Gearbox of the Horizontal Stabilizer Actuator for the Airbus A380.

 

This structure constitutes the housing for the complex gear mechanisms of the Tail Horizontal Stabilizer Actuator for the A380 commercial aircraft. The gearbox can receive the actuation inputs either from two identical hydraulic motors or from one electrical motor. The complexity of the design is due principally to the dual-path load feature implemented to satisfy the fail-safe requirements. The structural model was set up for evaluating the stress behavior within the gearbox when subjected to operating, limit and ultimate loads as well as global accelerations and dynamic excitation.

The finite element models were derived from three imported CATIA models of the three castings constituting the whole gearbox. The geometry of all three CAD models was repaired and modified in order to avoid singularities or bad discretization during the subsequent phases of fem model generation. The connection between each casting pair was obtained by coupling the nodes at each bolt interface. The resulting static fem model contains more than one million degrees of freedom, and is formed by 10-node tetrahedral solid elements. The dynamic model is similar, but it also contains the definition of the oil mass, the mass of internal shafts and gears and the mass of some external components (hydraulic motors, electrical motor, electronics box). The link between each rigid external component and the attachment areas on the gearbox was obtained through constraint equations. Once the overall stress behavior has been calculated by using the whole models, a detailed sub-model analysis was required in order to improve the design locally in the bearings housing region of the most loaded shaft. Sub-models contain almost all geometric details and the definition of the contact interface between the bearings and the housing surfaces. In order to handle efficiently the non-linear analysis in a so large model, the linear and non-linear portions must be treated separately with the aid of a substructuring procedure.