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Axially compressed NiTi tube buckling under the cyclic axial compression shown in the next slide

This and the next slide are from:

Sia Nemat-Nasser, Jeom Yong Choi, Jon B. Isaacs, and David W. Lischer (University of California, San Diego, Center of Excellence for Advanced Materials 9500 Gilman Drive, La Jolla, CA 92093-0416, “Experimental Observation of High-rate Buckling of Thin Cylindrical Shape-memory Shells”, Smart Structures and Materials 2005: Active Materials: Behavior and Mechanics, 347 Edited by William D. Armstrong, Proceedings of SPIE Vol. 5761 (SPIE, Bellingham, WA, 2005) doi: 10.1117/12.600238

ABSTRACT: We investigate the buckling behavior of thin cylindrical shape-memory shells at room temperature, using a modified split Hopkinson bar and an Instron hydraulic testing machine. The quasi-static buckling response is directly observed using a digital camera with a close-up lens and two back mirrors. A high-speed Imacon 200 framing camera is used to record the dynamic buckling modes. The shape-memory shells with an austenite-finish temperature less than the room temperature, buckle gradually and gracefully in quasi-static loading, and fully recover upon unloading, showing a superelastic property, whereas when suitably annealed, the shells do not recover spontaneously upon unloading, but they do so once heated, showing a shape-memory effect. The gradual and graceful buckling of the shape-memory shells is associated with the stress-induced martensite formation and seems to have a profound effect on the unstable deformations of thin structures made from shape-memory alloys.

This is Figure 4 of the paper cited above: Photographs of NiTi tube buckling (L/D= 1.5) in uniaxial compression under a displacement- controlled loading with a crosshead speed of 6.99␣10-3 mm/s; numbers correspond to the load-displacement states of Figure 3. (See the next slide.)

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