Effect of plunge depth on weld integrity of friction stir welds of dissimilar aluminium and copper
- Ewuola, Oluwatoyin O., Akinlabi, Esther Titilayo, Madyira, Daniel M.
- Authors: Ewuola, Oluwatoyin O. , Akinlabi, Esther Titilayo , Madyira, Daniel M.
- Date: 2016
- Subjects: Aluminum , Copper , Friction stir welding , Plunge depth , Lap welds
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/93322 , uj:20332 , Citation: Ewuola, O.O., Akinlabi, E.T. & Madyira, D.M. 2016. Effect of plunge depth on weld integrity of friction stir welds of dissimilar aluminium and copper.
- Description: Abstract: This paper presents the effects of plunge depth on the weld integrities of Friction Stir lap welds of aluminium and copper. 3 mm sheets of aluminium and copper were joined using the Friction Stir Welding (FSW) technique. The study focuses on understanding the relationship between the defects and the process parameters. The produced welds were characterized using visual inspection, microstructural evaluation and microhardness profiling. It was found that while all the typical FSW microstructural zones were present in the welds, the sizes of the voids observed in the welds were dependent on the plunge depth employed. Optimization of the processing parameters is in view.
- Full Text:
- Authors: Ewuola, Oluwatoyin O. , Akinlabi, Esther Titilayo , Madyira, Daniel M.
- Date: 2016
- Subjects: Aluminum , Copper , Friction stir welding , Plunge depth , Lap welds
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/93322 , uj:20332 , Citation: Ewuola, O.O., Akinlabi, E.T. & Madyira, D.M. 2016. Effect of plunge depth on weld integrity of friction stir welds of dissimilar aluminium and copper.
- Description: Abstract: This paper presents the effects of plunge depth on the weld integrities of Friction Stir lap welds of aluminium and copper. 3 mm sheets of aluminium and copper were joined using the Friction Stir Welding (FSW) technique. The study focuses on understanding the relationship between the defects and the process parameters. The produced welds were characterized using visual inspection, microstructural evaluation and microhardness profiling. It was found that while all the typical FSW microstructural zones were present in the welds, the sizes of the voids observed in the welds were dependent on the plunge depth employed. Optimization of the processing parameters is in view.
- Full Text:
'n Saamgestelde skakelmoduskragbron vir Tig-sweis
- Authors: Roux, Johannes Adam
- Date: 2014-02-17
- Subjects: Power electronics , Semiconductors , Electric welding , Aluminum
- Type: Thesis
- Identifier: uj:4054 , http://hdl.handle.net/10210/9405
- Description: M.Ing. (Electrical and Electronic Engineering) , The product of switching frequency and output power of solid state converters has increased dramatically during the past few years. This progress can mainly be attributed to the recent developments in power electronic switching devices. These developments are mainly responsible for a reduction in the physical size of the converter, especially that of the reactive components, and an increase in the dynamic response of the converter. The aim of this work is to use these characteristics of the power electronics converter in the development of an aluminum welding machine. This welding machine is developed for excisting welding processes namely: shield metal arc welding (STICK), and tungsten inert gas welding (TIG). More than one converter is necessary in order to shape the required output current and output voltage of the machine. Several different converters which can be used for the applications are compared. Each application has different conditions under which the converter must be able to work. The most convenient converter for each application is then fully described.
- Full Text:
- Authors: Roux, Johannes Adam
- Date: 2014-02-17
- Subjects: Power electronics , Semiconductors , Electric welding , Aluminum
- Type: Thesis
- Identifier: uj:4054 , http://hdl.handle.net/10210/9405
- Description: M.Ing. (Electrical and Electronic Engineering) , The product of switching frequency and output power of solid state converters has increased dramatically during the past few years. This progress can mainly be attributed to the recent developments in power electronic switching devices. These developments are mainly responsible for a reduction in the physical size of the converter, especially that of the reactive components, and an increase in the dynamic response of the converter. The aim of this work is to use these characteristics of the power electronics converter in the development of an aluminum welding machine. This welding machine is developed for excisting welding processes namely: shield metal arc welding (STICK), and tungsten inert gas welding (TIG). More than one converter is necessary in order to shape the required output current and output voltage of the machine. Several different converters which can be used for the applications are compared. Each application has different conditions under which the converter must be able to work. The most convenient converter for each application is then fully described.
- Full Text:
Prenatal exposure to aluminum and status of selected essential trace elements in rural South African women at delivery
- Röllin, Halina B., Nogueira, Claudina, Olutola, Bukola, Channa, Kalavati, Odland, Jon Ø.
- Authors: Röllin, Halina B. , Nogueira, Claudina , Olutola, Bukola , Channa, Kalavati , Odland, Jon Ø.
- Date: 2018
- Subjects: Aluminum , Maternal serum and urine , Essential trace elements
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/288068 , uj:31215 , Citation: Röllin, H.B. et al. 2018. Prenatal exposure to aluminum and status of selected essential trace elements in rural South African women at delivery. International Journal of Environmental Research and Public Health, 2018, 15, 1494; doi:10.3390/ijerph15071494
- Description: Abstract: This study sought to evaluate the in utero exposure to aluminum and status of selected trace elements in South African women at delivery since aluminum is known to be toxic in all developmental stages even at low concentrations. Serum aluminum was negatively correlated with aluminum in urine, both uncorrected and corrected for creatinine, which suggests the retention of aluminum in body stores. Serum copper and zinc levels were found to be high in this study population. Serum copper levels were negatively correlated with aluminum in serum (β = −0.095; p = 0.05). There was a marginal negative correlation between aluminum levels in serum and manganese levels in whole blood (β = −0.087; p = 0.08). Copper levels in maternal serum were negatively correlated with birth weight and the length of neonates. There were a number of positive correlations between maternal characteristics and birth outcomes. Mothers who consumed root vegetables frequently appeared to be protected from aluminum retention and increased body burden since their serum aluminum levels were found to be significantly lower. The findings of the current study can be used as a baseline for further research on aluminum exposure and its associated interactions and outcomes in vulnerable populations.
- Full Text:
- Authors: Röllin, Halina B. , Nogueira, Claudina , Olutola, Bukola , Channa, Kalavati , Odland, Jon Ø.
- Date: 2018
- Subjects: Aluminum , Maternal serum and urine , Essential trace elements
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/288068 , uj:31215 , Citation: Röllin, H.B. et al. 2018. Prenatal exposure to aluminum and status of selected essential trace elements in rural South African women at delivery. International Journal of Environmental Research and Public Health, 2018, 15, 1494; doi:10.3390/ijerph15071494
- Description: Abstract: This study sought to evaluate the in utero exposure to aluminum and status of selected trace elements in South African women at delivery since aluminum is known to be toxic in all developmental stages even at low concentrations. Serum aluminum was negatively correlated with aluminum in urine, both uncorrected and corrected for creatinine, which suggests the retention of aluminum in body stores. Serum copper and zinc levels were found to be high in this study population. Serum copper levels were negatively correlated with aluminum in serum (β = −0.095; p = 0.05). There was a marginal negative correlation between aluminum levels in serum and manganese levels in whole blood (β = −0.087; p = 0.08). Copper levels in maternal serum were negatively correlated with birth weight and the length of neonates. There were a number of positive correlations between maternal characteristics and birth outcomes. Mothers who consumed root vegetables frequently appeared to be protected from aluminum retention and increased body burden since their serum aluminum levels were found to be significantly lower. The findings of the current study can be used as a baseline for further research on aluminum exposure and its associated interactions and outcomes in vulnerable populations.
