Further numerical and experimental failure studies on single and multi-row riveted lap joints

Riveted lap joints are being used traditionally for long in the aerospace industry. These joints are the crucial zones that are designed under damage tolerance procedures in the civil aircraft industry. Conventional design procedures of riveted lap joints are based on the assumption that all rivets carry equal load. As this assumption is not entirely valid as found in research literature associated with fatigue and fracture, it is important to investigate this point in terms of the static strength of the riveted joint as well. Hence, in the present study, riveted joint’s static strength experiments and numerical studies are carried out on four different (single and multi-row) riveted lap joints with strain gauges placed at specified locations. The experiments show that all the riveted lap joints sustained the estimated ultimate load and failed only after reaching or exceeding the joint failure load. All these riveted lap joints are analyzed by non-linear finite element method, considering the rivet yielding, plate yielding, geometrical nonlinear and secondary bending effects of the lap joint. The analysis of riveted lap joints shows that though there is unequal load distribution among the rivets in the elastic regime, once the rivets start yielding, significant redistribution of the load takes place among the rivets and the load sharing between the rivets is nearly equal at the failure load of the joint. The agreement between the finite element analysis strains and experimental strains is reasonably good at the failure load and this in conjunction with the aforementioned experimental finding proves that the rivets share nearly equal load at the joint failure load and justifies the conventional design methodology of riveted joints. To the authors’ knowledge no previous research evidence for such correlation was found and this paper confirms conventional design procedures are adequate, though complex interactions between the plate and rivets tend to exist based on non-linear behavior.

► Riveted lap joint with large number of rivets shows joint behavior close to linear.
► Riveted lap joint with less number of rivets shows some non-linear joint behavior.
► FEA of joints considers secondary bending and nonlinearities in plates and rivets.
► If rivets do not yield, load sharing is unequal among the rivets of the lap joint.
► After rivets yield, load sharing among the rivets of the lap joint is nearly equal.