Effect of Atmospheric Environmental Conditions on Fatigue Crack Growth
J. Niebuhr, S. Galyon Dorman, S. Fawaz
Corrosion has a significant impact on the fatigue of aging aircraft. In service, an airframe will be exposed not only to a spectrum of mechanical loading due to variations in flight profile and mission types, but also to a spectrum of environmental conditions. Temperature, humidity, atmospheric gas composition, salt concentration, and UV light exposure all vary as a complex function of geographical location, seasonal weather patterns, diurnal cycle, and flight mission profiles. Since systems to apply and control multiple environmental parameters in conjunction with mechanical loading are not readily available, such a system is being developed. This system is being used to examine the effects of various environmental parameters and their combinations on fatigue crack growth rate in aerospace aluminum alloys. This research will provide improved testing methodologies and insight into the primary drivers of corrosion fatigue under realistic atmospheric environments.