Design and Validation of an Apparatus for High Temperature Fatigue Testing in an Inert Environment.
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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A synergistic interaction between creep and fatigue in structural materials at high temperature has previously been shown to exist. More recently, the importance of environmental effects on fatigue has been shown to frequently over-shadow the creep-fatigue interaction. As both creep and environmental effects are temperature and time dependent, the role of each is often difficult to separate. The topic of this thesis is the design and validation of an apparatus to study the interactions of environment and creep with fatigue damage at high temperature. The alloy 2 14 Cr - 1 Mo steel was selected for testing to validate the system as considerable creep-fatigue data exist on this alloy. Strain controlled fully reversed testing was conducted at temperatures of 482 C 900 F and 538 C 1000 F. The results of the testing at 1 total strain range agreed with published data from the same heat of material. Differences in results at 0.5 total strain range were, however, found to exist. The differences are believed to be due to different specimen geometries used by other studies. This research used uniform gage length instead of the standard hourglass specimens used by others. The uniform gage length samples have a lower fatigue life at the lower strain range than published data. The results from uniform gage length samples are believed to be a better representation of a materials bulk fatigue behavior. Author
- Properties of Metals and Alloys
- Test Facilities, Equipment and Methods