D.Ing. (Mechanical Engineering) / The local buckling of axially loaded thin walled circular aluminium tubes is investigated in this work. Various buckling modes can be identified depending on certain geometrical ratios. Tubes with a thickness to diameter ratio of between 0,016 and 0,1 will buckle according to the so called axi-symmetric mode which is a very efficient collapse mechanism for energy absorbing purposes. Although there are numerous analytical solutions for this collapse mode the results are not fully descriptive. A finite-element model was developed and is described in this work. With this model it is possible to analyse the collapse mechanism in detail and the results obtained compare favourably with experimental values. When a relatively long thin walled tube is loaded axially it will undergo Euler buckling. This is not an effective collapse mechanism for energy absorbing purposes and a concept that overcomes this disadvantage is presented. With this energy absorber it is possible for axially loaded longthin walled circular tubes to collapse into a mode that resembles the axi-symmetric collapse mode. A finite element model was developed and successfully used to analyse the proposed concept. The results obtained correlate well with experimental values. A low speed impact test rig was designed, manufactured and commissioned. This rig was used to conduct dynamic tests on the proposed energy absorber and it was concluded that the proposed concept is viable for applications that require an inexpensive, reliable energy absorber with a long strokelength.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:3647 |
| Date | 05 February 2014 |
| Creators | Coetzee, Gerhard |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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