Department of Industrial Engineering

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Browsing Department of Industrial Engineering by browse.metadata.advisor "Akdogan, G."

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    Development of a continuous improvement framework for a small scale steelmaking company
    (Stellenbosch : Stellenbosch University, 2018-03) Dondofema, Richmore Aron; Matope, Stephen; Akdogan, G.; Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering.
    ENGLISH ABSTRACT: The South African steelmaking industry is currently sailing through a turbulent economic period characterised with commodity price instability and competition from European and Asian markets. This research study focuses on creating a production cost advantage for a local steelmaking organisation through the implementation of a continuous improvement (CI) framework. Implementing CI activities focuses on product value creation by systematic identification and elimination of process waste in the production process on a continuous basis. Through a systematic literature review on the applications of lean manufacturing in South Africa, the research identified that there was limited application of continuous improvement techniques in steelmaking sector. The study further investigated the development of the South African steel industry and applications of Industrial Engineering (IE) principles to the industry. Findings of this review buttressed the absence of IE systematic research for steelmaking in South Africa. To understand continuous improvement, the student used conceptual framework analysis (CFA), a non-deterministic research tool that provides a method to conceptualise a specific subject. The identified concepts of continuous improvement are: CI process management, organisational infrastructure and supportive framework, and CI techniques. These three concepts were used to construct a CI implementation framework for Unica Iron and Steel Company in Hammanskraal, Pretoria. The implementation framework consists of a cycle with six CI process management steps which include process audit, identification of areas of improvement, improve, optimise, sustain and review. The framework is based on the following CI techniques: Lean Manufacturing, Toyota Production System, Six Sigma and Theory of Constraints. To successfully implement CI activities the organisation should have proper channels of communication between line employees, supervisors and operational managers as organisational infrastructure and supportive framework aspects. To assist in the validation of the CI implementation framework, Technomatix simulation software was used. From the results obtained through simulation, the first improvement cycle revealed 78% improvement in throughput per shift.
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    An investigation of fretting wear in aerospace applications
    (Stellenbosch : Stellenbosch University, 2011-12) Nortje, Hermann; Akdogan, G.; Oosthuizen, G. A.; Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering.
    ENGLISH ABSTRACT: Fretting wear results in the loss of fit and tolerance at contact interfaces. The aerospace and aircraft industry is severely impacted by fretting wear and fretting fatigue that frequently occurs in turbo machinery and riveted structural connections. There have been numerous studies, investigating the fretting phenomenon for these aerospace applications. Literature available in regard to fretting wear encountered in these aerospace applications is limited. This study is therefore aimed at investigating the fretting wear encountered in aerospace application. An in-house fretting test apparatus was specially designed and developed in order to perform the fretting wear experiments. Ti-6Al-4V and Al7075-T6 are the two aerospace materials that were tested using the fretting test apparatus. An extensive experimental study was conducted in order to investigate the effect of the normal force on the fretting wear and friction behaviour of the two aerospace materials. The most severe of these experiments were identified and then repeated for up to 106 fretting cycles. Additional fretting wear experiments were also conducted between the two aerospace materials and cemented carbides, since the carbides are currently being utilized as coatings in some aerospace contacts that are prone to fretting induced damage. The experimental study revealed that a decrease in the normal force resulted in an increase in the severity of the fretting wear of both aerospace materials. The additional fretting wear experiments involving carbide-metal contact couples found that Ti-6Al-4V and Al7075-T6 were prone to adhesive wear.
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    An investigation of sliding wear of Ti6Al4V
    (Stellenbosch : Stellenbosch University, 2012-03) Herselman, Emile Johan; Akdogan, G.; Oosthuizen, G. A.; Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering.
