Research Publications/Outputs

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2D numerical model for heat transfer on a laser deposited high entropy alloy baseplate using Comsol Multiphysics
(2021-12) Dada, A; Popoola, P; Mathe, Ntombizodwa R; Adeosun, S; Aramide, O
In an optimization study, cracks were observed in the microstructures of laser-deposited HEAs on a steel baseplate from residual stresses, thus, the optimization of crack-free microstructures was achieved by the optimization of the laser parameters by baseplate preheating attributed to the lowering of the thermal gradients of the deposition process. This study reports the finite element analysis on the temperature distribution by the moving laser modelled to achieve process optimization with the necessary boundary conditions. Simulation has been reported as a facilitating tool in predicting the behaviour of materials during process optimization. Comsol Multiphysics 4.4, was used to create a 2D transient heat transfer time-dependent model to simulate the temperature distribution and the laser heating of the A301 steel baseplate surface and determine the effect of temperature on the optimization process of the alloys. Gaussian profiles were used as the heat source distributed per time. The results are presented in terms of thermal fields and Gaussian temperature profiles. Which show the temperature distribution that occurred in the steel baseplate during fabrication and the high cooling rate of the laser additive manufacturing technique restricted thermal stresses, improving adhesion and facilitating the optimization process.
3D mapping and photogrammetry sensor payload for unmanned aerial vehicles
(2023-11) Purdon, Kyla; Van Niekerk, T; Phillips, R; Marais, Stephen T
Unmanned Aerial Vehicles (UAVs) have shown great potential for data collection and monitoring of areas. Sensors such as LiDARs and cameras can be used on UAVs for high-resolution data collection and used for various applications like Digital Surface Models (DSM), photogrammetry, inspection systems, and maintenance applications. This paper describes the design and implementation of a sensor payload for UAVs using a LiDAR sensor, camera, Inertial Measurement Unit (IMU), and Global Positioning System (GPS). The payload collects data that can be used to georeference LiDAR and camera data, which can later be used to generate a georeferenced map and perform object detection and classification.
3D printed microfluidic chip design for diagnostic studies
(2024-12) Sekhwama, Masindi; Mpofu, Kelvin T; Mcoyi, Michael P; Sivarasu, S
In this study, additive manufacturing (3D printing) is utilised to fabricate lateral flow microfluidic chips (LFMC). Our chips were designed using Autodesk design software and printed using a Formlabs 3D printer. They are printed using Formlabs V4 resin polymer. In this work, the design process is highlighted in detail and shows an LFMC design that is made for potential applications in diagnostics studies. Our study also tested the performance of one of the chip designs in actual diagnostics experiment on an optical transmittance setup with a peristaltic pump. The LFMC was integrated onto a custom-built transmittance optical biosensor to measure the transmission intensity. A real-time kinetic study was conducted using an HIV-1 oligonucleotide probe. The study involved performing real-time transmittance analysis by pumping the HIV-1 oligonucleotide probe at different flow rates, ranging from 9. 5 μm/min to 13 μm/min with intervals of 0.5 μm/min. During the experiment, transmission intensity or transmitted light was measured in real time as the oligonucleotide HIV probe bound to neutravidin immobilised on the Au metal surface. These measurements were recorded using a USB400 spectrometer, with a broad- band UV light source that emits wavelengths ranging from 400 to 800 nm. The study underscored the significance of microfluidic chips as devices capable of enhancing the performance of biosensors as well as the use of 3D printing in the design and manufacture of these microfluidic chips.
4-RRS PKM for stabilisation on a mobile sensor platform
(2023-11) Ramruthan, Kshir; Kuchwa-Dube, C
Disturbances experienced by an inspection robot can reduce the quality of its sensor measurements, which can in turn negatively affect the robot’s functionality. This research aimed to design a Parallel Kinematic Mechanism (PKM) for use as a stabilisation mechanism. The research focused on designing, simulating, building, testing, and analysing the mechanism. The PKM was modelled and simulated using MATLAB®, designed and developed using NX CAD software, and it was tested using a custom-built test rig that could simulate rotational disturbances. Using the metric of absement, the PKM significantly reduced the disturbances, depending on the disturbance induced.
