Mechanical Engineering

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An automated apparatus for non-contact inspecting of mass produced custom products.
(2009) Davrajh, Shaniel.; Bright, Glen.
The evolution of the manufacturing industry may be viewed as proceeding from Dedicated Manufacturing Systems (DMS) to Reconfigurable Manufacturing Systems (RMS). Customer requirements change unpredictably, and so DMS are no longer able to meet modern manufacturing requirements. RMS are designed with the focus of providing rapid response to a change in product design, within specified part families. The movement from DMS to RMS facilitates mass-production of custom products. Custom parts require inspection routines that can facilitate variations in product parameters such as dimensions, shape, and throughputs. Quality control and part inspection are key processes in the lifecycle of a product. These processes are able to verify product quality; and can provide essential feedback for enhancing other processes. Mass-producing custom parts requires more complex and frequent quality control and inspection routines, than were implemented previously. Complex, and higher frequencies of inspection negatively impact inspection times, and inherently, production rates. For manufacturers to successfully mass-produce custom parts, processes which can perform complex and varying quality control operations need to be employed. Furthermore, such processes should perform inspections without significantly impacting production rates. A method of reducing the impact of high frequency inspection of customized parts on production rates is needed. This dissertation focuses on the research, design, construction, assembly, and testing of a Non- Contact Automated Inspection System (NCAIS). The NCAIS was focused on performing quality control operations whilst maintaining the maximum production rate of a particular Computer Integrated Manufacturing (CIM) cell. The CIM cell formed part of a research project in the School of Mechanical Engineering, University of KwaZulu-Natal; and was used to simulate mass-production of custom parts. Two methods of maintaining the maximum production rate were explored. The first method was the automated visual inspection of moving custom parts. The second method was to inspect only specified Regions of Interest (ROIs). Mechatronic engineering principles were used to integrate sensor articulation, image acquisition, and image processing systems. A specified maximum production rate was maintained during inspection, without stoppage of parts along the production line occurring. The results obtained may be expanded to specific manufacturing industries.
Sensor based real-time mechatronic control of computer integrated manufacturing
(2008) Kumile, Christopher Matlalo
Industrial competition is characterised by increasing globalisation of markets, coupled with
Design of an autonomous underwater vehicle : vehicle tracking and position control.
(2010) Holtzhausen, Servaas.; Bright, Glen.
This project proposes the development of an autonomous underwater vehicle that can be used to perform underwater research missions..The vehicle can be pre-programmed to complete a specified mission. Missions may include underwater pipe inspection, a survey of the sea floor or just the transport of given sensors to a certain depth or position and take measurements of underwater conditions. The Mechatronics and Micro Manufacturing group at the CSIR is engaged in developing a portfolio of autonomous vehicles as well as fur- ther research into the development and implementation of such vehicles. Underwater vehicles will form part of the portfolio of autonomous vehicle research. Autonomous underwater vehicles (AUVs) are mostly used for research purposes in oceanographic studies as well as climate studies. These scientists use AUVs to carry a payload of sensors to specified depths and take measurements of underwater conditions, such as water temperature, water salinity or carbon levels as carbon is being released by plankton or other ocean organisms. Very little information is available about what is happening below the surface of the oceans and AUVs are being used to investigate this relatively unknown environment. The area covered by the world's ocean is 361 million km2 with an average depth of 3790 m. The deepest surveyed depth point in the ocean is at a depth of about 11 000 m at the southern end of the Mariana Trench in the Pacific Ocean. This just shows the need for research into this mostly unexplored world. Research and exploration in the oceans can be achieved through the use of autonomous underwater vehicles. A big problem to overcome is the fact that GPS is not available for navigation in an underwater environment. Other sensors need to be found to be used for navigational purposes. The particular vehicle developed for this study will be used to facili- tate further research into underwater vehicle navigation and underwater robotics.
Performance based analysis of current South African semi trailer and b-double trailer designs
(2010-08-31) Thorogood, Rhys L.
