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Use of shape memory alloy for active shock control bump application

A shape memory alloy (SMA) with composition of Ni50.1Ti49.9 (at. %) was used for fabrication of a 3-D bump structure intended for use as an active shock control bump (SCB) into a transonic wing. This kind of bump is a variable-geometry structure designed to reduce the drag induced by shock wave ensure wing’s aerodynamic performance over the entire range of operating conditions. To meet this target, the SMA bump requires to exhibit two-way shape memory effect (TWSME) so that it can yield continuous shape change by properly changing the driving temperature. Result from differential scanning calorimetry was first presented to provide material’s phase transformation temperatures. To obtain the TWSME, a thermo-mechanical training procedure was proposed and a set of training devices were designed for training SMA bump. The SMA bump in this paper is trained to have a relatively flat shape in high temperature and can swell up when cooling. After more than 80 times training, the TWSME of the material tends to be stable. Then the thermo-mechanical responses of the SMA bump which is subjected to about 100 times training was tested. The result shows that the trained SMA bump can generate about 1.2 mm maximum recoverable deformation during martensitic transformation, which is about 3% of the ratio of the deformation region. Finally, the influence of external load on the thermo-mechanical response of the trained SMA bump were also studied.