Academic Journal
Optical surface quality and molecular dynamics modelling of ultra-high precision optical silicon machining
| Τίτλος: | Optical surface quality and molecular dynamics modelling of ultra-high precision optical silicon machining |
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| Συγγραφείς: | Abdulkadir, Lukman Niyi |
| Στοιχεία εκδότη: | Nelson Mandela University Faculty of Engineering, the Built Environment, and Technology |
| Έτος έκδοσης: | 2019 |
| Συλλογή: | SEALS Digital Commons (South East Academic Libraries System, South Africa) |
| Θεματικοί όροι: | Engineering design -- Data processing, Manufacturing processes -- Data processing, Mechatronics |
| Περιγραφή: | Hard and brittle materials, such as silicon, silicon carbide etc., are widely used in aerospace, integrated circuit, and other fields due to their excellent physical and chemical properties. However, these materials display poor machinability owing to hardness, brittleness, non-linearity in machining process and complexities in selecting suitable machining parameters and tool geometry. These leads to low quality lenses due to subsurface damage and surface micro-crack. Additionally, it is experimentally very difficult to observe all nanoscale physical phenomena due to in-process measurement problems, inaccessible contact area of tool and workpiece, and the difficulty of surface analysis. With the use of molecular dynamics (MD) which is a comprehensive nanoscale modelling technique, proper selection of process parameters, tool geometry and online monitoring techniques, production of freeform optics is possible through Ultra-high precision diamond turning (UHPDT). Though, depending on view point, machinability in UHPDT may be in terms of tool wear rate, hardness, chip morphology, surface roughness, and other benchmarks. These situations have called for more insights, which on the long run will help to achieve high precision manufacturing with predictability, repeatability, productivity and high infrared (IR) optical quality. In this thesis, UHPDT of monocrystalline silicon at atomistic scale was conducted to investigate combined effects of edge radius, feed rate, cutting speed, depth of cut, rake and clearance angles hitherto not done so far. Using appropriate potential functions with the MD algorithm, comprehensive analysis of thermal effects, diamond tool wear, phase change, cutting forces and machining stresses (normal, shear, hydrostatic and von Mises) were carried out. Dislocation extraction algorithm (DXA) and radial distribution function (RDF) were used to evaluate dislocation nucleation, variations in bond lengths, microstructural transformation and represents structural changes in histogram form. Selected ... |
| Τύπος εγγράφου: | text |
| Περιγραφή αρχείου: | computer; online resource; application/pdf; 1 online resource (XXX pages); pdf |
| Γλώσσα: | English |
| Relation: | https://hdl.handle.net/10948/66552; vital:75601; http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:75601 |
| Διαθεσιμότητα: | https://hdl.handle.net/10948/66552 http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:75601 |
| Rights: | Nelson Mandela University ; All Rights Reserved ; Open Access |
| Αριθμός Καταχώρησης: | edsbas.31D7C87F |
| Βάση Δεδομένων: | BASE |
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