- Full Text:
'n Saamgestelde skakelmoduskragbron vir Tig-sweis
- Authors: Roux, Johannes Adam
- Date: 2015-09-10
- Subjects: Power electronics , Semiconductors , Aluminum , Electric welding
- Type: Thesis
- Identifier: uj:14090 , http://hdl.handle.net/10210/14522
- Description: M.Ing. , The product of switching frequency and output power of solid state converters has increased dramatically during the past few years. This progress can mainly be attributed to the recent developments in power electronic switching devices. These developments are mainly responsible for a reduction in the physical size of the converter, especially that of the reactive components, and an increase in the dynamic response of the converter ...
- Full Text:
- Authors: Roux, Johannes Adam
- Date: 2015-09-10
- Subjects: Power electronics , Semiconductors , Aluminum , Electric welding
- Type: Thesis
- Identifier: uj:14090 , http://hdl.handle.net/10210/14522
- Description: M.Ing. , The product of switching frequency and output power of solid state converters has increased dramatically during the past few years. This progress can mainly be attributed to the recent developments in power electronic switching devices. These developments are mainly responsible for a reduction in the physical size of the converter, especially that of the reactive components, and an increase in the dynamic response of the converter ...
- Full Text:
Aluminium triflate as a Lewis acid catalyst in some epoxide and aromatic transformations
- Authors: Lawton, Michelle Claire
- Date: 2012-03-14
- Subjects: Lewis acids , Aluminum , Alcoholysis , Epoxy compounds , Catalysts , Aromatic compounds , Substitution reactions
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/368554 , uj:2163 , http://hdl.handle.net/10210/4536
- Description: M.Sc. , Lewis acids play an important role in catalysis; they are associated with mild conditions, high selectivities and unique reactivities. Traditional Lewis acids such as AlCb and BF3 successfully catalyse such well known reactions as the Friedel-Crafts acylation reaction, Aldol condensation reactions and many more. These catalysts, however, must be used in a stoichiometric amount and are destroyed during the aqueous workup procedures. Lately, there has been a lot of interest in the role of metal triflate as Lewis acid catalysts. They were found to be effective in a wide range of reactions when used in catalytic amounts. They were also found to be recyclable and reusable without the loss of activity. Most of this research has been centred around the lanthanide triflates as well as scandium, bismuth and yttrium triflates. Very little research has been done using aluminium triflate and this triflate forms the focus ofthis study. The work contained in this dissertation demonstrates that Al(OTf)3 is an efficient catalyst for the ring opening of a variety of epoxides by alcohols when present in only ppm amounts. These reactions provided products in very high yields and selectivities. Simple acyclic and cyclic epoxides readily underwent ring opening reactions with a range of alcohols, typically providing the monoglycol ethers as single compounds (from the cyclic epoxides) or as mixtures of the two possible glycol monoethers (from the acyclic epoxides). In the case of styrene oxide, essentially a single compound was isolated. In contrast, the glycidyl ethers required slightly higher catalyst loadings before similar rates and conversions to product were observed. Additionally, an interesting selectivity was observed in the orientation of the attack of the alcohol onto the epoxide, which appeared to be chelation controlled. Similarly, the Al(OTf)3 also catalysed the aminolysis of a variety of epoxides. These reactions proceeded smoothly with catalytic amounts of the triflate present, and served to nicely highlight the role that steric and electronic factors played in these reactions. A preliminary study was carried out into the efficacy of Al(OTf)3 as a catalyst for Friedel-Crafts acylation and aromatic nitration reactions. From these studies it is evident that the Al(OTf)3 is indeed an effective catalyst for these reactions when present in substoichiometric levels and further studies will be carried out in this area in the future.
- Full Text:
- Authors: Lawton, Michelle Claire
- Date: 2012-03-14
- Subjects: Lewis acids , Aluminum , Alcoholysis , Epoxy compounds , Catalysts , Aromatic compounds , Substitution reactions
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/368554 , uj:2163 , http://hdl.handle.net/10210/4536
- Description: M.Sc. , Lewis acids play an important role in catalysis; they are associated with mild conditions, high selectivities and unique reactivities. Traditional Lewis acids such as AlCb and BF3 successfully catalyse such well known reactions as the Friedel-Crafts acylation reaction, Aldol condensation reactions and many more. These catalysts, however, must be used in a stoichiometric amount and are destroyed during the aqueous workup procedures. Lately, there has been a lot of interest in the role of metal triflate as Lewis acid catalysts. They were found to be effective in a wide range of reactions when used in catalytic amounts. They were also found to be recyclable and reusable without the loss of activity. Most of this research has been centred around the lanthanide triflates as well as scandium, bismuth and yttrium triflates. Very little research has been done using aluminium triflate and this triflate forms the focus ofthis study. The work contained in this dissertation demonstrates that Al(OTf)3 is an efficient catalyst for the ring opening of a variety of epoxides by alcohols when present in only ppm amounts. These reactions provided products in very high yields and selectivities. Simple acyclic and cyclic epoxides readily underwent ring opening reactions with a range of alcohols, typically providing the monoglycol ethers as single compounds (from the cyclic epoxides) or as mixtures of the two possible glycol monoethers (from the acyclic epoxides). In the case of styrene oxide, essentially a single compound was isolated. In contrast, the glycidyl ethers required slightly higher catalyst loadings before similar rates and conversions to product were observed. Additionally, an interesting selectivity was observed in the orientation of the attack of the alcohol onto the epoxide, which appeared to be chelation controlled. Similarly, the Al(OTf)3 also catalysed the aminolysis of a variety of epoxides. These reactions proceeded smoothly with catalytic amounts of the triflate present, and served to nicely highlight the role that steric and electronic factors played in these reactions. A preliminary study was carried out into the efficacy of Al(OTf)3 as a catalyst for Friedel-Crafts acylation and aromatic nitration reactions. From these studies it is evident that the Al(OTf)3 is indeed an effective catalyst for these reactions when present in substoichiometric levels and further studies will be carried out in this area in the future.
