Developing the capability to examine environmental effects on small fatigue crack growth

Date of Award


Degree Name

M.S. in Mechanical Engineering


Department of Mechanical and Aerospace Engineering


Advisor: Robert Brockman


It has been observed that the life limiting fatigue behavior in numerous superalloys is dominated by small crack growth behavior. While environmental effects on crack growth behavior of Ni-base superalloys are well documented within the literature, the published research is largely limited to long crack behavior due to the difficulty of measuring small cracks in a vacuum chamber. A testing capability for optical measurement of small cracks under ultra-high vacuum and at elevated temperatures has been developed. Optical measurement capabilities have been evaluated on a lab air machine to determine crack measurement accuracy. Vacuum tests were then run at 650⁰ C on a sub-solvus IN100 specimen to quantify the effect of vacuum on the propagation life within the small crack regime. The effectiveness of this test capability and the role of environment on small crack growth behavior will be discussed.


Nickel alloys Cracking, Heat resistant alloys Cracking, Materials at high temperatures Fatigue

Rights Statement

Copyright 2010, author