South African heavy vehicles are currently designed according to prescriptive standards designed and enforced by the National Department of Transport (DoT); these standards are regulated in terms of mass, dimensions and vehicle configuration. However, the current prescriptive standards leave little room for innovation in terms of heavy vehicle design. Performance Based Standards, or PBS, is a new Australian based innovative alternative to the current heavy vehicle prescriptive standards, mass, dimensions and vehicle configuration. PBS seeks to align actual vehicle performance efficiencies, productivity and safety objectives as well as road and bridge infrastructure to the current road network. Vehicle performance measures are based on engineering and science, supporting superior safety and known road and bridge wear performance criteria. PBS produces “a result orientated approach” to improved heavy vehicle operations and safety rather than a „one size fits all approach‟ utilised by the current prescriptive legislation. Currently, dynamic vehicle simulations are not carried out on South African manufactured vehicle combinations. Evidence exists that this has, in some cases, resulted in safety compromises. The computer dynamic vehicle simulation technology developed and validated could be employed for the credible assessments of the vehicle design concepts/prototypes for compliance with PBS. This service, which includes vehicle performance simulation and testing, development of high productivity vehicle concepts, assessment and development of risk management strategies, advice on safety and productivity issues, would have a substantial commercialisation potential for the implementation in the larger transport industry in South Africa.
A study and implementation analysis of an anti-sagging device for power transmission lines using shape memory alloys
(2010-08-31) Lüssi, Kevin M.
Shape memory alloys (SMA’s) are a family of metals that exhibit properties of pseudo-elasticity
Numerical simulation of the structural response of a composite rocket nozzle during the ignition transient.
(2009) Pitot de la Beaujardiere, Jean-Francois Philippe.; Bright, Glen.; Morozov, Evgeny.
The following dissertation describes an investigation of the structural response behaviour of a composite solid rocket motor nozzle subjected to thermal and pressure loading during the motor ignition period, derived on the basis of a multidisciplinary numerical simulation approach. To provide quantitative and qualitative context to the results obtained, comparisons were made to the predicted aerothermostructural response of the nozzle over the entire motor burn period. The study considered two nozzle designs – an exploratory nozzle design used to establish the basic simulation methodology, and a prototype nozzle design that was employed as the primary subject for numerical experimentation work. Both designs were developed according to fundamental solid rocket motor nozzle design principles as non-vectoring nozzles for deployment in medium sized solid rocket booster motors. The designs feature extensive use of spatially reinforced carbon-carbon composites for thermostructural components, complemented by carbon-phenolic composites for thermal insulation and steel for the motor attachment substructures. All numerical simulations were conducted using the ADINA multiphysics finite element analysis code with respect to axisymmetric computational domains. Thermal and structural models were developed to simulate the structural response of the exploratory nozzle design in reference to the instantaneous application of pressure and thermal loading conditions derived from literature. Ignition and burn period response results were obtained for both quasi-static and dynamic analysis regimes. For the case of the prototype nozzle design, a flow model was specifically developed to simulate the flow of the exhaust gas stream within the nozzle, for the provision of transient and steady loading data to the associated thermal and structural models. This arrangement allowed for a more realistic representation of the interaction between the fluid, thermal and structural fields concerned. Results were once again obtained for short and long term scenarios with respect to quasi-static and dynamic interpretations. In addition, the aeroelastic interaction occurring between the nozzle and flow field during motor ignition was examined in detail. The results obtained in the present study provided significant indications with respect to a variety of response characteristics associated with the motor ignition period, including the magnitude and distribution of the displacement and stress responses, the importance of inertial effects in response computations, the stress response contributions made by thermal and pressure loading, the effect of loading condition quality, and the bearing of the rate of ignition on the calculated stress response. Through comparisons between the response behaviour predicted during the motor ignition and burn periods, the significance of considering the ignition period as a qualification and optimisation criterion in the design of characteristically similar solid rocket motor nozzles was established.
