Health monitoring of bolted joints via electrical conductivity measurements

The use of electrical resistance as a diagnostic parameter in structural health monitoring of bolted joints is discussed in the paper. The proposed method is based on the phenomenon that the electrical constriction resistance of the rough contact interface between two conductive members clamped by a bolt is a sensitive indicator of bolted joint integrity. A simple formula for relationship between relative electrical conductance changes and relative tightening torque changes is analytically obtained. Based on this formula, a methodology is described for detecting a loosening failure of conductive bolted joints.