Fatigue Damage–Based Topology Optimization of Helicopter Tail Rotor Pitch Arm

Abstract

Topology optimization studies have found widespread use with advances in additive manufacturing technologies. A topology optimization method is proposed for the design of a fatigue critical part, namely, a pitch arm made of Al 7050, which transmits the commands to change the pitch attitude to the rotor blades of the helicopter. This study used the bidirectional evolutionary structural optimization (BESO) method with the fatigue failure criterion of a closed Soderberg (CS). The mean stress and stress amplitude values used in the procedure were obtained by applying the Manson-McKnight method. The calculations were performed using a Python-based script compatible with Ansys version 2021 R1 software. In the finite-element calculations, the sensitivity number of the elements was determined using the results of the linear static analysis. A volume constraint was applied in the formulation of the optimization problem to minimize the weight of the structure. The results of the classical topology optimization approach and the developed optimization method were compared. The final geometries of both approaches showed that the ranges of volume reduction differed from each other. It was found that the values for the new fatigue-optimized weight of the pitch arm were 18% higher than the values for the static-based classical topology optimization method. However, in general, the weight of the part obtained as a result of fatigue-based topology optimization was reduced by 34% in total.