In-flight tracking of helicopter rotor blades with tabs using shape memory alloy actuators

The objective of this research is to develop a methodology to track helicopter rotor blades in-flight with tabs using shape memory alloy actuators. Tracking is required to reduce vibratory loads that are generated due to dissimilarity of blades. The research was conducted in two phases. The first phase involved a study on the thermo-mechanical behavior of shape memory alloys and the development of an analytical model to describe the behavior of the tab actuator (SMA-SMA actuator). The second phase of the research involved applying the knowledge of the SMA behavior to develop, construct and test a tab actuator to deflect a trailing-edge tab.; In the first phase, four constitutive models for SMA were investigated and validated with test data. The models investigated were the Tanaka, Liang and Rogers, Brinson, and Boyd and Lagoudas models. These models were used to predict the quasi-static stress-strain-temperature behavior. All models showed acceptable correlation with test data. Then a constrained recovery model was developed for the case where the SMA wire is plastically deformed, clamped at both ends, and then heat activated. The Brinson model over-predicted the recovery stress-temperature behavior. The refined model developed in this dissertation showed acceptable correlation with test data.; In the second phase of the research, a NACA 0012 blade section with a tab actuator embedded was constructed. The actuator was tested on bench-top as well as in an open-jet wind tunnel to determine the actuator performance under different flight conditions. This task also included building and testing a locking mechanism and a position feedback controller. It was shown that a 2-wire actuator, with all wires plastically elongated to 4.21% initially, is able to deflect the tab of a blade section sufficiently at a forward velocity of 120 ft/sec for angles of attack up to 15°. The tab deflected up 9.35° and deflected down 31°. A 5-wire actuator with all wires plastically deformed 2.43% initially was also tested in the open-jet wind tunnel. The tab deflected up 14° and down 11.5° at a forward velocity of 120 ft/sec and an angle of attack of 15°. The position feedback controller demonstrated its ability to track to a desired tab position in about 10 seconds. The locking mechanism showed its ability to lock the tab in position for the tab deflecting up during bench-top tests. (Abstract shortened by UMI.)...