Session: 02-02 Shape Memory Alloy and Polymer Applications

Paper Number: 170081

170081 - Shape Memory Alloy Actuated Vortex Generators for Aircraft Quiet High-Lift System: Alloy Design 

Airframe noise during an aircraft's low-altitude approach is primarily caused by high-lift systems, such as the inboard flap edge and the outboard trailing edge flap. These latter flaps are fully deployed during approach and can generate significant noise, as the large lift gradient at the flap edges during landing creates strong roll-up vortices. The aim of this work is to develop vortex generators (VGs) for the outboard trailing edge (OBTE) flap to reduce the strength of these roll-up vortices and manage the flow around the edge to minimize radiated noise. Previous efforts utilizing shape memory alloy reconfigurable technology vortex generators (SMART-VGs) designed for drag reduction are now being applied to create new vortex generators with various shapes and functions aimed at noise reduction.

The VGs are driven by a shape memory alloy (SMA) torque tube positioned along the hingeline for on-demand deployment and stowing. The first set of VGs is designed for the outboard trailing edge of the main flap, using five actively actuated VGs. These VGs are designed to achieve a target range of motion from 0 to 135 degrees of rotation, with the hinge moment torque on the order of 339 N-mm. To meet the target activation temperatures and minimize hysteresis, a NiTiPd alloy was developed, leveraging the B2 (cubic) to B19 (orthorhombic) martensitic transformation path with low hysteresis. Given the thin-wall tube constraints on the SMA actuators, a clean melting process was adopted, based on arc melting and suction casting, to produce a microstructure free of any carbides or large oxides that could potentially lead to cracks. The cast rods were drawn to smaller diameter rods to introduce some grain refinement, followed by drilling and final machining. Initial training of the tubes was performed using a modified ASTM E3414-23 standard test method for constant torque thermal cycling of cylindrical shape memory alloy specimens. The alloy demonstrated an exceptionally low hysteresis of less than 7 °C, while still achieving a large transformation strain of 10% under torque and a two-way shape memory effect with more than 6% strain.

A second set of VGs was designed using spring-loaded mechanisms with superelastic NiTi alloys. Small, needle-like tubes were installed along the hingeline of five VGs on the outboard trailing edge of the aft flap. In this design, the VGs deploy passively as the flap extends and stow when they come into contact with the flap during retraction. The ramifications of using these methods and the design improvements of both alloys are discussed.

These VGs will be evaluated as part of Boeing’s Quiet High Lift project under the Federal Aviation Administration (FAA) Continuous Lower Energy, Emissions and Noise (CLEEN) III Program.

Presenting Author: Othmane Benafan NASA Glenn Research Center

Presenting Author Biography: Othmane Benafan has worked at the NASA Glenn Research Center (GRC) since 2011. He has been a materials research engineer in the High Temperature and Smart Alloys Branch, leading the development of shape memory alloy technology. His investigations have included theoretical and experimental research with a focus on fit-for-purpose shape memory alloy synthesis and processing. His has studied experimental mechanics of solid-state phase transformations to construct process-structure-property roadmaps for these alloys. Dr. Benafan has published over 80 peer-reviewed journal articles, 25 conference proceedings, and currently holds 5 issued patents. Dr. Benafan is active in the technical community serving numerous roles including graduate faculty doctoral advisory committees, editorial board member of the Shape Memory and Superelasticity journal, and ASM’s content and data products council. He is the President of the International Organization on Shape Memory and Superelastic Technologies (SMST), and the past executive chairman of the joint industry-government-academia Consortium for the Advancement of Shape Memory Alloy Research and Technology (CASMART). Dr. Benafan has received numerous awards during his career including the NASA Abe Silverstein Medal, the Presidential Early Career Award for Scientists and Engineers (PECASE), and the R&D100 Award. Dr. Benafan has a bachelor of science, a master of science and a doctoral (Ph.D.) degree in mechanical engineering from the University of Central Florida.