The R&D Journal (ISSN 0257-9669 (print until 2008); ISSN 2309-8988 (online)) is a peer-reviewed engineering science journal, the first issue of which was published during 1985. The Journal is presently fully accredited as a subsidised research journal with the South African State Department of Higher Education and is listed in the Directory of Open Access Journals (DOAJ). In line with international trends to increase the visibility and accessibility of mechanical engineering research, the SAIMechE Council, in consultation with the Editorial Advisory Board, has decided to publish SAIMechE's R&D Journal as an open-access internet edition from 2009 onwards.
South African Institution of Mechanical Engineering
This is an open access journal which means that all content is freely available without charge to the user or his/her institution. Users are allowed to read, download, copy, distribute, print, search, or link to the full texts of the articles, or use them for any other lawful purpose, without asking prior permission from the publisher or the author. This is in accordance with the Budapest Open Access Initiative (BOAI) definition of open access. Ownership of copyright of work published remains with the authors, and published in open access under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.
CENTRAL PATTERN GENERATOR FOR PNEUMATIC SOFT ROBOTS
Soft robots open many possibilities to embed intelligence within the structure of a robot. However, central control of external valves and many control lines typifies pneumatic soft robots. This study proposes a soft pneumatic pattern generator to control the activation of two pneumatic actuators simultaneously. The concept mimics biological locomotive control, where nerve clusters distributed throughout the body control the activation of muscle fibres rather than a central brain. The brain sends out relatively simple proportional signals, converted to more intricate patterns locally. Adapting this concept to soft robotics simplifies their typical control requirements. The proposed pattern generator controls two actuators connected to a single pressure supply, resulting in each actuator articulating out of phase with the other. The pressure curves are similar for each output, producing a balanced oscillation of the two actuators. Increasing the supply pressure increases the frequency of oscillation. This configuration is better suited to control symmetric, biomimetic locomotors than previous realisable pneumatic central pattern generators.
Copyright (c) 2025 Martin Philip Venter, Johannes Roelf Vegter (Author) https://creativecommons.org/licenses/by/4.0
Financing Renewable Energy in South Africa’s Wind Industry
The transition to green energy is a pivotal endeavour for countries worldwide, and South Africa has placed a substantial focus on wind energy in pursuit of this transition. This paper delves into the intricate relationship between the cost of finance and South Africa’s transition to green energy, particularly within the wind sector. The energy transition presents an opportunity for South Africa to tackle the current electricity supply constraints while addressing developmental goals of improving access and meeting decarbonisation efforts. Green economies are economic systems considering holistic remedial measures incorporating economic, environmental, and social challenges that halt or diminish economic activities and growth. Expanding renewable technologies like wind energy can support these efforts. Because of the nature and scale of these projects, they are capital-intensive, and financing costs have a significant role in their viability. Mobilising external funding entails substantial financial expenses, adding to the complexities associated with transitioning. Despite having abundant renewable resources, South Africa faces shortages in grid connectivity in several regions, elevating investment risks, particularly in the wind energy sector. Consequently, expanding the transmission and distribution infrastructure is essential to accessing and modernising grid capacity. This requires additional investment. By reviewing existing literature from peer-reviewed journals, industry reports, policy documents, and financial indicators on the relationship between the cost of finance and the viability of wind energy projects in South Africa, this study seeks to explore the key issues affecting the de-risking of finance for renewable and wind energy. This study identifies what impacts the substantially high cost of financing renewables in South Africa. The paper demonstrates that the success of this transition lies in looking for sustainable and creative financial avenues to secure investments to support costs associated with transitioning, requiring extensive policy reform. The implications of the research findings reverberate across policy formulation and investment strategies. For South Africa, favourable financing conditions are necessary to materialise the deployment of emerging low-carbon technologies and are conducive to increasing the overall degree of electrification of the energy system in South Africa.