Performance evaluation of WiMax for rural backhaul.
(2010-10-18) Singh, Verosha.
Technologies such as WiFi and WiMAX, can be a powerful driving force for increasing rural
Investigation and development of structural composite materials for use as electromagnetic shielding agents in the current aerospace industry.
(2010-10-20) Maharaj, Denver.
Due to the nature of today's competitive electronics market, the development of new electronic
Parallel robot design incorporating a direct end effector sensing system.
(2007) Shaik, Ahmed Asif.; Bright, Glen.
This dissertation details the development of a parallel robot with an integrated direct end effector sensing system, from concept to prototype model and includes details of research, design, simulation, construction, assembly and testing. Current research in parallel robots is insufficient as compared to serial type machines, even though their existence has been known for some time. The reasons are the difficulty in conceptualising unique parallel mechanisms, achieving machines that are capable of high accuracy, solving their complex kinematics, dynamics and control problems. There are many advantages of parallel machines that rival the serial type, and these warrant further studies. The second aspect of this project was the design of a direct end effector sensor system. Many existing automated multi-axis machines operate under overall 'open loop' control. The exact position in space of the end effector or tool head, for those machines, is not sensed directly but is calculated by software monitoring sensors on actuator axes. This sensor system and robot structure was designed specifically for use in the agricultural and general food processing/packaging industries. The accuracy and repeatability of such a machine and its sensor system are in the millimetre range.
Reconfigurable modular machine design for reconfigurable manufacturing environment.
(2006) Xing, Bo.
Manufacturing techniques are based on the principles of Flexible Manufacturing and
Modelling and empirical characterisation of environmental degradation of FRP laminates in southern Africa.
(2010-10-29) Sookay, N. K.
As polymeric composite materials are being increasingly used in Southern Africa, there is a
Molecular simulation and modeling of the phase equilibria of polar compounds.
(2006) Clifford, Scott Llewellyn.; Ramjugernath, Deresh.; Bolton, Kim.
The initial phase of the project involved an investigation into the modeling of binary carboxylic acid vapour-liquid equilibrium (VLE) data. This stemmed from the Masters research that led into the current study, in which the conventional gamma-phi formulation of VLE was found to inadequately describe the complicated acid chemistry. In an effort to correctly describe the dimerization occurring in both the liquid and vapour phases, the chemical theory of vapour-phase imperfections was applied. The chemical theory technique allowed the experimental liquid-phase activity coefficients to be accurately calculated by taking the vapour phase dimerization into account. Once these activity coefficients had been determined, standard Gibbs excess energy models were fitted to permit analysis of the VLE data's thermodynamic consistency. In addition, the typical bubble-point iteration scheme used for VLE data regression was adapted to include the chemical theory expressions necessary for satisfactory modeling of the carboxylic acids. The primary focus of this study was to determine the ability of currently available computer simulation techniques and technology to correctly predict the phase equilibria of polar molecules. Thus, Monte Carlo simulations in the NVT- and NPT- Gibbs ensembles were used to predict pure component and binary phase equilibrium data (respectively), for a variety of polar compounds. The average standard deviations for these simulation results lay between 1 and 2 % for the saturated liquid densities, and varied between 5 and 10 % for the saturated vapour pressures and densities. Pure component data were simulated for alcohols, carboxylic acids, hydrogen sulfide (ELS), sulfur dioxide (SO2) and nitrogen dioxide (NO2). For H2S, S02 and NO2, a potential model parameterized as part of this project was used to describe the molecular interactions. All the other compounds were simulated using the TraPPE-UA force field. The simulation results for the alcohols and acids showed a consistent saturated vapour pressure over-prediction of 5 - 20 % depending on the species and the system temperature. The liquid density predictions were, in general, good and on average differed from experiment by 1 - 2 %. The critical temperatures and densities were estimated from the pure component data by fitting to the scaling law and the law of rectilinear diameters. They were found to lie within 1 and 2 % of the experimental values for the carboxylic acids and alcohols, respectively. Clausius-Clapeyron plots of the saturated vapour pressures allowed the critical pressure and normal boiling points to be determined. The critical pressures were, as expected, over-predicted for both compound classes and the normal boiling points were under-estimated somewhat for the acids, but deviated from experiment by less than 0.5 % for the alcohols. A Lennard-Jones 12-6 plus Coulombic potential