Jeom Yong Choi

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The compressive response of a NiTi shape-memory alloy is investigated at various strain rates using UCSD’s modified 1 2-in. Hopkinson pressure bar and a conventional Instron machine. To obtain a constant strain rate during the formation of a stress-induced martensite in a Hopkinson test, a copper tube of suitable dimensions is employed as a pulse shaper,(More)
The compressive response of a Ni–Ti–Cr shape-memory alloy is investigated at various initial temperatures, over a wide range of strain rates, using an Instron hydraulic testing machine and one of the CEAM/UCSD s modified split Hopkinson bar systems. The alloy is superelastic over a range of initial temperatures and strain rates, for strains less than about(More)
The effect of the annealing conditions and the initial temperature on the compressive response of a ternary Ni–Ti–Cr shape-memory alloy is nvestigated at a strain rate of 10−3/s, using an Instron hydraulic testing machine. The annealing temperature and duration considerably influence he forward, from austenite to the stress-induced martensite, and the(More)
UNLABELLED BACKGROUND AND OBJECTIVE To examine the biophysical effects of photothermal heating on herniated intervertebral discs during laser decompression surgery. STUDY DESIGN/MATERIALS AND METHODS Ex vivo bovine nucleus pulposus specimens were irradiated with a Nd: YAG laser (lambda = 1.32 microm, 100 seconds exposure time, 9-31 W/cm(2), 4.8 mm spot(More)
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(More)
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