Copyright (c) 2025 Memory Reid, Declan Morkel (Author) https://creativecommons.org/licenses/by/4.0
Case Study: Evaluation of StressConcentration Factors in Shaft KeywaysThrough FE Analysis
The finite element method (FEM) is utilised in evaluating stresses in keyways of shafts loaded in torsion. These stress values are divided by their corresponding nominal stresses to arrive at so-called stress concentration factors, which are compared against published charts and experimental results for specific reference cases. FEM has become ubiquitous in the analysis and design of mechanical systems. While simple and well-known formulas for analytical solutions are employed to calculate nominal stresses in static design, dynamic or fatigue design is typically concerned with higher-than-nominal stresses that are associated with localised geometric stress raisers present in the system. These higher stresses are derived from nominal stresses by multiplication with an appropriate stress concentration factor. At present, though, the application of a multiplier to a nominal value seems somewhat redundant since the complete stress distribution – which includes the maximum stresses in areas of stress concentration – is a direct result from a finite element analysis (FEA). In this paper it is shown that FEA results not only compare favourably with available known results for commonly encountered stress raisers such as fillets and keyways but provide resolution to the stress distribution and paves the way for analysis and design of mechanical devices exhibiting uncommonly encountered stress raisers for which charts and formulas are not available.
Copyright (c) 2025 JP Jordaan (Author) https://creativecommons.org/licenses/by/4.0
Temperature Dependant Mechanical Property Characterisation Using Digital Image Correlation and Infrared Thermography
Accurate mechanical property charac-terisation of high-temperature high-performance materials, such as additively manufactured (AM) Inconel 718 (IN718), is crucial to ensure the reliability of components. A sudden drop in strength accompanied by significant embrittle-ment occurs in wrought IN718 near 700 ◦C. It is not clear whether AM IN718 exhibits this behaviour. The high cost of these materials and manufacturing methods necessitate the development of specimen-efficient testing techniques that allow material properties to be extracted simultaneously over a range of testing conditions. This paper presents a test setup, which is used to determine high-temperature mechanical properties over a range of operating temperatures by integrating digital image correlation (DIC) and full-field infrared thermography (IR). A purpose-designed specimen is resistively heated using a Gleeble 3800 thermomechanical simulator to create a thermal gradient across the length of the specimen. A high-temperature DIC setup and IR camera are used to capture the specimen surface’s displacement and full-field IR data. These datasets are temporally synchronised using a common triggering system and spatially correlated to allow for the extraction of temperature-dependent properties for a range of up to 100 ◦C from a single tensile test. The setup is shown to successfully capture the strength drop-off and embrittlement of AM IN718.
Copyright (c) 2024 Matthew Blackwell, Maxwell Vos, Sarah George, Melody Neaves, Thorsten Becker (Author) https://creativecommons.org/licenses/by/4.0
Determining the Upper Economic Limit of Wind Fleets
Wind fleets have become significant energy sources within national grids. However, future expansion of wind fleet capacity may result in little incremental benefit due to the inability of present grid architectures to absorb high levels of excess generation. Determining the upper economic limit is a topical issue but its solution is complicated by variations in energy system architectures and local weather conditions, making energy models essential to system planning. This paper outlines a simplified methodology, referred to as the histogram model, to calculate the upper economic limit for wind fleets, based on annual data for energy generation, recorded at hourly intervals, and the system’s headroom, defined as the difference between base load and demand. The amount of ‘useful energy’ is derived from the wind energy frequency table, the total installed wind fleet capacity, and the headroom. The calculations lead to values for the incremental decarbonisation cost, which can be directly compared to the cost of decarbonisation for gas-based energy generation. The results indicate that the upper economic limit is a wind fleet capacity of 3 times the headroom, where 78% of the required energy is derived from wind and the wind fleet efficiency is 82% (18%of the available wind energy is shed). The development of the model has implications for energy planners, who can now more easily simulate the performance of energy systems as a function of various input parameters.
Copyright (c) 2024 David R. Walwyn, Anthony D. Stephens (Author) https://creativecommons.org/licenses/by/4.0
Using Experimental Flow Visualisation Techniques to Interpret Computational Fluid Dynamics Data
A short overview of the application of schlieren and shadowgraph image construction has been presented, focusing on its use in interpreting compressible CFD data. Numerical flow visualisation methods have been used for the validation of numerical models of real flow fields but are also a valuable tool for identifying and interpreting flow field features and provide a useful means for extracting information from the numerical data that may not be readily apparent.
