A non-destructive quality assessment for blind-fastener installations based on the combination of ultrasound techniques and real-time monitoring of the fastening process

This paper proposes and evaluates a non-destructive method in assessing the quality of blind-fastener installations. The method is based on combining the time of flight of an ultrasonic pulse along the pin of the fastener and the fastener installation time. The former has to be measured after the fastening process; the latter has to be acquired at the machine during the fastening. The tests performed on carbon fibre reinforced plastic laminates joined by means of ABS0257 blind fasteners have proved that the method can distinguish incorrectly installed fasteners due to improper grip selection. The hit rate of the developed non-destructive method is above 95 % for the tested range of fastener sizes. The implementation of this method might prevent the use of extra fasteners, currently required, in order to compensate for the uncertainty of blind-fastener installations