Influence of a saline test environment on the Fatigue properties of laser metal deposition Ti-6al-4v specimens
- Authors: Botha, Sheldyn Jaye
- Date: 2021-04
- Subjects: Metal organic chemical vapor deposition , Salines
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59203 , vital:60304
- Description: This study investigated the effects of the position of extraction and a corrosive environment on the fatigue properties of Ti-6Al-4V Laser Metal Deposition (LMD) specimens. Additive manufacturing (AM) processes allow for a reduction in manufacturing time, whilst constructing complex geometries. AM induces a complex thermal history which influences the microstructure in the material (1). The microstructure affects the fatigue properties where a finer microstructure is more favourable for increasing the fatigue life (2). Fatigue failure is one of the main modes of failure during a material’s service life (3). Thus, it is imperative to investigate the material’s fatigue behaviour. Major parameters of the LMD process were investigated, allowing bulk LMD coupons to be manufactured, from which fatigue specimens were extracted at three different heights. Static properties were attained through tensile testing and a Vickers Micro-Hardness evaluation. These properties allowed for calculating benchmark stresses that were utilised for fatigue testing. The biocompatibility of Ti-6Al-4V makes it desirable for medical implants – the core influence of this study. An implant is constantly subjected to a corrosive saline environment, introducing a corrosive mechanism of failure, known to decrease the life of a material. A rotary bending fatigue platform was utilised as it allowed for modifications to introduce a corrosive saline environment through means of a saline dosing system. Literature reports a higher possibility of corrosion fatigue occurring under rotary bending fatigue conditions for Ti alloy specimens (4,5). The fatigue data indicated no significant effect on the fatigue properties was evident when comparing the position of extraction, attributed to the interrupted build strategy utilised for manufacturing the bulk coupons. The specimens displayed a shift in fatigue life when subjected to a corrosive saline environment. Upon analysis, there was little variation in the microstructures at each position of extraction, attributed to the interrupted build strategy. , Thesis (MA) -- Faculty of Engineering, the Built Environment, and Technology, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Botha, Sheldyn Jaye
- Date: 2021-04
- Subjects: Metal organic chemical vapor deposition , Salines
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59203 , vital:60304
- Description: This study investigated the effects of the position of extraction and a corrosive environment on the fatigue properties of Ti-6Al-4V Laser Metal Deposition (LMD) specimens. Additive manufacturing (AM) processes allow for a reduction in manufacturing time, whilst constructing complex geometries. AM induces a complex thermal history which influences the microstructure in the material (1). The microstructure affects the fatigue properties where a finer microstructure is more favourable for increasing the fatigue life (2). Fatigue failure is one of the main modes of failure during a material’s service life (3). Thus, it is imperative to investigate the material’s fatigue behaviour. Major parameters of the LMD process were investigated, allowing bulk LMD coupons to be manufactured, from which fatigue specimens were extracted at three different heights. Static properties were attained through tensile testing and a Vickers Micro-Hardness evaluation. These properties allowed for calculating benchmark stresses that were utilised for fatigue testing. The biocompatibility of Ti-6Al-4V makes it desirable for medical implants – the core influence of this study. An implant is constantly subjected to a corrosive saline environment, introducing a corrosive mechanism of failure, known to decrease the life of a material. A rotary bending fatigue platform was utilised as it allowed for modifications to introduce a corrosive saline environment through means of a saline dosing system. Literature reports a higher possibility of corrosion fatigue occurring under rotary bending fatigue conditions for Ti alloy specimens (4,5). The fatigue data indicated no significant effect on the fatigue properties was evident when comparing the position of extraction, attributed to the interrupted build strategy utilised for manufacturing the bulk coupons. The specimens displayed a shift in fatigue life when subjected to a corrosive saline environment. Upon analysis, there was little variation in the microstructures at each position of extraction, attributed to the interrupted build strategy. , Thesis (MA) -- Faculty of Engineering, the Built Environment, and Technology, 2021
- Full Text:
- Date Issued: 2021-04
Enhancement of domestic solar photovoltaic unit productivity through the use of a cost effective tracking system
- Authors: Cawood, John Henry
- Date: 2021-04
- Subjects: Photovoltaic power systems , Tracking (Engineering)
- Language: English
- Type: Doctoral's theses , text
- Identifier: http://hdl.handle.net/10948/59215 , vital:60313
- Description: The majority of new and existing small photovoltaic (PV) installations in South Africa are fixed-panel systems, largely due to the cost of photovoltaic panel components having reduced steadily in recent years where an increased requirement is met with a larger number of panels, whilst tracking system costs remain prohibitively expensive. Fixed installations realise only a part of their energy potential as they are truly effective for only short periods of the day. The aim of this study is to investigate and build on the current technology of PV tracking systems with the aim of specifying a simple control and actuation system which performs the tracking function. The eventual purpose of this thesis is to reliably produce more energy from solar photovoltaic installations than similar installations using fixed panels. This would be achieved by the use of an effective and affordable tracking system which yields acceptable accuracy and reliability and opens the potential for the system to be further developed for other purposes. These alternative uses could be the control of sunlight into green buildings, control of dampers for building ventilation and cooling and Trombe wall air control. This study has investigated the potential of several passive and active methods to actuate a sun tracking system. A useful closed loop system, which uses low pressure hydraulics, was developed and tested. The prototype is detailed in the drawings, Appendix D. , Thesis (PhD) -- Faculty of Engineering, the Built Environment, and Technology, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Cawood, John Henry
- Date: 2021-04
- Subjects: Photovoltaic power systems , Tracking (Engineering)
- Language: English
- Type: Doctoral's theses , text
- Identifier: http://hdl.handle.net/10948/59215 , vital:60313
- Description: The majority of new and existing small photovoltaic (PV) installations in South Africa are fixed-panel systems, largely due to the cost of photovoltaic panel components having reduced steadily in recent years where an increased requirement is met with a larger number of panels, whilst tracking system costs remain prohibitively expensive. Fixed installations realise only a part of their energy potential as they are truly effective for only short periods of the day. The aim of this study is to investigate and build on the current technology of PV tracking systems with the aim of specifying a simple control and actuation system which performs the tracking function. The eventual purpose of this thesis is to reliably produce more energy from solar photovoltaic installations than similar installations using fixed panels. This would be achieved by the use of an effective and affordable tracking system which yields acceptable accuracy and reliability and opens the potential for the system to be further developed for other purposes. These alternative uses could be the control of sunlight into green buildings, control of dampers for building ventilation and cooling and Trombe wall air control. This study has investigated the potential of several passive and active methods to actuate a sun tracking system. A useful closed loop system, which uses low pressure hydraulics, was developed and tested. The prototype is detailed in the drawings, Appendix D. , Thesis (PhD) -- Faculty of Engineering, the Built Environment, and Technology, 2021
- Full Text:
- Date Issued: 2021-04
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