A comparison of weldability and mechanical properties of additive manufactured and bulk Ti6Al4V alloy
(2024-11) Akinlabi, ET; Omoniyi, PO; Mahamood, RM; Arthur, Nana KK; Pityana, Sisa L; Skhosane, Besabakhe S; Okamoto, Y; Shinonaga, T; Maina, MR; Akinlabi, SA; Jen, TC
Titanium and its alloys, especially the Ti6Al4V, have tremendous use in the aerospace and biomedical industries. Since conceptualizing additive manufacturing techniques, it has been one of the most popular manufacturing techniques used on Titanium and its alloys. However, building large parts of the Ti6Al4V through additive manufacturing can be cumbersome due to the multiphysics involved in the heating and cooling of the material and the limited building space. This article examines the weldability of additive manufactured Ti6Al4V, manufactured through laser metal deposition (LMD) technique, and bulk sheet metal of Ti6Al4V manufactured through the rolling process. The welds were characterized using hardness, tensile, X-ray diffraction (XRD), and the evolving microstructure. Results show martensitic microstructure within the fusion zone, resulting in high hardness within the zone, which is confirmed in the XRD results. Failure occurred at the LMD heat-affected zone side of the sample due to the martensitic microstructure within the zone. The research further affirms the feasibility of joining Ti6Al4V manufactured through different routes through laser welding.
A digital twin framework to support vehicle interaction risk management in the mining industry
(2023-08) Verster, Jacobus J; Roux, Pieter W; Magweregwede, Fleckson; De Ronde, Willis; Crafford, Gerrie; Mashaba, Mathews M; Turundu, Safiya L; Mpofu, Mvikel; Prinsloo, Jacobus V; Ferreira, Pieta; Brodner, Hartmut D
In recent years, transport-related accidents, notably those involving trackless mobile machinery (TMM), have consistently ranked among the top three causes of fatalities and injuries in the South African mining industry (SAMI) [1]. These accidents arise from a combination of mechanical and technical malfunctions, environmental factors, and human or machine operator errors. Remarkably, these incidents persist despite the existence of specific regulations, standards, and codes of practice for transportation and machinery. This paper introduces a digital twin framework for TMM, which employs a systems engineering approach combined with software tools and computational analysis. This framework aims to enhance the current regulations by offering a continuous, quantitative risk assessment. By modelling and detecting non-conformance and adverse vehicle interaction events, the framework provides a quantitative risk analysis that complements the prevailing qualitative methods reliant on historical data and operational experience. A case study conducted at the CSIR main campus in Pretoria showcases the potential of the TMM Digital Twin.
Addition of Chromium and its effect on the microstructure and mechanical properties of laser- coated high carbon ferrochrome alloy on mild steel
(2021-08) Aramide, BP; Popoola, P; Sadiku, R; Jamiru, T; Pityana, Sisa L
Laser cladding is an additive manufacturing technology that can be utilized in surface strengthening, modification, and repair of components that are subjected to adverse working conditions. This can be accomplished by the addition of functionally graded material with a remarkable limit to enhancing an engaged credited property of monolithic material that is superior and better than its monolithic counterparts. Chromium addition to the microstructure of components has been found to increase the electrochemical stability, high-temperature strength and corrosion resistance of laser additive manufactured components. The current study investigates the effect of the extra addition of chromium on the hardness and microstructure of laser coated high carbon ferrochrome FeCrV15 on steel baseplate.
The adsorption of halogen molecules on Ti (110) surface
(2021-01) Tshwane, David M; Modiba, Rosinah; Govender, Gonasagren; Ngoepe, PE; Chauke, R
Adsorption of halogen on the metal surface has received much attention due to its technological applications and major relevance for material surface processing, corrosion protection and etching. In this work, first-principle approach was used to investigate the interaction of halogen molecules on Ti (110) surface. The present results revealed that adsorption of the halogen molecule is exothermic and occurs by dissociation bonding. The HF molecule was found to be more thermodynamically stable than the HI molecule. In addition, our results revealed that the adsorption of halogen ions on Ti (110) surface is energetically favourable than the adsorption of halogen molecule. The possible adsorption sites were tested, and the top site position was found to be the most favourable followed by the hollow and bridging site for both halogens. Furthermore, the results showed the linear relationship between adsorption energy strength and charge transfer. Also, the density of states and charge density difference was studied to investigate the electronic interaction. The charge redistribution showed an electron depletion on Ti atom and charge accumulation on the halogen region.
