Characterising the effect of springback on mechanically formed steel plates
- Akinlabi, Esther Titilayo, Matlou, Kagisho, Akinlabi, Stephen A.
- 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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- 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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Friction stir welding of dissimilar materials between aluminium alloys and copper - an overview
- Authors: Mubiayi., Mukuna P.
- Date: 2013
- Subjects: Aluminium , Copper , Friction stir welding
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/390844 , uj:4847 , ISBN 978-988-19252-9-9 , http://hdl.handle.net/10210/12514
- Description: Friction Stir Welding (FSW) is a solid state welding process used for welding similar and dissimilar materials. The process is widely used because it produces sound welds and does not have common problems such as solidification and liquefaction cracking associated with the fusion welding techniques. The FSW of Aluminium and its alloys has been commercialised; and recent interest is focused on joining dissimilar materials. However, in order to commercialise the process, research studies are required to characterise and establish process windows. In particular, FSW has inspired researchers to attempt joining dissimilar materials such as aluminium to copper which differ in properties and sound welds with none or limited intermetallic compounds has been produced. In this paper, we review the current research state of FSW between aluminium and copper with a focus on the resulting weld microstructure, mechanical testing and the tools employed to produce the welds and also an insight into future research in this field of study.
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- Authors: Mubiayi., Mukuna P.
- Date: 2013
- Subjects: Aluminium , Copper , Friction stir welding
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/390844 , uj:4847 , ISBN 978-988-19252-9-9 , http://hdl.handle.net/10210/12514
- Description: Friction Stir Welding (FSW) is a solid state welding process used for welding similar and dissimilar materials. The process is widely used because it produces sound welds and does not have common problems such as solidification and liquefaction cracking associated with the fusion welding techniques. The FSW of Aluminium and its alloys has been commercialised; and recent interest is focused on joining dissimilar materials. However, in order to commercialise the process, research studies are required to characterise and establish process windows. In particular, FSW has inspired researchers to attempt joining dissimilar materials such as aluminium to copper which differ in properties and sound welds with none or limited intermetallic compounds has been produced. In this paper, we review the current research state of FSW between aluminium and copper with a focus on the resulting weld microstructure, mechanical testing and the tools employed to produce the welds and also an insight into future research in this field of study.
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The status of used vegetable oil (UVO) biodiesel production in South Africa
- Mbohwa, Charles, Mudiwakure, Alexander
- Authors: Mbohwa, Charles , Mudiwakure, Alexander
- Date: 2013
- Subjects: Oil-derived biodiesel , Biodiesel production technology - South Africa , Biodiesel technology benchmarking
- Type: Article
- Identifier: uj:6040 , ISSN 2078-0966 , http://hdl.handle.net/10210/10440
- Description: This paper discusses the status of used oil derived biodiesel production in South African. It highlights the positives and shortcomings of the technology used and identifies the potential for improvement. All known South African used oil biodiesel producers were targeted. The response rate was 40% out of 200 producers. Technology used was benchmarked with established advanced biodiesel producing countries such as Germany, Brazil and the USA. Production rate, yield, product quality were the key performance indicators assessed. Results show that biodiesel production in South Africa is still in its infancy and production rates are low ranging from 100litres/day to a maximum 8000litres/day. Most plants are locally manufactured. Imports from India, China and Australia make up the remainder. Batch reactors are favoured over continuous reactors because of low acquisition cost, simple design and ease of operation. They allow for phase to phase quality control. This has resulted in low volume production militating against economies of scale. Yields, at up to 94% are acceptable and competitive. The products are contaminated with methanol and free fatty acids. The standards set for biodiesel quality were found to be restrictive and prohibitive but prospects for sustainable production are excellent.
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- Authors: Mbohwa, Charles , Mudiwakure, Alexander
- Date: 2013
- Subjects: Oil-derived biodiesel , Biodiesel production technology - South Africa , Biodiesel technology benchmarking
- Type: Article
- Identifier: uj:6040 , ISSN 2078-0966 , http://hdl.handle.net/10210/10440
- Description: This paper discusses the status of used oil derived biodiesel production in South African. It highlights the positives and shortcomings of the technology used and identifies the potential for improvement. All known South African used oil biodiesel producers were targeted. The response rate was 40% out of 200 producers. Technology used was benchmarked with established advanced biodiesel producing countries such as Germany, Brazil and the USA. Production rate, yield, product quality were the key performance indicators assessed. Results show that biodiesel production in South Africa is still in its infancy and production rates are low ranging from 100litres/day to a maximum 8000litres/day. Most plants are locally manufactured. Imports from India, China and Australia make up the remainder. Batch reactors are favoured over continuous reactors because of low acquisition cost, simple design and ease of operation. They allow for phase to phase quality control. This has resulted in low volume production militating against economies of scale. Yields, at up to 94% are acceptable and competitive. The products are contaminated with methanol and free fatty acids. The standards set for biodiesel quality were found to be restrictive and prohibitive but prospects for sustainable production are excellent.
