Technological Choices for Vibratory Robustness of Turbine Bladed Disk

Robustness of gas turbine, turbojet or turboprop components with respect to vibratory stress is a guarantee of the success of developments made on time and in service reliability objectives achievement. Currently, it is proposed to achieve the required robustness by components geometry optimization to reduce their mechanical stress levels. It may also be possible to improve the endurance limits of the materials. These optimizations and choices, consumers in time and complexity of manufacture, may be necessary when the required robustness is not found to be achieved during the engine verification. By taking the effects of potential uncertainties and dispersions into account earlier in the development process, technological choices may be more likely to achieve the desired robustness requirement. This paper investigates several simple technological choices to control and reduce the vibratory levels present on the rotors of helicopter turboshaft engines. These technological choices are major choices in the engine architecture with or without additional parts to increase mechanical resistance margins. Gas turbine architecture has a direct impact on the level of excitations and vibratory appropriations, particularly the choice of rotor-stator blade numbers or technologies and shapes of links between rotors. Additional parts allow to increase the vibratory margins on the scale of the component. In this category, the benefit of dampers and intentional mistuning will be recalled. Particular attention will be paid to the relative weight between these technological choices in comparison with the mistuning effect on dynamic levels. Technological choices will be quantified and illustrated by mechanical and statistical analysis and experimental industrial examples.