Doctoral Degrees (Mechanical Engineering)

Permanent URI for this collectionhttps://hdl.handle.net/10413/6861

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Analysis and design optimization of laminated composite structures using symbolic computation.
(1994) Summers, Evan.; Adali, Sarp.; Verijenko, Viktor.
The present study involves the analysis and design optimization of thin and thick laminated composite structures using symbolic computation. The fibre angle and wall thickness of balanced and unbalanced thin composite pressure vessels are optimized subject to a strength criterion in order to maximise internal pressure or minimise weight, and the effects of axial and torsional forces on the optimum design are investigated. Special purpose symbolic computation routines are developed in the C programming language for the transformation of coordinate axes, failure analysis and the calculation of design sensitivities. In the study of thin-walled laminated structures, the analytical expression for the thickness of a laminate under in-plane loading and its sensitivity with respect to the fibre orientation are determined in terms of the fibre orientation using symbolic computation. In the design optimization of thin composite pressure vessels, the computational efficiency of the optimization algorithm is improved via symbolic computation. A new higher-order theory which includes the effects of transverse shear and normal deformation is developed for the analysis of laminated composite plates and shells with transversely isotropic layers. The Mathematica symbolic computation package is employed for obtaining analytical and numerical results on the basis of the higher-order theory. It is observed that these numerical results are in excellent agreement with exact three-dimensional elasticity solutions. The computational efficiency of optimization algorithms is important and therefore special purpose symbolic computation routines are developed in the C programming language for the design optimization of thick laminated structures based on the higher-order theory. Three optimal design problems for thick laminated sandwich plates are considered, namely, the minimum weight, minimum deflection and minimum stress design. In the minimum weight problem, the core thickness and the fibre content of the surface layers are optimally determined by using equations of micromechanics to express the elastic constants. In the minimum deflection problem, the thicknesses of the surface layers are chosen as the design variables. In the minimum stress problem, the relative thicknesses of the layers are computed such that the maximum normal stress will be minimized. It is shown that this design analysis cannot be performed using a classical or shear-deformable theory for the thick panels under consideration due to the substantial effect of normal deformation on the design variables.
Best practice for personnel, material and rock transportation in ultra deep level gold mines.
(2003) Rupprecht, Steven Michael.; Verijenko, Viktor.
Ultra deep mining presents many challenges to the mining engineer, one of which is the logistics to support mining operations quickly and efficiently. Typically, Witwatersrand gold mines operate at depths in excess of 2000 m with stoping taking place to 3500 m and investigations underway to mine to a depth of 5000 m. As mining progresses deeper and further from the shaft, the role of logistics becomes increasingly important if production targets are to be achieved. Access to the workings is often via sub vertical and even tertiary subvertical shaft systems with working faces as far as five kilometers from the shaft. It is inevitable therefore, that distance will negatively impact the working time available at the stope face, material transportation and distribution, as well as the removal of broken ore. Possible solutions to these logistical problems may be found in the use of different transportation systems or by applying sound design and operational principles to transportation systems, both in the horizontal and instope areas. This thesis investigates the challenges of logistics for ultra deep level gold mining in the Witwaterstrand basin for mining layouts planning to mine between 3000 m and 5000 m underground with typical horizontal distances of over 3000 m. The transportation needs analysis recognised that vertical transportation is a wellmanaged and organised system and is mainly the same for both shallow and deep level operations. As a result of this, the thesis only focuses on the logistical issues of the horizontal and in-stope processes. The literature review indicates that the majority of work previously conducted on transportation focused around the area of horizontal transportation with limited inputs to in-stope transportation systems. The review concludes that the traditional locomotive transportation system is the most applicable mode of horizontal transportation. Thus, special emphasis is given to trackbound transportation. An integrated approach is taken towards mine transportation advocating that underground logistics be considered as equally important as any other discipline, Le. rock engineering, ventilation, etc. In addition, the transportation process should consider each area equally important. All to often, the transportation of rock is considered of paramount importance over the transportation of personnel and material. Thus, the planning any transportation system should incorporate personnel, material and rock. To enable this, scheduling, communication and control are important with special attention required for transfer points in the transportation system. As each site has its own particular requirement, thus the final transportation systems must be drawn up based on the specific requirements of each mine. A guideline is proposed for the design of ultra deep level underground transport systems for personnel, material and rock transportation. Thus, providing mining engineers with sufficient information and data to select an appropriate transportation system to meet specific mine requirements. The thesis highlights areas requiring consideration by mine engineers when designing a transportation system from shaft to the working face.
Combustion studies of hybrid nanoadditive doped waste cooking oil biodiesel and its blends in compression ignition engine.
(2021) Maverengo, Hilton.; Inambao, Freddie Liswaniso.