Copyright (c) 2024 Craig Law, Jan Nordströmb (Author) https://creativecommons.org/licenses/by/4.0
Viability of Open-Source Wind Resource Assessment Software
As the world shifts towards renewable energy sources, newer and larger projects come to fruition every year. Renewable energy projects require a complex analysis before proceeding with development. Part of this analysis procedure is resource assessment. This research aims to determine the viability of using open-source software for industry applications. This is performed through a comparison of the current industry standard software, WAsP, and Continuum. A site with a wide range of land cover conditions is chosen to see how the different software performs under varying conditions. Multiple different measured wind data inputs are used in the comparison, allowing for a comprehensive study. A focus is made on the software’s accuracy, while also comparing the analytics and outputs. The interface, workflow, input data, outputs, computational cost and additional requirements of each software package are discussed. It is found that Continuum is accurate within 8% when compared to WAsP’s annual energy production and capacity factor outputs. Due to the open-source nature of Continuum, it also lends itself to further customised developments that could be advantageous when performing resource assessments. WAsP is found to have preferential reporting outputs, however. This research highlights the opensource resource assessment process, from input to output.
Copyright (c) 2024 Stefan Karamanskia, Jan-Hendrik Grobler (Author) https://creativecommons.org/licenses/by/4.0
Recent Studies of Heat Transfer Mechanisms in a Fluidized Bed
A fluidized bed is mostly used in the thermochemical energy conversion of biomass and coal due to its high combustion and thermal efficiency, as well as its fuel flexibility, low emissions, and simple design. Heat transfer phenomena are vital in the operation of a fluidized bed reactor, therefore, it is imperative to understand the heat transfer modes in the bed for optimum design and operational performance output. This treatise presents an overview of the heat transfer status and predictions in fluidized bed combustion (FBC) for clean energy, with regards to power and heat generation. It accentuates the operational performance factors that affect the heat transfer in a fluidized bed combustion as well as the performance output. The study concludes with a summary of recent emerging trends and progress in a fluidized bed heat transfer knowledge and makes an outlook on the future regarding the challenges and opportunities for the technology. The paper also identifies areas related to fluidization, which is critical for the technology and, hence, will merit further research.
Copyright (c) 2018 F. Oppong (Author) https://creativecommons.org/licenses/by/4.0
Flow Characterisation of a Two-Phase Natural Circulation Loop
The focus of this paper is the experimental and theoretical analysis of the transient behaviour of a two-phase flow natural circulation heat transfer loop using water as the working fluid. The loop is a rectangular vertically orientated 32 mm inside diameter copper pipe of height 7 m and width 8 m. To theoretically simulate the loop, the working fluid is discretized into a series of one dimensional control volumes. When applying the conservation of mass, momentum and energy, and suitable property functions to each control volume, a series of time dependent partial differential equations is generated. Equations are then solved using an explicit finite difference method computer program created in Q-Basic64 programming language. A separated two-phase flow model is applied with frictional multipliers and vapour-liquid void fraction correlations similar to those originally suggested by Martinelli. One vertical side of the loop is heated using electrical heating elements and the other vertical side is cooled using a series of pipe-in-pipe heat exchangers. Transparent pipe lengths are inserted in the loop in order to observe the two-phase flow patterns. The loop is operated in single to two phase operating mode. A reasonable correlation between the experimental and theoretical simulations is found thereby validating the theoretical model. It is concluded that the theoretical model adequately represents the actual transient and heat transfer behaviour of the loop.