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A subsidy driven decision procedure to mitigate the tragedy of the commons and anti-commons
- Sumbwanyambe, M., Nel, A. L.
- Authors: Sumbwanyambe, M. , Nel, A. L.
- Date: 2012
- Subjects: Pricing policy , Quality of service , Information technology - Developing countries , Telecommunications - Developing countries , Subsidies
- Identifier: uj:6272 , ISSN 2078-0966 , http://hdl.handle.net/10210/8910
- Description: One of the main aims of telecommunication subsidies in developing countries is to extend the information and communication services to the information “have nots” through subsidized communication services. However, subsidies may have an impact on network resource utilization, quality of service and the amount of revenue generated. For example, subsidies may lead to low Quality of Service (QoS) and high resource utilization while in some instances unsubsidized services may lead to high quality of services and low utilization of resources. This see-saw effect may eventually lead to market failure and it may, now and then, destroy market efficiency. This phenomenon calls for a combined study, in which the relationship between subsidy, price, QoS and resource utilization is investigated. In this paper, the impact of subsidies on quality of service and resource utilization in multitier communities is investigated. We try to find a middle ground between implementation of subsidy policy and its effects on QoS and resource utilization in a network.
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- Authors: Sumbwanyambe, M. , Nel, A. L.
- Date: 2012
- Subjects: Pricing policy , Quality of service , Information technology - Developing countries , Telecommunications - Developing countries , Subsidies
- Identifier: uj:6272 , ISSN 2078-0966 , http://hdl.handle.net/10210/8910
- Description: One of the main aims of telecommunication subsidies in developing countries is to extend the information and communication services to the information “have nots” through subsidized communication services. However, subsidies may have an impact on network resource utilization, quality of service and the amount of revenue generated. For example, subsidies may lead to low Quality of Service (QoS) and high resource utilization while in some instances unsubsidized services may lead to high quality of services and low utilization of resources. This see-saw effect may eventually lead to market failure and it may, now and then, destroy market efficiency. This phenomenon calls for a combined study, in which the relationship between subsidy, price, QoS and resource utilization is investigated. In this paper, the impact of subsidies on quality of service and resource utilization in multitier communities is investigated. We try to find a middle ground between implementation of subsidy policy and its effects on QoS and resource utilization in a network.
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Non-destructive testing of dissimilar friction stir welds
- Akinlabi, Esther Titilayo, Levy, Adrian C. S., Akinlabi, Stephen A.
- 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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- 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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Design of a support system for a re-configured milling machine to achieve friction stir welds
- Akinlabi, Esther Titilayo, Levy, Adrian C. S., Akinlabi, Stephen A.
- Authors: Akinlabi, Esther Titilayo , Levy, Adrian C. S. , Akinlabi, Stephen A.
- Date: 2013
- Subjects: Friction Stir Welding , Friction stir welds
- Type: Article
- Identifier: uj:4830 , ISSN 2078-0966 , http://hdl.handle.net/10210/12423
- Description: The detailed design of a clamping and support system for a reconfigured milling machine to produce friction stir welds is reported in this paper. Two different concepts were considered and subjected to performance evaluation. The selected design concept is expected to effectively clamp and support the workpiece during the process of friction stir welding to achieve a good integrity.
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- Authors: Akinlabi, Esther Titilayo , Levy, Adrian C. S. , Akinlabi, Stephen A.
- Date: 2013
- Subjects: Friction Stir Welding , Friction stir welds
- Type: Article
- Identifier: uj:4830 , ISSN 2078-0966 , http://hdl.handle.net/10210/12423
- Description: The detailed design of a clamping and support system for a reconfigured milling machine to produce friction stir welds is reported in this paper. Two different concepts were considered and subjected to performance evaluation. The selected design concept is expected to effectively clamp and support the workpiece during the process of friction stir welding to achieve a good integrity.