South Africa, among the developing nations in sub-Saharan Africa lacks technologies for converting crude biooil into biodiesel to run fuel CI engines. The country has also struggled to identify a suitable feedstock that can be used for biodiesel production. This research was therefore aimed at analysing the suitability of mixed waste cooking oil (WCO) biodiesel doped with hybrid nano particles as a viable fuel for diesel engines. The utilization of WCO as feedstock for biodiesel is garnering attention since it does not impact on the food supply chain and provides a solution to the challenges associated with its disposal. Biodiesel acceptance has been hampered by three main issues. These are related to higher production costs linked to feedstock, higher nitrogen dioxide emissions, and a lack of economic evaluation of technologies incorporating different alcohols and catalysts. This research performed investigations to develop solutions to circumvent all these challenges. Regarding high feedstock cost, WCO was identified to present an easily available solution since it is acquired at a low cost and its usage helps to solve the disposal problem. Manufacture, assessment, and engine testing of biodiesel from WCO was conducted to evaluate its viability as a potential feedstock for biodiesel. From the derived results, WCO oil has higher oil yields and excellent fuel properties and therefore is a viable feedstock to create biodiesel. Transesterification, a biodiesel creation measure, was performed utilizing methanol and NaOH or KOH as catalysts. This feedstock showed some favourable engine exhaust emission behaviour, but on engine performance considerable shortfalls were noted when evaluated against fossil diesel (FD) fuels. Lower brake thermal efficiency and higher fuel consumption were noted when the neat fuel blends with fossil diesel were tested in two-cylinder compression ignition engines. Higher NOx emissions were also noted with WCO and its blends when evaluated against FD. Three options are available to dealt with the above problems, namely, engine modification, exhaust after-treatment, and fuel reformulation. Fuel reformulation is the most promising due to its easy implementation and cheaper cost. The researcher’s search for the most relevant solution resulted in identification of hybrid nanoparticles consisting of cerium oxide and aluminium oxide as the most appropriate solutions. WCO biodiesel and its blends were doped with nanoparticles and tested in two-cylinder compression ignition (CI) engines and results compared with those of FD. From the experimental analysis, addition of hybridized nano additives improved BTE by a maximum value of 6.22 % compared to FD fuel when evaluated against load. A maximum decrease in BSFC of 10.20 % was noted with hybrid nano fuel WCO20A50C50 compared to FD fuel. A significant reduction in NOX of 25.62 % was found compared to FD. CO, unburnt hydrocarbons (UBHC) and smoke opacity were reduced by 36.8 %, 27.8 % and 17.68 % respectively compared to FD. WCO20A50C50 produced the most superior characteristics of all the fuels tested in this research. To understand the combined impact of hybrid nanoparticles and other engine conditions on performance and emissions, design of experiments (DOE) using the response surface method (RSM) was performed to model and optimize WCO20 performance and emissions parameters. This was accomplished by utilizing a variable compression engine and selecting three variables, namely, hybrid nanoparticle blends (fuel blend), compression ratio (CR) and load as input parameters, while the analyzed responses were brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), nitrogen oxides (NOX), unburnt hydrocarbons (UBHC), carbon monoxide (CO) and smoke. The outcomes from this investigation showed that RSM is a viable technique for improvement of the parameters of biodiesel blends doped with nanoparticles in diesel engines. Considering the intricacy of biodiesel production measures, process development, technical assessment, and advancement of biodiesel according to the entire chain, is fundamental for improving its performance and increasing its global adoption. A detailed biodiesel process flow design was developed and economic assessment incorporating material performed. The designed plant is expected to produce 16.88 tons per annum. The cost of biodiesel was evaluated based on researched cost variables and plant data which resulted in a biodiesel production cost of ZAR10.10 per kg giving a total production cost of ZAR10,100.00 (US$673.33) per ton. A CaO ethanolysis catalysed process was shown to be the most appropriate process for WCO production – the reaction was faster and produced a high yield. South Africa, among the developing nations in sub-Saharan Africa, has a huge capacity to produce its own renewable fuels but at present there is an absence of localized and effective applicable techniques for converting crude bio-oil into biodiesel to run fuel CI engines. Therefore, the discoveries of the present doctoral study are important because they demonstrate that it is viable to convert WCO to biodiesel and that its properties can be enhanced with the addition of nano particles, thereby demonstrating that its performance is even better than that of FD. Furthermore, a more sustainable CaO catalysed ethanolysis, with superior yields and locally produced in comparison to methanolysis, has been effectively developed and evaluated, as per the objectives of the thesis.
Communication, mapping and navigational aspects for a free-ranging, automated guided vehicle.
(1992) Asbury, James.; Katz, Z.
A free-ranging automated guided vehicle incorporating navigation and radio communication for use in a fully automated flexible manufacturing system has been developed. A vehicle, operating as a complete subsystem, was built and tested in an integrated control environment and proved to have promising results. various radio communication techniques are examined and the design and testing of a low cost, wireless, two way communication link is detailed. A novel, flexible infrared navigation technique was developed and incorporated into the AGV subsystem. Path planning and a flexible real time path modification system was formulated using an innovative program with an interpolative visual display unit and digitiser. Data transfer to and from the vehicles in a real time integrated system is covered. System integration for an free-ranging automatic guided vehicle is discussed covering aspects of communication, mapping and navigation. Specific needs for a free-ranging automatic guided vehicle, are presented. The unique design features of navigation and mapping outlined in this thesis has resulted in a low cost, free-ranging, autonomous automatic guided vehicle.
Computational and analytical modelling of composite structures based on exact and higher order theories.
(1995) Tabakov, Pavel.; Adali, Sarp.; Verijenko, Viktor.
The objective of the present study is the computational and analytical modelling of a stress and strain state of the composite laminated structures. The exact three dimensional solution is derived for laminated anisotropic thick cylinders with both constant and variable material properties through the thickness of a layer. The governing differential equations are derived in a such form that to satisfy the stress functions and are given for layered cylindrical shell with open ends. The solution then extended to the laminated cylindrical shells with closed ends, that is to pressure vessels. Based on the accurate three-dimensional stress analysis an approach for the optimal design of the thick pressure vessels is formulated. Cylindrical pressure vessels are optimised taking the fibre angle as a design variable to maximise the burst pressure. The effect of the axial force on the optimal design is investigated. Numerical results are given for both single and laminated (up to five layers) cylindrical shells. The maximum burst pressure is computed using the three-dimensional interactive Tsai-: Wu failure criterion, which takes into account the influence of all stress components to the failure. Design optimisation of multilayered composite pressure vessels are based on the use of robust multidimensional methods which give fast convergence. Transverse shear and normal deformation higher-order theory for the solution of dynamic problems of laminated plates and shells is studied. The theory developed is based on the kinematic hypotheses which are derived using iterative technique. Dynamic effects, such as forces of inertia and the direct influence of external loading on the stress and strain components are included at the initial stage of derivation where kinematic hypotheses are formulated. The proposed theory and solution methods provide a basis for theoretical and applied studies in the field of dynamics and statics of the laminated shells, plates and their systems, particularly for investigation of dynamic processes related to the highest vibration forms and wave propagation, for optimal design etc. Geometrically nonlinear higher-order theory of laminated plates and shells with shear and normal deformation is derived. The theory takes into account both transverse shear and normal deformations. The number of numerical results are obtained based on the nonlinear theory developed. The results illustrate importance of the influence of geometrical nonlinearity, especially, at high levels of loading and in case when the laminae exhibit significant differences in their elastic properties.
