온도 변화에 따른 초탄성 니켈-티타늄 합금 와이어의 교정력 변화

Abstract

The purpose of this study was to investigate the force level changes of Ni-Ti wires with temperature changes during loading and unloading phases. Three-point bending tests were performed and the temperature was changed from initial 37℃ to 15℃～70℃ (three cycles). The loading force was measured at 1.5 mm deflection and the unloading force was measured at the same 1.5 mm deflection returning from 3.1 mm deflection. The results were as follows. 1. The three-point bending test performed at 37℃ showed that the loading force and stress hysteresis of Sentalloy were the largest, but the unloading forces of three Ni-Ti wires were similar. 2. After temperature changes, the loading forces decreased, and the unloading forces increased, so that the two forces became similar. But the remaining small difference between loading and unloading forces after initial temperature changes did not disappeared throughout the temperature changes. 3. After temperature changes, the forces of L&H Titan and Copper Ni-Ti 35°C became similar to the median force between initial loading and unloading forces, but the force of Sentalloy became closer to the initial loading force. 4. Copper Ni-Ti 35°C showed larger force during cooling phase 37℃ relative to the force during heating phase 37℃, and this was attributed to the larger temperature hysteresis of Copper Ni-Ti 35°C.