FASCO

On the axial force (remaining tightening force) of rivets and hack bolts
 
               1) Mechanism to generate axial force (residual clamping force):

 Rivet: While holding the rivet head, pull on the center pin and crush while crushing the hollow sleeve rear,
        Alternatively, it dives into the inside of the sleeve and applies a compressive force to the sleeve. A part of the sleeve is a yielding area, and a part of the sleeve is an elastic area. The base material is subjected to a compressive force via the sleeve's valving.
        If the base material is sufficiently elastic, the pin is broken and the sleeve is released from compression and returns some clamping force. In the opposite case, the rivets play and the board moves. It is necessary to select rivets and members. (We make trial and experiment and decide)