SMART, REUSEABLE AND ADAPTIVE INSERTS FOR AIRCRAFT FASTNERS

A typical aircraft requires extensive amounts of fasteners. Due to the harsh environment to which those fasteners are subjected locking systems for threaded connections are seriously critical to aircraft integrity. The most challenging environmental issue is the timperature range (-65F to +800F) in which the thread locking system must perform. Aircraft of mie-twentieth century design relied heavily on mechanical locking techniques, such as lockwires and castellated nuts, but the skill and time required for proper installation is excessive. Later, locking nuts fitted with nylon patches of rings were developed, however the inferent problems of limited temperature range and low reusability have not been surmounted. Likewise, all-metal self-locking nuts have serious shortcomings, skuch as limited vibration resistance and mechanical thread destruction. The proposed effort employs shape memory alloy (SMA) as the licking mechanism. By cleverly exploiting the recovery of SMA to its original form, adaptive locking mechanisms can be developed that provide extensive allowable reuse, a preatly enhanced temperature range, and superior locking force for improved vibration dampoing.