What do joggles in removed rivet shanks indicate?

Joggles in removed rivet shanks are indicative of shear failure. This type of failure occurs when rivets cannot withstand the loads applied to them, often leading to slippage or movement that causes the shank of the rivet to bend and create joggles.

In structural applications, rivets are typically subjected to shear loads—forces that act parallel to the cross-section of the fastener. When shear forces become excessive, the rivet can fracture, deforming and creating these noticeable joggles on the shank. This observation helps engineers determine the type of stress the rivets experienced before removal, which is crucial for assessing the structural integrity of the aircraft.

In contrast, bearing failure involves the contact area between the fastener and the material it is fastening, torsion failure refers to twisting forces, and tension failure concerns overstressed materials being pulled apart. These scenarios wouldn't typically produce the joggled appearance observed in rivet shanks. Recognizing the signs of shear failure through joggles can guide maintenance practices and help prevent future structural issues in aircraft.