Shape memory alloy (SMA) washers expand axially when heated, and the expansion for the one-way type SMA is permanent even if the heat is removed. We investigated a method to repair bolted joint loosening defects using SMA washers. We incorporated such a feature into our impedance-based structural health monitoring (SHM) system. An SMA washer wrapped with a heater is installed between a bolt and the nut. Upon detection of a loosening defect, the heater is turned on to expand the SMA washer, which in turn repairs the defect. Our experimental results show that (i) our enhanced SHM system can detect bolted-joint loosening defects, and (ii) it can repair such defects effectively. Our system suggests that self-repairing of some structural defects is feasible without human interventions.

Date Published: 8 April 2009
PDF: 8 pages
Proc. SPIE 7295, Health Monitoring of Structural and Biological Systems 2009, 729512 (8 April 2009); doi: 10.1117/12.816398

Published in SPIE Proceedings Vol. 7295:
Health Monitoring of Structural and Biological Systems 2009
Tribikram Kundu, Editor(s)