Method for controlling the quality of a blind fastener installation

A method for controlling the quality of installation of a blind fastener comprising a sleeve and a core bolt, the blind fastener being inserted into a pre-drilled bore hole in a structure, and then locally deformed by a tool that pulls or torques the core bolt to deform the sleeve into a bulb on a rear side of the structure until a driving portion of the core bolt fractures indicating that the installation of the blind fastener is complete, with at least one force-displacement signal and a torque-angle signal having been generated during the installation of the blind fastener, the checking process comprising the following steps:

• a) identifying at least two notable points from at least one signal, the at least two notable points having been selected from:
• a pulling start point (B0) or a screwing start point (S1);
• a buckling point of the sleeve (B1);
• a contact point of the sleeve (B2) between the bulb and the rear side of the structure or a contact point of the core bolt (S2) between the head of the core bolt and the collar of the sleeve;
• and a force setpoint (B3) or a fracture point (S3) of the driving portion of the core bolt;
• b) calculating at least one first parameter as a function of at least one of the at least two notable points identified in step a), in order to check that the bulb is formed and is in contact with the rear side of the structure;
• c) calculating at least one second parameter as a function of at least one of the at least two notable points identified in step a) in order to check that a predefined tension is applied in the core bolt once the blind fastener has been installed;
• d) for at least one of the first and second parameters, comparing the at least one parameter with an associated predefined condition that indicates a proper installation of the fastener;
• and
• producing a result signal that the installation is defective if at least one result of the comparison does not meet the predefined condition.