[1A3] Detecting the tension of bolts and fasteners by using ultrasonics to measure elongation
M Davison
Elcometer NDT, UK
Bolts and fasteners are used to join components in many critical applications. It is essential these bolts and fasteners are tightened to the correct initial tension and subsequently will continue to operate at the correct tension throughout their working lifetime. Bolt and fastener failures continue to be an ongoing issue for asset owners.
Torque based measurement to determine the tension applied to bolts and fasteners can suffer from inconsistencies caused by the inability to calibrate the frictional forces on the threads. Elongation (change in length, or stretch) has a direct relationship to force applied. Ultrasonic measurement of elongation is a proven and more reliable method of tension measurement.
The principles of elongation measurement using ultrasonics, how elongation can be converted to force, stress, strain, and the practical considerations of operations will be explained in this paper.
Torque based measurement to determine the tension applied to bolts and fasteners can suffer from inconsistencies caused by the inability to calibrate the frictional forces on the threads. Elongation (change in length, or stretch) has a direct relationship to force applied. Ultrasonic measurement of elongation is a proven and more reliable method of tension measurement.
The principles of elongation measurement using ultrasonics, how elongation can be converted to force, stress, strain, and the practical considerations of operations will be explained in this paper.
