Physical constraints in SMA applications. One study case: dampers in Civil Engineering

摘要

The application of Shape Memory Alloys (SMA) in mechanical engineering (ME) or in civil engineering (CE) requires the tuning of the physical properties with each particular need. When the target involves dampers for quakes in CE the number of full working cycles is relatively small (i.e. 200) but the application requires guaranteed behavior after several years of inactivity. On the contrary some devices in ME may need relatively high frequencies operating for a long period of time. In this work the mesoscopic effects in the SMA are quantified to ensure guaranteed behavior in the frame of dampers for CE applications. For instance, the actions of accumulated deformation in cycling and the changes induced by external temperature (i.e., summer-winter) are evaluated. Also, the perturbations induced by diffusive (induced by phase metastability, i.e. produced by microscopic interactions) are considered. In particular, the phase coexistence effects are visualized in Cu-based and partially in NiTi alloys. The practical creep induced by cycling and the coexistence actions are decisive in damping applications.