Characterization of aluminium and titanium carbide metal matrix composites produced via friction stir welding
- Abegunde, Olayinka Oluwatosin
- Authors: Abegunde, Olayinka Oluwatosin
- Date: 2015
- Subjects: Friction stir welding , Titanium alloys
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/212716 , uj:21011
- Description: Abstract: The Friction Stir Welding (FSW) process was invented and developed at The Welding Institute of United Kingdom in the year 1991 for solid state joining of aluminum and its alloys. Subsequently, this welding process has been used for joining other materials like magnesium, titanium and copper alloys, stainless steels and thermoplastics. In this research work, ample study was conducted on the material characterization of aluminium (Al) and titanium carbide (TiC) metal matrix composites produced via friction stir welding. Different process parameters were employed for the welding process. Rotational speeds of 1600 rpm to 2000 rpm at an interval of 200 rpm and transverse speeds of 100 to 300 mm/min at an interval of 100 mm/min were employed for the welding on an Intelligent Stir Welding for Industry and Research (I-STIR) Process development System (PDS) platform. The process parameters were carefully selected to represent low, medium and high for the rotation and the translation of the tool. The characterizations carried out include optical microscopy and the scanning electron microscopy analyses combined with Energy Dispersive Spectroscopy (SEM/EDS) techniques to investigate the particle distribution, microstructural evolution and the chemical analysis of the welded samples. Vickers microhardness tests was used to determine the hardness distribution of the welded zone and tensile testing was conducted to quantify the strength of the welded area to the base metal in order to establish the optimal process parameters. Based on the results obtained from the characterization analysis, it was found that the process parameters played a major role in the microstructural evolution. Homogenous distribution of the TiC particles was observed at high rotational speed of 2000 rpm and low transverse speed of 100 mm/min. The highest hardness value was measured at the stir zone of the weld due to the presence of the TiC reinforcement particles. The tensile strength also increased as the rotational speed increased and 92% joint efficiency was found in a sample produced at 2000 rpm and 100 mm/min. The EDS analysis revealed that Al, Ti and C made up the composition formed at the stir zone. The optimum process parameter setting was found to be at 2000 rpm and 100 mm/min and can be recommended. , M.Ing. (Mechanical Engineering Science)
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- Authors: Abegunde, Olayinka Oluwatosin
- Date: 2015
- Subjects: Friction stir welding , Titanium alloys
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/212716 , uj:21011
- Description: Abstract: The Friction Stir Welding (FSW) process was invented and developed at The Welding Institute of United Kingdom in the year 1991 for solid state joining of aluminum and its alloys. Subsequently, this welding process has been used for joining other materials like magnesium, titanium and copper alloys, stainless steels and thermoplastics. In this research work, ample study was conducted on the material characterization of aluminium (Al) and titanium carbide (TiC) metal matrix composites produced via friction stir welding. Different process parameters were employed for the welding process. Rotational speeds of 1600 rpm to 2000 rpm at an interval of 200 rpm and transverse speeds of 100 to 300 mm/min at an interval of 100 mm/min were employed for the welding on an Intelligent Stir Welding for Industry and Research (I-STIR) Process development System (PDS) platform. The process parameters were carefully selected to represent low, medium and high for the rotation and the translation of the tool. The characterizations carried out include optical microscopy and the scanning electron microscopy analyses combined with Energy Dispersive Spectroscopy (SEM/EDS) techniques to investigate the particle distribution, microstructural evolution and the chemical analysis of the welded samples. Vickers microhardness tests was used to determine the hardness distribution of the welded zone and tensile testing was conducted to quantify the strength of the welded area to the base metal in order to establish the optimal process parameters. Based on the results obtained from the characterization analysis, it was found that the process parameters played a major role in the microstructural evolution. Homogenous distribution of the TiC particles was observed at high rotational speed of 2000 rpm and low transverse speed of 100 mm/min. The highest hardness value was measured at the stir zone of the weld due to the presence of the TiC reinforcement particles. The tensile strength also increased as the rotational speed increased and 92% joint efficiency was found in a sample produced at 2000 rpm and 100 mm/min. The EDS analysis revealed that Al, Ti and C made up the composition formed at the stir zone. The optimum process parameter setting was found to be at 2000 rpm and 100 mm/min and can be recommended. , M.Ing. (Mechanical Engineering Science)
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Reinforcement of aluminium AA1100-MIG welds using copper powder
- Authors: Abima, Cynthia Samuel
- Date: 2017
- Subjects: Aluminum alloys - Welding , Welded joints - Reliability , Copper - Welding , Shielded metal arc welding , Gas tungsten arc welding
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269571 , uj:28637
- Description: M.Ing. (Mechanical Engineering) , Abstract: Metal matrix composites have been used in recent times to achieve better mechanical properties of materials and improved general performance of welded structures. Metal Inert Gas (MIG) welding also known as Gas Metal Arc welding (GMAW) is an arc-welding process, which joins metals by heating them with an arc between a continuously fed solid electrode and the work piece. Aluminium and its alloys provides unique properties which makes it one of the most attractive metallic, economical, versatile material for a broad range of uses in engineering applications, such as aerospace, automobile and mineral processing industries. Against this background, aluminium is not suitable for all engineering applications, and it sometimes requires some degree of reinforcement, particularly in a corrosive environment and/or at elevated temperatures. This study focuses on ascertaining the integrity of MIG welded pure aluminium reinforced with copper powder at the weld zone. Material characterizations of the aluminium (Al) and copper (Cu) metal matrix composites produced via the MIG welding process were conducted. The pure aluminium, AA1100 sheets were machined to a 45o v-grooved shape, and then filled with copper powder particles and welded. The welded samples were characterised by performing mechanical tests (tensile testing using the Zwick Roell 2250 tensile machine and microhardness profiling using a digital Vickers microhardness testing machine) and microstructural investigation via the scanning electron microscope (SEM), the energy-dispersive spectroscopy (EDS) and optical microscope. This was followed by X-ray diffraction analysis (XRD), and corrosion test by electrochemical polarization method. The results revealed that the addition of copper powder significantly increased the hardness property of the welds, as the welds with copper powder particles reinforcement showed higher hardness values when compared to those without the copper powder particle reinforcement. The highest tensile strength was obtained from the copper reinforced sample. Furthermore, the microstructures revealed finer grain structures for the reinforced samples. The samples with reinforcement also exhibited better corrosion properties. It was therefore, concluded that the aluminium (Al) and copper (Cu) metal matrix composite welded via MIG welding produced better mechanical properties, as well as increased corrosion resistance behaviour, and it can definitely be recommended for typical aerospace applications
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- Authors: Abima, Cynthia Samuel
- Date: 2017
- Subjects: Aluminum alloys - Welding , Welded joints - Reliability , Copper - Welding , Shielded metal arc welding , Gas tungsten arc welding
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269571 , uj:28637
