Development of new detecting method of clamping force of bolted joint

The clamping force of a bolted joint greatly influences its performance. But the clamping force is seldom checked after tightening. In this study, a new method to detect the clamping force after tightening has been proposed. In the proposed method, the clamping force is detected by pulling the bolt threads which protrude through the nut. Clamping forces of pre-tightened bolted joints were detected experimentally by the proposed method. Results show that the proposed method can detect the clamping force within to ±10% accuracy. Furthermore, a prototype wrench to detect clamping force has been developed using a commercial torque wrench. Results of the verification show that this wrench can also detect the clamping force within to ±10%.