Laser bending of commercially pure grade 2 titanium alloy plates: mechanisms analysis and characterisation of mechanical properties
- Authors: Mjali, Kadephi Vuyolwethu
- Date: 2014
- Subjects: Materials -- Mechanical properties , Bending , Titanium-aluminum alloys
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9642 , http://hdl.handle.net/10948/d1021147
- Description: The processing of materials has become a specialist field and the industry will continue to grow due to rising costs in labour and raw materials which has forced many automotive industry suppliers to invest heavily in this field. In order to be relevant and competitive in today’s industrial world, companies in South Africa are now forced to dedicate billions of rands in profits to research and development. Metals like titanium are finding favour with automotive and aviation companies in pursuit of savings in fuel consumption. This saving is achieved by reducing weight on aircraft and automobiles yet still meeting acceptable and improved structural integrity. In-depth research into the behaviour of various materials under varying loading conditions is therefore essential. The study on the processing of commercially pure grade 2 titanium alloy plates focuses on the development of process parameters for bending the material using a 4kW Nd: YAG laser to an approximate radius of curvature of 120mm. The resulting mechanical properties of laser formed plates are then compared to those obtained from mechanically formed samples. The titanium parent material was used to benchmark the performance of formed samples. The effect of process parameters on the mechanical properties and structural integrity also formed part of this study. To obtain the bending parameters for laser forming, various combinations of processing speeds and laser powers were used. The line energy is dependent on the power and scanning velocity parameters and these are shown in table 1. The laser power, line energy and scanning velocity were the main parameters controlled in this study and the beam diameter remained unchanged. Residual stress analysis, micro-hardness and fatigue life testing were carried out to analyse mechanical properties and the structural integrity of the plate samples. Microstructural analysis was also done to observe changes in the material as a result of the forming processes. From the results it is evident that laser forming is beneficial to the hardness of titanium but detrimental to the fatigue life at higher line energies. Residual stress analysis showed the amount of stress within the study samples increased with each forming operation. This information was vital in the analysis of the fatigue life of titanium. A fatigue life prediction model was developed from this study and it shed some light on the behaviour of titanium in fatigue testing. The model could be used to predict fatigue life when no fatigue data is available for commercially pure grade 2 titanium alloy plates. In conclusion, this study helped establish parameters that could be used to bend titanium while the analysis of mechanical properties showed the limits of working with this alloy.
- Full Text:
- Date Issued: 2014
Mechanisms, analysis and characterisation of mechanical properties of laser formed commercially pure grade 2 titanium alloy plates
- Authors: Mjali, Kadephi Vuyolwethu
- Date: 2014
- Subjects: Materials -- Mechanical properties , Bending , Titanium-aluminum alloys
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9641 , http://hdl.handle.net/10948/d1021083
- Description: The processing of materials has become a specialist field and the industry will continue to grow due to rising costs in labour and raw materials which has forced many automotive industry suppliers to invest heavily in this field. In order to be relevant and competitive in today’s industrial world, companies in South Africa are now forced to dedicate billions of rands in profits to research and development. Metals like titanium are finding favour with automotive and aviation companies in pursuit of savings in fuel consumption. This saving is achieved by reducing weight on aircraft and automobiles yet still meeting acceptable and improved structural integrity. In-depth research into the behaviour of various materials under varying loading conditions is therefore essential. The study on the processing of commercially pure grade 2 titanium alloy plates focuses on the development of process parameters for bending the material using a 4kW Nd: YAG laser to an approximate radius of curvature of 120mm. The resulting mechanical properties of laser formed plates are then compared to those obtained from mechanically formed samples. The titanium parent material was used to benchmark the performance of formed samples. The effect of process parameters on the mechanical properties and structural integrity also formed part of this study. To obtain the bending parameters for laser forming, various combinations of processing speeds and laser powers were used. The line energy is dependent on the power and scanning velocity parameters and these are shown in table 1. The laser power, line energy and scanning velocity were the main parameters controlled in this study and the beam diameter remained unchanged. Residual stress analysis, micro-hardness and fatigue life testing were carried out to analyse mechanical properties and the structural integrity of the plate samples. Microstructural analysis was also done to observe changes in the material as a result of the forming processes. From the results it is evident that laser forming is beneficial to the hardness of titanium but detrimental to the fatigue life at higher line energies. Residual stress analysis showed the amount of stress within the study samples increased with each forming operation. This information was vital in the analysis of the fatigue life of titanium. A fatigue life prediction model was developed from this study and it shed some light on the behaviour of titanium in fatigue testing. The model could be used to predict fatigue life when no fatigue data is available for commercially pure grade 2 titanium alloy plates. In conclusion, this study helped establish parameters that could be used to bend titanium while the analysis of mechanical properties showed the limits of working with this alloy.
- Full Text:
- Date Issued: 2014
Analysing the effect of FSP on MIG-laser hybrid welded 6082-T6 AA joints
- Authors: Mjali, Kadephi Vuyolwethu
- Date: 2007
- Subjects: Friction stir welding
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9610 , http://hdl.handle.net/10948/563 , Friction stir welding
- Description: Friction Stir Processing (FSP) of aluminium alloys has been used to modify and improve the microstructure and relevant properties of fusion welded aluminium alloys. The effect of FSP on MIG-Laser Hybrid (MLH) welded aluminium alloy 6082-T6 mechanical and microstructural properties has been studied in this research. The FSP process was used on 6mm thick aluminium alloy plates and a tool was designed specifically for FSP, and the effect of varying speeds was analysed before the final FSP welds were made. The effect of FSP was analysed by optical microscopy, tensile, microhardness and fatigue testing. The aim of the study was to determine whether the FSP process has a beneficial influence on the mechanical properties and metallurgical integrity of MIG-Laser Hybrid welded 6082-T6 aluminium alloy with varying gap tolerances. Three welding processes were compared, namely combined Friction Stir Processing on MIG-Laser hybrid process (FSP-MLH), MLH and Friction Stir Welding (FSW) as part of the analysis. (FSP was carried out on MLH components when it was found that FSP is not an entirely complete welding process but rather a finishing process per se.) The aim of this dissertation is to investigate the effects of the FSP process on the weld quality of MLH welded joints and also to compare this to individual processes like FSW and MLH. This investigation was undertaken in order to gain an understanding of the effect of these processes on fatigue performance and microhardness distribution on aluminium alloy 6082-T6 weld joints.
- Full Text:
- Date Issued: 2007