Adsorption of NH3 and NO2 molecules on sn-doped and undoped ZnO (101) surfaces using density functional theory
(2022) Dima, Ratshilumela S; Tshwane, David M; Shingange, Katekani; Modiba, Rosinah; Maluta, NE; Maphanga, Rapela R
The adsorption and interaction mechanisms of gaseous molecules on ZnO surfaces have received considerable attention because of their technological applications in gas sensing. The adsorption behavior of NH3 and NO2 molecules on undoped and Sn-doped ZnO (101) surfaces was investigated using density functional theory. The current findings revealed that both molecules adsorb via chemisorption rather than physisorption, with all the adsorption energy values found to be negative. The calculated adsorption energy revealed that the adsorption of the NH3 molecule on the bare ZnO surface is more energetically favorable than the adsorption of the NO2 molecule. However, a stable adsorption configuration was discovered for the NO2 molecule on the surface of the Sn-doped ZnO surface. Furthermore, the adsorption on the undoped surface increased the work function, while the adsorption on the doped surface decreased. The charge density redistribution showed charge accumulation and depletion on both adsorbent and adsorbate. In addition, the density of states and band structures were studied to investigate the electronic behavior of NH3 and NO2 molecules adsorbed on undoped and Sn-doped ZnO (101) surfaces.
Adsorption-desorption of F2 diatomic molecule on Ti (100) surface at different coverages
(2021-12) Tshwane, David M; Modiba, Rosinah; Govender, Gonasagren; Ngoepe, PE; Chauke, HR
Fluorine molecules and ions are used as an etchant for metal surface processing. The presence of fluorine significantly influences the electrochemical behaviour on a metal surface, which has major relevance for etching, corrosion, electro-catalysis and galvanic deposition processes. Although the fluorine ions play an important role in metal surface etching, the studies remain limited and unclear, especially at the atomistic scale. In this work, density functional theory is used to investigate the structural and electronic properties of F2 diatomic molecule adsorption on Ti (100) surface at different coverages. Results revealed a dissociative adsorption mechanism of F2 on the Ti (100) surface. Adsorption energy analysis of F2 on Ti (100) surface denotes an exothermic process. Moreover, increasing F2 coverage resulted in the formation of TiF4 and Ti2F6 molecules on the surface. In addition, the calculated heat of formation for TiF4 was found to be more favourable than Ti2F6 species. Calculated desorption energies for TiF4 and Ti2F6 is 11.73 eV/atom and 9.04 eV/atom, suggesting non-spontaneous.
An optical gas imaging technique based on strobed illumination
(2024-12) Chirindo, Mathews; Cox, Ettienne; Duness, Kahesh
Gas leakage from equipment poses undesirable safety, environmental and operational impacts. Many optimal gas imaging techniques exist which detect and visualize gas plumes. However, most of these techniques struggle to produce clear images when the temperature gradient between the scene background and the gas plume is small. This paper presents an optical gas imaging technique that is based on strobed illumination, wherein the strobing frequency of the illuminating device is associated with the camera frame rate. Experimental test results are presented to show the improved detection of volatile organic compound gases during strobed illumination under dark room laboratory conditions where the percentage contrast value of the illuminated gas relative to its background varies by 50.8% The test results for the detection of sulphur hexafluoride gas and liquid petroleum gas under an outside environment are also presented.
Analysis of dry sliding wear performance of tribaloy T-800/Tungsten carbide coating deposited via laser cladding assisted with preheating
(2022-10) Nyadongo, ST; Olakanmi, EO; Pityana, Sisa L
Shafts, gears, axles and crankshafts, which are exposed to severe sliding wear environment, are made from wear resistant EN8 medium carbon steel. The wear resistance of EN8 can be enhanced by depositing it with laser cladding assisted with preheat (LCAP) fabricated T-800/WC composite coating. A systematic study via accurate, reproducible ball on disk tests which explores how extreme sliding force and velocity influence wear resistance and mechanism of the coating and the uncoated EN8 is carried out. It was revealed that EN8 substrate has up to six (6) times more special specific wear rate (SSWR) relative to T-800/WC coating. An increase in sliding force increased the SSWR whilst an increase in sliding velocity reduced the SSWR for the LCAP coating. Alumina (Al2O3) counter wear body exhibited the highest SSWR compared to silicon carbide (SiC) and silicon nitride (Si3N4) counter wear body on both T-800/WC and EN8. Oxidative and abrasive wear mechanisms were evident on the coating. A wear mechanism for the T-800/WC was deduced which showed abrasive wear, oxide layer formation, breaking of the formed oxide layer and back to abrasive wear during dry sliding wear.