Contractible arms elevating search and rescue (Caesar) robot : improvements and modifications for urban search and rescue (Usar) robots.
(2010) Stopforth, Riaan.; Bright, Glen.; Harley, Ronald G.
Rescuers have lost their lives in events requiring them to go into dangerous areas that have unstable structures and gases. Robots are necessary for search and rescue purposes, to access concealed places and environments to which fire fighters and rescue personnel cannot gain entry. Robots that were previously used encountered problems with communication, chassis design, traction and sensory systems. Improvements are required for the successful localization of victims. Research on improvements in these areas were carried out for the use in the CAESAR (Contractible Arms Elevating Search And Rescue) robot. Contributions were made in the area of Urban Search And Rescue (USAR) robots focusing on antenna design, communication protocols, chassis design, traction system and artificial intelligence on decisions relating to gas danger levels for humans and the robot. The capabilities of CAESAR is audio, video and data communication irrespective of the orientation of the robot and the antennas. Penetration of radio frequencies through building material is possible. Reliable data communication is achieved with the designed Robotics Communication Protocol (RCP). The chassis is designed to have traction on unstable terrain and autonomously transform flipper arms for the best orientation. Materials for the body were selected and constructed to be able to withstand the unstable environments and high temperatures which they will encounter. The control station display gives the rescuers immediate indication of the gas concentrations detected by the on-board gas sensors. Developed analytical models determine the danger of the gas concentrations for victims, rescuers and the robots.
Coriolis effect on the stability of convection in mushy layers during the solidification of binary alloys.
(2000) Govender, Saneshan.; Vadasz, Peter.;
We consider the solidification of a binary alloy in a mushy layer subject to Coriolis effects. A near-eutectic approximation and large far-field temperature is employed in order to study the dynamics of the mushy layer in the form of small deviations from the classical case of convection in a horizontal porous layer of homogenous permeability. The linear stability theory is used to investigate analytically the Corio lis effect in a rotating mushy layer for, a diffusion time scale used by Amberg & Homsey (1993) and Anderson & Worster (1996), and for a new diffusion time scale proposed in the current study. As such, it is found that in contrast to the problem of a stationary mushy layer, rotating the mushy layer has a stabilising effect on convection. For the case of the new diffusion time scale proposed by the author, it is established that the viscosity at high rotation rates has a destabilising effect on the onset of stationary convection, ie. the higher the viscosity, the less stable the liquid. Finite amplitude results obtained by using a weak non-linear analysis provide differential equations for the amplitude, corresponding to both stationary and overstable convection. These amplitude equations permit one to identify from the post-transient conditions that the fluid is subject to a pitchfork bifurcation in the stationary case and to a Hopf bifurcation associated with the overstable convection. Heat transfer results were evaluated from the amplitude solution and are presented in terms of the Nusselt number for both stationary and overstable convection. They show that rotation enhances the convective heat transfer in the case of stationary convection and retards convective heat transfer in the oscillatory case, but only for low values of the parameter X I = 8 Pr ~ 0 So· The parameter 1/ X I represents the coefficient of the time derivative term in the Darcy equation. For high X I values, the contribution from the time derivative term is small (and may be neglected), whilst for small X I values the time derivative term may be retained.
Coupled heat and mass transfer in solar-powered liquid desiccant adiabatic dehumidifier and regenerator for air conditioning applications.
(2020) Oyieke, Andrew Young Apuko.; Inambao, Freddie Liswaniso.
Abstract available in PDF.
Crashworthiness modelling of thin-walled composite structures.
(2003) Morozov, Konstantin E.; Verijenko, Viktor.
This thesis is concerned with the study of the crashworthiness of thin-walled composite structures. Composites are being used more and more in different fields of engineering, particularly, in aerospace and automotive industries because of their high strength-to-weight and stiffness-to-weight ratios, quality and cost advantages. More and more metal parts in cars for instance become or are already replaced by new advanced materials. Composite materials are included in these new advanced materials with the following advantages: weight reduction, corrosion resistance, aesthetics and style, isolation and the ability to integrate several parts into one single structural component. The introduction of new composite structural components (body panels, bumpers, crash absorbers, etc.) requires the development and implementation of new approaches to structural analysis and design. Crashworthiness is one of the foremost goals of aircraft and automotive design. It depends very much on the response of various components which absorb the energy of the crash. In order to design components for crashworthy structures, it is necessary to understand the effects of loading conditions, material behaviour, and structural response. Due to the complexity of the material structure (matrix reinforced with fibres) and specific mechanical properties the nature of transforming the collision kinetic energy into material deformation energy differs from that of conventional metal alloys. The energy absorption mechanics are different for the advanced composites and depend on the material structure (type of reinforcement) and structural design. The primary function of the energy absorption for the composites belongs to the progressive crushing of the materials themselves and structural components (beams, tubes, etc.) made of such materials. Since the mechanics of composite materials and structural components differs substantially from the conventional applications there is a need to develop an appropriate way of modelling and analysis relevant to this problem. Currently there are a large variety of design approaches, test results, and research investigations into the problem under consideration depending on the type of composite material and design geometry of the parts. It has been found that in general an application of fibre reinforced plastics (FRP) to vehicle compartments can satisfy the structural requirements of the passenger compartment including high strength and light weight. Implementation of new advanced composite materials provides the opportunity to develop designs of reliable structural composite parts in high volume for improved automotive fuel economy. Structural optimisation and crashworthiness of composite components should be incorporated into design calculations to control the mechanical performance. The introduction which follows describes the aims of the present study of the crashworthiness modelling and simulation of the structural response of thin-walled composite components which are subjected to various loading conditions relevant to vehicle design. The research programme undertaken within the framework of this project includes development and validation of the modelling and simulation methodology applicable to the crashworthiness analysis of thin-walled composite structures. Development of computerised dynamic modelling of structural components offers the capability of investigating the design parameters without building the actual physical prototypes. In this approach, the dynamic behaviour of the structure is simulated for specified external inputs, and from the corresponding response data the designer is able to determine its dynamic response characteristics, and estimate the crashworthiness of the structure in vehicle engineering applications.