energy surface was parameterized for H2S, SO2 and NO2. For FbS, the proposed force field offers improved saturated vapour pressure and vapour density predictions when compared to the existing NERD force field, and comparable accuracy with the recent models of Kamath and co workers. SO2 and NO2 had not previously been parameterized for a Lennard-Jones 12-6 based force field. For SO2, there was excellent agreement with experimental data. In the case of NO2, the saturated liquid density predictions were very good, but the vapour pressures and densities were over-predicted. Binary VLE simulations were carried out for systems consisting purely of carboxylic acids, and also for H2S and SO2 with a selection of alkanes and alcohols. The liquid and vapour composition predictions were good for the acid systems, but the anticipated pressure and temperature deviations were observed in the isothermal and isobaric simulations, respectively. The H2S + alkane systems were generally good, as were the SO2 + alkane systems. For both H2S and SO2, the systems involving an alcohol displayed a characteristic pressure over-estimation. The azeotropes were, in most cases, predicted fairly well; the exception was the SO2 + methane binary. A sensitivity analysis of the Lennard-Jones unlike interaction parameters was also conducted. It was demonstrated that even minor changes to these parameters can have a significant effect on the final simulation results. The considerable affect that these parameters have on the simulation outputs was emphasized by studying the influence of different combining rules on the H2S + methane and H2S + ethane binary systems. Analysis of the radial distribution functions indicated that hydrogen bonding and dimerization were occurring in the alcohol and carboxylic acid systems, respectively. The H2S, SO2 and NO2 distribution functions showed little sign of any association, except for a small plateau in that of SO2. A radial distribution function from one of the carboxylic acid binary simulations was also analysed, and supported the assumption made in the chemical theory modeling work of using a geometric mean (instead of twice the geometric mean, which is favoured by some researchers) to determine the heterodimerization constant, KAB-
Molecular simulation of vapour-liquid equilibrium using beowulf clusters.
(2010-11-01) McKnight, Tyrone J.
This work describes the installation of a Beowulf cluster at the University of KwaZulu-Natal
Modelling of carbon nanotubes and carbon nanotube-reinforced polymers with applications to composite structures.
(2010-11-01) Wuite, Justin.
Owing to their exceptional mechanical and physical properties, carbon nanotubes seem to
A mechatronic approach to develop the concept of a materials handling system for a reconfigurable manufacturing environment.
(2010-11-01) Naidu, Priyen.
People are unique and display a variety of preferences with regard to the products that are
The measurement of axial turbine tip clearance flow phenomena in a moving wall annular cascade and in a linear cascade.
(1989) Morphis, George.; Bindon, Jeffrey Peter.
On unshrouded axial flow turbine rotors, the tip clearance, required for thermal expansion and manufacturing limitations, allows fluid to leak from the pressure side to the suction side of the blade. This flow across the blade tip causes a large proportion of the overall rotor loss. In this work, the flow was visualized, microscopic static pressures taken and flow field measurements were done in the blade tip region to investigate the complex nature of tip clearance flows. An annular turbine cascade with a rotating outer casing was used to simulate the relative motion at the tip of an axial rotor. It was found that relative motion did not have a significant effect on the basic structure of the micro-flow, even though it reduced the leakage mass flow rate which is important as far as mixing loss formation is concerned. The existence of a narrow, very low pressure depression, caused by the flow remaining attached around the sharp pressure corner edge, was confirmed. The width and pressure of the separation bubble were found to be strongly dependent on gap size but the relationship was not linear. The point at which the separation bubble reattaches was seen to coincide with a slight rise in static pressure. The separation bubble which caused the majority of the internal gap loss, and which was thought to contribute to the mixing loss, was shown to disappear when the pressure corner was given a radius of 2,5 gap widths.A linear cascade was used to evaluate the performance of two blade tip shapes that substantially reduced internal gap loss and to compare them to a standard sharp or flat tip blade. A method whereby linear cascade data was analyzed as if it were a rotor with work transfer, was used to evaluate the performance of the various blade tip geometries. It was found that both modified tips increased the mixing loss due to the extra leakage mass flow rate. The first tip with the radiused pressure corner was seen to have a lower efficiency than the flat tip blade. A second tip that was contoured to shed flow in a radial direction and thus decrease the leakage mass flow rate through the gap was seen to significantly increase the overall efficiency.