Analysis of failure characteristics of screen plates of ring hammer crusher used in coal handling applications
(2024-08) Kyekyere, E; Olakanmi, EO; Prasad, RVS; Matshediso, B; Motimedi, T; Botes, A; Pityana, Sisa L
The screen plate, a critical component within a ring hammer crusher (also known as a ring granulator or rolling ring crusher), plays a vital role in the secondary crushing of coal. Functioning both as a platform for coal crushing and as a sieve to achieve the desired coal size, it is essential to understand and examine its failure characteristics to enhance its mechanical and wear resistance properties in coal handling applications. This study thoroughly explored the failure modes, mechanisms, and underlying causes of screen plate failures. Microscopic techniques such as optical microscopy (OM), scanning electron microscopy (SEM), Vickers microhardness test and spectrochemical analysis were utilised to identify the failure mechanism. Failure modes identified from the macroscopic analysis were discharged hole widening, hole wall break-off, plate edge crack, plate fracture, one-sided edge slimming, and general surface wear of the screen plate. The fractographic and wear track analysis identified the principal failure mechanisms of three-body abrasive wear, two-body sliding abrasion wear, shear-induced fatigue fracture and brittle shear fracture. The root causes of the failures are the rotor’s direct impact, defects in the parent material, the presence of hard materials in the coal and the use of unsuitable steel grade in the screen plate manufacturing. The service life of the screen plate can be improved through proper material selection, uniform crusher feeding, surface modification of the surface of the “as purchase” screen plate with appropriate wear-resistant materials, and adherence to good maintenance practices.
Anomaly detection monitoring system for healthcare
(2021-01) Boloka, Tlou J; Crafford, Gerhardus J; Mokuwe, Mamuku W; Van Eden, Beatrice
Most developing countries suffer from inadequate health care facilities and a lack of medical practitioners as most of them emigrate to developed countries. The outbreak of the COVID-19 pandemic has left these countries more vulnerable to facing the worse outcome of the pandemic. This necessitates the need for a system that continuously monitors patient status and detects how their physiological variables will change over time. As a result, it will reduce the rate of mortality and mitigate the need for medical practitioners to monitor patients continuously. In this work, we show how an autoencoder and extreme gradient boosting can be merged to forecast physiological variables of a patient and detect anomalies and their level of divergence. An accurate detection of current and future anomalies will enable remedial action to be taken by medical practitioners at the right time and possibly save lives.
Applications of microfluidics in biosensing
(2024) Sekhwama, Masindi; Mpofu, Kelvin T; Sivarasu, S; Mthunzi-Kufa, Patience
Microfluidic devices have become a vastly popular technology, particularly because of the advantages they offer over their traditional counterparts. They have such a wide range of uses and can make complex tasks quite efficient. One area of research or work that has benefited greatly from the use of microfluidics is biosensing, where microfluidic chips are integrated into biosensor setups. There are growing numbers of applications of microfluidics in this area as researchers look for efficient ways to tackle disease diagnostics and drug discovery, which are critical in this era of recurring pandemics. In this work, the authors review the integration of microfluidic chips with biosensors, as well as microfluidic applications in biosensing, food security, molecular biology, cell diagnostics, and disease diagnostics, and look at some of the most recent research work in these areas. The work covers a wide range of applications including cellular diagnostics, life science research, agro-food processing, immunological diagnostics, molecular diagnostics, and veterinarian diagnostics. Microfluidics is a field which combines fundamental laws of physics and chemistry to solve miniaturization problems involving fluids at the nanoscale and microscale, and as such, the authors also examine some fundamental mathematical concepts in microfluidics and their applications to biosensing. Microfluidics has relatively new technologies with great potential in terms of applications.
Applying design for additive manufacturing to existing aerospace parts
(2023-11) Bester, Duwan C
Additive Manufacturing has widely been used in the aerospace industry. However, local uptake in the aerospace industry has been slow with mostly additively manufactured polymer parts being used. The Advanced High Performance Reconnaissance Light Aircraft (AHRLAC), which is a locally produced military aircraft, is well positioned to prove the local capabilities in Metal Additive Manufacturing to the local Aerospace industry. Two parts of this aircraft were identified through prior experience in Additive Manufacturing and taken through the Design for Additive Manufacturing process. The identified parts were a forward cockpit control cable mount and a canopy guide. The parts were redesigned using topology optimisation and, in both instances, a weight, cost, and lead time reduction was achieved.
