Browsing by Author "Sacks, N."

Now showing 1 - 6 of 6
  • Thumbnail Image
    Item
    Characteristics of single layer selective laser melted tool grade cemented tungsten carbide
    (Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering., 2016) Van Staden, A. C.; Hagedorn-Hansen, D.; Oosthuizen, G. A.; Sacks, N.
    Cemented carbide tools, specifically tungsten carbide based alloys, have found a wide range of application fields including manufacturing, agriculture, and mining, among others. A need for customised tooling solutions using cemented carbide alloys have been identified. Additive manufacturing is chosen as a novel manufacturing process due to its superior material and process flexibility. The study investigates the melting behaviour observable during the SLM process using a tool grade cemented tungsten carbide powder. The laser power, scan velocity, and hatch spacing of the SLM process are varied and single powder layers are sintered accordingly. This is done to determine the varying influence these parameter combinations have on the melting behaviour of the material during sintering. For each set of parameter combinations the test samples were analysed using microscopic imaging. It is found that a combination of high laser power, high hatch spacing, and low scan speed yields the best results.
  • Thumbnail Image
    Item
    The development of experimental machines in order to understand the demands of incremental sheet forming of titanium
    (Industrial Engineering, Stellenbosch University, 2011-09) Oosthuizen, G. A.; Nortje, H.; Herselman, E. J.; Akdogan, G.; Sacks, N.
    Titanium sheet-metal is extensively used for aerospace and biomedical applications. The diversified customer's demands have created a recent trend towards the small batch production. In this context incremental forming has attained great attention. Therefore, experimental machines are designed and manufactured to simulate the harsh forming conditions. In the fretting machine the combination of a normal force and small vibrations may constitute a wear phenomenon known as fretting wear. The friction and wear properties of the tool, lubrication and work piece materials are tested using the sliding test machine. The steps to evaluate and develop these machines as research tools are illustrated and discussed. The fretting- and sliding machines help to investigate suitable forming tools, forming parameters and lubricant strategies for incremental forming of titanium. It is concluded that these simulation tools provide more efficient and cost effective ways to understand the effects of changing the forming conditions.
  • Thumbnail Image
    Item
    Die sheet hydroforming of a complex-shaped AA2024-W aircraft skin panel — from concept to final component
    (Southern African Institute for Industrial Engineering, 2021) Serfontein, J. L.; Damm, O.; Sacks, N.; Gerber, W. T.; Botha, M. J.
    ENGLISH ABSTRACT: In terms of project risk management, ‘systemic risk’ is identified as risks which are artefacts of the environment which a project is executed in, and are related to (i) the project team’s actions, (ii) how project controls are managed and interact, and (iii) how the project is planned and executed. This paper proposes a methodology to estimate the cost impact of systemic risk on a portfolio of projects by using risk quantification and Monte Carlo simulation, in the absence of a validated parametric risk model, to estimate the systemic risks in an entire portfolio of projects. The case study simulation results indicate a significant effect of systemic risks on the project portfolio risk profile, where systemic risks increased the P80 value of the contingency requirement by +85.6%. The successful management of systemic risk would contribute to project success by limiting unnecessary waste.
  • Thumbnail Image
    Item
    Investigating the feasibility to remove alpha case from titanium alloys with machining
    (Faculty of Engineering, Department of Industrial Engineering, Stellenbosch University, 2016) Conradie, F. W.; Oosthuizen, G. A.; Sacks, N.
    Titanium as an alloy offers excellent material properties including corrosion resistance, biocompatibility and high specific strength. These properties make titanium alloys highly desirable in demanding applications and specialised industries such as aerospace and orthopaedic prosthesis. However, the formation of a hard and brittle alpha case layer at elevated temperatures requires hot forming processes to be conducted either in inert atmosphere, or vacuum. Alternatively, alpha case could be removed post process by chemical milling which requires high capital costs as well as stringent safety measures. Alternative removal techniques are therefore under investigation and one such option is machining removal which can make use of the already established South African machining industry. Excessive wear due to the hardened alpha case layer results in machining removal not currently being viewed as economically feasible. This investigation therefore focusses on identifying possible machining guidelines for the removal of alpha case from titanium alloys. Thereafter, a comparison is made between machining removal of alpha case with chemical milling in the context of the South African manufacturing industry. It was observed that alpha case is readily removed at all machining conditions and that excessive notching and accelerated wear rates are experienced at high cutting speeds. Wear rates more commonly attributed with titanium machining is observed at lower cutting speeds.
  • Thumbnail Image
    Item
    Investigating the performance of custom manufactured cermet mounted points when grinding Ti6Al4V alloys
    (Central University of Technology, 2017) Enever, A. A.; Oosthuizen, G. A.; Sacks, N.; Burger, M. D.; Oberholzer, J. F.
    ENGLISH ABSTRACT: The use and implementation of mounted grinding points in industrial applications are wide spread, ranging from the bio-medical and automotive industries to the aerospace and mining industries. These smaller variants of the larger, more conventional grinding wheels are more affordable to produce, but equally effective in grinding applications. Generally, the abrasive materials implemented in the manufacturing of mounted points do not include the cermet WC-12-wt-%-Co, but rather use alumina- or silicon carbide. This study investigates the use of this WC-12-wt-%-Co cermet as abrasive medium. The resin was varied to manufacture two sets of cermet WC-12-wt-%-Co mounted points that contained 12-wt-% and 16-wt-% resin content, respectively. The grinding performance of these mounted points were evaluated in terms of the tool wear rate, the surface finish and the surface hardening of the Ti6Al4V work piece. The grinding tool wear rate of the 16-wt-% mounted points were more gradual than for the 12-wt-%. The 16-wt-% mounted points produced a smoother surface finish and work hardening occurred on most of the Ti6Al4V work piece surfaces.
  • Thumbnail Image
    Item
    Performance evaluation of custom manufactured WC-12wt%Co abrasive grinding wheel
    (Faculty of Engineering, Department of Industrial Engineering, Stellenbosch University, 2016) Enever, A. A.; Oosthuizen, G. A.; Sacks, N.
    Grinding is a material removal process making use of geometrically nondefined tool edges, or abrasive particles, which is bonded together in the form of a grinding wheel to cut, or machine, a material into shape. The materials used as the abrasive is most commonly aluminium oxide or silicon carbide. These abrasives are normally bonded with a vitrified or resinoid bonding to form the grinding wheel. Grinding wheel applications typically range from wood and soft metal grinding to hard carbide steel and ceramic grinding. There is thus a gap in the variety of available grinding wheels for a multipurpose grinding wheel. This paper will explore the application of tungsten carbide (WC-12wt%Co) as an alternative abrasive material for a grinding wheel and will be bonded with inexpensive resin. Tungsten carbide falls in the cemented carbide family of hard materials, having a high hardness-to-toughness ratio. This is advantageous for the machining of titanium alloys and is the workpiece material. The paper will describe the process of custom manufacturing of the WC-12wt%Co grinding wheels for experimental purposes.