- Full Text:
Characterisation of tool geometries for friction stir lap welds of aluminium and copper
- Authors: Ewuola, Oluwatoyin Olabisi
- Date: 2015
- Subjects: Friction stir welding , Dissimilar welding , Welded joints - Cracking , Aluminum , Copper
- Language: English
- Type: Masters (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/370322 , http://hdl.handle.net/10210/212826 , uj:21032
- Description: Abstract: The patenting of the Friction Stir Welding (FSW) process in 1991 opened up a process that was known within a relatively small circle of researchers to the entire research community. As a ground-breaking process in the field of joining, FSW offered a chance for the types of joining that had been fraught with lots of difficulties using the prevalent traditional means of joining. Dissimilar metal joining had been plagued with more challenges compared to similar metal joining due to issues related to differences in thermal expansion and conductivity, wettability, melting properties, microstructural properties and other material properties. Fusion welding of some dissimilar materials such as Aluminium and titanium; Aluminium and Steel had been nearly impossible; the few welds that were successful resulted in defects (like wormhole, lack of penetration, porosity, cracks) and welding imperfections. Hence, the advent of FSW, a solid state welding technique, provided a way out of the many difficulties that arise in the joining of dissimilar metals. Aluminium and copper are also two of such dissimilar metals whose material properties make them useful for a wide range of applications. However, due to the wide differences in their material properties, both metals had been difficult to join using the fusion welding technology. Recently, lots of successes have been achieved in the joining of both dissimilar metals using FSW and a lot of these are recorded in the open literature. Nonetheless, most of the successes recorded in the FSW of aluminium and copper have been in the butt weld configuration. Literatures abound on the FSW of aluminium and copper in butt configuration, while there are... , M.Phil. (Mechanical Engineering)
- Full Text:
- Authors: Ewuola, Oluwatoyin Olabisi
- Date: 2015
- Subjects: Friction stir welding , Dissimilar welding , Welded joints - Cracking , Aluminum , Copper
- Language: English
- Type: Masters (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/370322 , http://hdl.handle.net/10210/212826 , uj:21032
- Description: Abstract: The patenting of the Friction Stir Welding (FSW) process in 1991 opened up a process that was known within a relatively small circle of researchers to the entire research community. As a ground-breaking process in the field of joining, FSW offered a chance for the types of joining that had been fraught with lots of difficulties using the prevalent traditional means of joining. Dissimilar metal joining had been plagued with more challenges compared to similar metal joining due to issues related to differences in thermal expansion and conductivity, wettability, melting properties, microstructural properties and other material properties. Fusion welding of some dissimilar materials such as Aluminium and titanium; Aluminium and Steel had been nearly impossible; the few welds that were successful resulted in defects (like wormhole, lack of penetration, porosity, cracks) and welding imperfections. Hence, the advent of FSW, a solid state welding technique, provided a way out of the many difficulties that arise in the joining of dissimilar metals. Aluminium and copper are also two of such dissimilar metals whose material properties make them useful for a wide range of applications. However, due to the wide differences in their material properties, both metals had been difficult to join using the fusion welding technology. Recently, lots of successes have been achieved in the joining of both dissimilar metals using FSW and a lot of these are recorded in the open literature. Nonetheless, most of the successes recorded in the FSW of aluminium and copper have been in the butt weld configuration. Literatures abound on the FSW of aluminium and copper in butt configuration, while there are... , M.Phil. (Mechanical Engineering)
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Elektriese eienskappe van aluminium kontakte op polikristallyne silikon
- Authors: Van der Merwe, Johan Petrus
- Date: 2012-08-28
- Subjects: Polycrystalline semiconductors. , Silicon - Electric properties. , Aluminum , Solar cells. , Semiconductors.
- Type: Thesis
- Identifier: uj:3336 , http://hdl.handle.net/10210/6737
- Description: M.Sc. , The efficiency of commercial polycrystalline silicon solar cells is currently 12% and 15% in the case of single crystalline cells. It is possible to lose about half of the open circuit voltage due to inferior contacts on the cell. It is thus clear that inferior contacts can seriously impede the relative low efficiency and care should be taken to make good ohmic contacts. Experiments were done to evaluate the influence of several factors on the quality and stability of the contacts. 1 C2•cm p-type polycrystalline silicon and 3 52.cm n-type single crystalline silicon were primarily used for these experiments. Results of molybdenum contacts on n-type silicon are also presented and the problems with silver epoxy contacts are discussed. It was found that aluminium contacts on p-type polycrystaline silicon improve with temperature and time, while those on single crystaline n-type degrade with temperature and time. These changes are already present at room temperature and are attributed to solid state diffusion of the aluminium into the silicon. This results in a p + layer. In the case of contacts on p-type, the behaviour is that of a Schottky diode. After the solid state diffusion, it becomes possible for the charges to quantum mechanically tunnel through the p+ layer. This results in an improvement of the contact. The contacts on n-type however, are ohmic just after evaporation. Similar to the p-material, the p+ layer causes a p+-n-junction with the depletion layer primarily in the n-type material. This causes a degradation in the contact quality. It is possible to achieve good quality contacts on polycrystaline p-type material, by annealing the contacts above 500°C for one minute. These contacts however, are non-ideal. SEM photographs show that the silicon surface is crated by pits due to solid state diffusion. It is only at these pits that conduction through the Schottkybarrier is possible. Since the area of the pits constitutes only a portion of the total area, only a portion of the surface will partake in conduction. Contact resistance is always present. For pm sized contacts on integrated circuits, the spesific resistance is of the order of 10 -6 Q.cm2. Contacts on solar cells, however, are of millimetre dimensions and the spesific resistance can be four orders of magnitude larger. The conduction through the surface can be modelled as conduction through a surface that is constituted of a mixture of minute ohmic and diode surfaces.
- Full Text:
- Authors: Van der Merwe, Johan Petrus
- Date: 2012-08-28
- Subjects: Polycrystalline semiconductors. , Silicon - Electric properties. , Aluminum , Solar cells. , Semiconductors.
- Type: Thesis
- Identifier: uj:3336 , http://hdl.handle.net/10210/6737
- Description: M.Sc. , The efficiency of commercial polycrystalline silicon solar cells is currently 12% and 15% in the case of single crystalline cells. It is possible to lose about half of the open circuit voltage due to inferior contacts on the cell. It is thus clear that inferior contacts can seriously impede the relative low efficiency and care should be taken to make good ohmic contacts. Experiments were done to evaluate the influence of several factors on the quality and stability of the contacts. 1 C2•cm p-type polycrystalline silicon and 3 52.cm n-type single crystalline silicon were primarily used for these experiments. Results of molybdenum contacts on n-type silicon are also presented and the problems with silver epoxy contacts are discussed. It was found that aluminium contacts on p-type polycrystaline silicon improve with temperature and time, while those on single crystaline n-type degrade with temperature and time. These changes are already present at room temperature and are attributed to solid state diffusion of the aluminium into the silicon. This results in a p + layer. In the case of contacts on p-type, the behaviour is that of a Schottky diode. After the solid state diffusion, it becomes possible for the charges to quantum mechanically tunnel through the p+ layer. This results in an improvement of the contact. The contacts on n-type however, are ohmic just after evaporation. Similar to the p-material, the p+ layer causes a p+-n-junction with the depletion layer primarily in the n-type material. This causes a degradation in the contact quality. It is possible to achieve good quality contacts on polycrystaline p-type material, by annealing the contacts above 500°C for one minute. These contacts however, are non-ideal. SEM photographs show that the silicon surface is crated by pits due to solid state diffusion. It is only at these pits that conduction through the Schottkybarrier is possible. Since the area of the pits constitutes only a portion of the total area, only a portion of the surface will partake in conduction. Contact resistance is always present. For pm sized contacts on integrated circuits, the spesific resistance is of the order of 10 -6 Q.cm2. Contacts on solar cells, however, are of millimetre dimensions and the spesific resistance can be four orders of magnitude larger. The conduction through the surface can be modelled as conduction through a surface that is constituted of a mixture of minute ohmic and diode surfaces.
