Simplified Analysis of the Tightening Process of Bolted Joint With a Bolt Heater

<jats:p>A bolt heater is frequently used when tightening large bolts that cannot be tightened with other methods. Although the tightening process inherently needs a fair amount of working hours, a bolt heater is less expensive than the other tightening tools and it can be applied to the tightening operation in a narrow space. In this paper, an elementary method is proposed to evaluate the tightening process with a bolt heater, aiming at its broader use for middle-sized bolts. One-dimensional finite difference method is employed to analyze the heating process with taking the effects of heat transfer through small gaps into consideration, by which the corresponding bolt elongation is calculated for the specified heating period. The equation relating the bolt elongation and axial bolt force is also proposed, in which the effects of interface stiffness due to surface roughness are incorporated for better estimation of the axial bolt force. The effectiveness of the elementary method proposed here is demonstrated by experiments.</jats:p>