- Description: M.Ing. (Mechanical Engineering) , Abstract: Metal matrix composites have been used in recent times to achieve better mechanical properties of materials and improved general performance of welded structures. Metal Inert Gas (MIG) welding also known as Gas Metal Arc welding (GMAW) is an arc-welding process, which joins metals by heating them with an arc between a continuously fed solid electrode and the work piece. Aluminium and its alloys provides unique properties which makes it one of the most attractive metallic, economical, versatile material for a broad range of uses in engineering applications, such as aerospace, automobile and mineral processing industries. Against this background, aluminium is not suitable for all engineering applications, and it sometimes requires some degree of reinforcement, particularly in a corrosive environment and/or at elevated temperatures. This study focuses on ascertaining the integrity of MIG welded pure aluminium reinforced with copper powder at the weld zone. Material characterizations of the aluminium (Al) and copper (Cu) metal matrix composites produced via the MIG welding process were conducted. The pure aluminium, AA1100 sheets were machined to a 45o v-grooved shape, and then filled with copper powder particles and welded. The welded samples were characterised by performing mechanical tests (tensile testing using the Zwick Roell 2250 tensile machine and microhardness profiling using a digital Vickers microhardness testing machine) and microstructural investigation via the scanning electron microscope (SEM), the energy-dispersive spectroscopy (EDS) and optical microscope. This was followed by X-ray diffraction analysis (XRD), and corrosion test by electrochemical polarization method. The results revealed that the addition of copper powder significantly increased the hardness property of the welds, as the welds with copper powder particles reinforcement showed higher hardness values when compared to those without the copper powder particle reinforcement. The highest tensile strength was obtained from the copper reinforced sample. Furthermore, the microstructures revealed finer grain structures for the reinforced samples. The samples with reinforcement also exhibited better corrosion properties. It was therefore, concluded that the aluminium (Al) and copper (Cu) metal matrix composite welded via MIG welding produced better mechanical properties, as well as increased corrosion resistance behaviour, and it can definitely be recommended for typical aerospace applications
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Acidic catalyzed magnesium hydride and nanocomposites for hydrogen generation : synthesis and application
- Authors: Adeniran, Joshua Adeniyi
- Date: 2019
- Subjects: High pressure chemistry , Biomass conversion , Biomass energy
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/443731 , uj:38755
- Description: Abstract: This study presents the successful synthesis, characterization and hydrolysis of magnesium hydride (MgH2) and MgH2 based nanocomposites for hydrogen generation, storage and wastewater treatment. The as-delivered MgH2 serves as a precursor in most of the substrates synthesized for hydrogen production and storage in this study. In addition, Mg scrap was also investigated for the same purpose. The nanocomposites were prepared by means of a ball milling process in different time spans. MgH2, germanium (Ge), lithium aluminium hydride (LiAlH4), sodium aluminium hydride (NaAlH4), magnesium (Mg) scrap were the hydrogen generation/ storage substrates used in this study. The nanocomposites from the substrates were synthesized through ball milling of the powders in argon. The phase-structural and morphological characteristics of the composites were evaluated using transmission electron microscopy (TEM), selected area diffraction (SAD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray dispersive diffraction (XRD) characterization techniques... , D.Phil. (Mechanical Engineering)
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- Authors: Adeniran, Joshua Adeniyi
- Date: 2019
- Subjects: High pressure chemistry , Biomass conversion , Biomass energy
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/443731 , uj:38755
- Description: Abstract: This study presents the successful synthesis, characterization and hydrolysis of magnesium hydride (MgH2) and MgH2 based nanocomposites for hydrogen generation, storage and wastewater treatment. The as-delivered MgH2 serves as a precursor in most of the substrates synthesized for hydrogen production and storage in this study. In addition, Mg scrap was also investigated for the same purpose. The nanocomposites were prepared by means of a ball milling process in different time spans. MgH2, germanium (Ge), lithium aluminium hydride (LiAlH4), sodium aluminium hydride (NaAlH4), magnesium (Mg) scrap were the hydrogen generation/ storage substrates used in this study. The nanocomposites from the substrates were synthesized through ball milling of the powders in argon. The phase-structural and morphological characteristics of the composites were evaluated using transmission electron microscopy (TEM), selected area diffraction (SAD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray dispersive diffraction (XRD) characterization techniques... , D.Phil. (Mechanical Engineering)
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Characterization of laser metal deposited 17-4 PH stainless steel and tungsten composite for surface engineering applications
- Authors: Adeyemi, A.A.
- Date: 2018
- Subjects: Pulsed laser deposition , Metal coating , Metals - Mechanical properties , Lasers - Industrial applications , Stainless steel
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/284734 , uj:30767
- Description: Abstract: 17-4 PH Stainless steel is a martensitic characterized precipitation hardened stainless steel with excellent mechanical properties that has been tailored to industrial applications such as aerospace, automobile, marine, food processing equipment, oil and gas industries and chemical processing industries. Despite the growth experienced in the use of this material, 17-4 PH stainless steels are prone to degradation due to long service use in applications that required extreme hardness and wear resistance. This limitation led to the research of property enhancement of the material using modern fabrication technique called laser metal deposition additive manufacturing technology. Laser metal deposition is a modern additive manufacturing technique used in fabricating physical components from the configuration of a 3D CAD data model using a high intensity laser beam while depositing metallic powder on a substrate one layer at a time. This process is flexible in its use as it allows addition of reinforcing particles to improve surface properties of a metallic material such as hardness and wear amongst others. This research study presents the use of laser metal deposition process to investigate the property enhancement of 17-4 PH stainless steel through various characterization process such as microstructural evaluation, microhardness and wear test. The deposition process was carried out using Rofin Sinar Ytterbium fibre laser system of laser capacity of 3.0 kW. The reinforcement material was 17-4 PH stainless steel and tungsten metallic powder deposited on 316 stainless steel substrate. The deposition process commenced firstly with a trial-run deposition of 5 samples with multiple-track of 17-4 PH stainless steel at 50% overlapping percentage on 316 stainless steel substrate to establish process window. The reason for the trial-run was to achieve a deposition with no defects such as pores and cracks. After this was achieved, 17-4 PH stainless steel metallic powder and tungsten metallic powder were now deposited in form of multiple track at 50% overlapping percentage at high laser power and low laser power of 2600 W and 1500 W at varied tungsten powder flow rate on 316 stainless steel substrate. The microstructural evaluation, geometrical analysis, microhardness profiling and wear resistance characteristics of the deposited composites were investigated. The microstructural evolution investigation was carried out using optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). Geometrical analysis was carried out on the deposited composite samples both at high and low laser power to investigate the extent of laser... , M.Ing. (Mechanical Engineering)
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- Authors: Adeyemi, A.A.
