3 results for Aitchison, D.

  • Wire fencing (part 1): Determinants of wire quality

    Pons, D.; Bayley, G.; Laurenson, R.; Hunt, M.; Tyree, C.; Aitchison, D. (2012)

    Journal Articles
    University of Canterbury Library

    Knotted wire fences are fabricated on specialised machines. The input material is typically galvanised steel wire. However, the quality of the input wire used by the Fence Producer is beyond control of the Machine Manufacturer. The problem is that wire strand breakages have been reported during fabrication and subsequent field erection. This is an issue for the Fence Producer because of the lost productivity, and the potential for reputation (brand) damage for both the Manufacturer and Producer. While existing standards do exist for wire, even wire that meets these standards is known to fail during fence fabrication. Thus there is a need to better understand how the quality of wire affects the manufacturability of fences, and to identify, or if necessary create, a test for wire quality that is able to be conducted by Fence Producers. In this research, samples were obtained from known good and failed fences and wire coils, and subjected to a variety of physical and metallurgical tests. These were then statistically examined and compared to the known fate of the fence, to determine the sensitivity of the test. Four potential tests were evaluated: Tensile strength (UTS), ductility, 3-point bending, microstructural, impact energy, plus a fifth novel new test called linear torsional ductility (LTD). From these tests, it was evident that the linear torsional ductility test was the most sensitive and reliable indicator for wire quality. This paper is part of a collection, with companion papers examining material properties of wire, microstructure, impact energy for wire, knot performance, and the testing of whole fences.

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  • An Investigation into the Prediction of Optimal Machining Conditions for Polystyrene Foam Cut with a Taut Hot-Wire

    Aitchison, D.; Brooks, H.; Bain, J.; Pons, D. (2009)

    Conference Contributions - Published
    University of Canterbury Library

    A series of tests were undertaken in which the feed force, wire temperature and kerf width were recorded for expanded polystyrene foam (EPS) and extruded polystyrene foam (XPS) being cut with a hot-wire cutting-tool. From the gathered data general relationships between cutting parameters, material properties and kerf width (cut surface accuracy) were sought and developed. The findings reported in this paper provide an insight into the associated hot-wire cutting mechanics and the potential for consistently applying optimal cutting conditions during automated machining operations.

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  • Modelling and system identification of a stiff stay wire fence machine

    Hann, C.E.; Aitchison, D.; Kirk, D.; Brouwers, E. (2010)

    Journal Articles
    University of Canterbury Library

    This paper investigates a severe gear backlash problem encountered in a stiff stay machine that is capable of producing a 26 line fence up to 2.6 metres in height at a speed of 80 stays/minute. Related problems in the literature, typically concentrate on the effect of gear backlash on the ability to control a shaft. However, in this case, very good control of the reference speed of the shaft was maintained in spite of the gear backlash. The problem was that the commanded torques were excessively large and threatened to damage the gear box. This problem motivated a complete analysis of the systems dynamics including the development of a model to better understand the response and allow the identification of external loads on the system. It was found that the method of sensing the shaft position (resolvers) was a major factor as well as the upgrading of the motor which was over responding to disturbances in the shaft. The model was validated using several torque limiting experiments and gave accurate prediction of the machine’s major dynamics. The simulation tool developed provides the basis to predict the effect of different loads, wire types and/or motors on the machine for future designs minimizing the amount of experimentation on the machine.

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