Regulation requires railway energy absorbers to dissipate the collision energy and to prevent overriding. There is no industrial consensus about which energy absorbing mechanism is the most suitable for the crash conditions present in a collision between railway vehicles. There is scope for improving the existing designs or creating new concepts. The combination of two energy absorption mechanisms, expansion and splitting of cylindrical tubes, was identified as an improved energy absorption mechanism. Quasi-static and dynamic testing of scaled splitting, expansion and expansion splitting (hybrid) tubes was carried out to assess their force, stroke, energy absorption and oblique loading efficiency. In addition, the standard requires a calibrated numerical model of the energy absorber to predict its behaviour. The fracture strain of the tube and the coefficient of friction between the tube and the die are needed to build accurate numerical models. The fracture strain was measured using a Digital Image Correlation technique and a new methodology was developed to overcome its limitations. The inclusion of the fracture strain correctly predicted the deformation of the splitting specimens. The friction coefficient was adjusted until the energy absorption matched that observed during testing. Quasi-static testing showed that the force efficiency was 80%, 100% and 90%, for the splitting, expansion and hybrid tubes respectively. The stroke efficiency was measured as 77%, 44% and 70%, respectively. The energy absorption efficiency of the hybrid tubes was assessed as 11% and 40% higher than that of the splitting and expansion tubes respectively. The testing also showed that the hybrid tubes were more insensitive than the expansion and splitting tubes to the application of oblique loading. More testing may be necessary to confirm this assertion. The results suggest that the hybrid energy absorbing mechanism could become a commercial energy absorber with improved performance over the existing solutions. The validation of the hybrid numerical models showed an accurate prediction of the test results. A full-scale hybrid demonstrator has been tested and a patent of the hybrid concept applied for.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:693218 |
| Date | January 2015 |
| Creators | Moreno, C. |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/81458/ |
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