Design and performance simulation of a hybrid sounding rocket.
(2012) Chowdhury, Seffat Mohammad.; Brooks, Michael John.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Roberts, Lancian Willett.
Sounding rockets find applications in multiple fields of scientific research including meteorology, astronomy and microgravity. Indigenous sounding rocket technologies are absent on the African continent despite a potential market in the local aerospace industries. The UKZN Phoenix Sounding Rocket Programme was initiated to fill this void by developing inexpensive medium altitude sounding rocket modeling, design and manufacturing capacities. This dissertation describes the development of the Hybrid Rocket Performance Simulator (HYROPS) software tool and its application towards the structural design of the reusable, 10 km apogee capable Phoenix-1A hybrid sounding rocket, as part of the UKZN Phoenix programme. HYROPS is an integrated 6–Degree of Freedom (6-DOF) flight performance predictor for atmospheric and near-Earth spaceflight, geared towards single-staged and multi-staged hybrid sounding rockets. HYROPS is based on a generic kinematics and Newtonian dynamics core. Integrated with these are numerical methods for solving differential equations, Monte Carlo uncertainty modeling, genetic-algorithm driven design optimization, analytical vehicle structural modeling, a spherical, rotating geodetic model and a standard atmospheric model, forming a software framework for sounding rocket optimization and flight performance prediction. This framework was implemented within a graphical user interface, aiming for rapid input of model parameters, intuitive results visualization and efficient data handling. The HYROPS software was validated using flight data from various existing sounding rocket configurations and found satisfactory over a range of input conditions. An iterative process was employed in the aerostructural design of the 1 kg payload capable Phoenix-1A vehicle and CFD and FEA numerical techniques were used to verify its aerodynamic and thermo-structural performance. The design and integration of the Phoenix-1A‟s hybrid power-plant and onboard electromechanical systems for recovery parachute deployment and motor oxidizer flow control are also discussed. It was noted that use of HYROPS in the design loop led to improved materials selection and vehicle structural design processes. It was also found that a combination of suitable mathematical techniques, design know-how, human-interaction and numerical computational power are effective in overcoming the many coupled technical challenges present in the engineering of hybrid sounding rockets.
Design and testing of a composite material for modelling wind turbine blade structures in tropical region.
(2018) Tefera, Getahun Akulu.; Adali, Sarp.; Bright, Glen.; Davidson, Innocent Ewean.
Currently large wind turbine blades have been installed in several offshore and onshore wind farms around the world, particularly in the desert areas of North East Africa where wind turbine blades and nacelles are affected by elevated temperatures. The aim of this study is to investigate the effect of temperature variation on the mechanical behaviour of composite wind turbine blades installed in tropical wind farms. The blades are constructed from unidirectional carbon fibre/epoxy, glass fibre/epoxy and hybrids of these two composite materials. ASTM standards were taken into account when the composite specimens were manufactured for testing purposes. Short Beam Shear (SBS), Dynamic Mechanical Analysis (DMA) and tensile tests were conducted under increasing temperatures to investigate the mechanical behaviour of composite materials when used for structural modelling of wind turbine blades. Experimental findings revealed that the strength and stiffness properties of composite specimens were reduced when temperatures increased. Betz’s element momentum theory and Glauert’s modelling methods were used to investigate the characteristics of composite wind turbine blades measuring 54m and generating 2MW power. Flap-wise loading was taken into account along the length of the wind turbine blades when they were analysed using the Blade Element Momentum (BEM) theory. The wind turbine blades were developed using carbon fibre/epoxy, glass fibre/epoxy, glass-carbon fibre/epoxy and carbon-glass fibre/epoxy composite materials. The tip deflection of the blades was analysed allowing for different flap-wise and thermal loadings. Simulation results indicated that a glass/epoxy blade has the highest and a carbon/epoxy blade the lowest tip deflection. The values for the tip deflections of the blades show minimal change under thermal loading. To study the mechanical behaviour of the blades under thermal loading, an element-wise approach was developed and the failure index for different composite materials was computed. Tsai-Wu failure criterion was employed to determine the failure index of each composite material under thermal and mechanical loadings. Blades failed when the thermal loading was above 40ºC irrespective of the flap-wise loading. This finding was similar to the experimental results mentioned above. Carbon/epoxy showed non-linear behaviour when the test temperature approached 40ºC. Generally, experimental and numerical results are comparable and can be considered valid. To conclude carbon-glass fibre/epoxy composite wind turbine blades are observed to be a better option for tropical wind farms based on experimental and simulation results. Iqoqa Njengamanje sekufakwe ophephela bomoya abakhulu emapulazini amaningi omoya asolwandle nasezweni emhlabeni jikelele, ikakhulukazi ezindaweni eziwugwadule zaseMpumalangantshonalanga Afrika lapho amazinga okushisa aphakeme enomthelela kophephela bomoya nakuzembozo zezihambisiphephela. Inhloso yalolu cwaningo ngukuhlola umthelela wokuguquguquka kwamazinga okushisa endleleni okusebenza ngayo ophephela bomoya abafakwe emapulazini asezindaweni ezishisa kakhulu. Ophephela bakhiwe ngomabhekanxazonke befayibha yekhabhoni/ ephoksi, ifayibha yengilazi/ephoksi, Kucatshangelwe amazinga e-ASTM ngenkathi kwakhiwa amasampula ayindidiyela ngenhloso yokuhlola. Kwenziwe uhlelo lwe-Short Beam Shear (SBS), Dynamic Mechanical