Finite element solutions of optimization problems with stability constraints involving columns and laminated composites.
(2006) Cagdas, Izzet Ufuk.; Adali, Sarp.
The primary aim of this study is to assess the applicability and performance of the finite element method (FEM) in solving structural optimization problems with stability constraints. In order to reach this goal, several optimization problems are solved using FEM which are briefly described as follows: The strongest column problem is one of the oldest optimization problems for which analytical solutions exist only for some special cases. Here, both unimodal and bimodal optimization of columns under concentrated and/or distributed compressive loads with several different boundary conditions and constraints are performed using an iterative method based on finite elements. The analytical solutions available in the literature for columns under concentrated loads and an analytical solution derived for simply supported columns under distributed loads are used for verification purposes. Optimization results are presented for fibre-reinforced composite rectangular plates under inplane loads. The non-uniformity of the in-plane stresses due to stress diffusion and/or in-plane boundary conditions is taken into account, and its influence on optimal buckling load is investigated. It is shown that the exclusion of the in-plane restraints may lead to errors in stability calculations and consequently in optimal design. The influences of the panel aspect ratio, stacking sequence, panel thickness, and the rotational edge restraints on the optimal axially compressed cylindrical and non-cylindrical curved panels are investigated, where the optimal panel is the one with the highest failure load. The prebuckling and the first-ply failure loads of the panels are calculated and minimum of these two is selected as the failure load. The results show that there are distinct differences between the behaviour of cylindrical and non-cylindrical panels. The formulations of the finite elements which are used throughout the study are given and several verification problems are solved to verify the accuracy of the methodology. The computer codes written in Matlab are also given in the appendix sections accompanied with the selected codes used for optimization purposes.
Experimental and numerical study of heat transfer on turbine blades.
(2007) Kennedy, Graham Stuart.
An experimental and numerical study of he aerodynamics and the associated heat transfer on turbine blades, has been carried out as part of the ongoing Armscor Denel aircraft engine maintenance program. The experimental tests were performed using an existing continuous flow cascade test facility at the University of KwaZulu-Natal, Durban. These experimental results were used to validate the two-dimensional numerical results, generated usmg a commercially available Computational Fluid Dynamics (CFD) package, FLUENT. The existing experimental turbine test facility utilises a continuous flow cascade technique where a cooled, instrumented blade is rapidly introduced to the hot-air stream exposing it to the cascade flow. This creates the heat transient required for measurement of the isothermal heat transfer coefficients, using thin-film heat flux gauges. A static pressure test blade is used in conjunction with a scanivalve system, to determine the blade mid-span pressure distribution. This latest research effort requires validation of de Villiers' [2002] results, whilst improving the error discrepancies between the experimental and numerical analyses. Maintenance on the test rig has been performed, including the addition of a new pressure control system to ensure the correct cascade flow conditions and boundary conditions are obtained. Experimental pressure distribution measurements were performed, to validate previous work by de Villiers [2002] and to ensure the correct operation of the test rig. Experimental error was identified in de Villiers' [2002] suction surface pressure distribution, and new experimental pressure results were acquired. Following the essential overhaul of critical rig components, experimental heat transfer tests were performed. The newly restored equipment produced new isothermal heat transfer coefficient results that validated the results of de Villiers' [2002]. Numerous CFD meshing techniques were investigated and implemented in FLUENT, to produce the numerical solution. The pressure correlation proved to be excellent with an average error of 3%. The varying cascade inlet turbulence intensity was identified as a major source of heat transfer error. Implementing this variance into FLUENT, a significant reduction in error was seen. The resulting average heat transfer error measured 12%, a major improvement from 29% error in 2002.
