What occurs to the stem of a self-plugging (friction lock) rivet during installation?

During the installation of a self-plugging (friction lock) rivet, the stem is pulled until it snaps off, leaving a flush finish with the rivet's head. This specialty rivet is designed with a unique mechanism that allows for a secure lock when the stem is pulled, essentially activating the rivet’s frangible attachment method.

As the rivet is installed, the tension applied to the stem causes it to deform and eventually break at a predetermined point, ensuring that the installation is both effective and efficient. The snapping action of the stem is critical because it allows the remaining part of the stem to remain flush with the rivet's head, preventing any protrusions that could interfere with the surface finish of the structure being riveted. This flush fit is important for aerodynamics and overall aesthetics of the aircraft structure.

Other options do not accurately represent the behavior of a self-plugging rivet during installation. For instance, the stem not remaining intact would contradict the design purpose of achieving a flush surface, while heating the stem until it melts or pushing it through until it fully exits are not how this type of rivet operates. These methods do not employ the necessary mechanical advantage or friction lock that is a hallmark of self-plug