Analysis (DMA) nokuhlola kwamathensayili ngaphansi kwamazinga okushisa anyukayo, ukuhlola indlela ezisebenza ngayo izakhi eziyindidiyela uma zisetshenziselwa ukubona ukuthi singama kanjani isakhiwo sophephela bomoya. Imiphumela yokuhlola iveze ukuthi amazinga amandla nokuqina kwamasampula ayindidiyela kwehlile uma kunyuswa amazinga okushisa. Kusetshenziswe injulalwazi ka-Betz yomthamosivinini kanye nezindlela zika-Glauret zesibonelokulinga ukuhlola izimpawu zophephela bomoya abayindidiyela, abanesikalo esingu-54m futhi esiphehla amandla angu-2MW. Kucatshangelwe isisindo sokuthwala uma ophephela bebheke phansi noma phezulu ngokunjalo nobude bophephela bomoya ngenkathi behlaziywa, kusetshenziswa injulalalwazi i-Blade Element Momentum (BEM). Ophephela bomoya benziwe kusetshenziswa izakhi eziyindidiyela zefayibha yekhabhoni/ ephoksi, ifayibha yengilazi/ ephoksi nefayibha yekhabhoni-ngilazi/ ephoksi. Impebezo yezihloko zophephela ihlaziywe kuvunyelwa okuhlukahlukene kwesisindo sokuthwala netemali, uma ophephela bebheke phansi noma phezulu. Imiphumela yokulingisa ikhombise ukuthi uphephela wengilazi/ ephoksi unempebezo yesihloko ephakene kanti uphephela wekhabhoni/ ephoksi unempebezo yesihloko ephansi. Amavelu empebezo yezihloko zophephela akhombisa uguquko olusesilinganisweni esincane, ngaphansi kokulayishwa kwetemali. Ukucwaninga okwenziwa ngophephela okuphathelene nokusebenza kwemishini uma kulayishwe itemali, kwenziwe ngokuqamba indlela evuna i-elementi, kwase kwenziwa uhlelo lokubala ngekhompyutha inkomba kwehluleka yezakhi eziyindidiyela ezihlukahlukene. Kuthathwe indlelakukhetha kuhluleka kaTsai-Wu ukubona inkomba kuhluleka yesakhi ngasinye esiyindidiyela uma kulayishwe itemali nokusebenza ngemishini. Ophephela behlulekile uma umthamo wetemali ungaphezu kuka-40ºC kungakhathaliseki izinga kulayisha elivuna ukubheka phansi noma phezulu kophephela. Okutholakele bekufana nemiphumela yokuhlola ebalulwe ngenhla. Ikhabhoni/ ephoksi ikhombise indlela okwenza ngayo ophephela engaqondile uma amazinga okushisa okuhlola esondela ku-40ºC. Ezimweni eziningi, imiphumela yokulinga neyezibalo iyaqhathaniseka futhi ingase ibhekwe njengekholakalayo. Ukuphetha, ophephela bomoya abayindidiyela yefayibha yekhabhoningilazi/ ephoksi babonakala beyisu elingalunga kahle emapulazini omoya uma kuthathelwa emiphumeleni yokuhlola nokufanisa.
Design, modelling and optimisation of an isolated small hydropower plant using pumped storage hydropower and control techniques.
(2015) Ilupeju, Samuel Ayanrohunmu Olusegun.; Inambao, Freddie Liswaniso.
Pumped Storage Hydropower (PSH) has proved to be a reliable power generation technology, especially in cases of emergency peak power demand. It is best utilised in areas where the availability of water is a challenge because it allows water retention and reuse using the pump back mechanism instead of the water being discharged to continue its course. A pumped storage hydropower system consists of two reservoirs, one higher in elevation than the other lower, the turbine house (power station) and pumping plant between the two reservoirs. During off-peak periods, excess electricity which is cheap pumps water from the lower to the upper reservoir because power demand is low. The stored energy is released to run back into the lower reservoir through the turbines to generate electricity in peak demand period, converting the stored potential energy into electricity at a higher economic value. South Africa is among the highest emitters of carbon dioxide in the world, with more than 75% of primary energy requirement from fossil fuels. Specifically South Africa is ranked 12th in the world in terms of top emitters of carbon dioxide, exposing its citizens to risks associated with this emission [1]. Therefore there is an urgent need to protect lives by technically reducing release of the poisonous gases through reducing fossil fuel dependency. Renewable Energy (RE), which is abundant and sustainable, can be quickly implemented, offer many work opportunities and have a much lower impact on the environment. With over 8 000 potential small Hydropower sites identified in Eastern Cape and KwaZulu Natal (KZN) Provinces, generation can improve. The system proposed is the design, optimisation and integration of a control system to a standalone micro hydropower hybrid. The conventional hydropower plant, which is a primary electricity source, allocates power to pump from the lower reservoir to the upper at off-peak periods when consumption and price of electricity is low at regulated flow. Various calculations were derived to compute the primary design parameters (flow, head and system efficiencies) with the other inputs. Matlab Simulink was engaged to describe the interaction between these variables and to vary parameters for optimum output, especially in reducing pumping mode power input for maximum pumped storage hydropower plant generation. Different categories of small hydropower plant sizes can be determined and analysed using this model which will give suitable results. Though the value of generation output from the PSH is small compared to input pump power it is able to compensate for peak load demand. The control system is introduced using Flowcode software to automate every technical process to ensure optimum system performance. The automation considers, time of the day, the volume of the upper reservoir and the available pumping power to efficiently manage the hydropower plant model. With the introduction of this generation technique, the results have shown that generation of more electricity at peak time when the price of selling the electricity is very high can be easily accomplished. The control effectively minimises electricity losses, breakdown of equipment, and ensures availability of resource at the exact time of demand. With this design, existing hydro plants may be upgraded for optimum generation without posing any negative effect on the environment in the way that coal fired plants do. Other renewable energy sources may be exploited in pumping activities to reduce the effect of pumping to the upper reservoir on the conventional hydropower plant.
Design, modelling and simulation of 2 novel 6 DOF hybrid machines.
(2012) Shaik, Ahmed Asif.; Bright, Glen.
