April_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | A P R I L 2 0 2 0 6 0 SHAPEMEMORY ALLOY ACTUATED VORTEXGENERATORS Shape memory alloy reconfigurable technology—vortex generators (SMART-VG) can reduce fuel consumption and improve aircraft efficiency. F.T. Calkins,* A.W. Fassmann, and P.M. Vijgen, The Boeing Co., Seattle D.E. Nicholson and M.A. Bass, The Boeing Co., St. Louis O. Benafan,* D.J. Gaydosh,* G.S. Bigelow, and R.D. Noebe, NASA Glenn Research Center, Cleveland C onventional vortex generators (VG) in aeronautical ap- plications are static vanes mounted on aircraft surfaces and can be used to improve aircraft efficiency during take-off and landing. However, during the cruise phase of flight, these static devices are deployed even when their func- tionality is not needed and produce a drag penalty. With the goal of improving aircraft efficiency, Boeing in collaboration with NASA Glenn Research Center (GRC) have developed and successfully flight tested environmentally activated SMART- VGs that passively, repeatedly, and accurately retract during cruise and deploy during take-off and landing phases. This ap- plication is distinctively enabled by the ability of shape mem- ory alloy (SMA) actuation to produce large work outputs in compact volumes and operate as both a sensor and actuator. The SMART-VG project discussed here was built upon recent advancements in SMA rotary-actuation technology, which in- cluded improved alloy systems, design tools, best practices, published standards, and previous wind tunnel and flight test demonstrations [1] . Commercially available SMAs generally are not suitable for use in passive (environmentally activated) aerospace appli- cations where precise actuation at extreme temperatures cou- pled with functional and geometrical constraints are required tomeet demandingmission requirements. Consequently, over the past decade, NASA GRC developed a suite of stable, high- strengthSMAs tuned for use inbothhigh- and low-temperature applicationsinvariousformsincludingrotaryactuationtomeet challengingaerospaceneeds.High-temperatureSMAs(HTSMA) have been developed, flight tested, and mission flown raising their technology readiness level (TRL) to >7 (e.g., flight-tested in the spanwise adaptive wing project [1] and flown in the AlBus cubesatmission [2] ). Boeing successfully integratedanddemon- strated SMA actuation systems with precise control fromwind tunnel models to full-scale flight tests for a range of aero- space applications. These demonstrations included variable geometry chevrons (VGC) [3] , the adaptive trailing edge (ATE) [4] , and remote control actuated (RCA) wind-tunnel models [5] . The latest demonstration is an environmentally activated SMART-VGsystem. ThreeSMART-VGsweredesigned, produced, and integrated into a “piano” panel above the nacelle on the *Member of ASM International right wing of the 777-200 test aircraft, shown in Fig. 1. The VG design involves a deployment range of 90°, with a fully retract- ed position of 0° above 9753 m (32,000 ft) and a fully deployed position of 90° below 3048 m (10,000 ft) for cruise and take-off or landing, respectively. The VGs were designed to handle in- flight aerodynamic loads of up to 1 N · m (8.85 lbf in.) of torque and operate in a thermal environment between −50 and 0°C in a production-like VG form. The SMAmaterial, with transforma- tion temperatures and actuation properties tailored to match typical commercial aircraft-flight profiles, was developed and produced in rod form. The rods were trained as rotary actua- tor components to produce stable two-way capability. Fol- lowing training, the rods were integrated into the hingeline of the adaptive VG devices. To assess in-flight performance, the SMART-VGs were instrumented with position, tempera- ture, and load sensors, and data was acquired using a wireless data-acquisitionsystem. TheSMART-VG’s in-flightperformance was validated as part of Boeing’s 2019 EcoDemonstrator pro- gram [6] . This article highlights the focused SMA development effort; flight test results; and successes, challenges, and future of this promising technology. TARGETED ALLOY DEVELOPMENT A set of requirements for the SMART-VGs consisting of temperature range, pressure altitude, loads at speed, and foot- print, together with the anticipated functionality were used as the basis for developing a new shape memory alloy. Un- like previous studies where the alloys needed to transform at higher temperatures to activate an aircraft exterior surface on command [1] , the current undertaking features the need for ac- tuation below0°C commensuratewith passive environmental- ly induced actuation during a typical commercial aircraft-flight profile (i.e., typical temperatures associated with take-off, cruise, and landing). In addition, based on aerodynamic data, the current VGs can experience loads between 0 and 1 N · m depending on speed and placement. The VGs configuration (deployed or retracted) as a function of altitude was checked against the atmospheric ambient-temperature standards [7] , which determined functional temperatures of 0°C for fully de- ployed and −50°C for fully retracted. 6 FEATURE