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Fracture location characterizations of dissimilar friction stir welds.

  • Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
  • Date: 2011
  • Subjects: Fracture location , Friction stir welding , Intermetallics , Metallography
  • Type: Article
  • Identifier: uj:5322 , http://hdl.handle.net/10210/8230
  • Description: This paper reports the tensile fracture location characterizations of dissimilar friction stir welds between 5754 aluminium alloy and C11000 copper. The welds were produced using three shoulder diameter tools; namely, 15, 18 and 25 mm by varying the process parameters. The rotational speeds considered were 600, 950 and 1200 rpm while the feed rates employed were 50, 150 and 300 mm/min to represent the low, medium and high settings respectively. The tensile fracture locations were evaluated using the optical microscope to identify the fracture locations and were characterized. It was observed that 70% of the tensile samples failed in the Thermo Mechanically Affected Zone (TMAZ) of copper at the weld joints. Further evaluation of the fracture surfaces of the pulled tensile samples revealed that welds with low Ultimate Tensile Strength either have defects or intermetallics present at their joint interfaces.
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Design of an innovative accelerant detector

  • Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A. , Isvarial, Milan
  • Date: 2012
  • Subjects: Accelerant detectors
  • Type: Article
  • Identifier: uj:5338 , ISSN 2010-3778 , http://hdl.handle.net/10210/8898
  • Description: Today, canines are still used effectively in acceleration detection situation. However, this method is becoming impractical in modern age and a new automated replacement to the canine is required. This paper reports the design of an innovative accelerant detector. Designing an accelerant detector is a long process as is any design process; therefore, a solution to the need for a mobile, effective accelerant detector is hereby presented. The device is simple and efficient to ensure that any accelerant detection can be conducted quickly and easily. The design utilizes Ultra Violet (UV) light to detect the accelerant. When the UV light shines on an accelerant, the hydrocarbons in the accelerant emit florescence. The advantages of using the UV light to detect accelerant are also outlined in this paper. The mobility of the device is achieved by using a Direct Current (DC) motor to run tank tracks. Tank tracks were chosen as to ensure that the device will be mobile in the rough terrain of a fire site. The materials selected for the various parts are also presented. A Solid Works Simulation was also conducted on the stresses in the shafts and the results are presented. This design is an innovative solution which offers a user friendly interface. The design is also environmentally friendly, ecologically sound and safe to use.
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Friction stir welding of dissimilar materials – statistical analysis of the weld data

  • Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
  • Date: 2012
  • Subjects: Friction stir welding
  • Type: Article
  • Identifier: uj:5336 , ISSN 2078-0966 , http://hdl.handle.net/10210/8879
  • Description: This paper reports the results of statistical analysis conducted on the weld data obtained from friction stir welding of aluminium and copper. The welds were produced by varying the process parameters; the rotational speed was varied between 600 to 1200 rpm and the welding speed varied between 50 and 300 mm/min. The Statistica (version 9.0) statistical analysis software package was used to generate the scatter and surface plots relative to the experimental results obtained from the tensile testing and the FSW data. Regression analysis was also done on the weld data. It was found that the downward vertical force has a significant effect on the Ultimate Tensile Strength of the weld and a strong relationship exist between the heat input into the welds and the measured electrical resistivities of the welds.
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Friction stir welding process : a green technology

  • Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
  • Date: 2012
  • Subjects: Friction stir welding , Green technology
  • Type: Article
  • Identifier: uj:5335 , ISSN 2010-3778 , http://hdl.handle.net/10210/8878
  • Description: Friction Stir Welding (FSW) is a solid state welding process invented and patented by The Welding Institute (TWI) in the United Kingdom in 1991 for butt and lap welding of metals and plastics. This paper highlights the benefits of friction stir welding process as an energy efficient and a green technology process in the field of welding. Compared to the other conventional welding processes, its benefits, typical applications and its use in joining similar and dissimilar materials are also presented.
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Laser forming of titanium and its alloys – an overview