Copyright (c) 2018 P.T. Senda, R.T. Dobson (Author) https://creativecommons.org/licenses/by/4.0
Unsteady Analysis of a Generic Non- Axisymmetric Hub Endwall Contour as Applied to a Rotating Turbine at On and Off- Design Conditions
Numerous researchers have investigated various techniques to reduce loss in gas turbine engines. One such technique that has shown promise is endwall secondary flow control using non-axisymmetric endwall contouring. Previous steady state investigations have shown that the generic endwall contour designed for a cascade reduced the loss in a rotating turbine test rig. The current investigation was to determine if there were unsteady effects introduced by the contour at design and off design conditions. An experimental and numerical study was performed to investigate the rotor flow field for any unsteady changes to the rotor exit flow field. The investigation was performed at an increased loading condition, design and a decreased loading condition to determine how changes in operating condition altered the flow field. The experimental results showed that the velocity magnitude of the hub endwall secondary flow vortex system for the contoured rotor was reduced. The peak difference in oscillation of the flow was also reduced. The effect of the endwall contour reduced the over and under turning of the endwall secondary flow vortex system as well. The magnitude of the FFT at the blade passing frequency was reduced below midspan.
Copyright (c) 2018 D.I. Dunn, T.W. von Backström, G.C. Snedden (Author) https://creativecommons.org/licenses/by/4.0
Practical Adaptive Method for Heat Sealing Parameter Selection Using a Response Surface Methodology Approach
Response surface methodology was followed to construct a predictive model for the strength of film to gland seals in liquid liner bags bonded through an established heat sealing process. The method provides a structured alternative to the current trial and error approach. Once the response surface has been trained, the manufacturer can determine the effect of process changes to a known level of confidence. The model was further used to investigate how much the known process parameters contribute to variance of the established process. A model constructed using sealing head temperature, actuation pressure and dwell time is able to account for 90%of the total observed variance. Independent validation tests were conducted to verify the model, results obtained were within the constructed 95%confidence interval, and the mean approximated the true response. The model accounted for 89% of the observed variance of the validation set and is suitable for a generalized prediction.
Copyright (c) 2018 I. van Jaarsveld, M.P. Venter (Author) https://creativecommons.org/licenses/by/4.0
Composite Tube Testing and Failure Theory Computational Comparison
Composites are used in lightweight structural designs. This paper describes experimental tests conducted on composite tubes and a comparison with computational results. A test method was developed which involves an applied axial compressive load on tubes fabricated using Unidirectional (UD) carbon fibre set at +35°, to induce compressive and shear stresses along the fibres. Four major failure criteria were compared against test results: Tsai-Wu, Hoffman, Tsai Hill and Maximum Strain. The Hoffman and Tsai-Wu criteria were shown to be accurate and conservative. The Tsai-Hill criteria produced high strength ratios. The Maximum Strain criteria had the highest strength ratio, proving to be the least conservative and deviated most from computational results. This paper shows that the Hoffman and Tsai-Wu failure criteria may be used confidently in applications such as filament winding and continuous pultrusion methods, which are widely used in producing closed sections. Additionally, elastic and shear moduli were varied in simulations to show that small inaccuracies in those properties do not substantially change the maximum failure index output.
Copyright (c) 2018 M. Narsai, S. Adali, K. Veale, J. Padayachee (Author) https://creativecommons.org/licenses/by/4.0
Microstructure and Material Properties of LENS Fabricated Ti-6Al-4V Components
Cylindrical components of dimensions 15 mm in diameter and 11 mm in height were laser printed by additive manufacturing using a LENS™ system. Process parameters used in layer by layer build-ups showed that energy densities in the range of 200 – 300 J/mm3 were sufficient to produce adequate builds with improved physical structures and mechanical properties of Ti-6Al-4V ELI alloy, and subsequently used to produce tensile specimen that showed encouraging yield and tensile strengths in excess of 900 MPa. An approach to estimating the achievable tensile properties is proposed and investigated against experimental results as a means of identifying parameters to be used in studies aimed at tailoring mechanical properties of materials.