Industrial robot arms are an essential part of automated manufacturing, and perform tasks such as component assembly, welding, light machining, spray painting, etc. They are highly repeatable, can be calibrated to be sufficiently accurate and they eliminate human error. The serial robot architecture is by far the most ubiquitous in modern day manufacturing, as the technology is highly refined in its current state; the machine architecture provides great dexterity and it has a large useful workspace. This architecture however does have some problems, one of which is a large machine moving mass. The primary reason for this lies in the location of its motors and gearboxes. Due to the robot's significant inertia it utilizes a large amount of energy. This thesis focused on the mechanical design, mathematical modelling and simulation of 2 robotic arm designs which had a hybrid nature. They were classified as hybrid due to the fact that their architectures departed from both the classic definitions of serial kinematics manipulators/machines (SKMs) and parallel kinematics manipulators/machines (PKMs). The primary design goal was to merge some of the advantages of both architectures, i.e. a large workspace to footprint ratio and high end-effector dexterity which was found in serial robots, combined with the low inertia of a parallel robot for improved dynamics. Serial and parallel robots were complementary, and these design goals could not co-exist in a single purist robot architecture. The designs had a full complement of 6 DOFs (degrees of freedom), 3 DOFs for spatial position of the wrist and 3 DOFs for orientation of that wrist. They also had a lower machine moving mass, a fact that was thought to improve speed and energy usage. A major contribution of this research PhD project was a comparative energy usage study, which was performed against the serial robot as a measure. This was done for both hybrid designs as well as another model which represented 2 existing patented designs. The purpose of that was to determine if lowering the machine moving mass would improve energy efficiency, and to determine which design was best.
Designing a photovoltaic-microbial fuel cell (pv-mfc) renewable hybrid system based on public-private partnership and other South Africa’s policies: a case study Umhlathuze municipality.
(2021) Nhleko, Melusi Velolwenkosi.; Inambao, Freddie Liswaniso.
Abstract available in PDF.
Development and fabrication of functionally graded aluminium metal matrix composite for automobile component applications.
(2021) Owoputi, Adefemi Oluwaniyi.; Inambao, Freddie Liswaniso.; Ebhota, Williams Saturday.
In recent times, interest in aluminium matrix composites (AMCs) have garnered traction over conventional aluminium alloys as the material of choice in the manufacturing of components for various engineering applications. Engineering components developed from single-element material are increasingly less favored over materials engineered from two or more elements. The rise in the demand for a multifunctional engineering material to exhibit opposing yet complementary engineering properties at different spatial positions within the material due to functionality requirements, has birthed several innovative fabrication processes. This study focuses on the development and fabrication of functionally graded aluminiummetal matrix composite (FGAMMC) through the liquid metallurgy route for proposed automobile component production. Industrially produced A356 aluminium alloy and silicon carbide powders (Al-SiC) was adopted as the base matrix and reinforcement materials for the fabrication of the metal matrix composites. Centrifugal casting technique was used to fabricate seven samples of Al-SiC functionally graded aluminium metal matrix composites with varied reinforcements particle size and weight percent addition. Samples A, B, and C contained 1 wt.%, 3 wt.%, and 5 wt.% of SiC of size 7 μm reinforcement, respectively, while samples E, F, and G had 1 wt.%, 3 wt.%, and 5 wt.% of SiC of size 15 μm reinforcement respectively. Sample D with no reinforcement additions served as the control sample for the experiment. Microstructural characterization showing the elemental composition and reinforcement distribution of silicon carbide particles within the matrix of the cast composite was carried out using optical microscopy (OM), optical emission spectroscopy (OES), energy dispersion xray (EDX), and scanning electron microscopy (SEM). The influence of SiCp on the mechanical, wear behavior and thermal properties of the cast aluminium composites were determined by subjecting the cast samples to mechanical, tribological, and thermal tests. Sample C with 5 wt.% and 7 μm of SiC particle reinforcement recorded improved hardness,compressive strength, Young's modulus, shear strength, and shear modulus of 112.7 HV0 1, 3107 MPa, 6.39 GPa, 14.4 GPa, and 9.29 GPa, respectively. Tribological analysis show an increase in the cast composites' wear resistance and frictional coefficient proportional to the frequency of contact between the counterface ball of the tribometer and the dispersed SiC reinforcements in the composites' matrices. Thermogravimetric analysis showed the weight loss and heat flow rates exhibited by the cast samples as the temperature was increased from 25 °C to 1000 °C in an Argon environment. Although negligible weight loss was recorded for all the cast composites within the experimental temperature boundary, sample C with 7 𝜇m
Development of a decision support system for decision-based part/fixture assignment and fixture flow control = Ukusungulwa kohlelo lokuxhaswa kwezinqumo mayelana nokwabiwa kwezingxenye ezakhiwayo kanye nokuhanjiswa kwazo.
(2018) Kasie, Fentahun Moges.; Bright, Glen.; Walker, Anthony John.