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Characterisation of sandstones : mineralogy and physical properties
- Authors: Mubiayi, Mukuna P.
- Date: 2013
- Subjects: Sandstone - South Africa - Qwa Qwa
- Type: Article
- Identifier: uj:4850 , ISBN 978-988-19252-9-9 , http://hdl.handle.net/10210/12517
- Description: Sandstones from Qwa Qwa in South Africa were characterised for their mineralogical and physical properties. Six samples (whitish, greenish, blackish, reddish, yellowish and greyish) were collected and studied. The X-ray Diffraction (XRD) revealed that the samples were quartz based. Scanning Electron Microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS) revealed the differences in the morphology and Silicon element was found present in all the samples. The X-Ray Fluorescence (XRF) exhibited that the samples contained 43.14% of Silicon (whitish). The grain sizes of the samples ranged from coarse, medium to fine grains. The Greyish sample had the highest compressive strength value of 56.74 MPa. Dielectric properties measurements were also conducted on the samples; and the results were temperature dependant. The water absorption by total immersion revealed that the blackish sand stones had the highest percentage of 6.62%.
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- Authors: Mubiayi, Mukuna P.
- Date: 2013
- Subjects: Sandstone - South Africa - Qwa Qwa
- Type: Article
- Identifier: uj:4850 , ISBN 978-988-19252-9-9 , http://hdl.handle.net/10210/12517
- Description: Sandstones from Qwa Qwa in South Africa were characterised for their mineralogical and physical properties. Six samples (whitish, greenish, blackish, reddish, yellowish and greyish) were collected and studied. The X-ray Diffraction (XRD) revealed that the samples were quartz based. Scanning Electron Microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS) revealed the differences in the morphology and Silicon element was found present in all the samples. The X-Ray Fluorescence (XRF) exhibited that the samples contained 43.14% of Silicon (whitish). The grain sizes of the samples ranged from coarse, medium to fine grains. The Greyish sample had the highest compressive strength value of 56.74 MPa. Dielectric properties measurements were also conducted on the samples; and the results were temperature dependant. The water absorption by total immersion revealed that the blackish sand stones had the highest percentage of 6.62%.
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Operational study and simulation of a biogas upgrading plant
- Masebinu, S. O., Aboyade, A. O., Muzenda, E.
- Authors: Masebinu, S. O. , Aboyade, A. O. , Muzenda, E.
- Date: 2014
- Subjects: Gas permeation , Biogas , Methane recovery
- Type: Article
- Identifier: uj:5020 , http://hdl.handle.net/10210/13163
- Description: The drive for finding alternative energy to supplement fossil based fuel within the South African energy sector has led to research on waste to energy in particular biomethane as vehicular fuels. Biogas is produced from the anaerobic decomposition of organic matter with 40-70% vol. of methane. Biogas if upgraded, by removing the non-combustible component, can achieve 99% methane concentration which makes it a potent vehicle fuel and a direct substitute to natural gas. In this paper, a biogas upgrading plant operation that uses gas permeation technique for methane enrichment of biogas was studied and simulated. The effect of recycling permeate stream on methane recovery was studied. Recycling of the permeate stream improved the methane recovery of the simulated process by 18%. The overall methane recovery of the simulated process is 81.23%.
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- Authors: Masebinu, S. O. , Aboyade, A. O. , Muzenda, E.
- Date: 2014
- Subjects: Gas permeation , Biogas , Methane recovery
- Type: Article
- Identifier: uj:5020 , http://hdl.handle.net/10210/13163
- Description: The drive for finding alternative energy to supplement fossil based fuel within the South African energy sector has led to research on waste to energy in particular biomethane as vehicular fuels. Biogas is produced from the anaerobic decomposition of organic matter with 40-70% vol. of methane. Biogas if upgraded, by removing the non-combustible component, can achieve 99% methane concentration which makes it a potent vehicle fuel and a direct substitute to natural gas. In this paper, a biogas upgrading plant operation that uses gas permeation technique for methane enrichment of biogas was studied and simulated. The effect of recycling permeate stream on methane recovery was studied. Recycling of the permeate stream improved the methane recovery of the simulated process by 18%. The overall methane recovery of the simulated process is 81.23%.
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