This thesis presents a new finite element analysis (FEA) method for calculating the critical stress in an aircraft wheel’s lock-ring. The lock-ring is used on many modern designs in place of the bolts that join the two main sections of the wheel. The lock-ring is a safety critical component of the wheel as a failure could lead to an explosive release of tyre pressure. The stress field in this wheel forms a fatigue cycle as the wheel rotates when the aircraft manoeuvres on the ground. The stress field at the critical location on the lock-ring is strongly dependent on the contacting surfaces of three structural components of the wheel: the main hub, the lock-ring and the freeflange. Until completion of this work no method existed to calculate the fatigue stress cycle at this design critical location. Modern wheel designs, to minimise aircraft weight and therefore fuel use, are of minimum weight designs. This means that the aluminium material in the latest wheel designs is subjected to greater stress than in previous designs, therefore the ‘margin of safety’ for the wheels is reduced. It is important that methods are developed to calculate the stress in all regions of the wheel, including the lock-ring. Lock-ring wheel designs were originally used on military aircraft and more recently they have become common on business jet aircraft. Very recently the feasibility of their use on large commercial aircraft that carry upwards of 100 passengers is being considered. The operating environment on large commercial aircraft is very harsh for wheels and the methodology developed in this work is required to correctly assess the use of these wheels in this harsh and safety critical environment. The calculation method is compared against physical test data measured on two wheels using strain gauges. The wheels, with tyres installed, were loaded and rolled on a road wheel dynamometer to simulate aircraft ground manoeuvres. Measuring the critical location is difficult as access to it is limited; it had not been measured before. The measured data are used to verify the new FEA method. The new FEA method was developed with the potential for use by both a nonspecialist engineer and use in a modern Concurrent Engineering environment as requirements. The FEA is linked directly to the CATIA 3D computer aided design (CAD) model, using CADNexus software. This link is made in such a way that a modification to the design, once included in the CAD model, can be easily and automatically followed by an update to the FEA. The FEA requires solution of a non-linear model because contact between three structural components is critical and therefore must be modelled in detail. The general perception in industry is that non-linear FEA is a complex subject and must be undertaken by an experienced FEA specialist – this work provides strong supportive evidence to contradict this general perception. The FEA itself is implemented using ANSYS® Workbench software. The new analysis method, including the model set-up parameters is stored in an analysis template. This analysis template effectively captures the knowledge of a specialist FEA engineer so that it can be used, for design purposes, by a non-special engineer. The final FEA method is useful not only to non-specialist engineers but also, because the specialist knowledge is contained within the ANSYS® Workbench template, for outsourcing this structural analysis work to lower cost economies. The works creates a new FEA method of specific use to manufactures and designers of weight optimised aerospace wheels. Furthermore, in a more general context, it demonstrates that even complex non-linear FEA can be defined within knowledge capturing templates. This makes it accessible to engineers without specialist expertise with FEA. Empowering the design engineer to structurally optimise their own designs will lead to leaner design teams, which will consequently reduce development costs. The new method can be competed as part of a Concurrent Engineering process. This is advantageous as it can expedite the design process, therefore allowing FEA results to be available early enough in the programme to be made use of.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:560333 |
| Date | January 2012 |
| Creators | Butcher, Kent |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/49611/ |
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