- Date: 2018
- Subjects: Pulsed laser deposition , Metal coating , Metals - Mechanical properties , Lasers - Industrial applications , Stainless steel
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/284734 , uj:30767
- Description: Abstract: 17-4 PH Stainless steel is a martensitic characterized precipitation hardened stainless steel with excellent mechanical properties that has been tailored to industrial applications such as aerospace, automobile, marine, food processing equipment, oil and gas industries and chemical processing industries. Despite the growth experienced in the use of this material, 17-4 PH stainless steels are prone to degradation due to long service use in applications that required extreme hardness and wear resistance. This limitation led to the research of property enhancement of the material using modern fabrication technique called laser metal deposition additive manufacturing technology. Laser metal deposition is a modern additive manufacturing technique used in fabricating physical components from the configuration of a 3D CAD data model using a high intensity laser beam while depositing metallic powder on a substrate one layer at a time. This process is flexible in its use as it allows addition of reinforcing particles to improve surface properties of a metallic material such as hardness and wear amongst others. This research study presents the use of laser metal deposition process to investigate the property enhancement of 17-4 PH stainless steel through various characterization process such as microstructural evaluation, microhardness and wear test. The deposition process was carried out using Rofin Sinar Ytterbium fibre laser system of laser capacity of 3.0 kW. The reinforcement material was 17-4 PH stainless steel and tungsten metallic powder deposited on 316 stainless steel substrate. The deposition process commenced firstly with a trial-run deposition of 5 samples with multiple-track of 17-4 PH stainless steel at 50% overlapping percentage on 316 stainless steel substrate to establish process window. The reason for the trial-run was to achieve a deposition with no defects such as pores and cracks. After this was achieved, 17-4 PH stainless steel metallic powder and tungsten metallic powder were now deposited in form of multiple track at 50% overlapping percentage at high laser power and low laser power of 2600 W and 1500 W at varied tungsten powder flow rate on 316 stainless steel substrate. The microstructural evaluation, geometrical analysis, microhardness profiling and wear resistance characteristics of the deposited composites were investigated. The microstructural evolution investigation was carried out using optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). Geometrical analysis was carried out on the deposited composite samples both at high and low laser power to investigate the extent of laser... , M.Ing. (Mechanical Engineering)
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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...
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- 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...
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Surface engineering : advanced protective coating and characterization of functionalised hydrophobic organic nanocoating
- Authors: Baruwa, Akinsanya Damilare
- Date: 2019
- Subjects: Surfaces (Technology) , Protective coatings
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/430361 , uj:37091
- Description: Abstract: Mitigation against corrosion and the improvement of other properties requires surface engineering. Many ways have been adopted to achieve this purpose, including processes, methods, and materials' compositional alteration. The chromium-based coating entails surface modification processes for diverse property enhancements, such as improved mechanical and electrochemical gains with stable microstructure and chemical evolutions, as well as thermal stability, but its carcinogenic nature has demanded alternative material that is green in nature; and therefore it is legislated to be phased out. Among the green materials developed, enhanced chemical and/or thermal properties have been achieved; while some demonstrated improved mechanical properties – without a combination of chemical or thermal stability. These have limited its deployments into applications. Hence, the quest for new and advanced solutions to have green or organic materials that can potentially replace chromium-based coatings is still on course – in an attempt to beat the new extended date of phase-out, particularly from the European Union Nations by 2024. .. , D.Ing. (Mechanical Engineering)
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- Authors: Baruwa, Akinsanya Damilare
- Date: 2019
- Subjects: Surfaces (Technology) , Protective coatings
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/430361 , uj:37091
- Description: Abstract: Mitigation against corrosion and the improvement of other properties requires surface engineering. Many ways have been adopted to achieve this purpose, including processes, methods, and materials' compositional alteration. The chromium-based coating entails surface modification processes for diverse property enhancements, such as improved mechanical and electrochemical gains with stable microstructure and chemical evolutions, as well as thermal stability, but its carcinogenic nature has demanded alternative material that is green in nature; and therefore it is legislated to be phased out. Among the green materials developed, enhanced chemical and/or thermal properties have been achieved; while some demonstrated improved mechanical properties – without a combination of chemical or thermal stability. These have limited its deployments into applications. Hence, the quest for new and advanced solutions to have green or organic materials that can potentially replace chromium-based coatings is still on course – in an attempt to beat the new extended date of phase-out, particularly from the European Union Nations by 2024. .. , D.Ing. (Mechanical Engineering)
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Advanced material development : functionally graded stainless steel alloy composites
- Authors: Bayode, A.
- Date: 2018
- Subjects: Metallic composites , Metal coating , Pulsed laser deposition
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/284879 , uj:30784
- Description: D.Ing. (Mechanical Engineering) , Abstract: Laser metal deposition (LMD) is one of the additive manufacturing technologies that is used in the production of fully dense parts layer by layer. This innovative manufacturing process shows real promise in reducing component fabrication time, cost and weight. One of the major advantages of this technology is in the ability to manufacture components with multi-material properties such as Functionally Graded Materials (FGM). FGM is a class of advanced materials that combine the benefits of its component materials together as a whole, while minimizing the problems produced by material property mismatch of the constituent materials. Several studies have been conducted on FGMs processed by LMD. Most of these studies are on metal-ceramic composites, however, there is a growing need for bimetallic components with different properties along their axial or radial directions for modern engineering applications. In this study, the laser metal deposition process was evaluated as a candidate for manufacturing a compositionally graded bimetal material consisting magnetic and non-magnetic metals. The materials used were 17-4PH powder, AISI 316L powder and AISI 316 substrate. Since this study has not been done and there were no known models or strategies to follow in building this particular FGM. Trial and error experiments were first adopted in selecting the process conditions for building the FGM. The trial and error experiments, referred to as preliminary study involved the production of 17- 4PH and AISI 316L clads. This was done primarily to evaluate the solidification behaviour of the individual powders and also identify the process window that will successfully produce fully dense clads with good bonding and wettability that are structurally harmonised. Based on the findings of the preliminary studies, a set of parameters was obtained as a standard for producing the compositionally graded composite...
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- Authors: Bayode, A.
- Date: 2018
- Subjects: Metallic composites , Metal coating , Pulsed laser deposition
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/284879 , uj:30784
- Description: D.Ing. (Mechanical Engineering) , Abstract: Laser metal deposition (LMD) is one of the additive manufacturing technologies that is used in the production of fully dense parts layer by layer. This innovative manufacturing process shows real promise in reducing component fabrication time, cost and weight. One of the major advantages of this technology is in the ability to manufacture components with multi-material properties such as Functionally Graded Materials (FGM). FGM is a class of advanced materials that combine the benefits of its component materials together as a whole, while minimizing the problems produced by material property mismatch of the constituent materials. Several studies have been conducted on FGMs processed by LMD. Most of these studies are on metal-ceramic composites, however, there is a growing need for bimetallic components with different properties along their axial or radial directions for modern engineering applications. In this study, the laser metal deposition process was evaluated as a candidate for manufacturing a compositionally graded bimetal material consisting magnetic and non-magnetic metals. The materials used were 17-4PH powder, AISI 316L powder and AISI 316 substrate. Since this study has not been done and there were no known models or strategies to follow in building this particular FGM. Trial and error experiments were first adopted in selecting the process conditions for building the FGM. The trial and error experiments, referred to as preliminary study involved the production of 17- 4PH and AISI 316L clads. This was done primarily to evaluate the solidification behaviour of the individual powders and also identify the process window that will successfully produce fully dense clads with good bonding and wettability that are structurally harmonised. Based on the findings of the preliminary studies, a set of parameters was obtained as a standard for producing the compositionally graded composite...
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Effect of scanning speed on the laser metal deposited ti-6al-2sn-2mo-2cr-0,25si alloy
- Authors: Boshoman, Salaminah Bonolo
- Date: 2019
- Language: English
- Type: Master (Thesis)
- Identifier: http://hdl.handle.net/10210/399039 , uj:33245
- Description: Abstract : Please refer to full text to view abstract. , M.Tech. (Mechanical Engineering)
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- Authors: Boshoman, Salaminah Bonolo
- Date: 2019
- Language: English
- Type: Master (Thesis)
- Identifier: http://hdl.handle.net/10210/399039 , uj:33245
- Description: Abstract : Please refer to full text to view abstract. , M.Tech. (Mechanical Engineering)
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Material characterization and analysis of laser cladding of titanium alloy
- Authors: Du Plooy, R.
