The driven rivet head dimensions as an indication of the fatigue performance of aircraft lap joints

Solid aluminium alloy rivets are used in joints of aircraft structures. Riveting implies a squeezing process of the rivet stem with large plastic deformations to form the driven rivet head. The dimensions of the driven rivet head (diameter D and height H) depend on the applied squeeze load Fsq. High squeeze loads are beneficial for the fatigue properties of riveted joints. The present investigation is focused on the relation between Fsq and the rivet head dimensions during controlled squeezing. Measurements of D or H will then allow estimation of the applied squeeze load for quality control of the riveting process with respect to the fatigue properties of the joint. Extensive test series were carried out with five rivet materials, three rivet diameters and two sheet materials (2024-T3 and Glare). An equation was derived for Fsq(D) and Fsq(H) based on assuming a zero volume change of the rivet during plastic deformation. The two material constants in the equations were empirically determined for the rivet materials. A satisfactory correlation was obtained.