V. Torra, A. Isalgue, C. Auguet, Polytechnical University of Catalonia, Barcelona, Spain; F. C. Lovey, J. L. Pelegrina, Centro Atomico Bariloche and Instituto Balseiro, Bariloche, Argentina
The use of NiTi in dampers for Civil Engineering applications require well stabilized behavior. In particular, the use of pre-stressed samples improves the damping efficiency. As earthquakes can appear after several years (or decades) without any oscillation, it is required that the alloy works with guaranteed behavior after long time in the pre-stressed situation. The experimental analysis in parent, in phase coexistence and in martensite phase shows minor actions after only one month at pre-stressed situation and, also increased actions when the room temperature is increased from 293 to 303 K. After several decades at stressed situation also several room temperature yearly actions can be produced acting with relevant changes in the working point inside the hysteresis cycle. The study of aging at 373 K shows, by calorimetry, relevant changes of transformation temperatures in R and martensite phases (up 20 K) with time constants near 70 days and coherent results using X-rays.
Summary: The use of NiTi in dampers for Civil Engineering applications require well stabilized behavior. In particular, the use of pre-stressed samples improves the damping efficiency. As earthquakes can be produced after several years (or decades) without any oscillation, it is required that the alloy works with guaranteed behavior after long time in the pre-stressed situation. The experimental analysis in parent, in phase coexistence and in martensite phase shows minor actions after only one month at pre-stressed situation and, also increased actions when the room temperature is increased from 293 to 303 K. After several decades at stressed situation also several room temperature yearly actions can be produced acting with relevant changes in the working point inside the hysteresis cycle. The study of aging at 373 K shows, by conduction calorimeter, relevant changes of transformation temperatures in R and martensite phases (up 20 K) with time constants near 70 days and coherent results using X-rays.