- Full Text:
Ethers and acetals in aluminium triflatepromoted reactions
- Authors: Henning, Hendrik
- Date: 2013-07-24
- Subjects: Aluminum , Ethers , Lewis acids , Metal catalysts
- Type: Thesis
- Identifier: uj:7695 , http://hdl.handle.net/10210/8561
- Description: M.Sc. (Chemistry) , The work in this thesis describes some catalytic reactions of aluminium triflate. This Lewis acid has been shown to be of great value in the catalysis of several types of organic transformations. These include but are not limited to the alcoholysis and aminolysis of epoxides, uses in methoxycarbonylation catalysis and in esterification reactions. Therefore, aluminium triflate holds promise for application in both the bulk and fine chemistry industries. Aluminium triflate has received little interest compared to some other, more costly triflates such the lanthanide triflates. Oxetanes were used in various catalysis experiments during this study, yet few are commercially available. Therefore, various synthetic approaches to the synthesis of 2-phenyl-oxetane were explored. There were many failed attempts, but the preparation was eventually successful using a sulfur ylide route with good yield. The next part of this thesis explores the boundaries of ring-opening reactions of oxetanes. Lewis acid ring-opening of oxetanes has been neglected compared to that of epoxides, likely because it is a more difficult undertaking. Yet, alcoholysis reactions showed good yields with a variety of different alcohol substrates. Some of the alcohols contained functionality which could provide access to further modification. Furthermore, the aminolysis and thiolysis of oxetanes were explored, essentially without success. However, with an activated oxetane it was shown that oxetanes could be opened with good yield under mild conditions with amines and thiols...
- Full Text:
- Authors: Henning, Hendrik
- Date: 2013-07-24
- Subjects: Aluminum , Ethers , Lewis acids , Metal catalysts
- Type: Thesis
- Identifier: uj:7695 , http://hdl.handle.net/10210/8561
- Description: M.Sc. (Chemistry) , The work in this thesis describes some catalytic reactions of aluminium triflate. This Lewis acid has been shown to be of great value in the catalysis of several types of organic transformations. These include but are not limited to the alcoholysis and aminolysis of epoxides, uses in methoxycarbonylation catalysis and in esterification reactions. Therefore, aluminium triflate holds promise for application in both the bulk and fine chemistry industries. Aluminium triflate has received little interest compared to some other, more costly triflates such the lanthanide triflates. Oxetanes were used in various catalysis experiments during this study, yet few are commercially available. Therefore, various synthetic approaches to the synthesis of 2-phenyl-oxetane were explored. There were many failed attempts, but the preparation was eventually successful using a sulfur ylide route with good yield. The next part of this thesis explores the boundaries of ring-opening reactions of oxetanes. Lewis acid ring-opening of oxetanes has been neglected compared to that of epoxides, likely because it is a more difficult undertaking. Yet, alcoholysis reactions showed good yields with a variety of different alcohol substrates. Some of the alcohols contained functionality which could provide access to further modification. Furthermore, the aminolysis and thiolysis of oxetanes were explored, essentially without success. However, with an activated oxetane it was shown that oxetanes could be opened with good yield under mild conditions with amines and thiols...
- Full Text:
Friction stir spot welding between copper and aluminium : microstructural evolution
- Mubiayi, Mukuna P., Akinlabi, Esther Titilayo
- Authors: Mubiayi, Mukuna P. , Akinlabi, Esther Titilayo
- Date: 2015-03-18
- Subjects: Aluminum , Copper , Friction stir spot welding , Energy dispersive spectroscopy mapping
- Type: Article
- Identifier: uj:5129 , ISBN 9789881925398 , http://hdl.handle.net/10210/14092
- Description: Friction Stir Spot Welding (FSSW) process was employed to produce lap spot welds of C11000 copper and aluminium alloy AA1060. The microstructures of the spot welds produced at different processing parameters were analyzed. Copper rings with different lengths were observed in all the spot welds. An Energy Dispersive Spectroscopy (EDS) mapping of a region of the keyhole and the Copper rings was conducted, results showed the presence of Copper particles in the Aluminium matrix and almost no Aluminium particles are found in the Copper rings. Furthermore, the distribution of the fine Copper fragments and particles in the zone close to the Aluminium parent material of some of the produced spot welds were seen in the Scanning Electron Microscopy (SEM) images.
- Full Text: false
- Authors: Mubiayi, Mukuna P. , Akinlabi, Esther Titilayo
- Date: 2015-03-18
- Subjects: Aluminum , Copper , Friction stir spot welding , Energy dispersive spectroscopy mapping
- Type: Article
- Identifier: uj:5129 , ISBN 9789881925398 , http://hdl.handle.net/10210/14092
- Description: Friction Stir Spot Welding (FSSW) process was employed to produce lap spot welds of C11000 copper and aluminium alloy AA1060. The microstructures of the spot welds produced at different processing parameters were analyzed. Copper rings with different lengths were observed in all the spot welds. An Energy Dispersive Spectroscopy (EDS) mapping of a region of the keyhole and the Copper rings was conducted, results showed the presence of Copper particles in the Aluminium matrix and almost no Aluminium particles are found in the Copper rings. Furthermore, the distribution of the fine Copper fragments and particles in the zone close to the Aluminium parent material of some of the produced spot welds were seen in the Scanning Electron Microscopy (SEM) images.
- Full Text: false
Adsorption, kinetic and thermodynamic study of Al, Mn and Fe adsorption with natural attapulgite
- Ntuli, Freeman, Falayi, Thabo, Mabasa, Cyril
- Authors: Ntuli, Freeman , Falayi, Thabo , Mabasa, Cyril
- Date: 2015
- Subjects: Attapulgite , Aluminum , Manganese , Iron , Adsorption
- Type: Article
- Identifier: uj:5126 , ISBN 978-1-61804-270-5 , http://hdl.handle.net/10210/14089
- Description: Natural attapulgite was utilized as an adsorbent for the removal of Al, Fe and Mn from a mixed metal effluent. Adsorption experiments were carried out by agitation of a fixed amount of attapulgite with a fixed volume of effluent waste stream in a thermostatic shaker for varying times. Attapulgite showed that it was capable of neutralising the acidic waste stream effluent as pH after 3 hour rose from 2 to 7.46. 4% solid loading of attapulgite could remove 85% Mn(II), 90% Al(III) and 100% Fe(III) The experimental data best fit Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models and the adsorption mechanism was physisorption. The adsorption process fitted well the pseudo second order kinetics for all metal ions studied. Thermodynamic data showed that Fe(III) and Mn(II) adsorption was thermodynamically spontaneous whilst Al(III) was not thermodynamically spontaneous. The process is endothermic for all metal ions. An increase in temperature resulted in an increase in spontaneity of the adsorption process. An increase in metal concentration resulted in an increase in amount of metal ion adsorbed per unit weight of attapulgite.
- Full Text:
- Authors: Ntuli, Freeman , Falayi, Thabo , Mabasa, Cyril
- Date: 2015
- Subjects: Attapulgite , Aluminum , Manganese , Iron , Adsorption
- Type: Article
- Identifier: uj:5126 , ISBN 978-1-61804-270-5 , http://hdl.handle.net/10210/14089
- Description: Natural attapulgite was utilized as an adsorbent for the removal of Al, Fe and Mn from a mixed metal effluent. Adsorption experiments were carried out by agitation of a fixed amount of attapulgite with a fixed volume of effluent waste stream in a thermostatic shaker for varying times. Attapulgite showed that it was capable of neutralising the acidic waste stream effluent as pH after 3 hour rose from 2 to 7.46. 4% solid loading of attapulgite could remove 85% Mn(II), 90% Al(III) and 100% Fe(III) The experimental data best fit Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models and the adsorption mechanism was physisorption. The adsorption process fitted well the pseudo second order kinetics for all metal ions studied. Thermodynamic data showed that Fe(III) and Mn(II) adsorption was thermodynamically spontaneous whilst Al(III) was not thermodynamically spontaneous. The process is endothermic for all metal ions. An increase in temperature resulted in an increase in spontaneity of the adsorption process. An increase in metal concentration resulted in an increase in amount of metal ion adsorbed per unit weight of attapulgite.