Copyright (c) 2018 N.K.K. Arthur, S. Pityana (Author) https://creativecommons.org/licenses/by/4.0
Wind Tunnel Testing Considerations in Expansion Fan/Shock Wave Interaction Studies
In the research into expansion fan/shock wave interactions, wind tunnel testing is an essential tool allowing controlled freestream conditions and variation of parameters of interest. However, certain considerations must be accounted for in the wind tunnel model design, data collection, and interpretation of the results in order to ensure good quality results and accurate interpretation thereof. Model design involved sizing of the model such that the tunnel is able to start, design of an attachment mechanism to allow mounting into the tunnel, prediction of the aerodynamic loads encountered by the model both on tunnel startup and during operation, and ensuring that the material strength of the model and support structure was sufficient to prevent failure. Schlieren flow visualization is the appropriate tool for the study of compressible flows, and careful attention was paid during setup to reduce the schlieren angle and place the cut-off at the correct location to minimise the optical aberrations of coma and astigmatism. When studying the schlieren results, visualization of the three-dimensional shock waves as regions, rather than lines, and the shock wave emanating from the lower surface of the expansion generator were taken into account for accurate interpretation. Adhering to these considerations allowed the physics involved in an expansion fan/shock wave interaction to be investigated.
Copyright (c) 2024 L. Nel, B.W. Skews (Author) https://creativecommons.org/licenses/by/4.0
CFD Investigation of the Transonic Flowfield for a Decelerating Axisymmetric Cylinder
This study is a fundamental investigation to demonstrate the effect of significant deceleration on the transonic flow field around a blunt cylindrical projectile through a numerical approach implemented in ANSYS Fluent. The projectile geometry and order of acceleration magnitude is based on a study by Jiang et al. [1], who investigated the near blast flow-field of a supersonic projectile emerging from a barrel into ambient air using an Euler solver. This study considers the region of flight once the projectile has travelled away from the barrel outlet. Two projectile shapes is considered (25×25 mm and 50×25 mm cylinders) and two deceleration magnitudes (10 000 m/s2 and 5 000 m/s2). The projectiles are decelerated from steady state Mach 1.2 to 0.8, at zero-incidence. The bow shock and wake recovery compression waves are shown to propagate forward relative to the body where the wake recovery compression waves overtake the body and appear ahead of the nose. Strong coupling exists between the near wake flow field and outer region of the separation bubble on the cylinder for an aspect ratio of 1, influencing the shock dynamics during deceleration.
Copyright (c) 2018 I. Mahome, H. Roohani, B.W. Skews, I.M.A. Gledhill (Author) https://creativecommons.org/licenses/by/4.0
Time-accurate Transonic CFD Simulation of a Generic Store Release Case
Store release from a parent aircraft in the transonic regime is a complex transient interaction to simulate, due to both compressibility effects and the strong interference flow field generated between the parent and store bodies. This work presents the results from a time-accurate transonic numerical simulation of a generic store release case, with detailed attention to ejector force profiles. Confidence limits for time-accurate trajectory calculations with STAR-CCM+® have been improved for this standard benchmark case.
Copyright (c) 2018 D. MacLucas, I.M.A. Gledhill (Author) https://creativecommons.org/licenses/by/4.0
Four-point Bending Fatigue Test Specimen Design by FEA
The FEA method is utilised in the geometric design of test specimens for use in four-point plane beam bending fatigue testing. A purpose-designed and -made testing jig is employed in the test routines. The specimen geometry is adjusted from a standard, prismatic, rectangular cross-section to a unique or nonstandard, non-prismatic, complex geometry that nearly ensures fatigue crack initiation on the free surface of the specimen away from areas of contact. The proposed method enables the engineer to retain the in-service or prevailing surface condition of the specimen material, while evaluating fatigue properties of interest at full force reversal. Due to the relatively complex specimen geometry, simple analytical methods typically used for average stress calculations in mechanical testing routines are substituted by the FEA method, allowing for accurate predictions of bending stresses, as well as reliable predictions of the location of fatigue crack initiation. The process of interaction between analysis and testing is demonstrated, resulting in a specimen design that is easy to manufacture and simple to test. Several test specimens are subjected to fatigue testing, demonstrating the accuracy and predictability of results.
