Bolt Preload Variations During Repeated Tightenings

Abstract

Bolt preload prediction, through torque value, is challenged by friction variations within the bolted joint. Accurately estimating the initially achieved preload, is a persistent problem. This study aims to examine the repeatability of the bolt tightening process, under constant torque values, using experimental data. The experiments were conducted on bolts and nuts with a black finish surface, and the preload and nut factor variations were examined under four lubrication scenarios.