Assemblages boulonnés : mesure de la tension de serrage par méthode ultrasonore

Bolted joints : tightening tensions measured by ultrasonic method

Chef du secteur Comportement des matériaux (Cetim, établissement de Saint-Etienne)

Abstract

The tightening tensions can be measured by an ultrasonic impulse method using echographs with a time base.

After a preliminary calibration, the preload or tightening load - main parameter of the behaviour of a bolted joint - can be known accurately during the initial tightening (assembly quality control aspect). Under certain conditions, the residual tension after a certain time in service (maintenance aspect) can also be measured.

In industrial environments, the inaccuracy of the tightening measurement can be less than ± 5% if the tested bolts meet some simple geometrical criteria.

In the short term, the authors expect to put this method into general use by eliminating the calibration stage and thereby permitting the control of tightening operation in any bolted joint. In the latter case, the inaccuracy would not be so large (less than ± 10%) ; however, far better than the inaccuracies (greater than ± 20%) by the best tightening devices that are based on torque measurement.