- Title
- The machinability of rapidly solidified aluminium alloy for optical mould inserts
- Creator
- Otieno, Timothy
- Subject
- Aluminum alloys
- Subject
- Automobiles -- Materials Materials -- Mechanical properties
- Date Issued
- 2018
- Date
- 2018
- Type
- Thesis
- Type
- Doctoral
- Type
- DPhil
- Identifier
- http://hdl.handle.net/10948/23097
- Identifier
- vital:30415
- Description
- Ultra-high precision machining is a material removing process under the nanotechnology regime whereby the highest dimensional accuracies are attained. Critical components for optical devices and optical measuring systems are mainly produced through ultra-high precision machining. Their mass production is usually implemented by utilising optical moulds. Aluminium alloys have proven to be advantageous and very commonly used in the photonics industry for moulds. This ever-increasing use and demand within optics have led to the development of newly modified grades of aluminium alloys produced by rapid solidification in the foundry process. The newer grades are characterised by finer microstructures and improved mechanical and physical properties. The main inconvenience in their usage currently lies in their very limited machining database. This research investigates the machinability of rapidly solidified aluminium, RSA 905, under varying cutting conditions in single point diamond turning. The machining parameters varied were cutting speed, feed rate and depth of cut. The resulting surface roughness of the workpiece and wear of the diamond tool were measured at various intervals. Acoustic emissions and cutting force were also monitored during machining. The results were statistically analysed and accurate predictive models were developed. Generally, very low tool wear, within 3 to 5 μm, and very low surface roughness, within 3 to 8 nm, was obtained. Acoustic emissions recorded were in the range of 0.06 to 0.13 V and cutting forces were in the range of 0.08 to 0.94 N. The trends of the monitored acoustic emissions and cutting force showed to have a linked representation of the tool wear and surface roughness results. Contour maps were generated to identify zones where the cutting parameters produced the best results. In addition, a range of machining parameters were presented for optimum quality where surface roughness and tool wear can be minimised. As the machining is of a nanometric scale, a molecular dynamics approach was applied to investigate the underlying mechanisms at atom level. The nanomachining simulations were found to have a correlation to the actual machining results and microstructural nature of the alloy. This research proves that rapidly solidified aluminium is a superior alternative to traditional aluminium alloys and provides a good reference with room for flexibility that machinists can apply when using rapidly solidified aluminium alloys. Efficiency could be improved by reducing the required machining interruption through effective monitoring and performance could be improved by maintaining quality and extending tool life through parameter selection.
- Format
- xii, 188 leaves
- Format
- Publisher
- Nelson Mandela University
- Publisher
- Faculty of Engineering, the Built Environment and Information Technology
- Language
- English
- Rights
- Nelson Mandela University
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