Research Articles (Mechanical and Mechatronic Engineering)
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- ItemInfluence of powder characteristics on the spreadability of pre-alloyed tungsten-carbide cobalt(Southern African Institute for Industrial Engineering, 2021) Govender, Preyin; Blaine, Deborah Clare; Sacks, NatashaWith rising interest in additive manufacturing (AM) techniques, there is an increased focus on research that evaluates critical parameters that guide the selection of powders that are suitable for AM. One such parameter is a powder’s spreadability, described by metrics such as powder bed density and percentage coverage. This study focused on three spray-dried WC-Co powders (two 12 wt% and one 17 wt% Co) and evaluated the influence of typical powder characteristics, such as particle size and shape, apparent density, and flow rate, on their spreadability. It was found that particle size distribution influenced the powder spreadability. Larger particles hindered the even spreading of powder over the base plate, resulting in low powder bed density and percentage coverage. This also correlated with the powders’ apparent densities. The flow rate and angle of repose gave an indication of how cohesive the powders are. The more cohesive a powder, the poorer the spreadability, resulting in a lower powder bed density and percentage coverage.
- ItemTransient model and simulation of a single Effect water/lithium-bromide vapour absorption system(2016-12) Jeggels, D. H.; Dobson, R. T.; Mechanical and Mechatronic Engineering
- ItemExperimentally determined material parameters for temperature prediction of an automobile tire using finite element analysis(SAIMechE, 2019) Van Blommestein, W. B.; Venter, G.; Venter, M. P.The material parameters of an automotive truck tire were experimentally determined and validated for use in a thermal finite element analysis to determine the temperature distribution in the tire due to different operating conditions. Uni-axial tensile tests were performed on tire samples. The force displacement response of each was used to determine material properties by means of direct curve-fitting and iterative numerical procedures. Equivalent finite element simulation models were used to validate the properties. Hysteresis behaviour of the rubber regions were identified by dynamic mechanical analysis. Material definitions were incorporated into a finite element model to predict the steady-state heat generation and temperature distribution within a tire due to hysteresis. Experimental rolling tire temperature measurements were taken on a test bench. A comparison of the results with those obtained from the equivalent thermal models was used to validate the numerical models.
- ItemPeridynamic approach to predict ductile and mixed-mode failure(SAIMechE, 2019) Conradiea, J. H.; Becker, T. H.; Turner, D. Z.The peridynamic theory has been developed to address problems in solid mechanics regarding fracture through its integral non-local basis. It has been successful in predicting brittle cracking, however, uncertainty still remains with regards to mixed mode and ductile fracture. This work presents a study in using peridynamics to simulate fracture in mixed mode or ductile type fractures. The results are presented as a quantitative comparison between experimental tests and numerical simulations. Standard compact tension tests were performed on polymethyl methacrylate (PMMA), stainless steel 304L and aluminium 1200H4 to obtain the respective JR-curves and critical energy release rates, 𝑱ı𝖼. In addition, digital image correlation was employed to allow for qualitative observation of the fracture process and choice in peridynamic input parameters. An equivalent critical stretch was determined for each material and applied to an Arcan geometry. It is shown that the energy release rate for mode I and mode II should be considered separately. Mixed mode type failures cannot be simulated accurately by a single critical stretch criterion. Furthermore, ductile fracture requires careful consideration when selecting peridynamic input parameters.
- ItemA review of robotics research in South Africa(SAIMechE, 2019) Boje, E.; Christopher, R. L.; Fernandes, J.; Hepworth, J. H.; Kuriakose, R. B.; Kruger, K.; Lorimer, T.; Luwes, N.; Mouton, H. D.; Patel, A.; Rosmang, B.; Smit, W. J.; Stopforth, R.; Van Eden, B.; Van Niekerk, T.; Vermaak, H.; Withey, D.Robots are increasingly being used in the industry. Businesses that use robots can produce products and provide services at lower costs and with higher quality. Some industries, like automotive manufacturing, have become dependent on robots. The impact of robots on society and the greater economy is not clear. Robots threaten the jobs of lowskilled workers and even middle-skilled workers. While researchers and governments are trying to understand the impact of robots on the economy, it is commonly accepted that robots will be used more widely across all industries. With this in mind, it is useful to consider the current research in robotics at South African research institutions. This paper is such a review. It is not exhaustive, but it provides a sense of the robotics research being done in South African research institutions. It appears that research institutions do not work on common themes, yet many research groups relate their work to Industry 4.0. The review suggests that each research group is working on topics of interest to them. The implication of this is that a wide variety of robotic themes are being researched in South Africa.