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Table 1 Comparison of conventional bolt tension confirmation methods [1, 11]

From: Research Review of Principles and Methods for Ultrasonic Measurement of Axial Stress in Bolts

Method

Measurement

Accuracy

Complexity

Torque

Torque

± 25%

Ordinary

Turn-of-the-nut

Torque + nut rotation angle

± 15%

Slight

Yield point

Torque rate

± 8%

Slight

Electric resistance strain gauge

Resistance of strain gauge

–

Extreme

Elongation

Elongation of bolts

± 5%

Extreme