hardness tests were conducted to determine the
yield strengths, tensile strengths, impact strengths,
and hardness of the annealed steel. The yield
strength, tensile strength, hardness and toughness of
the nail are greater in the non-treated nails when
compared to the fully annealed nails at 60 minutes
soaking time. The microstructure analysis showed
that rate of grain nucleation and recrystallization
increased with increasing degree of cold-drawn
deformation. Grain growth was observed at higher
degree of deformation leading into reduction in the
mechanical properties of the material. I t i s
e v i d e n t f r om t h e r e s u l t i n g me c h a n i c a l
p r o p e r t i e s o f t h e n a i l s a n d t h e
mi c r o s t r u c t u r e a n a l y s i s t h a t d e s i r e d
p r o p e r t i e s o f t h e n a i l s c o u l d b e
o b t a i n e d b y c o n t r o l l i n g t h e
mic r o s t r u c t u r e e v o l u t i o n o f t h e l ow
c a r b o n s t e e l i n a n n e a l i n g

Journal of Engineering and Applied Sciences, 2010

Engineering and Technology Research Journal, 2018

Journal of Engineering and Applied Sciences, 2010