Multi-objective Optimization for Aeronautical Gears

This MSc. thesis has been carried out at GE Avio Aero S.r.l. under a mutual industrial agreement between Politecnico di Torino and the company. The aim of this thesis is the development of a tool able to optimize the performances of toothed wheels typically employed in the gearbox of aircraft propulsion systems. According to aeronautical trends, components and gears must weigh less and less e so they tend to vibrate. Forced vibrations at resonance conditions reduce the fatigue life of the component and for this reason, to achieve better dynamic properties is in contrast with the need to reduce its mass. For this reason, the purpose of this thesis activity is the search of the best compromise between the two optimization objectives: reduce gear mass end improve the gear response to the excitation. To ensure a longer fatigue life of toothed wheels it was chosen to minimize the amplitude of static displacements and vibrations end to move away the resonance peaks from the operating speed ranges, leveraging on the available design space. To characterize the dynamic behaviors of each configuration and to compare them with each other, the function Risk Factor is defined, which gives as an output a factor related to the dangerous presence of resonance peaks inside gear operative ranges and to the static displacement. The optimization tool has been developed entirely in MATLAB environment and in a generic form, in order to guarantee its application for whatever gear’s typology it is wanted to take into analysis.