ARGUS: A pole climbing surveillance robot
(2023-11) De Ronde, Wiilis; Bosscha, Peter A; Marais, Stephen T; Pretorius, A
Due to the high prevalence and unpredictability of violent protest action in South Africa, a need has arisen for rapidly deployable surveillance. This paper proposes an Automated Robotic Guardian for Urban Surveillance (ARGUS) platform, a wheeled, pole climbing robot as a potential solution. The platform is designed to attach to and traverse up existing cylindrically shaped infrastructure, such as light posts, enabling easy deployment in urban environments. The robot is intended for varioussurveillance needs, such as public safety at events, and periods of unrest or protest action. Following a detailed concept design stage, simulated results are presented for the proposed robot. This includes comprehensive CAD modelling, static force and torque calculations of the pole climbing robot, and finite element analysis of the component stresses while positioned on the pole. The robotic platform is currently in production and future work will include experimental validation of the simulated system.
Assembly line quality assurance through hand tracking and object detection
(2022-10) Mokuwe, Mamuku W; Goorun, Yurisha; Crafford, Gerhardus J
This work presents a vision-based quality assurance system that does assembly line monitoring. The system is developed using machine learning hand tracking and object detection methods to monitor the worker’s hand movement while evaluating the correctness of the assembly. Feedback about the order of the steps the worker has taken is continuously shown to the user. This work has the potential to reduce the amount of manual work required for quality assurance in assembly line.
Assessing the nanomechanical, wear and thermal stability of Ti-Al-Si-V alloys produced via laser engineered net shaping (LENS) in-situ alloying
(2024-12) Raji, SA; Popoola, API; Pityana, Sisa L; Tlotleng, Monnamme
Titanium aluminide (TiAl) intermetallic alloys are highly recognized because of their lightweight qualities and are particularly useful for replacing heavier Nickel-based (Ni-based) superalloys in high- temperature components. This study fossed on the investigation of the nanomechanical, wear, and thermal stability of intermetallic Ti-Al-Si-V alloys fabricated by in situ alloying with elemental metal powders using the laser engineered net shaping (LENS) technology. The impact of Vanadium (V) feed rate was examined both before and during the annealing heat treatment, which involved 60mins at temperatures of 1200 and 1400°C, and furnace cooling (FC) conditions. After heat treatment (1200°C and 1400°C), it was discovered that V addition enhances the Ti-Al-Si-V alloy's nanomechanical properties. According to the nanoindentation results, the mechanical characteristics of the heat-treated samples were typically better than those of the as-deposited alloy and were equivalent to the qualities of commercially available TiAl alloys. The alloy that was heat-treated at a temperature of 1200°C exhibited better tribological and thermal stability. Lastly, the as-deposited sample performed better in terms of tribological and thermal stability aspects than the sample that was heat-treated at 1400°C.
Biosensing multidrug-resistant TB genes using SPR
(2024-01) Chauke, Sipho H; Ombinda-Lemboumba, Saturnin; Dube, FS; Mthunzi-Kufa, Patience
Tuberculosis (TB) is one of the most prevalent infectious diseases globally. Although it is curable, several factors, such as the inappropriate use of treatment drugs lead to drug-resistant strains of TB. The burden of infection is disproportionately high in low-income and resource-limited settings. Furthermore, this disparity is exacerbated in patients with already compromised immune systems. Therefore, early detection and treatment of TB play an important role in reducing the spread and progression to drug-resistant disease forms. There are currently a few rapid multi-drug resistant TB diagnostic tests available, however, most are limited due to costs and accessibility. Several genes, such as catalase-peroxidase (katG) and enoyl reductase (inhA) genes, contain mutations that are responsible for resistance to the TB drug, isoniazid. We therefore, aim to use a custom-built surface plasmon resonance (SPR) system to detect katG and inhA genes. Deoxyribonucleic acid (DNA) probes, specific for katG and inhA, were used as biorecognition elements to capture katG and inhA target DNA. The katG and inhA gene-specific DNA probes were immobilized on a gold-coated glass sensor chip before the target DNA was introduced for detection. As a negative control, a mismatched probe, unspecific to both genes was used for confirmation of the absence of the two genes in the experimental setup. The specificity and sensitivity of the capture probes to the target DNA were investigated using the gold-coated glass sensor chip on the SPR setup. The changes in the resonance angle dip indicated the hybridization of the target DNA and the capture probe. The results from this study will contribute to the optimization of an optical-based biosensor detecting drug-resistant mutations.

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