Carbon face seals, used in the aircraft engines manufactured by AlliedSignal Engines, are assembled via a shrink-fit procedure which generates residual stresses in both components, resulting in 30-50% of the seals not meeting the required flatness tolerance of three helium light bands (3 HeLB, equal to 0.762 mum). A two-dimensional, axisymmetric finite element analysis is carried out here to provide a means for better understanding the geometric and processing parameters of the face seals in order to improve their flatness. Results indicate that to obtain a lower value of f(d), the flatness deviation, the seal should have a larger inner radius (R-i), a smaller initial radial interference (delta), a larger thickness of the steel ring (t(s)), a smaller thickness of the carbon ring (t(c)), and a smaller height (h(t)). Also, it is preferable to have a slower cooling rate during the assembly process. It is observed that the coefficient of friction at the interface, mu, does not have any effect on f(d). Finally, the process of an "expansion" fit does not contribute towards a reduction in f(d), and hence is not worth the effort and cost. (C) 2002 Elsevier Science B.V. All rights reserved.