- Date: 2018
- Subjects: Pulsed laser deposition , Lasers - Industrial applications , Titanium alloys
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269630 , uj:28645
- Description: M.Ing. (Mechanical Engineering) , Abstract: This study focused on laser cladding of Ti6Al4V, used as both the substrate and the powder material. The goal was to determine the most effective parameters for laser cladding, when using this alloy. The criteria used were both efficiency (i.e. how quickly a certain amount of area / volume could be cladded) and quality. To determine the most efficient and the highest quality cladding, the following was done: firstly, the samples were prepared by cladding multiple tracks, using varying scanning speeds for each track. The scanning speed was varied from 3.5m/min to 0.5m/min in increments of 0.5m/min; while the laser power, powder flow rate and gas flow rate was kept constant. Thereafter, a geometrical analysis, porosity analysis, microscopic analysis in the form of optical microscopy and scanning electron microscopy, atomic force microscopic analysis, Vickers microhardness testing and corrosion testing were all performed. One observation made from the optical and scanning electron microscopy was that the microstructure of the cladded area was consistent for sample scanning speeds ranging from 0.5m/min to 2.0m/min. This consistency also showed in the microhardness testing with the average hardness values for the scanning speeds ranging from 0.5m/min to 2.0m/min being almost equal at approximately 340HV. Corrosion resistance testing confirmed that the corrosion resistance of the clad was related to the scanning speed at which the clad tack was produced. In general it was shown that the slower the scanning speed the better the corrosion resistance. Further geometrical analysis of the micrographs obtained through optical microscopy revealed that sample five, with a scanning speed of 1.5m/min, yielded the best all-round clad, being the most efficient clad for the quality produced. The clads with higher scanning speeds, between 2.0m/min and 3.5m/min, could achieve area cladding rates greater than 50 000mm2/min; however the quality of the clad was not acceptable. The clads produced with slower scanning speeds (0.5 and 1.0m/min), did not produce a significant (or any) increase in the quality of the clad, when being compared with sample five. Overall this work proved successful; and it also yielded a number of ways whereby the current understanding and capabilities when considering the Laser Cladding of Titanium Alloys can be further improved.
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- Authors: Du Plooy, R.
- Date: 2018
- Subjects: Pulsed laser deposition , Lasers - Industrial applications , Titanium alloys
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269630 , uj:28645
- Description: M.Ing. (Mechanical Engineering) , Abstract: This study focused on laser cladding of Ti6Al4V, used as both the substrate and the powder material. The goal was to determine the most effective parameters for laser cladding, when using this alloy. The criteria used were both efficiency (i.e. how quickly a certain amount of area / volume could be cladded) and quality. To determine the most efficient and the highest quality cladding, the following was done: firstly, the samples were prepared by cladding multiple tracks, using varying scanning speeds for each track. The scanning speed was varied from 3.5m/min to 0.5m/min in increments of 0.5m/min; while the laser power, powder flow rate and gas flow rate was kept constant. Thereafter, a geometrical analysis, porosity analysis, microscopic analysis in the form of optical microscopy and scanning electron microscopy, atomic force microscopic analysis, Vickers microhardness testing and corrosion testing were all performed. One observation made from the optical and scanning electron microscopy was that the microstructure of the cladded area was consistent for sample scanning speeds ranging from 0.5m/min to 2.0m/min. This consistency also showed in the microhardness testing with the average hardness values for the scanning speeds ranging from 0.5m/min to 2.0m/min being almost equal at approximately 340HV. Corrosion resistance testing confirmed that the corrosion resistance of the clad was related to the scanning speed at which the clad tack was produced. In general it was shown that the slower the scanning speed the better the corrosion resistance. Further geometrical analysis of the micrographs obtained through optical microscopy revealed that sample five, with a scanning speed of 1.5m/min, yielded the best all-round clad, being the most efficient clad for the quality produced. The clads with higher scanning speeds, between 2.0m/min and 3.5m/min, could achieve area cladding rates greater than 50 000mm2/min; however the quality of the clad was not acceptable. The clads produced with slower scanning speeds (0.5 and 1.0m/min), did not produce a significant (or any) increase in the quality of the clad, when being compared with sample five. Overall this work proved successful; and it also yielded a number of ways whereby the current understanding and capabilities when considering the Laser Cladding of Titanium Alloys can be further improved.
- Full Text:
Advanced coating and surfacing : enhancement of surface integrity of laser metal deposited titanium alloy with copper
- Authors: Folorunsho, Erinosho Mutiu
- Date: 2015
- Subjects: Copper-titanium alloys , Metal coating
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/57249 , uj:16373
- Description: Abstract: Please refer to full text to view abstract , D.Ing. (Mechanical Engineering)
- Full Text:
- Authors: Folorunsho, Erinosho Mutiu
- Date: 2015
- Subjects: Copper-titanium alloys , Metal coating
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/57249 , uj:16373
- Description: Abstract: Please refer to full text to view abstract , D.Ing. (Mechanical Engineering)
- Full Text:
Operation system and its impact on customer service : case study of estate agency affairs board in South Africa
- Authors: Khakhu, Nthambeleni
- Date: 2017
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/262917 , uj:27788
- Description: M.Tech. (Operations Management) , Abstract: The data set in different categories of the questionnaire includes background information, customer service, employee satisfaction, customer satisfaction, operations systems and productivity. Data analysed using Statistical Package for the Social Sciences interprets that there is normality within the data set. Data spread is within 68% of the standard deviation from the mean; the mean average, mode and median are approximately three which mean the data set is asymmetrical normal distribution. Data reliability analysis shows that there is internal consistency with the alpha value of at least 0.7. The level of significant is more than 0.05 which interprets that the null hypothesis must be accepted which also interprets that there is a significant difference in different groups of categories. The Lean Supply/System is one of the world class services that has achieved high productivity and led to improved efficiency in the provision of customer service within any kind of organisation. As much as the purpose of the study is to improve operations and customer service in relation to lean supply implementation, the study is done to solve the research problem which is, ―The inefficiencies in the quality of service‖. The research design used is qualitative research; the population is all the employees of Estate Agency Affairs Board (EAAB) and sample of estate agents; a census sample has been used while the subjects were selected from EAAB population. The Lean System needs to be implemented within EAAB operations and processes in order to achieve a high level of customer service. The main aim of the study is to increase the level of efficiency in relation to customer services through lean supply implementation within services and operations processes.
