Adib, A., Baptista, C., Barboza, M., and Andrade, M., "Damage Evolution in Thin-Walled Titanium Ducts for use in Aircraft Pneumatic Systems," SAE Technical Paper 2007-01-2849, 2007, doi:10.4271/2007-01-2849.
An important energy source in commercial aircrafts is the high pressure, high temperature air that is bled from the engines and routed throughout the airframe to secondary systems. This hot air is transported by the engine bleed system, a set of thin-walled ducts whose reliability and durability are important for flight safety. Among the various materials suited for use in this system, titanium stands out because of its favorable characteristics, such as high strength-to-weight ratio and corrosion resistance. The effects of aging must be taken in account when predicting the useful life of the bleed system parts. In order to understand and describe the damage accumulation process suffered by the titanium ducts, a set of cyclic pressurization tests simulating the service conditions was conducted in a pneumatic workbench. Tensile and fatigue ring-shaped specimens were further cut from these ducts and tested in laboratory air at room temperature in a servo-hydraulic machine. The tensile and fatigue properties of the specimens were correlated to the pressurization parameters (pressure, temperature and number of cycles), in order to evaluate the damage accumulation suffered by the ducts during the cyclic pressurization stage. Further research will include the investigation of the physical nature of damage. The final objective of this project is to establish the safe service conditions for the titanium ducts.