A three-dimensional finite element investigation of the bolt stresses in an aero-engine Curvic coupling under a blade release condition

Curvic couplings transmit torque between parallel in-line shafts or turbine/compressor discs. They are used extensively within the aero-engine industry but can also be found in industrial gas turbines. The manufacture of Curvic couplings involves the precision cutting and grinding of mating teeth on the adjacent ends of the components; the assembly is then clamped together with bolts. The use of Curvic couplings in engineering transmission components is relatively widespread, although the publication of work in the open literature is currently limited. An attempt has been made to investigate the factors influencing the load imparted to a fan Curvic coupling in a large aerospace gas turbine. Owing to the very complicated nature of the current problem, some geometric and especially loading simplifications have been necessary. The results presented provide an initial solution to the problem of the three-dimensional numerical modelling of a fan Curvic coupling during a blade release event. This work is intended to provide data to help make decisions at the design stage and, together with aero-engine fan blade-off tests, will contribute to an improved design of Curvic couplings. The current work has been carried out using the three-dimensional finite element elastic-plastic contact method in an attempt to achieve realistic displacements of the fan Curvic teeth and bolts.