- Full Text:
- Authors: Khakhu, Nthambeleni
- Date: 2017
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/262917 , uj:27788
- Description: M.Tech. (Operations Management) , Abstract: The data set in different categories of the questionnaire includes background information, customer service, employee satisfaction, customer satisfaction, operations systems and productivity. Data analysed using Statistical Package for the Social Sciences interprets that there is normality within the data set. Data spread is within 68% of the standard deviation from the mean; the mean average, mode and median are approximately three which mean the data set is asymmetrical normal distribution. Data reliability analysis shows that there is internal consistency with the alpha value of at least 0.7. The level of significant is more than 0.05 which interprets that the null hypothesis must be accepted which also interprets that there is a significant difference in different groups of categories. The Lean Supply/System is one of the world class services that has achieved high productivity and led to improved efficiency in the provision of customer service within any kind of organisation. As much as the purpose of the study is to improve operations and customer service in relation to lean supply implementation, the study is done to solve the research problem which is, ―The inefficiencies in the quality of service‖. The research design used is qualitative research; the population is all the employees of Estate Agency Affairs Board (EAAB) and sample of estate agents; a census sample has been used while the subjects were selected from EAAB population. The Lean System needs to be implemented within EAAB operations and processes in order to achieve a high level of customer service. The main aim of the study is to increase the level of efficiency in relation to customer services through lean supply implementation within services and operations processes.
- Full Text:
Application of digital technology in TQM business processes
- Authors: Khwela, Nozipho C.
- Date: 2019
- Subjects: Total quality management , Organizational effectiveness , Artificial intelligence - Industrial applications , Technological innovations
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/444923 , uj:38905
- Description: Abstract: TQM (Total Quality Management) has become the world`s dominant quality solution in improving quality systems and continuous improvement. Industries are using the ISO 9001 standard for compliance, while other organizations practice TQM to further develop and sustain the organizational strategic goals and income growth. The revelation on the application of a quality management system and ISO 9001 has by far been the quality requirement from customers and regulators as evidence of commitment and ability of every organization. Various industries have implemented TQM to advance their quality systems in order to control and better the organizational culture. Competition within industries indicated the importance of customer satisfaction for corporate profitability and survival, where quality has become the key factor for the survival and competitiveness of a business [1]. Currently all industries have become competitive. According to Hendricks and Singhal [2], firms that have effectively implemented Total Quality Management outperform firms within the same level caliber that have not implemented total quality management in terms of cost, income, profits, total assets, number of resources and capital outlay. Aleksandrova, Vasiliev, Letuchev [3], emphasized on the integration of quality management methods with modern information technology that it may ensure competitiveness in existing organizations. Total Quality Management has only been applied in manufacturing industries but has over the years evolved into diverse business sectors to gain reputation as the main factor to achieve competitive advantage... , M.Ing. (Engineering Management)
- Full Text:
- Authors: Khwela, Nozipho C.
- Date: 2019
- Subjects: Total quality management , Organizational effectiveness , Artificial intelligence - Industrial applications , Technological innovations
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/444923 , uj:38905
- Description: Abstract: TQM (Total Quality Management) has become the world`s dominant quality solution in improving quality systems and continuous improvement. Industries are using the ISO 9001 standard for compliance, while other organizations practice TQM to further develop and sustain the organizational strategic goals and income growth. The revelation on the application of a quality management system and ISO 9001 has by far been the quality requirement from customers and regulators as evidence of commitment and ability of every organization. Various industries have implemented TQM to advance their quality systems in order to control and better the organizational culture. Competition within industries indicated the importance of customer satisfaction for corporate profitability and survival, where quality has become the key factor for the survival and competitiveness of a business [1]. Currently all industries have become competitive. According to Hendricks and Singhal [2], firms that have effectively implemented Total Quality Management outperform firms within the same level caliber that have not implemented total quality management in terms of cost, income, profits, total assets, number of resources and capital outlay. Aleksandrova, Vasiliev, Letuchev [3], emphasized on the integration of quality management methods with modern information technology that it may ensure competitiveness in existing organizations. Total Quality Management has only been applied in manufacturing industries but has over the years evolved into diverse business sectors to gain reputation as the main factor to achieve competitive advantage... , M.Ing. (Engineering Management)
- Full Text:
Performance and emission evaluation of a bi-fuel car
- Authors: Kukoyi, Temitope Oladayo
- Date: 2016
- Subjects: Alternative fuel vehicles , Spark ignition engines - Alternative fuels , Motor fuels , Biogas , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242306 , uj:24988
- Description: M.Ing. (Mechanical Engineering) , Abstract: A fundamental shift towards alternative sources of energy particularly in the transport sector has led to the use of fuels such as liquefied petroleum gas and natural gas in spark ignition (SI) engines. However, these fuels retain the challenges associated with fossil fuels which are primarily their finite reserves and negative effects on the ecosystem. This study assesses the use of biogas, a renewable and environmentally friendly high octane fuel in the more popular spark ignition powered passenger vehicle using the simplest single-point fuel delivery conversion kit available on the market. The vehicle powered by a 1.5 litre 1UF-ZE spark ignition engine was converted to a bi-fuel vehicle. Torque, power, and transient emissions were measured with a single roller chassis dynamometer and a gas analyser while running on vehicle quality biogas also referred to as biomethane. The data collated from the use of biogas was pitched with that of petrol in the same system to compare performance and tailpipe emissions. The biogas was simulated by mixing 95% methane (CH4) with 5% carbon dioxide (CO2). The experiments also afforded the opportunity to validate biogas similarity with natural gas (CNG) when used to power vehicles. The research further looked into enhancing system efficiency by investigating the addition of a measure of 2% hydrogen to create a biomethane-hydrogen mix (HCBG) which is within allowable limits of the mix used in a conventional spark ignition (SI) system to curb the negative impacts associated with hydrogen use as a fuel in internal combustion engines. The HCBG was derived by mixing 93% CH4 with 5% CO2 and 2% H2. Biogas recorded a reduction of 16% in maximum power and torque values when pitched with petrol while similar maximum power and torque values to that of biogas were derived from the experiments using natural gas to power the same vehicle. When the hydrogen-biomethane mix was utilised, a 1% power drop was noticed. However, slight increments in power and torque values at mid-speed ranges showed promise for higher hydrogen concentrations in the HCBG in fine-tuned systems. With respect to the mass emission of pollutants, the Inspection and Maintenance 240 (IM240) Drive Cycle was employed to determine the carbon dioxide (CO2), carbon monoxide(CO), hydrocarbon (HC), nitrous oxide (NOx) values in grammes per kilometer (g/km). Biogas recorded an 18% CO2 emission reduction compared to the data obtained using petrol (152.2 g/km). With reference to biogas, CNG recorded 0.4 g/km more CO2 mass emissions while the enhanced HCBG...
