Method and apparatus for evaluating clamp force in a bolt by means of ultra-sonic measurements

US9482588B2 · kind B2 · utility

Assignee

• ATLAS COPCO INDUSTRIAL TECHNIQUE AB · SE

Inventors

• Erik Vilhelm Persson · Bissenkamp, SE
• Arne Torgny Roloff · Stockholm, SE

Key dates

• Filing date: Dec 10, 2013
• Grant date: Nov 1, 2016
• Expiry date: Dec 10, 2033

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N2291/2691
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

In an apparatus and a method of evaluating a clamp force (F) in a threaded joint between a bolt and a matching threaded piece during a tightening operation, a torque (T) provided to the joint is continuously measured and ultra-sonic pulses are simultaneously induced into the bolt such that a time of flight (TOF) of the pulses in the bolt is measured. In response to an increase of the measured torque (T) an increase rate (dT/dα) of the torque (T) is determined, from which an initial rotation angle (α0) where the torque (T) starts to increase due to bolt deformation is determined. An increase rate (dTOF/dα) of the time of flight (TOF) is also determined. A total increase of the time of flight (ΔTOF) during the tightening operation is then determined based on the initial rotation angle (α0) and the increase rate (dTOF/dα) of the time of flight (TOF).