- Full Text:
The flexural buckling strength of aluminium columns
- Authors: Van der Merwe, Etienne
- Date: 2012-08-17
- Subjects: Aluminum, Structural , Aluminum , Buckling (Mechanics)
- Type: Mini-Dissertation
- Identifier: uj:2631 , http://hdl.handle.net/10210/6078
- Description: M.Ing. , It should be the objective of every engineer to design as cost-effective as possible. This study is part of a much larger programme in which the most effective column design method is to be found by comparing the different column design criteria and methods of design which are in use for different materials. The materials under consideration are carbon and low-alloy steels (structural steels), stainless steels and an aluminium alloy that is regarded as suitable for structural design. It has been judged that sufficient experimental data is available to the Chromium Steels Research Group (CSRG) at the Rand Afrikaans University on carbon and low-alloy steels and stainless steels and that sufficient data on the mechanical properties of the aluminium alloy 6261-T6, which is regarded suitable for structural applications, is available to the CSRG after previous research done by the author. This short dissertation reports on a preliminary study of the different design criteria and methods for the design of columns. It also reports on the experimental study through which the results of column tests done on the abovementioned aluminium alloy are compared with different column design curves. These curves were obtained by using the previously determined mechanical properties for the aluminium alloy under consideration in the different design criteria and methods for the design of columns.
- Full Text:
- Authors: Van der Merwe, Etienne
- Date: 2012-08-17
- Subjects: Aluminum, Structural , Aluminum , Buckling (Mechanics)
- Type: Mini-Dissertation
- Identifier: uj:2631 , http://hdl.handle.net/10210/6078
- Description: M.Ing. , It should be the objective of every engineer to design as cost-effective as possible. This study is part of a much larger programme in which the most effective column design method is to be found by comparing the different column design criteria and methods of design which are in use for different materials. The materials under consideration are carbon and low-alloy steels (structural steels), stainless steels and an aluminium alloy that is regarded as suitable for structural design. It has been judged that sufficient experimental data is available to the Chromium Steels Research Group (CSRG) at the Rand Afrikaans University on carbon and low-alloy steels and stainless steels and that sufficient data on the mechanical properties of the aluminium alloy 6261-T6, which is regarded suitable for structural applications, is available to the CSRG after previous research done by the author. This short dissertation reports on a preliminary study of the different design criteria and methods for the design of columns. It also reports on the experimental study through which the results of column tests done on the abovementioned aluminium alloy are compared with different column design curves. These curves were obtained by using the previously determined mechanical properties for the aluminium alloy under consideration in the different design criteria and methods for the design of columns.
- Full Text:
Weld reliability characterisation of dissimilar friction stir welds of aluminium alloys
- Authors: Azeez, Sarafadeen Tunde
- Date: 2017
- Subjects: Friction stir welding , Dissimilar welding , Welded joints - Reliability , Metals - Weldability , Aluminum
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/269883 , uj:28676
- Description: D.Phil. (Mechanical Engineering) , Abstract: Welding is a crucial joining technique that is generally employed in the fabrication industry. The integrity of weld joints is of great importance, because of its safety and the economic implications. This research provides a glimpse into the basic concept of weld reliability, failure prediction, mechanical and microstructure characterization, with respect to friction stir welding (FSW) of similar and dissimilar Aluminium alloys. The establishment of this concept will enhance welds in service performance and their application in setting criteria for the evaluation of materials’ integrity. Friction stir welding (FSW) of a 6 mm thick AA6082-T6 Aluminium alloy was performed for the preliminary experiment. Three welding speeds of 90 mm/min, 120 mm/min and 150 mm/min at a tool-rotational speed of 950 rpm were used. A solution heat treatment carried out on the specimen revealed a drastic response by an over 120 % increment in strength. The welds at welding speed 150mm/min and the tool-rotation speed of 950rpm (i.e. sample S3) have maximum UTS values of 101MPa at as-weld and 234MPa after heat treatment (i.e. sample H3). The lowest values of strength were observed at 84MPa, at as-weld (i.e. sample S2) and 167MPa when heat-treated (i.e. 90mm/min and 950rpm, sample H1), respectively. The higher the heat input the softer the weld joints. However, the as-weld samples (S1-S6) deviate from the conventional trend unlike the heat treated samples (H1-H6). This is due to overlapping of the temperature field for friction stir bead at the end of each welds. All the samples (i.e. similar welds) fractured at the heat-affected zone (HAZ), due to the reduction in hardness, as a result of a dissolution mechanism. Aside from the point of fracture, the disparities in composition evolution and physical integrity of the weld joints are similar. Ductility is a material property that is inversly related to the strength of the materials. However, a solution heat treatment of the samples (H1-H6) has an increment of over 120% in UTS...
- Full Text:
- Authors: Azeez, Sarafadeen Tunde
- Date: 2017
- Subjects: Friction stir welding , Dissimilar welding , Welded joints - Reliability , Metals - Weldability , Aluminum
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/269883 , uj:28676
- Description: D.Phil. (Mechanical Engineering) , Abstract: Welding is a crucial joining technique that is generally employed in the fabrication industry. The integrity of weld joints is of great importance, because of its safety and the economic implications. This research provides a glimpse into the basic concept of weld reliability, failure prediction, mechanical and microstructure characterization, with respect to friction stir welding (FSW) of similar and dissimilar Aluminium alloys. The establishment of this concept will enhance welds in service performance and their application in setting criteria for the evaluation of materials’ integrity. Friction stir welding (FSW) of a 6 mm thick AA6082-T6 Aluminium alloy was performed for the preliminary experiment. Three welding speeds of 90 mm/min, 120 mm/min and 150 mm/min at a tool-rotational speed of 950 rpm were used. A solution heat treatment carried out on the specimen revealed a drastic response by an over 120 % increment in strength. The welds at welding speed 150mm/min and the tool-rotation speed of 950rpm (i.e. sample S3) have maximum UTS values of 101MPa at as-weld and 234MPa after heat treatment (i.e. sample H3). The lowest values of strength were observed at 84MPa, at as-weld (i.e. sample S2) and 167MPa when heat-treated (i.e. 90mm/min and 950rpm, sample H1), respectively. The higher the heat input the softer the weld joints. However, the as-weld samples (S1-S6) deviate from the conventional trend unlike the heat treated samples (H1-H6). This is due to overlapping of the temperature field for friction stir bead at the end of each welds. All the samples (i.e. similar welds) fractured at the heat-affected zone (HAZ), due to the reduction in hardness, as a result of a dissolution mechanism. Aside from the point of fracture, the disparities in composition evolution and physical integrity of the weld joints are similar. Ductility is a material property that is inversly related to the strength of the materials. However, a solution heat treatment of the samples (H1-H6) has an increment of over 120% in UTS...
