Failure analysis of Ti-6Al-4V specimens subjected to fatigue

Fatigue is a frequent cause of failure in aircraft components. The fatigue life is influenced by the environmental and loading conditions, by the geometry and material of the components, by the manufacturing process adopted for their production and by the presence of defects [1]. Ti6Al4V titanium alloy is commonly used for the production of structural airframe and engine parts due to its high specific strength and excellent corrosion resistance [2]. The work presents the results of fatigue tests on Ti-6Al-4V specimens. The experimental re- sults are compared with the theoretical ones, obtained using the Wohler and Haigh (modified- Goodman) diagrams. This comparison, together with the observation of the fracture surfaces of the tested specimens (Figure 1), enables the identification of the failure mechanism. The micro notches introduced by the machining of the specimens prove to be preferential sites for the initiation of cracks, with a consequent reduction of fatigue life.