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Mechanical Engineering

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Browsing Mechanical Engineering by Author "Bodger, Robert."

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    Buckling of short, thin-walled cylinders, as applied to storage tanks.
    (2001) Du Poujol, Geraldine Touche.; Bodger, Robert.; Adali, Sarp.
    This is an investigation of the buckling characteristics of short, thin-walled cylinders. This study was required as large storage tanks, which were converted from Boating roof to fixed roofed tanks, were found to buckle when severe atmospheric temperature drops and thus pressure differentials occurred. These severe ambient temperature changes are characteristic of the Highveld in South Africa where the tanks in question are situated. Since this modification is an uncommon procedure, codes of practice for storage vessels do not cover this type of cylinder. For the same reason, research performed in this field is limited. Buckling due to axial loading, lateral external pressure, hydrostatic pressure and a combination of axial loading and hydrostatic pressure are explored in this study. To compare with and verify theory, existing research for each case is examined, and the Finite Element Analysis package MSC Nastran used to determine trends. In some cases, to the best of the author's knowledge, no research exists and numerical analysis is performed to establish the relationships present in those cases. The study is extended to include the design of imperfect cylinders, as defined in the tank code AD Merkblatter where it is stated as being dependant on the major and minor diameters of the imperfect section . The study is also extended to the case of variable wall thickness cylinders, where the thickness variation is symmetrical about the axis of the cylinder.
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    Design and optimization of prototype trip steel smart aircraft bolt.
    (2008) Mukosa, Namanyenu Sheleni.; Bodger, Robert.; Verijenko, Belinda-Lee.
    Aviation is known to have some of the most stringent structural health monitoring standards in the world. An example of this would be the fact that certain bolts in the aircraft assembly must be periodically removed and inspected for fatigue damage. This can be a very costly endeavour: a case in point being the Hercules C130 aircraft, which requires approximately 200 man hours of down-time for the inspection of the bolts that attach the wings to the fuselage. The substitution of TRIP (Transformation Induced Plasticity) steel bolts for the current HSLA steel (AISI 4340) from which the bolts are manufactured, allows the bolt to act in the capacity of load bearing member as well as damage detector. This unique feature is a consequence of the transformation characteristic exhibited by TRIP steels when they are strained: an irreversible change within their microstructure from paramagnetic austenite parent phase to permanent ferromagnetic state occurs in direct proportion to the peak strain. This property allows us to establish a relationship from which the service life of the component can be determined. A prototype of a smart aircraft bolt and washer system has been developed, where the bolt acts as damage detector and the washer effectively examines the health of the bolt by reading the changing magnetic susceptibility of the bolt. This study presents both material development and product development phases of the Smart Aircraft Bolt prototype. A prediction of transformation characteristic due to deformation is carried out using finite element analysis (mechanical model) and a constitutive model (strain induced martensitic transformation kinetics) to predict the best situation for the smart washer. In addition, experimental work is performed in the form of cyclic temperature testing (with and without external loading) and tension-tension fatigue testing. For both sets of experimental testing, two positions of washer placement are tested. A correlation between volume fraction of martensite present and remaining life, is therefore possible.
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    Investigation and design of wet-mill equipment and process technology.
    (2003) Smith, Lisa Noelle.; Bodger, Robert.; Adali, Sarp.
    need to dry-mill the wheat into flour, and as a result, the total cost of conversion from wheat to bread is reduced. The resulting product has been perceived as being more filling than normal bread and it is also more nutritious and more affordable. The wet-mill concept was developed in a laboratory environment and no process methodology or equipment has existed to enable the technology to be used in a real bakery environment. The focus of this research was to design the particular equipment required for a medium plant-bakery production facility based on the wet-mill technology. Due to severe overcapacity in the bread-making industry, the research focuses on how best to integrate this equipment into an existing production facility. Three broad areas are investigated: • Product Development • Process Design • Machine Design The aim of the Product Development phase was to create a recipe that would withstand the rigours of the plant bakery environment, while at the same time satisfying consumer demand for taste and texture. The Process Design phase ensured that any new equipment had the capacity to match the throughput rate of the rest of the plant bakery, so that wet-mill dough could seamlessly continue downstream. Process control variables were examined to ensure that a consistent quality product was delivered. Inbound material handling was also investigated and designed to ensure safe and uncontaminated delivery of perishable raw material. Since the end product is edible, hygiene design requirements were also considered by completing a HACCP study to ensure a consumer-safe product. The Machine Design phase involves the development and design of a completely new food machine: a vertical wet-mill cutter. Many ideas are evaluated and a prototype machine, based on the optimal design, was built to test the concept. This prototype was then used to define process and design constraints for a scaled, large plantbakery machine. The final detailed design of a plant bakery wet-mill cutter was then completed. It includes drive, belt, bearing and pneumatic cylinder selection, and shaft and blade design. Safety considerations were an important part of the design process and production facility. Conformity to OHS Act regulations required investigation into the safe operation of the designed equipment with particular reference to driven and rotating machinery sub-regulations of the Act. A hazard analYSis and operability study was also undertaken. Lastly, the research calculates a financial valuation of the project to ascertain whether a plant baker should be interested in implementing wet-mill technology. The research concludes with a discussion of the various successes of the three research areas, and states any further investigation that may be required before full implementation.