In recent Smart Wing wind tunnel tests at NASA Langley, we demonstrated over 5°of span-wise wing twist at M=O.205. This was a considerable improvement over the 1.25° of twist demonstrated during the initial tunnel test. Key to the improvements were two developments. First a different torque loading path in the structure, which resulted in torque being directly reacted from root to wing tip. Secondly, a new SMA actuator was developed, with a measured blocking torque of 3500 in-lb. The second round of tunnel tests not only demonstrated increased wing twist; we also were able to command a variety of twist angles and were able to show that the wing could maintain a predetermined twist for over an hour with a stability of 0.05°. Power consumption was recorded, with maximum power of 200W during twisting, and a power demand of2OW for maintaining wing twist.
Shape Memory Effect (SME) TiNi torque tubes were fabricated, tested and installed to supply 2500 in.lbs and 500 in.lbs of torque for inboard and outboard sections, respectively, of the DARPA smart wing wind tunnel model . Structural connections to the tubes were designed so that the entire assembly would fit within the interior of the wing, whose maximum dimensions of depth ranged from 1.125" to 0.375", depending on the position along the wing span. The torque tubes themselves were made by gun drilling a TiNi ingot and ElectroSpark Discharge Machining (EDM ) to the required dimensions, which were calculated from a simple model described in a previous paper. The torque tubes were placed into the wing and twist deflections were measured. Deflections on the wing were measured at 1.3°, which provided a significant increase (-8%) in the wing rolling moment.
IntroductionThe Shape Memory Effect (SME) is due to a first order martensitic phase transformation from a low modulus martensitic phase to a high modulus austenitic phase. Relevant phase transformation temperatures are denoted as Mf (Martensitic finish temperature) below which the material is fully
To verify the predicted benefits of the smart wing concept, two 1 6% scale wind tunnel models, one conventional and the other incorporating smart wing design features, were designed, fabricated and twice tested at NASA Langley's 16ft Transonic Dynamic Tunnel, in two series oftests, conducted in May 1996 and June 1998, respectively. A key objective of the Smart Wing Phase 1 program was not only to construct wind tunnel models that could be used to validate the predicted benefits of using smart materials, but also to identif' and reduce the risks involved in eventually integrating smart materials into an actual flight vehicle. Among the challenges encountered in developing the wind tunnel model were the attachment ofthe shape memory alloy (SMA) control surfaces to the wing box, integration of the SMA torque tube in the wing structure, installation of the instrumentation, and development of fail safe control mechanisms to protect the model and the tunnel in the event offailure ofthe smart systems.In this paper, design and fabrication details of the two Smart Wing Phase 1 wind tunnel models are presented. Among the topics covered are 1) model design requirements, model design and static testing ; 2) manufacturing techniques with particular emphasis on the improvements in the design and fabrication of the SMA control surfaces from the first to the second test; 3) system integration; and 4) post-test analysis and planned improvements. Lessons learned from the Phase 1 effort are discussed along with plans for the Smart Wing Phase 2 program.
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