- Full Text:
Characterisation of the evolving properties of friction stir spot aluminium and copper welds
- Authors: Mubiayi, Mukuna Patrick
- Date: 2015
- Subjects: Friction stir welding , Dissimilar welding , Aluminum
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/213368 , uj:21144
- Description: Abstract: Dissimilar metal joining techniques are necessary for the manufacturing of a number of structures and parts in the industries. Aluminium and copper are widely used in engineering structures, due to their unique performances, such as higher electrical conductivity, heat conductivity, corrosion resistance and mechanical properties even if they have considerable differences in their melting points. Among the aims for future years in the automotive industry is the development and implementation of new technologies, including a broad application of friction stir spot welding (FSSW) of similar and dissimilar materials. Friction stir spot welding (FSSW) is a variant of friction stir welding (FSW) for spot welding applications. Joining aluminium and copper to meet the requirements from the electrical industry have been conducted by using different joining techniques, such as ultrasonic welding, friction welding and laser welding. However, the major challenge with these techniques is the occurrence of brittle intermetallic compounds in the joint zone. FSSW has been successfully used to join aluminium and copper by a few researchers; but more research is needed to investigate the evolving properties of FSSW between copper and aluminium. The current research project joined 3 mm thick AA1060 and C11000, by using friction stir spot welding (FSSW), and by using different tool geometries namely a flat pin/flat shoulder and a conical pin/concave shoulder and different process parameters, in order to fill the gap in the literature in this field of study. Limited research results exist on friction stir spot welding between aluminium and copper. However, the successful joining of these two materials has the potential for many applications in the industry. The spot welds were produced and characterised through optical microscopy, and by scanning electron microscopy for the microstructural evolution; while the chemical and phase identification were analysed using energy dispersive spectroscopy and X-ray diffraction, respectively. Furthermore, tensile testing, microhardness profiling, residual stress analysis, electrical resistivity and statistical analysis were also conducted. This was done to investigate the relationship between the process parameters, the tool geometry and the produced welds. The real time forces acting during the welding process were monitored and analysed. It was observed that the maximum forge... , D.Phil. (Mechanical Engineering Science)
- Full Text:
- Authors: Mubiayi, Mukuna Patrick
- Date: 2015
- Subjects: Friction stir welding , Dissimilar welding , Aluminum
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/213368 , uj:21144
- Description: Abstract: Dissimilar metal joining techniques are necessary for the manufacturing of a number of structures and parts in the industries. Aluminium and copper are widely used in engineering structures, due to their unique performances, such as higher electrical conductivity, heat conductivity, corrosion resistance and mechanical properties even if they have considerable differences in their melting points. Among the aims for future years in the automotive industry is the development and implementation of new technologies, including a broad application of friction stir spot welding (FSSW) of similar and dissimilar materials. Friction stir spot welding (FSSW) is a variant of friction stir welding (FSW) for spot welding applications. Joining aluminium and copper to meet the requirements from the electrical industry have been conducted by using different joining techniques, such as ultrasonic welding, friction welding and laser welding. However, the major challenge with these techniques is the occurrence of brittle intermetallic compounds in the joint zone. FSSW has been successfully used to join aluminium and copper by a few researchers; but more research is needed to investigate the evolving properties of FSSW between copper and aluminium. The current research project joined 3 mm thick AA1060 and C11000, by using friction stir spot welding (FSSW), and by using different tool geometries namely a flat pin/flat shoulder and a conical pin/concave shoulder and different process parameters, in order to fill the gap in the literature in this field of study. Limited research results exist on friction stir spot welding between aluminium and copper. However, the successful joining of these two materials has the potential for many applications in the industry. The spot welds were produced and characterised through optical microscopy, and by scanning electron microscopy for the microstructural evolution; while the chemical and phase identification were analysed using energy dispersive spectroscopy and X-ray diffraction, respectively. Furthermore, tensile testing, microhardness profiling, residual stress analysis, electrical resistivity and statistical analysis were also conducted. This was done to investigate the relationship between the process parameters, the tool geometry and the produced welds. The real time forces acting during the welding process were monitored and analysed. It was observed that the maximum forge... , D.Phil. (Mechanical Engineering Science)
- Full Text:
Effect of rotational speed on joint inegrity of friction stir lap welded aluminium
- Akinlabi, Esther Titilayo, Akinlabi, Stephen A.
- Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
- Date: 2016
- Subjects: Friction stir welding , Aluminum , Rotational speed
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/93262 , uj:20326 , Citation: Akinlabi, E.T. & Akinlabi, S.A. 2016. Effect of rotational speed on joint inegrity of friction stir lap welded aluminium.
- Description: Abstract: Friction stir welding is a newly developed solid state welding process, which was developed by The Welding Institute in the year 1991. The development of FSW has allowed the process to be used in different applications for different industries, which include aerospace and automobile industry. Due to the increase in the demand of high strength and low weight components in different manufacturing applications, there is a need for using pure aluminium and its alloys in lap configuration. Research studies are required to characterize and obtain optimum process parameters, which can be used to produce good quality lap welds. This paper reports lap welded 1050 Aluminium Alloy using friction stir welding process and established the effect of rotational speed on the joint integrity of the welds. The welds were produced by varying the rotational speed in the range of 1200 and 2000 rpm, and maintaining the traverse speed constant at 150 mm/min. The welds were characterized through microstructural evaluation, microhardness profiling and tensile testing in order to determine the joint integrity of the welds. The results from the macrograph of the welded joints, show a basin shaped nugget resulting from the stirring of the tool during the welding process. Fine and equiaxed grains characterized the microstructure in the stirred zone, which was a result of a dynamic recrystallization. The tensile test data revealed that as the tool rotational speed was increased, the fracture strength also increases, the highest value of the fracture strength was 195 N/mm and was found on the welds produced at 2000 rpm. High Vickers microhardness values were measured at the nugget zone with the highest value found to be 31.88 HV. It was revealed that the welds produced at the rotational speed of 2000 rpm exhibited the optimum welding parameters to join 1050 Aluminium Alloy.
- Full Text:
- Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
- Date: 2016
- Subjects: Friction stir welding , Aluminum , Rotational speed
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/93262 , uj:20326 , Citation: Akinlabi, E.T. & Akinlabi, S.A. 2016. Effect of rotational speed on joint inegrity of friction stir lap welded aluminium.
- Description: Abstract: Friction stir welding is a newly developed solid state welding process, which was developed by The Welding Institute in the year 1991. The development of FSW has allowed the process to be used in different applications for different industries, which include aerospace and automobile industry. Due to the increase in the demand of high strength and low weight components in different manufacturing applications, there is a need for using pure aluminium and its alloys in lap configuration. Research studies are required to characterize and obtain optimum process parameters, which can be used to produce good quality lap welds. This paper reports lap welded 1050 Aluminium Alloy using friction stir welding process and established the effect of rotational speed on the joint integrity of the welds. The welds were produced by varying the rotational speed in the range of 1200 and 2000 rpm, and maintaining the traverse speed constant at 150 mm/min. The welds were characterized through microstructural evaluation, microhardness profiling and tensile testing in order to determine the joint integrity of the welds. The results from the macrograph of the welded joints, show a basin shaped nugget resulting from the stirring of the tool during the welding process. Fine and equiaxed grains characterized the microstructure in the stirred zone, which was a result of a dynamic recrystallization. The tensile test data revealed that as the tool rotational speed was increased, the fracture strength also increases, the highest value of the fracture strength was 195 N/mm and was found on the welds produced at 2000 rpm. High Vickers microhardness values were measured at the nugget zone with the highest value found to be 31.88 HV. It was revealed that the welds produced at the rotational speed of 2000 rpm exhibited the optimum welding parameters to join 1050 Aluminium Alloy.
