U. Mariani

Comparison of Fatigue Crack Propagation Behavior of Al 2024 and Al–Li 8090 Helicopter Fuselage Panels

A comparison between two types of helicopter fuselage panels with a traditional design of skin and stringers was carried out. Panels were made with the same geometrical shape and dimensions but with two different aluminium alloys for the skin: Conventional 2024 and 8090 Al–Li alloy. Two different crack locations were considered to be taken into account for the damage tolerant behavior of the two panel typologies: A crack into the skin between two stringers and a crack into the skin under the stringer after the removal of a complete section of the stringer. The crack growth was monitored during the fatigue load application, and a finite element (FE) model was utilized in order to calculate the fracture mechanics parameters. The experimental data (crack growth rate da/dN) and the FE results (stress intensity range ΔKI) were checked with the crack propagation material data, with good agreement. According to these results, it is possible to compare the damage tolerant behaviors of the panels made by the two different materials, with the purpose of optimizing crack propagation behavior versus weight in this fundamental helicopter component.

Improvements in Fatigue Evaluations of Helicopter Transmissions

Helicopter transmission is a critical assembly which significantly contributes to helicopter performance, life cycle costs and safety. Any improvement in fatigue evaluation can therefore give relevant benefits to the customer. AgustaWestland and Politecnico di Milano have carried out several research and development activities which can be considered a comprehensive project toward improved fatigue evaluation of transmissions.