- Full Text:
- Authors: Kukoyi, Temitope Oladayo
- Date: 2016
- Subjects: Alternative fuel vehicles , Spark ignition engines - Alternative fuels , Motor fuels , Biogas , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242306 , uj:24988
- Description: M.Ing. (Mechanical Engineering) , Abstract: A fundamental shift towards alternative sources of energy particularly in the transport sector has led to the use of fuels such as liquefied petroleum gas and natural gas in spark ignition (SI) engines. However, these fuels retain the challenges associated with fossil fuels which are primarily their finite reserves and negative effects on the ecosystem. This study assesses the use of biogas, a renewable and environmentally friendly high octane fuel in the more popular spark ignition powered passenger vehicle using the simplest single-point fuel delivery conversion kit available on the market. The vehicle powered by a 1.5 litre 1UF-ZE spark ignition engine was converted to a bi-fuel vehicle. Torque, power, and transient emissions were measured with a single roller chassis dynamometer and a gas analyser while running on vehicle quality biogas also referred to as biomethane. The data collated from the use of biogas was pitched with that of petrol in the same system to compare performance and tailpipe emissions. The biogas was simulated by mixing 95% methane (CH4) with 5% carbon dioxide (CO2). The experiments also afforded the opportunity to validate biogas similarity with natural gas (CNG) when used to power vehicles. The research further looked into enhancing system efficiency by investigating the addition of a measure of 2% hydrogen to create a biomethane-hydrogen mix (HCBG) which is within allowable limits of the mix used in a conventional spark ignition (SI) system to curb the negative impacts associated with hydrogen use as a fuel in internal combustion engines. The HCBG was derived by mixing 93% CH4 with 5% CO2 and 2% H2. Biogas recorded a reduction of 16% in maximum power and torque values when pitched with petrol while similar maximum power and torque values to that of biogas were derived from the experiments using natural gas to power the same vehicle. When the hydrogen-biomethane mix was utilised, a 1% power drop was noticed. However, slight increments in power and torque values at mid-speed ranges showed promise for higher hydrogen concentrations in the HCBG in fine-tuned systems. With respect to the mass emission of pollutants, the Inspection and Maintenance 240 (IM240) Drive Cycle was employed to determine the carbon dioxide (CO2), carbon monoxide(CO), hydrocarbon (HC), nitrous oxide (NOx) values in grammes per kilometer (g/km). Biogas recorded an 18% CO2 emission reduction compared to the data obtained using petrol (152.2 g/km). With reference to biogas, CNG recorded 0.4 g/km more CO2 mass emissions while the enhanced HCBG...
- Full Text:
Characterization of Tribocorrosion properties of friction stir processed 6061 Aluminium Alloy
- Authors: Mabotja, Boitumelo
- Date: 2019
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/398648 , uj:33197
- Description: Abstract : Please refer to full text to view abstract. , M.Ing. (Engineering Management)
- Full Text:
- Authors: Mabotja, Boitumelo
- Date: 2019
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/398648 , uj:33197
- Description: Abstract : Please refer to full text to view abstract. , M.Ing. (Engineering Management)
- Full Text:
Life cycle assessment of a biogas digester : case study of a South African system
- Authors: Madushele, Nkosinathi
- Date: 2018
- Subjects: Biogas , Product life cycle - Environmental aspects , Greenhouse gases - Environmental aspects , Biomass gasification
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/263076 , uj:27804
- Description: D.Ing. (Mechanical Engineering Sciences) , Abstract: Sustainable energy is a huge point of discussion amongst policy makers and academics alike. This stems from an increase in the world’s population, with shrinking finite energy sources that are currently used. The University of Johannesburg seeks to address this challenge through the development of a biogas digester plant. The study analysed a gate to gate model of a domestic biogas digester, with the intention of both evaluating the environmental impact of the University’s biogas digester, while also making use of fundamental computations in performing a Life Cycle Assessment initiative, as opposed to using commercially available software. This was done in the hopes of gaining deeper understanding on the computational structure of Life Cycle Assessments, and this can then be translated to developing more region specific databases for future studies. It was found that the designed digester produces more greenhouse gases (GHGs) during operation, than when the digester is manufactured and commissioned. This enabled a design alteration that minimised the GHGs prior to the completion of the design. Amongst a number of environmental impacts investigated, it is interesting to note that during the operational stage of the digester, there are chemicals that contribute to photochemical ozone depletion, and that in turn resulted in the recommendation of revising mechanical equipment that was initially proposed by the designer.
- Full Text:
- Authors: Madushele, Nkosinathi
- Date: 2018
- Subjects: Biogas , Product life cycle - Environmental aspects , Greenhouse gases - Environmental aspects , Biomass gasification
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/263076 , uj:27804
- Description: D.Ing. (Mechanical Engineering Sciences) , Abstract: Sustainable energy is a huge point of discussion amongst policy makers and academics alike. This stems from an increase in the world’s population, with shrinking finite energy sources that are currently used. The University of Johannesburg seeks to address this challenge through the development of a biogas digester plant. The study analysed a gate to gate model of a domestic biogas digester, with the intention of both evaluating the environmental impact of the University’s biogas digester, while also making use of fundamental computations in performing a Life Cycle Assessment initiative, as opposed to using commercially available software. This was done in the hopes of gaining deeper understanding on the computational structure of Life Cycle Assessments, and this can then be translated to developing more region specific databases for future studies. It was found that the designed digester produces more greenhouse gases (GHGs) during operation, than when the digester is manufactured and commissioned. This enabled a design alteration that minimised the GHGs prior to the completion of the design. Amongst a number of environmental impacts investigated, it is interesting to note that during the operational stage of the digester, there are chemicals that contribute to photochemical ozone depletion, and that in turn resulted in the recommendation of revising mechanical equipment that was initially proposed by the designer.
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Effect of post-weld heat treatment on the evolving properties of P355NL1
- Authors: Mamabolo, Masemenya
- Date: 2017
- Subjects: Welding , Shielded metal arc welding , Stainless steel - Welding , Gas tungsten arc welding , Residual stresses
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269810 , uj:28667
- Description: M.Ing. (Mechanical Engineering) , Abstract: Post Weld Heat Treatment (PWHT) in the form of stress relieving consists of heating the steel to a temperature below the critical range to relieve the stresses resulting from welding. The mechanical and microscopic properties may also be affected during this process. The study of the effects of Post-Weld Heat Treatment on the evolving properties of the fine-grain carbon alloy steel P355NL1 was conducted, and presented in this report. The study focused on the mechanical and metallurgical properties of the material. The plates used were 6 mm thick with a length of 350 mm and a width of 150 mm; and they were welded using the Gas Metal Arc Welding (GMAW) method. After the welding; PWHT was performed on the plates, using a furnace with the specified temperature and time. A total of four plates were studied; where three plates underwent the same PWHT method, apart from the cooling methods. There was a control sample wherein the plate did not undergo any PWHT; the second plate was furnace-cooled; the third was air-cooled; while the fourth plate was water-cooled. A comparative study was done on the P355NL1 plates, using three testing methods, namely: the tensile test; the microstructure examination; and the microhardness test to investigate how the different cooling methods had affected the properties of the steel, compared to the control as the basis point of comparison. The hardness properties of air and furnace cooled P355NL1 steel decreased compared to the without sample. The tensile strength properties of the sample had shown some improvement for the water-cooled plate; the furnace and air-cooled samples had, however, decreased in terms of their tensile strength. The yield strength properties of the samples revealed similar findings. Although the metallurgical structures revealed different concentrations of darker (pearlite) and lighter (ferrite) grains in the base metal, the overall study showed that there were no significant changes in the microstructure, however, the cooling media employed can be recommended as required for tailored applications.
