| Industry and the military are always looking for ways to stretch their dollar. One way to do this is to make the equipment they currently own last longer in lieu of buying new. For example, many of the aircraft in the USAF have gone beyond their expected service life and over that time have experienced changes in usage. In order for the USAF, or others in the aviation industry, to make their aircraft last longer, they must understand how the changes in usage affect their aircraft.;The purpose of this study was to determine the sensitivity of a representative stainless steel specimen to two different load spectra, spectrum A and spectrum B. This was accomplished by conducting fatigue experiments, baselines for each spectrum and three different combinations of the two spectra, performing fractographic examinations of the fracture surfaces and developing computer simulations, using AFGROW, to represent test data. The results showed that crack growth under spectrum B type loading conditions was significantly slower than under spectrum A. The fractography showed clear distinctions between the spectra fracture surfaces. Also, AFGROW simulations were successful in replicating test data. These results emphasize the need for continual monitoring of fatigue critical locations to better maintain aircraft. |
