The high fracture tough alloys give comparable strength levels with an increase in fracture toughness and better resistance to stress corrosion cracking. These alloys may make possible the consideration of new procedures for operation, maintenance, and inspection. For the present, these materials in the 220 to 280 ksi strength range, cannot be certified to damage tolerant design criteria. They may not yield critical cracks readily detectable using normal in-service inspection methods. Even though they may not qualify as damage tolerant in single load path applications, the improved mechanical properties alone may justify the consideration of these materials, especially in corrosive environments. In the future, they may allow on-condition maintenance, crack growth monitoring, and increased potential for rework.
This document identifies serveral available materials. It compares properties of selected low-alloy steels to the higher alloyed steels. It also compares failure modes, maintenance, and inspection techniques. Although cost should be a factor when considering the material selection for landing gear applications, this document will only focus on the technical aspects.
