Stress analysis and assessment of Hirth couplings and Curvic couplings: A comparative study

Hirth couplings and Curvic couplings are widely used in high-speed rotating turbomachinery such as gas turbines and aero-engines. Nominal stress assessment has been commonly applied in industry for strength evaluation and structural design. However, the complexity of stress resulting from various external loads (preloads, centrifugal force, bending moment and torques) has not been thoroughly explored. This paper presents improved nominal stress evaluation approaches based on cantilever beam models. A detailed nominal stress analysis under symmetric and asymmetric loads is provided by introducing the cross-section factor and the stress concentration factor. Finite element simulations yield stress distributions for Hirth couplings and Curvic couplings, derived from an impeller and a real gas turbine rotor, respectively. For the Curvic couplings of a four-stage gas turbine rotor, stress assessments are conducted in compliance with the ASME BPVC standard and the FKM guideline.