An experimental and numerical convective heat transfer analysis over a transonic gas turbine rotor blade.
(2006) Cassie, Keith Baharath.; Govender, Saneshan.
An experimental and numerical investigation of the flow and convective heat transfer distribution around a high turning angle gas turbine rotor blade has been carried out at the University of Kwa-Zulu, Durban campus. This study in gas turbine blade aerothermodynamics was done to meet the research and development requirements of the CSIR and ARMSCOR. The experimental results were generated using an existing continuously running supersonic cascade facility which offers realistic engine conditions at low operating costs. These results were then used to develop and validate a 2-D model created using the commercially available Computational Fluid Dynamics (CFD) software package, FLUENT. An initial phase of the study entailed a restoration of what was an unoperational experimental facility to a state capable of producing test simulation conditions. In the analysis, a 4-blade cascade system with provisions for an interchangeable, test blade was subjected to the steady state conditions set up by the facility. Firstly, the flow was characterised by evaluating the static pressures around the midspan of a pressure measurement test blade. This was done using two pressure transducers, a scanivalve, an upgraded data acquisition system and LABview software. The method for measuring the heat transfer distributions made use of a transient measuring technique, whereby a pre-chilled Macor test blade, instrumented with thin film heat flux gauges was rapidly introduced into the hot cascade flow conditions by displacing an aluminum dummy blade while still maintaining the flow conditions. Measurement of the heat flux and generation of the isothermal heat transfer co-efficient distributions entailed re-instrumentation of the test blade section with gauges of increased temperature sensitivity along with modifications of the associated electrical circuitry to improve on the quality of experimental data. Both the experimental flow and heat transfer data were used to validate the CFD model developed in FLUENT. An investigation into different meshing strategies and turbulence models placed emphasis on the choice of model upon correlation. The outcome of which showed the k -co model's superiority in predicting the flow at transonic conditions. A feasibility study regarding a new means of implementing a film cooled turbine test blade at the supersonic cascade facility was also successfully investigated. The study comprised of experimental facility modifications as well as cascade and blade redesigns, all of which were to account for the requirements of film cooling. The implementation of this project, however, demanded the resources of both time and money of which neither commodity was available.
The formulation of process variables for the elimination of defects in a semi-solid high pressure die cast component.
(2006) Reinhardt, Carl Jurgen.; Verijenko, Belinda-Lee.
Semi-Solid Metal (SSM) forming has distinct advantages: strength, near net shape, thick and thin sections and a large scope of materials able to be cast. The aim of this project is to produce a near net shape component using SSM casting with A356 primary Semi Solid Aluminum feed stock from SAG. The selected Short Arm Component was identified as a suitable component for SSM forming, it is used as part of an insulated securing mechanism in overhead pylons, demands high strength and has relatively thick sections. A combination of full and short shot castings from the component and modular die were produced, on the real time shot controlled 62.5 ton high pressure die casting machine, at varying casting parameters of die temperature between 140-250°C, gate velocities of between 1.01-2.87ms_1 and a billet temperature of between 578-582°C. To understand fluid flow and locate possible defects, X-ray radiography and naked eye surface observations of the castings were used to locate possible defects and irregularities, which were cross sectioned and analysed using a Scanning Electron Microscope with an Energy Dispersion Spectroscopy module. It was apparent from the current project, as well as from literature, that increases in the die cross-sectional area reduce the shear surface area and increase the viscosity causing undesirable mould filling behaviour.

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