Self-Sensing and Self-Repairing Joints Using Smart Material

Recently the shape memory alloys are using as new functional materials for many applications such as couplings, sensors, and actuator. This project deals with the new Idea of self-sensing and self-repairing of bolted joint using piezoelectric material and shape memory alloys (SMA). Power transmission loss occurs due to the loosening of nut. This loosening is occur due to the vibratory motion of the system. The SMA has good damping capacity, so it is used as an actuator to retain power loss. The basic principles behind this concept are piezoelectric effect and shape memory effect. Piezoelectric effect produces voltage corresponding to loosening of nut. The produced voltage in the range of millivolts is not sufficient to heat the SMA. So produced voltage is amplified by using amplifier. This voltage is used to heat the Nitinol-SMA washers, which in turns expand to maintain torque transmission. Also cryogenic SMA washer act as a locking device.