ABSTRACT: An intense competition in a dynamic situation has increased the requirements that must be considered in the current manufacturing systems. Among those factors, fixtures are one of the major problematic components. The cost of fixture design and manufacture contributes to 10-20% of production costs. Manufacturing firms usually use traditional methods for part/fixture assignment works. These methods are highly resource consuming and cumbersome to enumerate the available fixtures and stabilise the number of fixtures required in a system. The aim of this study was to research and develop a Decision Support System (DSS), which was useful to perform a decision-based part/fixture assignment and fixture flow control during planned production periods. The DSS was designed to assist its users to reuse/adapt the retrieved fixtures or manufacture new fixtures depending upon the state of the retrieved fixtures and the similarities between the current and retrieved cases. This DSS combined Case-Based Reasoning (CBR), fuzzy set theory, the Analytic Hierarchy Process (AHP) and Discrete-Event Simulation (DES) techniques. The Artificial Intelligence (AI) component of the DSS immensely used a fuzzy CBR system combined with the fuzzy AHP and guiding rules from general domain knowledge. The fuzzy CBR was used to represent the uncertain and imprecise values of case attributes. The fuzzy AHP was applied to elicit domain knowledge from experts to prioritise case attributes. New part orders and training samples were represented as new and prior cases respectively using an Object-Oriented (OO) method for case retrieval and decision proposal. Popular fuzzy ranking and similarity measuring approaches were utilised in the case retrieval process. A DES model was implemented to analyse the performances of the proposed solutions by the fuzzy CBR subsystem. Three scenarios were generated by this subsystem as solution alternatives that were the proposed numbers of fixtures. The performances of these scenarios were evaluated using the DES model and the best alternative was identified. The novelty of this study employed the combination of fuzzy CBR and DES methods since such kinds of combinations have not been addressed yet. A numerical example was illustrated to present the soundness of the proposed methodological approach. Keywords: Decision support systems, case-based reasoning, analytic hierarchy process, fuzzy set theory, object-oriented methods, discrete-event simulation, fixtures. IQOQA LOCWANINGO : Ukuncintisana okunezinhlelo eziguquguqukayo kulesi sikhathi samanje sekwenze ukuthi kube nezidingo ezintsha ezinhlelweni zokukhiqiza. Phakathi kwakho konke lokhu izingxenye (fixtures) zingezinye zezinto ezidala izinkinga. Intengo yokwakha uhlaka lwengxenye kanye nokuyikhiqiza kubiza amaphesenti ayi-10 kuya kwangama-20 entengo yokukhiqiza. Amafemu akhiqizayo avamise ukusebenzisa izindlela ezindala zomsebenzi wokwaba izingxenye. Lezi zindlela zidla kakhulu izinsizangqangi futhi kuthatha isikhathi eside ukubala izingxenye ezikhona nokuqinisekisa ukuthi kunesibalo esanele kulokho okumele kube yikho ohlelweni lokusebenza. Inhloso yalolu cwaningo bekungukucwaninga nokusungula i-Decision Support System (DSS) ebe lusizo ekwenzeni umsebenzi wokuthatha izinqumo ngokwabiwa kwezingxenye kanye nokuhanjiswa kwazo ngezikhathi ezimiselwe ukukhiqiza. I-DSS yakhelwa ukusiza labo abayisebenzisayo ukuze basebenzise noma bazisebenzise lapho zingakaze zisetshenziswe khona lezo zingxenye ezibuyisiwe, noma kwakhiwe ezintsha kuya ngokuthi zibuyiswe zinjani lezi ezibuyisiwe nokuthi ziyafana yini nalezo ezintsha. I-DSS isebenzise amasu ahlanganise i-Case-Based Reasoning (CBR), injulalwazi echazwa ngokuthi i-fuzzy, ne-Analytic Hierarchy Process (AHP) ne-Discrete-Event Simulation (DES). I-Artificial Intelligence (AI) eyingxenye ye-DSS isebenzise kakhulu uhlelo lwe-fuzzy CBR luhlangene ne-fuzzy AHP kulandelwa imithetho yolwazi olumayelana nohlobo lomsebenzi. I-CBR isetshenziswe ukumelela lezo zimo zamanani ezingaqondakali nezingaphelele kulezo zingxenye. I-AHP e-fuzzy yasetshenziswa ukuze kutholakale ulwazi kochwepheshe olubeka phambili lezo zingxenye. Ama-oda ezingxenye ezintsha kanye namasampuli asetshenziselwa ukuqeqesha avezwe njengamasha kanye nabekade evele ekhona ngokulandelana kusetshenziswa indlela eyaziwa ngokuthi yi-Object-Oriented (OO) method lapho kubuyiswa izinto noma kunezinqumo eziphakanyiswayo. Izindlela ezijwayelekile zokulandelanisa nokufanisa zisetshenziswe ohlelweni lokubuyisa izinto. Kusetshenziswe isu eliyi-DES ukuhlaziya ukusebenza kwezisombululo eziphakanyiswe yindlela ye-CBR e-fuzzy. Le ndlela iphinde yaveza izimo ezintathu eziphakanyiswe ukuba zibe yisisombululo esibalweni sezingxenye ezihlongozwayo. Ukusebenza kwalezi zimo kuhlungwe ngokusebenzisa indlela ye-DES kwase kuvela inqubo engcono. Ukungajwayeleki kwalolu cwaningo kusebenzise ingxube yezindlela ze-fuzzy CBR ne-DES ngoba lolu hlobo lwengxube belungakaze lusetshenziswe. Kusetshenziswe isibonelo sezibalo ekwethuleni ukusebenza kwale nqubo yokusebenza ehlongozwayo.
Development of high strength material for smart aircraft bolt.
(2005) Vugampore, Jean-Marie Vianney.; Verijenko, Belinda-Lee.
Scientists are constantly seeking new and convenient non-destructive damage assessment techniques. In fact, a global market has developed for structural health monitoring products. Many of the currently available techniques are expensive and difficult to implement. An inexpensive alternative is technology based on strain memory alloys. These materials encompass a vast array of alloys, from austenitic stainless steels through to the extremely high strength TRIP steels. All, however, have in common the transformation from paramagnetic austenite to ferromagnetic martensite upon application of strain. The degree of ferromagnetism can be directly correlated to the peak strain undergone by the material. Strain memory alloys are not as expensive to manufacture as some smart materials, and in addition are capable of bearing significant load, and it is therefore possible to manufacture entire components from these alloys, thereby producing what is known as a smart component, i.e. one that is capable of doing the job of an ordinary component while at the same time assessing its own peak damage levels. A possible application of this technology is that of wing bolts for the Hercules e130 aircraft. The material usually used to manufacture the aircraft wing bolts is HSLA steel (AISI 4340). A strain memory alloy was therefore developed to match the mechanical properties of 4340 steel, while also having the requisite properties to perform the self damage-assessment. Ultra high strength TRIP steels were identified as possible candidates, and four alloys selected for investigation. These alloys were melted and then thermo-mechanically processed using a rolling operation. All alloys were tensile tested and magnetic susceptibility monitored. The final material selected possesses an ultimate tensile strength (UTS) of between 1270 and 1500 MPa with 10 to 12% elongation. The stress / strain induced transformation begins to occur before the yield point, which is important because bolts must be replaced before they fail. Compression tests were also performed, and yielded similar results to those of the tensile tests, with martensitic transformation again beginning before plastic yield. The strain induced phase transformation was confirmed not only by magnetic susceptibility measurements, but also by metallographic inspection before and after testing. A subscale Smart bolt was designed, manufactured and tested for magnetic sensitivity using a smart washer.
The development of instrumentation for the direct measurement of heat loss from man in a normal working mode.
(1974) Hodgson, T.; Bindon, Jeffrey Peter.; Reed, M.
