Exploitable results Advanced Surface Engineering Techniques for Future Aerospace Transmissions High performance gears/bearings in modern aerospace transmissions are required to operate at ever increasing speed and load, whilst still remaining competively priced, highly reliable and safe. The net consequence of the increasing torque and speed is that fatigue damage will be accumulated more rapidly limiting the design options using conventional materials/processes. The ASETT project was therefore conceived with the primary objective of achieving three main aims:- To systematically study and optimize the parameters affecting the load carrying capacity for a number of advanced surface engineering techniques, with the aim of achieving a fundamental advance in fatigue performance. To assess and validate the predictive accuracy of several analytical models with the aim of reducing development time scales and thereby producing favorable cost reductions. To provide a means by which life cycle costs could be determined for these novel materials/processes with the aim of assigning a cost of ownership. From the experimental results two techniques, i.e. Duplex Hardening (DH) and PVD coating using WC/C achieved the fundamental advance in fatigue performance when compared to conventional materials/processes. Namely tooth root bending fatigue strength and rolling contact fatigue life were increased by approximately 30% and 700% respectively. In order to achieve the highest level of fatigue resistance however, it is important that the surface engineered layer contains the following factors:- A high level of residual stress A low level of surface roughness A high level of surface hardness Absence of microstructural precipitation around the grain boundaries The industrial impact will largely depend on the design requirements, however by utilizing the enhanced fatigue properties associated with either the DH or PVD systems a gearbox could be designed to achieve either (a) a 20% increase in performance, (b) an enhanced level of safety or (c) a 15% reduction in weight, resulting in environmental benefits. Based on the results obtained from the theoretical models assessed in the ASETT contract, it would appear that several are capable of predicting performance when compared to the experimental test data however their accuracy is highly dependant on the quality of the input data. For example, although the fatigue deterministic models were all capable of assessing and characterizing the significant certain variables (surface hardness, roughness etc) have on surface distress, none were capable of predicting fatigue life with a high degree of accuracy. Commercially, the models appear capable of reducing the amount of initial testing that would be required, thereby shortening the development timescales, leading to a reduction in the time to market and thereby producing an overall reduction in cost. Both the DH and WC/C surface engineering systems would appear to offer reductions in life cycle costs when compared to conventional materials. Based on the the analysis performed reductions in the range 13-52% were determined. However, the choice of surface engineering system used is very much application specific, i.e. DH being favoured by the helicopter industry, whereas the WC/C coating system tended to be preferred for fixed wing transmission applications, eg engine reduction/accessory gear boxes. The industrial advantages attained with surface engineering systems developed/evaluated in ASETTwould largely be a lower cost of ownership. È in corso la ricerca di dati su OpenAIRE... Si è verificato un errore durante la ricerca dei dati su OpenAIRE Nessun risultato disponibile