Microstructural characterizations of dissimilar friction stir welds

  • Authors: Akinlabi, Esther Titilayo , Reddy, Randall D. , Akinlabi, Stephen A.
  • Date: 2012
  • Subjects: Friction stir welding , Scanning Electron Microscopy , Aluminum alloys , Copper
  • Type: Article
  • Identifier: uj:5332 , ISSN 2070-3740 , http://hdl.handle.net/10210/8871
  • Description: This paper reports the microstructural characteristics of dissimilar friction stir welds between 5754 aluminium alloy and C11000 copper. Dissimilar Friction Stir Welds of 5754 aluminium and C11000 copper were produced by varying the rotational speeds between 600 and 1200 rpm and the feed rate between 50 and 300 mm/min. The welds were characterized through Scanning Electron Microscopy (SEM). The SEM analysis revealed the levels of metallurgical bonding achieved at the joint interfaces of the welds produced and it can be established that better metallurgical bonding and good mixing of both materials joined were achieved in welds produced at lower feed rates of 50 mm/min and 150 mm/min while defect population was found to be common in the welds produced at high feed rate of 300 mm/min.
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Non-destructive testing of dissimilar friction stir welds

  • Authors: Akinlabi, Esther Titilayo , Levy, Adrian C. S. , Akinlabi, Stephen A.
  • Date: 2012
  • Subjects: Friction stir welding , Non-destructive testing , Aluminum alloys , Copper
  • Type: Article
  • Identifier: uj:5333 , ISSN 2078-0966 , http://hdl.handle.net/10210/8876
  • Description: friction stir welds between 5754 aluminium alloy and C11000 copper. The Friction stir welds of 5754 aluminium alloy and C11000 copper were produced at different tool rotational speeds and feed rates. The tool rotational speed was varied between 600 and 1200 rpm while the feed rate was varied between 50 and 300 mm/min. The visual inspection and the x-ray radiographic testing techniques were employed to conduct the tests; these tests were conducted on the welds to ascertain the joint integrity before characterization to have an idea of the quality of the welds. No visual defects were observed on all the welds considered but the x-ray radiography technique revealed the presence of wormhole defects and discontinuities in some of the welds. It was found that the welds produced at 950 rpm with varied feed rates were the best quality welds produced and this was substantiated with the microstructural evaluation of the joint interface. It was found that these welds have good mixing and metallurgical bonding at the interfaces.
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Characterising the effect of springback on mechanically formed steel plates

  • Authors: Akinlabi, Esther Titilayo , Matlou, Kagisho , Akinlabi, Stephen A.
  • Date: 2013
  • Subjects: Mechanical forming , Springback
  • Type: Article
  • Identifier: uj:4724 , ISSN 2078-0958 , http://hdl.handle.net/10210/11549
  • Description: In the bending operation, springback causes geometrical inaccuracies of bent parts. To curb springback, various factors such as bending parameters and material properties need to be considered. This paper reports the effects of springback on mechanically formed steel plates. Experimental work using circular bending was conducted to analyse the effect of springback on the formed steel sheets. The sheets were bent using a punch and die having a radius of curvature of 120 mm. In addition, the formed samples were characterized through microstructure, microhardness and tensile results. The results revealed an error due to springback of 4.24%. Furthermore, the Vickers microhardness of the formed samples compared to the parent materials shows an increase of 6% while the Ultimate Tensile Strength also increased by 7%. The effects of strain hardening resulting from the bending process led to the increased hardness and strength of the material. The formed samples had elongated grains when compared to the equiaxed grains of the parent material. The increase in the grains can be attributed to the stretching of the material during the bending process.
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Characterising the effects of sand blasting on formed steel samples

  • Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A. , Ogunmuyiwa, Enoch
  • Date: 2013
  • Subjects: Metal forming , Sand blasting , Ultimate tensile strength
  • Type: Article
  • Identifier: uj:4880 , http://hdl.handle.net/10210/12593
  • Description: The present research study focuses on the investigation of the influence of sand blasting on formed mild steel samples. The investigation involved the examinations on the parent material and a sand blasted material. The results were compared to the mechanically formed materials (sand and non-sand blasted) as well as a laser formed material (sand and non-sand blasted). Each material was characterized for the grain sizes and hardness. The percentage change in the grain sizes was quantified and correlation to the microhardness values was established. The Ultimate Tensile Strength (UTS) of the materials was also quantified using the obtained hardness values. The investigations revealed that the sand blasting causes an increase in the Vickers microhardness values of all the materials which also led to an increase in the UTS. After the forming operation, the microstructure revealed elongated grains as compared to almost equiaxed obtained from the parent non-sand blasted materials.
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Design of a support system for a re-configured milling machine to achieve friction stir welds

Designs of temperature measuring device for a re-configured milling machine

  • Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
  • Date: 2013
  • Subjects: Friction stir welding , Milling machines
  • Type: Article
  • Identifier: uj:4876 , http://hdl.handle.net/10210/12552
  • Description: The design of temperature measuring approach for a re-configured milling machine to produce friction stir welds is reported in this paper. The product design specifications for the redesigning of a milling machine were first outlined and the ranking criteria were determined. Three different concepts were generated for the temperature measurement on the reconfigured system and the preferred or the best concept was selected based on the set design ranking criteria. Further simulation and performance analysis was then conducted on the concept. The Infrared Thermography (IRT) concept was selected for the temperature measurement among other concepts generated because it is an ideal and most effective system of measurement in this regard.
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Effects of processing parameters on the corrosion properties of dissimilar friction stir welds of aluminium and copper

  • Authors: Akinlabi, Esther Titilayo , Anthony, Andrews , Akinlabi, Stephen A.
  • Date: 2013
  • Subjects: Aluminium alloy , Copper , Corrosion , Friction stir welding
  • Type: Article
  • Identifier: uj:5019 , http://hdl.handle.net/10210/13159
  • Description: The influence of friction stir welding processing parameters on dissimilar joints conducted between aluminium alloy (AA5754) and commercially pure copper (C11000) was studied. The welds were produced by varying the rotational speed from 600 to 1200 r/min and the feed rate from 50 to 300 mm/min. The resulting microstructure and the corrosion properties of the welds produced were studied. It was found that the joint interfacial regions of the welds were characterized by interlayers of aluminium and copper. The corrosion tests revealed that the corrosion resistance of the welds was improved as the rotational speed was increased. The corrosion rates of the welds compared to the base metals were improved compared with Cu and decreased slightly compared with the aluminium alloy. The lowest corrosion rate was obtained at welds produced at rotational speed of 950 r/min and feed rate of 300 mm/min which corresponds to a weld produced at a low heat input.
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Experimental investigation of laser beam forming of titanium and statistical analysis of the effects of parameters on curvature

  • Authors: Akinlabi, Stephen A. , Akinlabi, Esther Titilayo
  • Date: 2013
  • Subjects: Laser beam forming , Titanium alloys
  • Type: Article
  • Identifier: uj:4746 , ISSN 2078-0966 , http://hdl.handle.net/10210/11732
  • Description: Laser beam forming, a non-contact manufacturing process has become a viable manufacturing process for shaping metallic components. The capability of laser beam forming and bending demands more experimental studies to identify an optimized parameter setting and the likely parameters influencing the formed curvature. This paper investigates experimental laser beam forming of Ti6Al4V titanium alloy using a 4.4 kW Nd: YAG laser and studied the effects of the process parameters on the formed curvature. It was established that an increase in both the laser beam power and the number of scan tracks reduces the radius of curvature in the formed sheets having a more dome shape. The scan speed on the other hand, achieved the same good curvature at a slower or reduced scan speed to allow enough laser – material interaction. Furthermore, both the ANOVA and the regression analysis confirmed the repeatability of the experimental data. A simple regression model was developed based on the known active parameters to determine approximate curvatures instead of running a series of experiments.
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Material characterization studies on the laser beam formed AISI 1008 mild steel

