Patent ID: 9482588
Filing Date: 2016-11-01
CPC Classification: B25B,F16B,G01L,G01N

Claim Text:
1. A method of evaluating a clamp force (F) in a threaded joint between at least one bolt and a matching threaded piece during a tightening operation, comprises: tightening the joint by means of a torque delivering device, registering a rotation angle (α) between the at least one bolt and the matching threaded piece during tightening of the joint, measuring a torque (T) provided to the joint during tightening thereof, simultaneously inducing ultra-sonic pulses into the at least one bolt and measuring a time of flight (TOF) of the pulses in the at least one bolt, monitoring, in response to a measured increase of the torque (T), the torque (T) as a function of the rotation angle (α) in order to determine an increase rate (dT/dα) of the torque (T), monitoring a time of flight (TOF determining, based on the determined increase rate (dT/dα) of the torque (T), an initial rotation angle (α defining the initial rotation angle (α determining a total increase of the time of flight (ΔTOF) during the tightening operation based on the initial rotation angle (α evaluating an established clamp force (F) in the joint based on the total increase of the time of flight (ΔTOF), the clamp force (F) being presumed to be proportional to the total increase of the time of flight (ΔTOF) according to the equation F=k