Study on Preload of Bolted Connections in Pitch Bearing Based on Vibration Modal Analysis

Table 2

Tightening torque coefficient, K.

Surface state	K value
	With lubrication	No lubrication
Finishing	0.1	0.12
General processing	0.13∼0.15	0.18∼0.21
Galvanize	0.18	0.22
Surface oxidation treatment	0.2	0.24