Abstract:During the development of aerospace structures, typically many fatigue tests are conducted. During these tests, much effort is put into inspections in order to detect the onset of failure before complete failure. Strain sensor data may be used to reduce inspection effort. For this, a sufficient number of sensors need to be positioned appropriately to collect the relevant data. In order to minimize cost and effort associated with sensor positioning, the method proposed here aims at minimizing the number of necessary strain sensors while positioning them such that fatigue-induced damage can still be detected before complete failure. A suitable detection criterion is established as the relative change of strain amplitudes under cyclic loading. Then, the space of all possible crack lengths is explored. The regions where the detection criterion is satisfied before complete failure occurs are assembled into so-called detection zones. One sensor in this zone is sufficient to detect criticality. The applicability of the approach is demonstrated on a representative airplane structure that resembles a lower wing section. The method shows that four fatigue critical spots can be monitored using only one strain sensor in a non-intuitive position. Furthermore, we discuss two different strain measures for crack detection. The results of this paper can be used for reliable structural health monitoring using a minimum number of sensors.Keywords: structural health monitoring; predictive maintenance; crack detection; fatigue damage; aerospace structures
Born and raised in Montgomery, Alabama, Boss studied dance performance at Southern Union State Community College and Chapman University. A contestant on "So You Think You Can Dance," he later became a judge on the dance competition show. He also appeared on "Star Search," "The Wade Robson Project," and in films like "Hairspray," "Step Up: All In," "Step Up 3D," "Magic Mike XXL," the 2016 "Ghostbusters," and "The Hip Hop Nutcracker."
After dropping out of college in Kansas, Alley moved to Hollywood to work as an interior designer. She appeared on game shows as a contestant, on "Match Game" and "Password Plus." But she was hired, despite no professional experience and a faked résumé, to play Lt. Saavik, the half-Vulcan, half-Romulan protégé of Mr. Spock, in "Star Trek II: The Wrath of Khan." She noted at a 2016 "Star Trek" convention panel in Las Vegas that, as a teenager, friends had made fun of her eyebrows' ability to arch: "I have no control over it," she said. "So, I would watch [the original 'Star Trek' series] and when Mr. Spock would come on, I would say, 'Wow, if I was ever an actress, I could play Spock's daughter.'" 2b1af7f3a8