Tension Monitoring Devices Development for Bolted Joints

The present paper reviews recent patents disclosing various ways to monitor the variation of the bolt tension in order to timely readjust the torque to initial specifications. The recent advances related to bolted joints have seen tremendous developments to ease inspection of the fastening tension in both visual and remote inspections. Precision of bolt tightening is one of the major issues noted in industrial plants where accurate preload is questioned whether it is achieved or not. Insufficient preload, caused by an inaccurate tightening method, is a frequent cause of bolted joint failure which may lead to potentially catastrophic structural failures. The loss of tension may occur due to vibration, thermal effects, change in the material characteristics and so on. Reviews of recent related developments are discussed in this paper with proposal of intended features for smart bolts.