Copyright (c) 2018 J.P. Jordaan (Author) https://creativecommons.org/licenses/by/4.0
Transfer Learning Strategy for Fault Identification in Wind Turbine High-Speed Shaft Bearing with Limited Samples
The application of deep learning algorithms for fault identification in wind turbine components is contingent on extensive data. Such data is often scarce, especially in the faulty category. While adversarial data augmentation helps, biases from the original data persist, and larger datasets strain computational resources. As a solution, experts are turning to transfer learning. Leveraging insights from related domains, transfer learning enables machine learning models to circumvent the exigency of training from scratch with extensive data. This study proposed a transfer learning strategy for fault identification in high-speed wind turbine shaft bearings. Two-dimensional matrices extracted from vibration signals sampled from the turbine bearings are employed to train ResNet50 and VGG16 convolutional neural network models with frozen weights based on transfer learning. While both models performed well on the normal test samples, they showed differing robustness when evaluated with noise-induced test samples. Contrarily, the ResNet50 had an accuracy, F-score, and training time of 82.21%, 78.34%, and 26.3 s, respectively, while the VGG16 model had an accuracy and F-score of 95.55% and 95.35%, respectively, but trained for 46 s. The ResNet50 may have converged quickly due to “skip connection” in its architecture, typical of residual learning models. While the VGG16 is computationally intensive, its superior performance and resilience to noise make it suited for vibration-based defect detection in the high-speed shaft bearing, where severe background noise is prevalent.
Copyright (c) 2024 S.M. Gbashi, O.O. Olatunji, P.A. Adedeji, N. Madushele (Author) https://creativecommons.org/licenses/by/4.0
The ROSIN Project and its Outreach to South Africa
In this paper, we report on the H2020 funded project ROSIN and its outreach activities to South Africa. ROSIN is concerned with developing and maintaining highquality software components for ROS-Industrial. ROSIndustrial is the industry branch of the Robot Operating System (ROS), a popular open source robot middleware. The ROSIN project is trying to overcome common criticism towards ROS and ROS-Industrial which until recently was preventing larger penetration of industrial applications with ROS. This is done by improving the quality of existing and the availability of new components. Also, educational activities are flanking the ROSIN effort to drastically increase the number of both students and industry professionals trained in ROS. This helps to increase spreading ROS-based application. As an EU project, ROSIN is active across Europe, but especially the education activities are being conducted in Africa as well. The outreach to South Africa is particularly strong here. Many students and industry professionals have already been trained and projects have been funded to advance the state of ROS-Industrial. ROS-Industrial will shape the future of automation and industrial robotics. Proficiency in ROS-Industrial thus is key to leapfrog progress in these fields. With our outreach activities to South Africa we aim to enable brilliant young minds to have part in this development.
Copyright (c) 2019 N. Limpert, P. Wiesen, A. Ferrein, S. Kallweit, S. Schiffer (Author) https://creativecommons.org/licenses/by/4.0
A Review of Robotics Research in South Africa
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 low skilled 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.
Copyright (c) 2019 E. Boje, R.L. Christopher, J. Fernandes, J.H. Hepworth, R.B. Kuriakose, K. Kruger, T. Lorimer, N. Luwes, H.D. Mouton, A. Patel, B. Rosman, W.J. Smit, R. Stopforth, B. van Eden, T. van Niekerk, H. Vermaak, D. Withey (Author) https://creativecommons.org/licenses/by/4.0
This publication presents a novel concept for an electromechanical piezoelectric actuator. This concept is intended to enable a piezoelectric actuator that exceeds the current state of the art in terms of achievable deflection at operating frequencies in the range of 0 Hz to 100 Hz. This will be realised by merging the strokes of individual piezo stacks. The concept enables linear or rotational movement. The linear version will be discussed here. An actuator of this type enables high-speed positioning of, for example, shafts, valves or lasers.
Copyright (c) 2019 O. Raffler, U. Becker, T. van Niekerk (Author) https://creativecommons.org/licenses/by/4.0
Slip Factor Prediction for Impellers with Straight, Back-swept Blades
Slip factor accounts for the deviation of the flow angle from the trailing edge blade angle at the exit of radial impellers. Accurate values are required to predict impeller torque and energy input. The slip factor prediction method for back-swept radial bladed impellers is based on the so-called single relative eddy (SRE) method, which is an approximation of the classical, two-dimensional analytical solution to the inviscid flow problem. The relatively accurate prediction of the slip factors of 19 impellers found in four data sets published since its formulation, shows the reliability of the SRE method. The characteristics of straight-bladed impeller layouts are explored and incorporated into the SRE method. It turns out that the SRE method as developed for logarithmic spiral blades predicts the inviscid flow slip factor of 42 different straight bladed impeller geometries accurately, when a correction for the critical radius ratio at low blade numbers is introduced. Predicted slip factor values are also compared to new experimental data for five different impellers with straight, back-swept blades, over a range of three blade angles and three blade numbers. Agreement is excellent near the flow coefficient corresponding to the volute design angle.