- Full Text:
- Authors: Mamabolo, Masemenya
- Date: 2017
- Subjects: Welding , Shielded metal arc welding , Stainless steel - Welding , Gas tungsten arc welding , Residual stresses
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269810 , uj:28667
- Description: M.Ing. (Mechanical Engineering) , Abstract: Post Weld Heat Treatment (PWHT) in the form of stress relieving consists of heating the steel to a temperature below the critical range to relieve the stresses resulting from welding. The mechanical and microscopic properties may also be affected during this process. The study of the effects of Post-Weld Heat Treatment on the evolving properties of the fine-grain carbon alloy steel P355NL1 was conducted, and presented in this report. The study focused on the mechanical and metallurgical properties of the material. The plates used were 6 mm thick with a length of 350 mm and a width of 150 mm; and they were welded using the Gas Metal Arc Welding (GMAW) method. After the welding; PWHT was performed on the plates, using a furnace with the specified temperature and time. A total of four plates were studied; where three plates underwent the same PWHT method, apart from the cooling methods. There was a control sample wherein the plate did not undergo any PWHT; the second plate was furnace-cooled; the third was air-cooled; while the fourth plate was water-cooled. A comparative study was done on the P355NL1 plates, using three testing methods, namely: the tensile test; the microstructure examination; and the microhardness test to investigate how the different cooling methods had affected the properties of the steel, compared to the control as the basis point of comparison. The hardness properties of air and furnace cooled P355NL1 steel decreased compared to the without sample. The tensile strength properties of the sample had shown some improvement for the water-cooled plate; the furnace and air-cooled samples had, however, decreased in terms of their tensile strength. The yield strength properties of the samples revealed similar findings. Although the metallurgical structures revealed different concentrations of darker (pearlite) and lighter (ferrite) grains in the base metal, the overall study showed that there were no significant changes in the microstructure, however, the cooling media employed can be recommended as required for tailored applications.
- Full Text:
Laser additive manufacturing technology for crack repairs in titanium alloy components
- Authors: Marazani, Tawanda
- Date: 2016
- Subjects: Laser welding , Welded joints - Cracking , Manufacturing processes , Titanium alloys
- Language: English
- Type: Masters (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/366385 , http://hdl.handle.net/10210/213019 , uj:21067
- Description: Abstract: Laser additive technology (LAT) uses a laser beam which locally melts the target material surface. The technology has been widely used for high value and critical components mainly in the aerospace and the biomedical industries. Due to its favourable properties, titanium has become a workhorse metal, particularly the grade 5 titanium alloy (Ti-6Al-4V). Recent years have seen increased research and development studies on the application of the laser additive technology in the production of Ti-6Al-4V components. These ranged from free form fabrication, materials processing, manufacturing, maintenance and repairs. Attempts to use the laser additive technology for the repair of cracks in Ti alloy components have been recently reported where V-grooves have been recommended. Further attempts to use narrow U-grooves for crack repairs were not successful and hence not widely adopted. There is limited published work on the use of narrow rectangular grooves for crack repairs in Ti-6Al-4V.There is therefore a need to further investigate the potential repairing of U-cracks using LAT. This research work established through experimental design, mechanical and metallographic characterization, a process that was used for the laser additive repair of cracks in Ti-6Al-4V components. The preliminary repairs were made without laser re-melting. They were analysed for defects using the optical microscopy (OM) and their macrographs revealed lack of sidewall fusion, lack of interlayer fusion, lack of intralayer fusion, unmelted powder and porosity. The matrix used for the preliminary repairs was then optimised using the observations made during the preliminary phase. It was from this preliminary phase optimization that the final experimental matrix of the research was developed. Controlled laser re-melting, reduction of the spot size diameter and lowering of the scanning speed were introduced as main process parameters of the optimized matrix. The optimized repairs were further characterized using the optical microscopy (OM) and the scanning electron microscopy (SEM). The optimized repairs were observed to have very limited defects. The energy dispersive spectroscopy (EDS) analyses revealed that the deposits were dominated by Ti, Al and V which were the main compositions of the material. The Vickers microhardness tests, microhardness-tensile strength correlations and the Charpy impact tests obtained results confirmed mechanically sound repairs with good evolving microstructural properties... , M.Ing. (Mechanical Engineering)
- Full Text:
- Authors: Marazani, Tawanda
- Date: 2016
- Subjects: Laser welding , Welded joints - Cracking , Manufacturing processes , Titanium alloys
- Language: English
- Type: Masters (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/366385 , http://hdl.handle.net/10210/213019 , uj:21067
- Description: Abstract: Laser additive technology (LAT) uses a laser beam which locally melts the target material surface. The technology has been widely used for high value and critical components mainly in the aerospace and the biomedical industries. Due to its favourable properties, titanium has become a workhorse metal, particularly the grade 5 titanium alloy (Ti-6Al-4V). Recent years have seen increased research and development studies on the application of the laser additive technology in the production of Ti-6Al-4V components. These ranged from free form fabrication, materials processing, manufacturing, maintenance and repairs. Attempts to use the laser additive technology for the repair of cracks in Ti alloy components have been recently reported where V-grooves have been recommended. Further attempts to use narrow U-grooves for crack repairs were not successful and hence not widely adopted. There is limited published work on the use of narrow rectangular grooves for crack repairs in Ti-6Al-4V.There is therefore a need to further investigate the potential repairing of U-cracks using LAT. This research work established through experimental design, mechanical and metallographic characterization, a process that was used for the laser additive repair of cracks in Ti-6Al-4V components. The preliminary repairs were made without laser re-melting. They were analysed for defects using the optical microscopy (OM) and their macrographs revealed lack of sidewall fusion, lack of interlayer fusion, lack of intralayer fusion, unmelted powder and porosity. The matrix used for the preliminary repairs was then optimised using the observations made during the preliminary phase. It was from this preliminary phase optimization that the final experimental matrix of the research was developed. Controlled laser re-melting, reduction of the spot size diameter and lowering of the scanning speed were introduced as main process parameters of the optimized matrix. The optimized repairs were further characterized using the optical microscopy (OM) and the scanning electron microscopy (SEM). The optimized repairs were observed to have very limited defects. The energy dispersive spectroscopy (EDS) analyses revealed that the deposits were dominated by Ti, Al and V which were the main compositions of the material. The Vickers microhardness tests, microhardness-tensile strength correlations and the Charpy impact tests obtained results confirmed mechanically sound repairs with good evolving microstructural properties... , M.Ing. (Mechanical Engineering)
- Full Text:
Fabrication and characterization of functionally graded titanium alloy with commercially pure titanium and titanium carbide deposited by laser metal deposition technique
- Authors: Mdlalo, X. M.
- Date: 2015
- Subjects: Titanium alloys - Fatigue , Lasers - Industrial applications , Pulsed laser deposition , Metal coating
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/225271 , uj:22748
- Description: Abstract: Titanium and Titanium –based alloys have been used for aerospace materials for many years. Recently, those alloys are now being increasingly utilised for automotive, industrial, chemical, energy industries and consumer applications because of its excellent tensile and fatigue strength, corrosion resistance and high toughness- to- mass ratio, temperature strength and Young modulus’s values. However, despite these numerous applications, their general usages are often restricted because of limitations in mechanical properties and poor anti-friction properties exhibited in selected service conditions. There are different rapid solidification methods that have been put forward by some authors to address these deficiencies. Laser Metal Deposition has the potential to offer all specific solutions to key engineering problems over the traditional metal-working techniques. However, the purpose of this research work focuses on the laser metal deposition of CpTi /TiC composites coatings on Ti6A14V as a substrate by the laser melting of CpTi and TiC elemental powder mixtures. The process parameters involved with the LMD method include the laser power, traverse speed, powder-flow rate, and gas-flow rates. The characterization was done using OM, SEM, EDS, microhardness and tensile testing. The laser power was varied between 800W to 1600 W, while all the other parameters were kept constant. The results show that as laser power increases, the average hardness and the strength values also increase continuously. The results revealed that the microhardness values increases from 383 HV0.1 for the substrate and they reach a peak as high as 460 HV0.1 for sample A3 and the lowest value of 364 HV0.1 for sample A2. The tensile test showed that the average UTS for the four samples were 1545.18 MPa while the YTS and the percentage elongation were 932.60 MPa and 67% respectively. The average grain size of the substrate materials was determined to being 44.4 μm. The highest average grain size for sample A4 and lowest is for sample A1 of the deposited samples were found to be 79.8 μm and 67.7 μm respectively. , M.Ing. (Mechanical Engineering)
- Full Text:
- Authors: Mdlalo, X. M.