  • Authors: Kumpaty, Subha , Brossard, Bradley , Kamara, Sheku , Akinlabi, Stephen A. , Akinlabi, Esther Titilayo , Raju, Govinda , Panda, Nirmal , Balasubramanian, K.
  • Date: 2013
  • Subjects: Metal-work , Metals , Thermal stresses , Steel - Heat treatment
  • Type: Article
  • Identifier: uj:5097 , http://hdl.handle.net/10210/13713
  • Description: Laser Beam Forming is a new non-contact method without the use of a die, to achieve deformation in metals, which traditionally involved the application of mechanical forces to change the shape and form of the material permanently. Laser forming causes deformation by introducing thermal stresses from an external heat source as opposed to the simple application of forces in mechanical forming. In this study, samples were formed mechanically by using a dynamic press brake machine, whereby, a punch and die apply the force. A 4.4 kW Nd:YAG laser system was used to form a second set of samples made from cold rolled AISI 1008 mild steel using laser forming. In this collaborative work involving researchers from the USA, South Africa and India, the mechanical and metallurgical properties of the unformed, mechanically formed and laser formed samples were experimentally investigated. The objective is to compare these properties amongst the different samples in order to analyze the impact of the varying methodologies especially the laser energy effects on the samples. The conclusions from these tests have provided valuable information on the applicability of laser forming to attain the appropriate surface modifications yielding the desired mechanical and metallurgical properties of the metal.
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Microstructural development during mechanical forming of steel sheets

  • Authors: Akinlabi, Stephen A. , Akinlabi, Esther Titilayo
  • Date: 2013
  • Subjects: Microhardness , Metal forming , Steel - Deformation
  • Type: Article
  • Identifier: uj:4852 , ISBN 978-988-19251-0-7 , http://hdl.handle.net/10210/12519
  • Description: Metal forming is used synonymously with deformation, a process during which an object gets changed due to the applied force. These changes can either be reversible or irreversible depending on the type of material; size and geometry of the object and the magnitude of the applied force to the object. This paper reports the microstructural development after mechanical forming of steel sheet material by varying the applied loads. The microstructural evaluations showed that the applied loads employed caused an increase in the magnitude of the grain sizes in each loaded specimen. Furthermore, the increase in the grain size of the microstructure was observed to be directly proportional to the loads applied. In addition, the microhardness values of the cross sections investigated were found to increase with the applied loads. Hence, the grain size growth and the hardness were linearly dependent on the applied loads, and this implies that there is a correlation between the applied loads and the resulting microstructure of the material and the hardness of the material.
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Characterising the effects of heat treatment on 3CR12 and AISI 316 stainless steels

  • Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
  • Date: 2014
  • Subjects: Stainless steel - Heat treatment
  • Type: Article
  • Identifier: uj:4736 , http://hdl.handle.net/10210/11722
  • Description: This paper reports on the effects of heat treatment on 3CR12 and AISI 316 stainless steel grades. Heat treatment was conducted on the steel grades and cooled using two different media; air and water in order to study the effect of each medium on the evolving properties of the samples. The heat treated samples were characterized through the evolving microstructure and hardness. It was found that there was a significant grain size reduction in both the heat treated stainless steel specimens compared to the parent materials. The finer grain sizes were achieved as a result of impediment to growth of one phase by the other. The Vickers microhardness values of the heat treated samples were higher compared to the parent materials due to the fact that each of the steel grades had a proportion of martensitic structures in their microstructures thereby improving the integrity of the material.
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Effect of number of laser scans on the corrosion behavior of laser formed titanium alloy

Friction stir welding of aluminium and copper : fracture surface characterizations

  • Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
  • Date: 2014
  • Subjects: Aluminium , Copper , Fracture surfaces , Friction stir welding
  • Type: Article
  • Identifier: uj:4745 , ISSN 2078-0966 , http://hdl.handle.net/10210/11731
  • Description: Butt welds of aluminium alloy and copper alloy were produced by Friction Stir Welding by varying the feed rate and keeping all other parameters constant. The final weld matrix was composed of welds produced by a constant rotational speed of 600 rpm and the feed rate varied between 50 and 300mm/min. The microstructure and fracture surfaces of the joint interfaces were investigated. The results revealed that the joint interface was characterised with mixed layers of both materials joined. The strongest weld was produced at the highest feed rate employed at 300 mm/min. The fracture surfaces were characterised with thin layers of intermetallic compounds and can be considered fit for practical applications.
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Material characterization studies on the laser beam formed AISI 1008 mild steel

  • Authors: Kumpaty, Subha , Brossard, Bradley , Kamara, Sheku , Akinlabi, Stephen A. , Akinlabi, Esther Titilayo , Raju, Govinda , Panda, Nirmal , Balasubramanian, K.
  • Date: 2014
  • Subjects: Mechanical forming , Laser beam forming , Metal deformation
  • Type: Article
  • Identifier: uj:4743 , ISSN 978-93-81505-62-5 , http://hdl.handle.net/10210/11729
  • Description: Laser Beam Forming is a new non-contact method without the use of a die, to achieve deformation in metals, which traditionally involved the application of mechanical forces to change the shape and form of the material permanently. Laser forming causes deformation by introducing thermal stresses from an external heat source as opposed to the simple application of forces in mechanical forming. In this study, samples were formed mechanically by using a dynamic press brake machine, whereby, a punch and die apply the force. A 4.4 kW Nd:YAG laser system was used to form a second set of samples made from cold rolled AISI 1008 mild steel using laser forming. In this collaborative work involving researchers from the USA, South Africa and India, the mechanical and metallurgical properties of the unformed, mechanically formed and laser formed samples were experimentally investigated. The objective is to compare these properties amongst the different samples in order to analyze the impact of the varying methodologies especially the laser energy effects on the samples. The conclusions from these tests have provided valuable information on the applicability of laser forming to attain the appropriate surface modifications yielding the desired mechanical and metallurgical properties of the metal.
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Characterization of functionally graded commercially pure titanium (CPTI) and titanium carbide (TiC) powders

  • Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
  • Date: 2015-07-01
  • Subjects: Functional graded materials , Laser metal deposition , Titanium , Titanium carbide
  • Type: Article
  • Identifier: uj:5136 , ISBN 9789881404701 , http://hdl.handle.net/10210/14102
  • Description: Functionally Graded Materials (FGM) are advanced materials fabricated using additive manufacturing techniques. It belongs to a class of advanced material characterization in which the properties of the material composition is varied. The resulting property of the composite is always different from the properties of the individual material employed in the formation of the composite. They are known to also exhibit good mechanical and chemical properties and as such, are used for different industrial applications. One of the techniques employed in the fabrication of FGMs is called Laser Metal Deposition (LMD) technique. It uses laser beam to melt powder material on a substrate forming a melt pool that solidifies upon cooling. This paper reports on the material characterization of functionally graded Titanium and Titanium Carbide (TiC) powders deposited on Titanium substrate by laser metal deposition approach. The formed deposits were fabricated by varying the processing parameters such as laser power, scanning speed and the powder flow rate. From the result obtained, the microstructures showed that the laser power has much influence on the grain growth of the material. In addition, with the SEM analysis of the microstructure since the percentages of the titanium and titanium carbide were varied, it was observed that the sharp boundaries of the Titanium Carbide were reduced greatly and this resulting effect can be attributed to the thermal effect of the laser. The microstructures further revealed that as the percentage of TiC decreases, it becomes more difficult to see the TiC as a different material in the composite, emphasizing this as one of the best characteristics of functionally graded materials, which is the elimination of sharp interfaces and layers. Furthermore, it was observed that the laser power has great influence on the evolving hardness of the material compared to the TiC content.
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