    ENGLISH ABSTRACT: Sliding wear is a complicated form of wear involving different factors. The factors affecting the process are the mechanical properties of the materials, sliding distance, sliding speed, and normal force applied to the contact. An experimental study was conducted to assess the performance of Ti6Al4V in self-mated and various counterface material contact couples subjected to linear reciprocating dry sliding motion. The normal force was varied for all the experiments to understand the effect it had on specific couples. Sliding wear experiments were also conducted on cemented carbides coupled with Ti6Al4V. In certain applications carbide coatings are used and could possibly come into contact with Ti6Al4V. Cemented carbides used in the study were manufactured through spark plasma sintering and liquid phase sintering. An in depth study was conducted to assess the spark plasma sintered materials and compare these to those manufactured through liquid phase sintering. The experimental study revealed that an increase in normal force, in sliding experiments, led to an increase in friction and wear volume loss of the Ti6Al4V pin. In addition the experiments found that Ti6Al4V was prone to adhesion and surface oxidation.
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    Wear characterisation in milling of Ti6Al4V : a wear map approach
    (Stellenbosch : University of Stellenbosch, 2010-12) Oosthuizen, Gert Adriaan; Van der Merwe, A. F.; Akdogan, G.; University of Stellenbosch. Faculty of Engineering. Dept. of Industrial Engineering.
    ENGLISH ABSTRACT: Information on the milling of Ti6Al4V is limited; with most studies concluding that it is not possible to obtain a significant increase in the material removal rate (Qw). Tool wear maps can be a diagnostic instrument for failure analysis. Cutting speed (vc), maximum un-deformed chip thickness (heMax) and the radial immersion percentage (ae/Ø %) are the key variables in understanding the milling of titanium alloys. The objective of this research study was to construct tool wear maps for the milling of Ti6Al4V. This will form the foundation of understanding the cutting demands on the tool, in order to analyse the main wear mechanisms. Remedial actions, which are developed by tool suppliers, can be considered and integrated via this understanding of the failure modes and related mechanisms. Firstly, experimental data from background studies, literature and industry on wear rates and wear mechanisms pertaining to the milling conditions was gathered to construct the tool wear map. Mathematical models describing the wear behaviour for these conditions were also investigated. Secondly, work piece failure maps have been superimposed onto the tool wear maps constructed to understand the global failure boundaries. Experimentation was carried out to validate the constructed maps. The tool wear map could then be used to discuss the observed effects and consider remedial actions. Cutting speed corresponds to the magnitude of the thermal load and heMax represents the mechanical load. The ae/Ø % defines the duration of the exposure to the thermal load at the edge of the cutting tool. This investigation has shown the following issues to be of importance when considering tool performance via the tool wear map approach: 1. The key to designing tool wear maps is to identify the most economic Scheduled Replacement Time (SRT) for the specific components. Knowing the correct SRT makes it possible to optimize the milling conditions so that the cutting tool wears gradually under the cutting conditions, and lasts longer than the economic SRT. 2. Increased vc will decrease tool life (TL). However, in low transverse rupture strength tools there may be a minimum vc below which mechanical overload may occur. Similarly, a local maximum TL (a sweet spot) may exist if there is a phase change in the work piece material. 3. Increased heMax will decrease TL. However, heMax must be kept below a maximum critical value to avoid mechanical overload, but above a minimum critical value to avoid work hardening. 4. Increased ae/Ø % will decrease TL. The best balance of high Qw and economic TL is found with ae/Ø between 30-40% for rough milling. In finish milling the radial cut is limited to 1 mm finishing stock of the work piece. This study revealed the following important factors when considering work piece failure in the milling of Ti6Al4V: 1. Increased vc will reduce the cutting resistance of the work piece and increase Qw. However, vc must be kept below a maximum critical value to avoid work piece material burn, but above a minimum critical value to avoid burring and poor surface finish, due to tool build-up and chip jamming. 2. Increased heMax will increase the cutting resistance of the work piece and increase Qw. The heMax must be kept below a maximum critical value to avoid poor surface finish, poor flatness and parallelism (due to work piece bending). Likewise, heMax must be kept above a minimum critical value to avoid work hardening and burring. The constructed tool wear maps are validated with experimental work. This research work identified safe zones to productively mill Ti6Al4V, while producing components with a sufficient surface integrity.