- Date: 2015
- Subjects: Titanium alloys - Fatigue , Lasers - Industrial applications , Pulsed laser deposition , Metal coating
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/225271 , uj:22748
- Description: Abstract: Titanium and Titanium –based alloys have been used for aerospace materials for many years. Recently, those alloys are now being increasingly utilised for automotive, industrial, chemical, energy industries and consumer applications because of its excellent tensile and fatigue strength, corrosion resistance and high toughness- to- mass ratio, temperature strength and Young modulus’s values. However, despite these numerous applications, their general usages are often restricted because of limitations in mechanical properties and poor anti-friction properties exhibited in selected service conditions. There are different rapid solidification methods that have been put forward by some authors to address these deficiencies. Laser Metal Deposition has the potential to offer all specific solutions to key engineering problems over the traditional metal-working techniques. However, the purpose of this research work focuses on the laser metal deposition of CpTi /TiC composites coatings on Ti6A14V as a substrate by the laser melting of CpTi and TiC elemental powder mixtures. The process parameters involved with the LMD method include the laser power, traverse speed, powder-flow rate, and gas-flow rates. The characterization was done using OM, SEM, EDS, microhardness and tensile testing. The laser power was varied between 800W to 1600 W, while all the other parameters were kept constant. The results show that as laser power increases, the average hardness and the strength values also increase continuously. The results revealed that the microhardness values increases from 383 HV0.1 for the substrate and they reach a peak as high as 460 HV0.1 for sample A3 and the lowest value of 364 HV0.1 for sample A2. The tensile test showed that the average UTS for the four samples were 1545.18 MPa while the YTS and the percentage elongation were 932.60 MPa and 67% respectively. The average grain size of the substrate materials was determined to being 44.4 μm. The highest average grain size for sample A4 and lowest is for sample A1 of the deposited samples were found to be 79.8 μm and 67.7 μm respectively. , M.Ing. (Mechanical Engineering)
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Benchmarking best practice in new product development project : a South African cinema study
- Authors: Mohono, Thobela
- Date: 2016
- Subjects: New products , New products - Management , Motion picture theaters , Knowledge management , Benchmarking (Management)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/233814 , uj:23880
- Description: M.Phil. (Engineering Management) , Abstract: Please refer to full text to view abstract
- Full Text:
- Authors: Mohono, Thobela
- Date: 2016
- Subjects: New products , New products - Management , Motion picture theaters , Knowledge management , Benchmarking (Management)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/233814 , uj:23880
- Description: M.Phil. (Engineering Management) , Abstract: Please refer to full text to view abstract
- Full Text:
Determining the optimum welding material of 3CR12 stainless steel
- Molabe, Ramaisele Mapule Constance
- Authors: Molabe, Ramaisele Mapule Constance
- Date: 2018
- Subjects: Stainless steel - Welding
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280493 , uj:30141
- Description: M.Ing. (Mechanical Engineering) , Abstract: This research study called for investigation on a filler metal, which would yield improved benefits, when welding 3CR12 stainless steel. The compared filler metals included AISI 308L, 309L and 316L. The study was performed by welding 2mm thick 3CR12 test plates – using the TIG welding process by testing of welded material’s behaviour by tensile testing, microstructural analysis, and hardness testing. The experimental set-up and procedure were based on the findings from previous studies and recommendations. Defect-free welds were achieved on all the welded samples. The parent metal showed ferrite and pearlite microstructure; while the Heat Affected Zone (HAZ) contained coarse grains, as compared with Base Material (BM) and the fusion zone, it had more ferrite and less pearlite microstructure. The coarse grains were due to the higher heat input in this region. The fusion zone consisted of austenite, ferrite and martensite laths; this was probably due to the dissimilar weld joints of the austenitic filler metal and the ferritic base metal. The fracture of the tensile specimens was consistently located in the parent-metal zone, suggesting that the strength of the welded joint is greater than that of the parent metal. The ultimate tensile strength of all the samples is above the minimum (450MPa) ultimate tensile strength of the 3CR12. Owing to their fine grains at the weld joint, the welded joints displayed a higher tensile strength than that of the parent metal. The microstructural analysis indicated that the 309L sample has larger grains on the HAZ than on the PM and fusion zone; this implies that the 309L is more susceptible to heat in the HAZ when compared with the 308L and 316L samples. The maximum hardness was found to be in the fusion zone in all the welded samples; as a result of the fine solidification structure. The hardness values for 309L samples are lower than those of 308L and 316L samples. The root of the weld was weaker than the weld cap for all the filler metals tested. Filler metal 308L was found to be the optimum welding material for 3CR12; and it can be recommended for producing welds with high quality and strong integrity.
- Full Text:
- Authors: Molabe, Ramaisele Mapule Constance
- Date: 2018
- Subjects: Stainless steel - Welding
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280493 , uj:30141
- Description: M.Ing. (Mechanical Engineering) , Abstract: This research study called for investigation on a filler metal, which would yield improved benefits, when welding 3CR12 stainless steel. The compared filler metals included AISI 308L, 309L and 316L. The study was performed by welding 2mm thick 3CR12 test plates – using the TIG welding process by testing of welded material’s behaviour by tensile testing, microstructural analysis, and hardness testing. The experimental set-up and procedure were based on the findings from previous studies and recommendations. Defect-free welds were achieved on all the welded samples. The parent metal showed ferrite and pearlite microstructure; while the Heat Affected Zone (HAZ) contained coarse grains, as compared with Base Material (BM) and the fusion zone, it had more ferrite and less pearlite microstructure. The coarse grains were due to the higher heat input in this region. The fusion zone consisted of austenite, ferrite and martensite laths; this was probably due to the dissimilar weld joints of the austenitic filler metal and the ferritic base metal. The fracture of the tensile specimens was consistently located in the parent-metal zone, suggesting that the strength of the welded joint is greater than that of the parent metal. The ultimate tensile strength of all the samples is above the minimum (450MPa) ultimate tensile strength of the 3CR12. Owing to their fine grains at the weld joint, the welded joints displayed a higher tensile strength than that of the parent metal. The microstructural analysis indicated that the 309L sample has larger grains on the HAZ than on the PM and fusion zone; this implies that the 309L is more susceptible to heat in the HAZ when compared with the 308L and 316L samples. The maximum hardness was found to be in the fusion zone in all the welded samples; as a result of the fine solidification structure. The hardness values for 309L samples are lower than those of 308L and 316L samples. The root of the weld was weaker than the weld cap for all the filler metals tested. Filler metal 308L was found to be the optimum welding material for 3CR12; and it can be recommended for producing welds with high quality and strong integrity.
- Full Text: