Conference Proceedings (Mechanical and Mechatronic Engineering)

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    Development of a model for predicting cycle time in hot stamping
    (Elsevier, 2018) Muvunzi, R.; Dimitrov, D. M.; Matope, S.; Harms, T. M.
    In manufacturing, reducing the cycle time results in lower production costs. The cycle time in a hot stamping process affects the quality characteristics (tensile strength) of formed parts. A faster cooling rate (˃27 K/s) of the blank guarantees the production of a part with the required microstructural properties (martensite). This compels researchers to continuously develop ways of increasing the manufacturing speed. On the other hand, it is important to predict the minimum cycle time for a given set of parameters which does not compromise the quality of formed parts. In this paper, a model for predicting the cycle time for a hot stamping process is presented. The lumped heat capacitance method is used in formulating the model since the temperature gradient across the blank and heat transfer within the plane of the blank are considered negligible. To validate the equation, a finite element simulation was conducted using Pam-Stamp software. The results show that the proposed model can be useful in further studies targeted towards cycle time reduction in hot sheet metal forming processes.
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    Solution heat treatment of single crystal castings of CMSX-4 nickel-base superalloy
    (Faculty of Engineering, Department of Industrial Engineering, Stellenbosch University, 2016) Rzyankina, E.; Pytel, M.; Mahomed, N.; Nowotnik, A.
    An investigation of the microstructure and mechanical properties for heat treated directionally cast rods, produced from the nickel-based superalloy, CMSX-4, is presented. The rods were cast using the Bridgman method for manufacturing single crystal structures. The microstructure of the cast rods consists of γ and γ' precipitates. This microsegregation has a negative effect on the microstructure and, hence, the mechanical properties of the castings. The solution heat treatment of the second generation, single crystal Ni-base superalloy, CMSX-4, is known to dissolve the eutectic γ and γ' region. This requires temperatures up to 1316°C and approximately 45 hours total time. These high temperatures and long processing times result in high costs. The aim of this study is to investigate the effect of the heat treatment protocol on the extent of improvement of quality of single crystal castings, as a basis for determining cost feasibility in practice.
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    Investigating the energy efficiency and surface integrity when machining titanium alloys
    (Faculty of Engineering, Department of Industrial Engineering, Stellenbosch University, 2016) Tayisepi, N.; Laubscher, R. F.; Oosthuizen, G. A.
    Sustainable manufacturing strategies will need to address the resource efficiency and surface quality challenges in cutting processes. This paper aims to provide a systematic methodology for modelling the input and outputs of a turning process to find the best balance between production rate and input cost, while improving or adhering to the quality standards. Ti6Al4V were cut under flood cooling using carbide cutting tools and a Taguchi design of experiments was used with ANOVA. Surface integrity and energy use were measured and analysed for selected cutting parameters. The experimental results highlighted the importance of selecting optimum cutting parameters and machining strategy. More energy was consumed at lower cutting parameters, whilst higher feed rates resulted in less energy consumption, but lower surface finish quality. These results will also assist to define the boundary conditions for various input parameters.
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    Communication in a LabVIEW based holonic controller
    (Faculty of Engineering, Department of Industrial Engineering, Stellenbosch University, 2016) Masendeke, D. M.; Basson, A. H.
    ENGLISH ABSTRACT: This paper presents a communication approach for a holonic controller developed in LabVIEW. The controller is aimed at station that forms part of a reconfigurable assembly cell. The objective of the research was to evaluate the extent to which LabVIEW facilitates reconfigurability in this context. The holons were implemented by using LabVIEW’s producer/consumer (to achieve asynchronous inter- and intra-holon communication) and state machine architectures. The paper discusses some implementation considerations. The paper shows that LabVIEW offers some attractive facilities for lower levels of reconfigurable control systems.
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    A concentrating solar power value proposition for South Africa
    (Energy Research Centre, University of Cape Town, 2013) Gauche, Paul; Von Backstrom, Theodore W.; Brent, Alan C.
    Concentrating solar power (CSP) offers the potential for a high degree of localization and an alternative strategy to meet electricity demand for South Africa in a future of uncertain conventional resources. The integrated resource plan (IRP) makes strides to introduce renewables to the electricity generation system by 2030, but we argue that the proposed energy mix is too reliant on resources that are not only unsustainable but also at risk in the short to medium term. Coal and other conventional resources may be more limited than originally anticipated, which if true, requires action to be taken soon. CSP is currently the only sustainable and dispatchable energy technology that could domestically supply a significant portion of South Africa’s electricity needs. A balanced mix of PV, wind and CSP can provide the energy supply needed in South Africa, but steps are required soon to take advantage of the localization potential and excellent sustainable energy resources.