- Full Text:
Effect of tool geometries on butt dissimilar friction stir welds of 5754 aluminium
- Authors: Reddy, Randall Dwain
- Date: 2015
- Subjects: Friction stir welding , Dissimilar welding , Aluminum
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213567 , uj:21169
- Description: Abstract: Friction Stir Welding (FSW) is regarded as the most significant development in joining over the past two decades. In FSW, process parameters and tool geometry play a fundamental role in obtaining desirable mechanical properties and microstructures in the welded zone. The tool geometry plays an important role in producing sound friction stir welds. Tool designs are however, generally propriety to individual researchers and only limited information is available in open literature. There are however, continuous efforts to understand the material flow and the influence that the FSW tool design has on the friction stir welded material. Within industries that use various welding techniques it well known that FSW is particularly suited for the welding of aluminium; there is great potential for FSW of copper. Given the limited supply, high cost, copper theft and commercial demand associated with copper, engineers and scientists will either attempt to reduce the quantity of copper consumed by industries or alternatively replace copper with a substitute metal that exhibits similar attributable properties. On account of the limited supply and consequently the high cost associated with copper and copper alloys; the need to join aluminium and copper and its’ alloys is anticipated to increase in the near future. FSW of dissimilar alloys/metals has attracted extensive research interest due to potential engineering prominence and inherent problems associated with conventional welding methods. This research identifies the choice of suitable tool designs and process parameters to produce sound dissimilar friction stir welds of 5754 aluminium and C11000 copper. This research focuses primarily on determining the effect of FSW process parameters on the forces experienced by the FSW tool and the relationship that this has on the electrical conductivity properties of the friction stir dissimilar weld. The experimental work was performed by completing dissimilar friction stir welds on 3 mm thick butt welds of the two materials by means of an I-stir FSW platform. During the experimental work, the rotational speed was varied between 600 and 1200 rpm in intervals on 300 related to low, medium and high rotational speeds respectively and four different FSW tool geometries were tested. The first tool was a new design with a unique shoulder topography and a cylindrical pin named the “Reddy tool”. The second tool was a tool consisted of a concave shoulder and conical pin. Tests were performed using the second tool at a 0 degree tilt and at a 2 degree tilt relative to the work-piece. The third tool consisted of a concave shoulder and cylindrical pin. The forth tool design consisted of a flat shoulder and a cylindrical pin. This research forms part of the initial experimental work to determine the forces and electrical resistance of dissimilar friction stir welds of aluminium and copper by employing different tool shoulder designs. The welds were characterised through visual inspection, weld defect and material flow analysis, microstructural evaluation, electrical resistance measurements and tool forces and tool torque analysis. Microstructural evaluation results revealed complex flow patterns of copper and aluminium material. Lamellae structures composed of copper particles with a streamline shape and continuous aluminium strips were present. Some evidence of dynamic recrystallization was observed in the nugget of the defect free welds. Based on material flow evaluation and defect formation results, the Reddy tool design is most suitable for high and low rotational speeds, the conical Shoulder tool at no tilt is most suitable for medium rotational speeds, the conical shoulder tool at a two degree tool tilt is most suitable for medium rotational speeds, the... , M.Ing. (Mechanical Engineering)
- Full Text:
- Authors: Reddy, Randall Dwain
- Date: 2015
- Subjects: Friction stir welding , Dissimilar welding , Aluminum
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213567 , uj:21169
- Description: Abstract: Friction Stir Welding (FSW) is regarded as the most significant development in joining over the past two decades. In FSW, process parameters and tool geometry play a fundamental role in obtaining desirable mechanical properties and microstructures in the welded zone. The tool geometry plays an important role in producing sound friction stir welds. Tool designs are however, generally propriety to individual researchers and only limited information is available in open literature. There are however, continuous efforts to understand the material flow and the influence that the FSW tool design has on the friction stir welded material. Within industries that use various welding techniques it well known that FSW is particularly suited for the welding of aluminium; there is great potential for FSW of copper. Given the limited supply, high cost, copper theft and commercial demand associated with copper, engineers and scientists will either attempt to reduce the quantity of copper consumed by industries or alternatively replace copper with a substitute metal that exhibits similar attributable properties. On account of the limited supply and consequently the high cost associated with copper and copper alloys; the need to join aluminium and copper and its’ alloys is anticipated to increase in the near future. FSW of dissimilar alloys/metals has attracted extensive research interest due to potential engineering prominence and inherent problems associated with conventional welding methods. This research identifies the choice of suitable tool designs and process parameters to produce sound dissimilar friction stir welds of 5754 aluminium and C11000 copper. This research focuses primarily on determining the effect of FSW process parameters on the forces experienced by the FSW tool and the relationship that this has on the electrical conductivity properties of the friction stir dissimilar weld. The experimental work was performed by completing dissimilar friction stir welds on 3 mm thick butt welds of the two materials by means of an I-stir FSW platform. During the experimental work, the rotational speed was varied between 600 and 1200 rpm in intervals on 300 related to low, medium and high rotational speeds respectively and four different FSW tool geometries were tested. The first tool was a new design with a unique shoulder topography and a cylindrical pin named the “Reddy tool”. The second tool was a tool consisted of a concave shoulder and conical pin. Tests were performed using the second tool at a 0 degree tilt and at a 2 degree tilt relative to the work-piece. The third tool consisted of a concave shoulder and cylindrical pin. The forth tool design consisted of a flat shoulder and a cylindrical pin. This research forms part of the initial experimental work to determine the forces and electrical resistance of dissimilar friction stir welds of aluminium and copper by employing different tool shoulder designs. The welds were characterised through visual inspection, weld defect and material flow analysis, microstructural evaluation, electrical resistance measurements and tool forces and tool torque analysis. Microstructural evaluation results revealed complex flow patterns of copper and aluminium material. Lamellae structures composed of copper particles with a streamline shape and continuous aluminium strips were present. Some evidence of dynamic recrystallization was observed in the nugget of the defect free welds. Based on material flow evaluation and defect formation results, the Reddy tool design is most suitable for high and low rotational speeds, the conical Shoulder tool at no tilt is most suitable for medium rotational speeds, the conical shoulder tool at a two degree tool tilt is most suitable for medium rotational speeds, the... , M.Ing. (Mechanical Engineering)
- Full Text:
Couplant effect and evaluation of FSW AA6061-T6 butt welded joint
- Authors: Mumvenge, Itai
- Date: 2017
- Subjects: Welded joints - Testing , Friction stir welding , Aluminum
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269294 , uj:28607
- Description: M.Ing. (Mechanical Engineering) , Abstract: Aluminium is an alloy material vastly used for manufacturing components in aviation, transport and a host of commercial use. Friction stir welding is a novelty solid state welding technique that was invented at The Welding Institute (TWI) of UK in 1991. This study presents the effects of process parameters on achieving sound welds of the friction stir butt welded joint of similar AA6061-T6 Aluminium alloys. The only parameters used and varied for this study were rotational speed and feed rate. The geometry of the tool was kept constant and the material used was tool steel, W302. Friction stir welds were evaluated both by visual inspection and non-destructive testing methods. Evaluation allowed for assessment of the weld integrity by examining for the presence of weld defects. The results indicated that the welds do not have any defects. The weld macrostructure and microstructure were examined and mechanical properties evaluated. The microhardness was also evaluated which showed that optimum speeds are required to achieve uniform hardness value across the weld traverse. The base metal showed higher hardness values when compared to the weld region. However, higher rotational speeds and higher feed rates result in increased hardness values, with the highest values recorded in the weld nugget and the least values recorded in the HAZ/TMAZ interfaces with a W-shaped hardness distribution. Couplant attenuation effect was investigated using four different types of couplants, employing Ultrasonic Testing contact pulse-echo longitudinal wave to detect weld defects. The attenuation effect was minimal when the Ultrasonic gel, oil and water were used. This was attributed to the coupling conditions such as the acoustic impedance values and the viscous properties of the couplants. Conversely, grease provided poorer frequency gain than all the couplants though it had comparable acoustic impedance values. This was attributed to its poor wetting properties and development of air pockets on contact with weld sample to be examined.
