Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.697498
Title: Characterisation and Evaluation of thermally treated recycled glass for mass finishing and superfinishing processes
Author: Jamal, Mikdam
ISNI:       0000 0004 5993 0253
Awarding Body: Liverpool John Moores University
Current Institution: Liverpool John Moores University
Date of Award: 2015
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Abstract:
This thesis presents the work on the characterisation and evaluation of an entirely new mass finishing product based wholly on thermally treated recycled glass, which acts as both a bond and abrasive for mass finishing and superfinishing processes. The recycling of glass is excellent in respect of sustainability and environmental efficiency. The aim of the study was to establish requirements for the high volume manufacture of thermally treated recycled glass preforms to satisfy stated performance criteria. Several powder characterization techniques were employed to assess morphology and flowability of various grades of soda lime glass powder. The results obtained have demonstrated that flowability and packing properties improve with an increase of particle size. Thermal analyses were successfully employed for various types of mould material to determine the optimal glass powder size in terms of crystallinity and mechanical properties. It was found that by controlling the time transformation temperature TTT relationship, it is possible to consistently produce abrasive media possessing particular mechanical and physical properties that deliver target mass finishing performance. The residual stresses developed during different thermal cycles were investigated numerically and experimentally. Compressive stress was observed near the media edge and tensile stress in the mid-plane at the end of the solidification process. The results showed that the numerical FEA code is a suitable tool for the prediction of residual stresses of thermally treated recycled glass. A study concerned with the tip geometry of the Vickers and Berkovich indenters was completed to ensure an accurate contact area determination. A new method is proposed for the determination of contact area based on residual imprint measurements using 3-D optical profilometry. The outcomes show that by measuring contact area with the new method the overall relative error in the obtained mechanical properties is improved. A combined Finite Element Analysis FEA and optimization algorithm has been developed using various indentation processes to determine the mechanical properties of a wide range of materials, using target FE indentation curves which were then extended to actual glass media taking into account the predicted residual stress in the material. The results obtained from the proposed methods of dual indenters and optimization algorithm have demonstrated that excellent convergence can be achieved with the target FE indentation curve of complex material systems; and also accurate results have been obtained for the actual glass. The material characterization tests were extended to investigate the fracture toughness based on the stress fields mapped at the unloading stage of the Vickers indentation. The median and Palmqvist crack systems were analysed separately using FEA. Dimensionless analyses were then carried out, and the critical SIF (fracture toughness) derived for the measured crack length and material properties. The developed numerical models were validated with the experimental data proposed by many researchers over a wide range of material properties as well as Vickers indentation induced cracking of thermally treated glass. The performance programme was designed as a comparative study with a range of conventional media that included an industrial benchmark media. Performance indicators included surface roughness and brightness. The results of the laboratory based research studies provided promising evidence that the thermally treated glass media has a process capability and performance comparable to that of conventional media. The glass media was trailed on a production machine annexed for this purpose. Turbine blades were employed as the component for these trails. The results though very promising did identify that a heavy workpiece may crush some media thereby generating small shards that may scratch or impair a fine surface finish (contribute against Ra). However, a novel jig arrangement was designed to hold the part in a horizontal position and allowed free rotation of the workpiece with the media flow in the trough. The new system was successfully used to deliver better performance results with the conventional and thermally treated recycled glass media. The kinematics of the mass finishing process were investigated with a two-dimensional discrete element model (DEM) developed to perform single-cell circulation in a vibratory bed. The sensitivity of the predicted model corresponding to the contact parameters was considered and the parameters were optimized with respect to the experimental results of media velocity vectors using particle image velocimetry (PIVLab). The results suggested that the bulk circulation increases with increasing bed depth resulting in an increase in pressure and shear forces between particle layers. The optimization of the advanced mass finishing (Drag and Stream finishing process) process has been studied using the design and analysis of experiment (DOE) approach. Regression analyses, analysis of variance (ANOVA), Taguchi methodology and Response Surface Methodology (RSM) have been chosen to aid this study. The effects of various finishing parameters were evaluated and the optimal parameters and conditions determined. The interaction of finishing parameters was established to illustrate the essential relationship between process parameters and surface roughness. The predicted models were confirmed by experimental validation and confirmation finishing trials.
Supervisor: Morgan, Michael ; Chen, Xun Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.697498  DOI: Not available
Keywords: TA Engineering (General). Civil engineering (General)
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