Dynamic properties of 3 MM TI-6AL-4V laser beam and friction stir welded sheets
- Authors: Mashinini, Peter Madindwa
- Date: 2015-03
- Subjects: Alloys , Metals , Welding
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/53340 , vital:45138
- Description: Ti6Al4V alloy usage is increasing due to high demand from the aerospace and automotive industries as well as the field of medical implants. Therefore, identifying the most effective joining technique is critically important to ensure that optimum life can be achieved by welded components. This is especially important for the aerospace industry where fatigue life of the welded joints is vital. This research identified two relatively new joining technologies for Titanium sheet, namely, Friction Stir Welding (FSW), a solid-state process, and Laser Beam Welding (LBW), a fusion joining process. It was therefore vital to conduct a systematic study of these two processes and compare results to illustrate which process attributes to static and dynamic properties. This investigation was accomplished by varying the process heat input for both FSW and LBW. The main parameters used to control process heat input were rotational and traverse speed for FSW and laser power and traverse speed for LBW. In FSW, a reaction torque was used to describe the process energy in order to achieve the plasticised material condition. Preliminary work was done to establish the influencing factors for a successful weld which included tool optimisation, but process optimisation was not discussed in elaborative detail. In LBW, traverse speed was identified as the critical control parameter to ensure good weld penetration. Weld width was recorded as it showed strong correlation to heat input rates. , Thesis (MEng) -- Faculty of Engineering, the Built Environment and Technology, Mechanical Engineering, 2021
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- Date Issued: 2015-03
The development of amine-based extractants for separation of base metals in a sulfate medium
- Authors: Magwa, Nomampondo Penelope
- Date: 2015
- Subjects: Extraction (Chemistry) , Sulfates , Ligands , Benzimidazoles , Infrared spectroscopy , Nuclear magnetic resonance spectroscopy , Metal ions , Metals
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4559 , http://hdl.handle.net/10962/d1020010
- Description: Tridentate benzimidazole-based ligands, bis((1H-benzimidazol-2-yl)methyl)sulfide (BNSN) and bis((1H-benzimidazol-2-yl)methyl)amine (BNNN), along with dinonylnaphthalene sulfonic acid (DNNSA) as a synergist, were investigated as potential selective extractants for Ni2+ from base metals in a solvent extraction system using 2-octanol/Shellsol 2325 (8:2) as diluent and modifier. However, extraction studies show a lack of pH-metric separation of the later 3d metal ions with bis((1-octylbenzimidazol-2-yl)methyl)sulfide (BONSN) and bis((1- decylbenzimidazol-2-yl)methyl)amine (BDNNN) as extractants, but extractions occurred in the low pH range with an opportunity for back extraction. This investigation suggested that tridentate ligands (at least those of the nature investigated here) are not feasible extractants for separation of base metal ions due to their lack of stereochemical “tailor-making.”
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- Date Issued: 2015