Fatigue crack growth mechanics for Ti-6Al-4V (RA) in vacuum and humid air

The effects of environment and cyclic stress intensity factor on crack opening displacement and crack tip strain have been measured, and discontinuous crack growth has been observed directly under high resolution conditions in the Scanning Electron Microscope. This information is used in a crack tip failure model together with cyclic stress-strain, low cycle fatigue, and microstructural characteristics of the material to derive the expected crack growth increment. Agreement with measured striation spacings is reasonable.