Calibration of the bolt pretension by strain gauges vs. FEA

Abstract

When applying high strength bolts in friction connections, a load-bearing capacity depends on pretension force in the bolts as well as on friction coefficient found on friction surfaces. It is important to get the reliable value of the pretension force, so friction connections often undergo experimental research. In order to use strain gauges, which are inserted into the bolt shank, bolts need to be calibrated before we even use them in experimental research. Research that has been conducted shows a great difference between nominal and experimental strain in bolts, therefore FEA calibration of the bolts had to be carried out. Good results matching were obtained, hence a use of strain gauges was justified even for bolts without a shank.

Keywords

• high strength bolts
• pretension force
• calibration
• experiment
• fea
• longitudinal strain
• 'strain plateau'