Copyright (c) 2019 T.W. von Backström (Author) https://creativecommons.org/licenses/by/4.0
A Parametric Design and Optimization Approach to Enhance the Fatigue Life of a Male Pyramid Socket Adapter
This research paper presents a parametric design approach to optimize a male pyramid socket adapter as used on a transtibial prosthetic limb for enhanced fatigue life. These adapters are prone to premature failure when used by individuals partaking in athletic sports. A parametric design and optimization approach is presented and applied. A current design was assessed for structural integrity by finite element analysis in combination with the load criteria as recommended by the ISO 10328:2016 code of practice. Highly-stressed regions where identified and improved using a parametric design approach to reduce the maximum 1st Principal stress while adhering to the industry code of practice as applicable to pyramid socket adapter design. The optimization was validated by experimentally comparing the current design and the optimised design for an appropriate load case by low cycle fatigue testing. The socket adapters were manufactured from Ti6Al4V and subjected to a simulated resultant knee bending moment. The fatigue validation indicated a significant improvement in fatigue life for the optimized socket geometry commensurate with a reduction in stress and comparison to an appropriate SN curve for Ti6Al4V. The parametric optimization process as utilized was found to be effective and should be applicable to many different applications in a more general sense.
Copyright (c) 2019 P.A. le Roux, R.F. Laubscher (Author) https://creativecommons.org/licenses/by/4.0
A Computational Study on Additively Manufactured Welding Electrodes
Advances in additive manufacturing technology present new design opportunities for metal parts that would otherwise be infeasible with subtractive manufacturing technologies. Clifford Machines & Technology (Pty) Ltd is an international producer of large mesh welding machines. The research was conducted with the aim of investigating the advantages that can be provided through the redesign of the mesh welding electrodes, for production using additive manufacturing. Simulation studies were applied in order to evaluate the performance of the redesigned electrodes and the results were compared to the existing electrodes. The results show that the electrodes designed for additive manufacturing achieved mass reductions of up to 58.2%. The electrodes were also able to support increases of current density by up to 98%, while operating at a lower temperature than the original electrodes. The study has identified the high initial cost of production and increased power consumption to be the disadvantages of additively manufactured electrodes.
Copyright (c) 2019 D.M. Kirkman, J. Pillay, J. Padayachee (Author) https://creativecommons.org/licenses/by/4.0
Bagasse-Based Desiccant Wheel Dehumidifier
Green desiccants are obtained from natural waste products like bagasse. They are fully biodegradable and cause no harm to the environment compared to chemical desiccants. A bagasse-based desiccant wheel dehumidifier that uses a green desiccant like sugarcane bagasse to remove humidity from air has been implemented and tested. Sugarcane bagasse was chosen as the main desiccant since it not only shows high adsorption properties but is also abundant in Mauritius and is much cheaper compared to other desiccants. The prototype was implemented and tested under various input parameters. A mathematical model was constructed to show how the dehumidification rate varies with airflow, desiccant wheel speed and bagasse thickness. It was found that dehumidification rate increases with an increase of the previously mentioned parameters. Another finding showed that as dehumidification rate increases, a higher regeneration rate for the desiccant is required. At maximum operating conditions, the dehumidifier has a Coefficient of Performance of 0.0118 and a Moisture Removal Capacity of 2.06 g/min. It could also be deduced that at lower temperature, the prototype has a better efficiency. A controller was implemented and incorporated in the dehumidifier which responded well to different inlet air relative humidity and temperature.
Copyright (c) 2019 H. Ramchurreetoo, B. Rajkumarsingh (Author) https://creativecommons.org/licenses/by/4.0
Experimentally Determined Material Parameters for Temperature Prediction of an Automobile Tire using Finite Element Analysis
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.
