| 主权项 |
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 (TOF1) of the ultra-sonic pulses as a function of the rotation angle (α), in order to determine an increase rate (dTOF/dα) of the time of flight (TOF), determining, based on the determined increase rate (dT/dα) of the torque (T), an initial rotation angle (α0) of the tightening operation where the torque (T) starts to increase as a function of bolt deformation, defining the initial rotation angle (α0) of the tightening operation as a rotation angle where the time of flight (TOF) starts to increase, determining a total increase of the time of flight (ΔTOF) during the tightening operation based on the initial rotation angle (α0) of the tightening operation and the increase rate (dTOF/dα) of the time of flight (TOF), and 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=k1*ΔTOF, where k1 is a bolt specific constant dependent on the geometry and material of the bolt. |