- Full Text:
- Authors: Mumvenge, Itai
- Date: 2017
- Subjects: Welded joints - Testing , Friction stir welding , Aluminum
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269294 , uj:28607
- Description: M.Ing. (Mechanical Engineering) , Abstract: Aluminium is an alloy material vastly used for manufacturing components in aviation, transport and a host of commercial use. Friction stir welding is a novelty solid state welding technique that was invented at The Welding Institute (TWI) of UK in 1991. This study presents the effects of process parameters on achieving sound welds of the friction stir butt welded joint of similar AA6061-T6 Aluminium alloys. The only parameters used and varied for this study were rotational speed and feed rate. The geometry of the tool was kept constant and the material used was tool steel, W302. Friction stir welds were evaluated both by visual inspection and non-destructive testing methods. Evaluation allowed for assessment of the weld integrity by examining for the presence of weld defects. The results indicated that the welds do not have any defects. The weld macrostructure and microstructure were examined and mechanical properties evaluated. The microhardness was also evaluated which showed that optimum speeds are required to achieve uniform hardness value across the weld traverse. The base metal showed higher hardness values when compared to the weld region. However, higher rotational speeds and higher feed rates result in increased hardness values, with the highest values recorded in the weld nugget and the least values recorded in the HAZ/TMAZ interfaces with a W-shaped hardness distribution. Couplant attenuation effect was investigated using four different types of couplants, employing Ultrasonic Testing contact pulse-echo longitudinal wave to detect weld defects. The attenuation effect was minimal when the Ultrasonic gel, oil and water were used. This was attributed to the coupling conditions such as the acoustic impedance values and the viscous properties of the couplants. Conversely, grease provided poorer frequency gain than all the couplants though it had comparable acoustic impedance values. This was attributed to its poor wetting properties and development of air pockets on contact with weld sample to be examined.
- Full Text:
Microstructural characterization of friction stir lap welds of aluminium incorporated with titanium carbide
- Abegunde, O. O., Akinlabi, Esther Titilayo, Madyira, D. M.
- Authors: Abegunde, O. O. , Akinlabi, Esther Titilayo , Madyira, D. M.
- Date: 2015-07-01
- Subjects: Aluminium , Friction stir welding , Titanium carbide , Aluminum
- Type: Article
- Identifier: uj:5123 , ISBN 9789881404701 , http://hdl.handle.net/10210/14085
- Description: In this research study, the characterization of the microstructure evolution of friction stir lap welds (FSLW) of Aluminium incorporated with Titanium Carbide powder to form Aluminium based composites is presented. The Titanium Carbide powder was infused at the weld interface to produce a composite. The FSLW were conducted on an Intelligent Stir Welding for Industry and Research (I-STIR) Process Development System (PDS). Different welding parameters were used for the welding process. Rotational speeds of 1600 rpm and 2000 rpm and transverse speeds of 100 mm/min, 200 mm/min and 300 mm/min were employed. The process parameters were carefully selected to represent a low, medium and high setting for the feed rates. The microstructural evolution of the samples were studied. Optical microscope and scanning electron microscopy (SEM) techniques were used to investigate the particle distribution of the welded samples. The results obtained revealed the influence of the welding parameters on the particle distribution of the welded samples. A homogenous mixture of the materials was observed at higher rotational speed of 2000 rpm.
- Full Text:
- Authors: Abegunde, O. O. , Akinlabi, Esther Titilayo , Madyira, D. M.
- Date: 2015-07-01
- Subjects: Aluminium , Friction stir welding , Titanium carbide , Aluminum
- Type: Article
- Identifier: uj:5123 , ISBN 9789881404701 , http://hdl.handle.net/10210/14085
- Description: In this research study, the characterization of the microstructure evolution of friction stir lap welds (FSLW) of Aluminium incorporated with Titanium Carbide powder to form Aluminium based composites is presented. The Titanium Carbide powder was infused at the weld interface to produce a composite. The FSLW were conducted on an Intelligent Stir Welding for Industry and Research (I-STIR) Process Development System (PDS). Different welding parameters were used for the welding process. Rotational speeds of 1600 rpm and 2000 rpm and transverse speeds of 100 mm/min, 200 mm/min and 300 mm/min were employed. The process parameters were carefully selected to represent a low, medium and high setting for the feed rates. The microstructural evolution of the samples were studied. Optical microscope and scanning electron microscopy (SEM) techniques were used to investigate the particle distribution of the welded samples. The results obtained revealed the influence of the welding parameters on the particle distribution of the welded samples. A homogenous mixture of the materials was observed at higher rotational speed of 2000 rpm.
- Full Text:
Evaluering van dieptrekbaarheid van aluminiumplaat
- Authors: Kruger, Martin J.
- Date: 2015-09-08
- Subjects: Finite element method , Aluminum , Sheet-metal work
- Type: Thesis
- Identifier: uj:14063 , http://hdl.handle.net/10210/14479
- Description: M.Ing. , To investigate the effect of plastic anisotropy in 1200H14 Aluminium sheet, simulations of the Swift Cupping Test were carried out using the finite element program ABAQUS. Anisotropy was built into all simulations based on the plastic strain ratio which was calculated from tensile tests on specimen cut in three directions in the plane of the sheet. Deep drawing tests were carried out using a punch and die sub-assembly as described by the Swift Cupping Test. Holder loads were kept constant while the punch load and displacement were recorded. Punch force-punch displacement curve and the formation of ears were compared with experimental results.
- Full Text:
- Authors: Kruger, Martin J.
- Date: 2015-09-08
- Subjects: Finite element method , Aluminum , Sheet-metal work
- Type: Thesis
- Identifier: uj:14063 , http://hdl.handle.net/10210/14479
- Description: M.Ing. , To investigate the effect of plastic anisotropy in 1200H14 Aluminium sheet, simulations of the Swift Cupping Test were carried out using the finite element program ABAQUS. Anisotropy was built into all simulations based on the plastic strain ratio which was calculated from tensile tests on specimen cut in three directions in the plane of the sheet. Deep drawing tests were carried out using a punch and die sub-assembly as described by the Swift Cupping Test. Holder loads were kept constant while the punch load and displacement were recorded. Punch force-punch displacement curve and the formation of ears were compared with experimental results.
- Full Text:
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