Surface Damage in Riveted Aircraft Aluminium Lap Joints, in the Presence of Lubricants

Abstract

This paper discusses experiments investigating the effect of lubrication on surface damage in riveted lap joints which experience fatigue loading in aircraft structure. As part of a larger investigation into the effect of lubricants (specifically Corrosion Inhibiting Compounds, CICs) on fatigue performance, the fracture surfaces were examined to determine the crack initiation sites, and the failure modes involved. Scanning Electron Microscopy was also utilized to assess the nature of the fracture surfaces. The results showed that under the loading used, all the specimens which had not been treated with the CICs, and some treated specimens, failed by tensile failure of the sheet. Some treated specimens failed by rivet shearing. The results suggested that the presence of lubrication at the contacting surface might have reduced frictional load transfer, contributing to the change in failure mode. For specimens that failed in the sheet material, fatigue cracking and micro-void coalescence were the fracture modes, with the potential influence of fretting as a fatigue source.

Influence of corrosion preventive compounds on the friction force in aircraft lap joints

“…Side effects were revealed in some experiments with aviation lap rivet joints. Investigations were carried out with approved in aviation CPCs and rivet joints of transport category planes [6][7][8][9] and of light planes. 10 Authors of the experiments [6][7][8][9][10] founded essential reduction of the rivet joints fatigue life and have proposed probable mechanism of the phenomena.…”

“…The treatment is carried out during the overhaul and maintenance. Protective properties of CPCs are proved and explained by numerous researches and current practice, for example, 4,5 but the probability of negative side effects [6][7][8][9][10] requires special attention and methods for testing.…”