Based on a theoretical analysis of the heat transfer process between the human body and its environment, graphs are presented for determining the theoretical skin surface temperatures and sweat rates as a function of the physiological conductance, under certain assumed environmental conditions with regard to air temperature, relative humidity and wind speed. In addition, the development of unique measuring techniques for the direct measurement of the evaporative and radiative heat transfer rates between a human body in a natural working position and its environment as well as the development of a low-cos~ radiometer for the measurement of the emissivity and temperature of human skin are described. The heat loss measuring equipment was installed in the horizontal test section of the climatic chamber of the Human Sciences Laboratory of the Chamber of Mines. Basically the evaporative heat loss measuring system consists of two air-sampling probes, for sampling the air on the upstream and downstream sides of the body , a double circuit heat exchanger, for equalising the dry- bulb temperatures of the two air samples and a differential humidity- measuring system incorporating electrical resistance hygrometero, for measuring the difference in specific humidity between the two air samples. In addition, a steam generator is provided for introducing a known amount of steam at a predetermined rate into the wake of the body. Since the output of the humidity-measuring system is linearly related to the evaporative heat loss rate, the unknown rate of evaporation of moisture from the human body can be determined relatively easily from a knowledge of the respective outputs of the humidity-measuring system due to the moisture evaporation rate of the human body and the known vapour production rate by the steam generator. The direct- measuring instrument for determining the radiation energy exchange rate of a working subject is in the form of a rotating hoop. The inside and outside surfaces of the hoop are lined with thermal radiation-sensing elements, so connected as to measure the net radiation energy exchange between the subject and the surroundings. The hoop integrates over the circular strip formed by the elements and upon rotation, integrates the radiation over the total 4n surface enveloping the subject . While the interposition of a surface between the body and its surroundings must of necessity influence the radiation exchange, the method introduces a small surface only . The significance of the evaporative and radiative heat loss measuring techniques which were successfully used in animate studies, is reflected in the, hitherto unknown, accuracy regarding partial calorimetric studies . The low- cost radiometer for measuring the skin temperature and emissivity is equipped with two non-selective thermal radiation detectors in the form of semi-conductor thermocouples. The one radiation-sensing element faces a built-in reference black body. The other detector, which can be temperature controlled, is used to detect the incoming radiation from the target. The output of the radiation-sensing elements which is sufficiently high to be measured on a recorder without the use of a chopper-amplifier system, can either be measured differentially or the output of the radiation-sensing element facing the target can be measured separately; for the purpose of temperature and emissivity measurements, respectively. The unique facility of being able to vary the temperature of the radiation detector enabled a new method of determining the emissivity of a surface to be developed. As a result, accurate measurements of the emissivities of samples of excised skin could be carried out. An improvement in the response of the radiometer would, however, be necessary for the rapid determination of the emissivity of . living skin by this means. The accuracy with which surface temperatures could be determined by means of the radiometer compared favourably with more sophisticated radiometers.
The development of methods for the design and evolution of reconfigurable cellular manufacturing systems.
(2016) Padayachee, Jared.; Bright, Glen.
The concept of reconfigurable manufacturing is presently being researched due to the need for production systems that are able to economically respond to changes in markets and the rapid introduction of new products. Cellular Manufacturing Systems (CMS) are a central concept in just-in-time and lean manufacturing. Although CMS are able to provide a strategic operating advantage, machine cell clusters do not remain optimal over an extended period of time. The concept of a Dynamic CMS (DCMS) has received attention in recent years; a DCMS is a system where the layout of machines change in order to improve the responsiveness of CMS to changing production requirements. A deficiency in existing DCMS methods is that reconfiguration plans are generated without the consideration of an initial design of the factory floor space for future change. This research distinguishes Reconfigurable CMS (RCMS) from DCMS, as a system that is designed at the outset for changes to system layout and cell configurations. The concept of a Factory Configuration Template (FCT) is proposed in this research; the FCT is a design of the factory floor space to ensure the feasible implementation of reconfiguration plans generated by mathematical models. A nine step method for FCT design is presented that uses a Simultaneous Fuzzy Clustering Heuristic to develop manufacturing cells and part families. A Tabu Search algorithm was develop to generate the optimal arrangement of machine sites in cells. Three multi-period machine assignment models were developed that determine reconfiguration plans based on changing product demand and the introduction of new products. The models that were developed included two integer linear programs that determine the distribution of machine resources among cells over multiple periods. A quadratic zero-one programming model was developed that distributes machines among available sites in cells to promote unidirectional part flow. The results show that RCMS is able to provide a more economical solution than traditional CMS with the added advantage of improved part flow in the system.
Distributed control synthesis for manufacturing systems using customers' decision behaviour for mass customisation.
(2013) Walker, Anthony John.; Bright, Glen.
The mass customisation manufacturing (MCM) paradigm has created a problem in manufacturing control implementation, as each individual customer has the potential to disrupt the operations of production. The aim of this study was to characterise the manufacturing effects of customers’ decisions in product configuration, in order to research steady state control requirements and work-in-process distributions for effective MCM operations. A research method involving both analytic and empirical reasoning was used in characterising the distributed control environment of manufacturing systems involved in MCM. Sequences of job arrivals into each manufacturing system, due to customers’ decisions in product configuration, were analysed as Bernoulli processes. A customer model based on this analysis captured the correlation in product configuration decisions over time. Closed form analytic models were developed from first principles, which described the steady state behaviour of flow controlled manufacturing systems under generalised clearing policy and uncorrelated job arrival sequences. Empirical analysis of data sets achieved through discrete event simulation was used in adjusting the models to account for more complex cases involving multiple job types and varying correlation. Characteristic response surfaces were shown to exist over the domains of manufacturing system load and job arrival sequence correlation. A novel manufacturing flow control method, termed biased minimum feedback (BMF) was developed. BMF was shown to posses the capability to distribute work-in-process within the entire manufacturing facility through work-in-process regulation at each manufacturing system, so as to increase the performance of downstream assembly stations fed from parallel upstream processing stations. A case study in the production of a configurable product was used in presenting an application for the models and methods developed during this research. The models were shown to be useful in predicting steady state control requirements to increase manufacturing performance.

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