The Effects of Truncation and Marker Loads on Spectrum Fatigue Crack Growth
Abstract
The US Air Force is operating a large fleet of aging aircraft. Some examples of problems that aging aircraft can encounter are fatigue and corrosion. Throughout the Air Force and industry, many research efforts are being conducted to deal with the aging aircraft problems. Many of these efforts require a significant amount of fatigue testing, both constant amplitude testing, which can be relatively fast, and spectrum fatigue testing, which can take a significant amount of testing and inspection time. One of the main objectives of this research effort was to determine whether spectrum truncation has a noticeable effect on crack growth rates. In order to save valuable testing time, the duration of spectrum fatigue tests can be shortened by truncating the spectrum. When truncating a spectrum, small fatigue cycles that are not expected to contribute to the overall crack growth life of the specimen or structure, can be removed from the spectrum. By doing so, a significant amount of test time can be saved. It is very important though that by excluding these small fatigue cycles from the spectrum, the overall crack growth behavior will not change. Another important objective of this effort was to verify that the insertion of marker loads into a fatigue spectrum has no or a negligible effect on the crack growth rate when compared to a fatigue test without the marker loads. When running a fatigue test to determine crack growth rates, regular inspection is necessary to check the crack size versus cycle count, which can be very time consuming and might prevent running tests overnight. When inserting marker loads in a fatigue test, the test can be
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 2005
- Accession Number
- ADA437170
Entities
People
- Stephan Verhoeven
Organizations
- United States Air Force Academy