Model-based contact fatigue design of surface engineered titanium gears

In order to fully realise the potential of advanced surface engineering in the automotive sector, a contact mechanics model has been developed based on modern theories of multi-layered surface contact, taking into account the multi-layered structure, real surface roughness and friction effects. With this model, the performance of surface engineered titanium automotive gears can be successfully predicted thus making possible the design of optimised surface engineering systems to meet particular engineering demands within the shortest possible time and with least cost. This paper presents the predictive contact fatigue design of Ti6Al4V based gears in racing car engines using the developed contact mechanics model for the real rough multilayered surface systems. Evaluation of the effectiveness of the predictive design is carried out through cam rig tests of real gears, simulating the in-service loading conditions. Good agreement between theoretical prediction and service performance has been achieved. By way of example, the present paper demonstrates a number of major steps towards designing dynamically loaded titanium automotive gears.