Copyright (c) 2019 W.B. van Blommestein, G. Venter, M.P. Venter (Author) https://creativecommons.org/licenses/by/4.0
Statistical Analysis of Effects on Weld Response Variables during Friction Hydro- Pillar Processing
The article provides insight to the complex relationships that exist between the selected weld process parameters and the associated effects on weld responses by application of statistical analysis relating to response predictive models for Friction Hydro-Pillar Processing (FHPP). The literature review focused at obtaining the current assumptions made with regards to the relationship between FHPP and conventional Friction Welding (FW) variations. Experimental welds were produced at varying selected process parameters; motor speed, axial force, consumed length and forging time. These parameters were compared to five weld response variables through a 27-run full factorial Design of Experiment and multiple regressions. The analysis focussed on quantifying the main effects of process parameters on energy input, temperature profile, friction time, torque and consumed rate. Comparison with experimental results served to validate the effect of dominant process parameters. The process and statistical analysis are explained in detail to assist further understanding of the applied methodology and the effect of the various process parameters on weld responses presented. Results indicate that the mathematical equation based models predict the responses adequately within the limits of welding parameters used and that no single parameter solely control the weld responses during FHPP. This study provides a clearer understanding of FHPP showing that generalised conclusions, with regards to the influences of process parameters on weld responses during conventional FW, cannot be made as the effects of these inputs differ depending on the combination of levels included in a parameter set.
Copyright (c) 2019 C. van Zyl, D. Hattingh (Author) https://creativecommons.org/licenses/by/4.0
Peridynamic Approach to Predict Ductile and Mixed-Mode Failure
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.
Copyright (c) 2019 J.H Conradie, T.H. Becker, D.Z. Turner (Author) https://creativecommons.org/licenses/by/4.0
This journal invited authors to submit two themed papers under the guest editorship of Dr Willie Smit. The purpose of the papers is to showcase robotics research in South Africa. While we tried to be as inclusive as possible, we quickly realised that the activity is larger than expected and we were unable to include all the work done in South Africa. The two papers are: E. Boje, R.L. Christopher, J. Fernandes, J.H. Hepworth, R.B. Kuriakose, K. Kruger, T. Lorimer, N. Luwes, H.D. Mouton, A. Patel, B. Rosman, W.J. Smit, R. Stopforth, B. van Eden, T. van Niekerk, H. Vermaak, D. Withey. A Review of Robotics Research in South Africa. R&D Journal, 35:75-97, 2019. N Limpert, P Wiesen, A Ferrein, S Kallweit, S Schiffer. The ROSIN Project and its Outreach to South Africa. R&D Journal, 35:98-104, 2019.
Copyright (c) 2019 Kristiaan Schreve (Author) https://creativecommons.org/licenses/by/4.0
Fall Detection System using XGBoost and IoT
This project aims to design and implement a fall detection system for the elders using machine learning techniques and Internet-of-Things (IoT). The main issue with fall detection systems is false alarms and hence incorporating machine learning in the fall detection algorithm can tackle this problem. Therefore, choosing the right machine learning algorithm for the given problem is essential and several factors need to be considered in making that choice. For this project, the XGBoost algorithm is used and the machine learning model is trained on the Sisfall dataset. A wearable device that is worn on the waist is designed using an accelerometer, a microcontroller, a Global Positioning System (GPS) module and a buzzer. The acceleration data obtained is converted into features and fed into the machine learning model which will then make a prediction. If a fall event has occurred, the buzzer is activated and emergency contacts of the victim are notified immediately using IoT and Global System for Mobile Communications (GSM). This allows the fall victim to be attended quickly, thus reducing the negative consequences of the fall. The details of the fall are stored on the cloud so that they can be easily accessed by healthcare professionals. Testing the system concluded that the XGBoost machine learning algorithm is well suited for this problem due to the small percentage error obtained.
Copyright (c) 2020 D.K. Cahoolessur, B. Rajkumarsingh (Author) https://creativecommons.org/licenses/by/4.0