Laser welding of thin-walled stainless steel tubing
- Authors: Mabveka, Greystone Graham
- Date: 2019
- Subjects: Laser welding , Welding Mechanical engineering
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/40690 , vital:36223
- Description: Longitudinal butt welds in the motor industry are increasingly being made by laser welding. One of the materials being welded is thin walled type 441 stainless steel tubing. The welding process parameters should however be optimised to give a weld that possesses acceptable properties. In this research, a Yb:YAG laser machine was used to weld a 1.2mm thick tubing. Laser power and welding speed were varied to achieve an optimum weld whose properties compare well with the parent metal. The two parameters were combined such that the heat input was in the range of 7.5 to 25kJ/m. The welds were characterised by the microstructure from the weld, intergranular attack and mechanical properties. It has been shown by microstructure study that grains originated from ‘weld metal/base metal’ interface and elongated towards the weld centreline. A defined line ran through the interface through the thickness of the plate. Smaller grains were noted around the interface in some welds. Susceptibility to intergranular attack tests showed random ditching in the weld metal microstructure which indicated that the weldments produced were acceptable. Mechanical tests of all welds showed a slight increase in micro-hardness in the weld metal. While the base metal had a micro-hardness range of 160 –199HV0.1, it increased to 187 – 242HV0.1 in the fusion zone. An ANOVA regression of tensile test results predicted an expected maximum of 471MPa to occur when a 1000W power is used at a welding speed of 0.06m/s. Fracture morphology of tensile test samples showed that all failures were by overload. This showed that the weld metal still exhibited similar ductility properties with the base metal.
- Full Text:
- Date Issued: 2019
- Authors: Mabveka, Greystone Graham
- Date: 2019
- Subjects: Laser welding , Welding Mechanical engineering
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/40690 , vital:36223
- Description: Longitudinal butt welds in the motor industry are increasingly being made by laser welding. One of the materials being welded is thin walled type 441 stainless steel tubing. The welding process parameters should however be optimised to give a weld that possesses acceptable properties. In this research, a Yb:YAG laser machine was used to weld a 1.2mm thick tubing. Laser power and welding speed were varied to achieve an optimum weld whose properties compare well with the parent metal. The two parameters were combined such that the heat input was in the range of 7.5 to 25kJ/m. The welds were characterised by the microstructure from the weld, intergranular attack and mechanical properties. It has been shown by microstructure study that grains originated from ‘weld metal/base metal’ interface and elongated towards the weld centreline. A defined line ran through the interface through the thickness of the plate. Smaller grains were noted around the interface in some welds. Susceptibility to intergranular attack tests showed random ditching in the weld metal microstructure which indicated that the weldments produced were acceptable. Mechanical tests of all welds showed a slight increase in micro-hardness in the weld metal. While the base metal had a micro-hardness range of 160 –199HV0.1, it increased to 187 – 242HV0.1 in the fusion zone. An ANOVA regression of tensile test results predicted an expected maximum of 471MPa to occur when a 1000W power is used at a welding speed of 0.06m/s. Fracture morphology of tensile test samples showed that all failures were by overload. This showed that the weld metal still exhibited similar ductility properties with the base metal.
- Full Text:
- Date Issued: 2019
The perceptions of Chinese tourists of the Western Cape Region travel destination
- Authors: Hu, Jiang
- Date: 2008
- Subjects: Chinese -- Travel -- South Africa -- Western Cape -- Attitudes , Tourism -- South Africa -- Marketing , Tourism -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9365 , http://hdl.handle.net/10948/967 , Chinese -- Travel -- South Africa -- Western Cape -- Attitudes , Tourism -- South Africa -- Marketing , Tourism -- South Africa
- Description: As a result of significantly improving relationship between South Africa and China, Chinese tourists traveling to South Africa have become a more noticeable group of travelers. More and more Chinese tourists choose South Africa as a tourism destination; especially Cape Town in the Western Cape region for a variety purposes such as relaxation, business and/or shopping. This research investigates the perceptions and motivation of Chinese tourists coming to the Western Cape region of South Africa. The proposed strategy of promoting the Western Cape region as a travel destination can be made based on the perceptions and motivation of Chinese tourists to the Western Cape. The study focuses on clearly understanding the perception of Chinese tourists by studying tourist behaviour and consumer motivation. The process of decision making and factors impacting on decision making are addressed in the research. A survey questionnaire was administered to Chinese tourists visiting South Africa. The primary data received by questionnaire was analyzed to show what actually Chinese tourists consider Western Cape as a travel destination. The Statistical Package of Social Science (SPSS) was utilized for analysis of data collected by the questionnaire. These general groups of data are discussed in the research. There are personal information, the motivation for travelling, and perceptions of respondents in the Western Cape region in South Africa.
- Full Text:
- Date Issued: 2008
- Authors: Hu, Jiang
- Date: 2008
- Subjects: Chinese -- Travel -- South Africa -- Western Cape -- Attitudes , Tourism -- South Africa -- Marketing , Tourism -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9365 , http://hdl.handle.net/10948/967 , Chinese -- Travel -- South Africa -- Western Cape -- Attitudes , Tourism -- South Africa -- Marketing , Tourism -- South Africa
- Description: As a result of significantly improving relationship between South Africa and China, Chinese tourists traveling to South Africa have become a more noticeable group of travelers. More and more Chinese tourists choose South Africa as a tourism destination; especially Cape Town in the Western Cape region for a variety purposes such as relaxation, business and/or shopping. This research investigates the perceptions and motivation of Chinese tourists coming to the Western Cape region of South Africa. The proposed strategy of promoting the Western Cape region as a travel destination can be made based on the perceptions and motivation of Chinese tourists to the Western Cape. The study focuses on clearly understanding the perception of Chinese tourists by studying tourist behaviour and consumer motivation. The process of decision making and factors impacting on decision making are addressed in the research. A survey questionnaire was administered to Chinese tourists visiting South Africa. The primary data received by questionnaire was analyzed to show what actually Chinese tourists consider Western Cape as a travel destination. The Statistical Package of Social Science (SPSS) was utilized for analysis of data collected by the questionnaire. These general groups of data are discussed in the research. There are personal information, the motivation for travelling, and perceptions of respondents in the Western Cape region in South Africa.
- Full Text:
- Date Issued: 2008
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