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2 Fatigue of Aircraft Structures

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Experimental and Numerical Study of NACA and Conventional Riveting Procedure

Wronicz W., Kaniowski J., Malicki M., Kucio P., Klewicki R.

Fatigue of Aircraft Structures

2017

Iss. 9

157--170

Fatigue behaviour is one of the most important properties of modern airplanes and rivets influence it strongly. According to the literature, the NACA riveting offers a multiple increase in the fatigue life of joints. The aim of this paper is to investigate the benefits offered by the NACA riveting procedure with respect to the residual stress and strain distribution after riveting as well as rivet hole expansion. Experimental and numerical approaches were adopted. The conventional riveting with both the universal and countersunk rivets was compared with the NACA riveting. The countersunk angle and depth in the case of the NACA riveting was modified somewhat relative to the values met in the literature. For these three cases, strain gauge measurements during riveting, hole expansion measurements and FE calculations were performed. The hole expansion measurement with the use of Computer Tomography(CT) was proposed. Only the FE calculations unambiguously indicate better fatigue properties of the NACA riveting. The proposed method of hole expansion measurement requires further research to increase its accuracy.

Comparison of Residual Stress State on Sheets Faying Surface after Standard and NACA Riveting-Numerical Approach

Wronicz W.

Fatigue of Aircraft Structures

2016

Iss. 8

116--126

One crucial characteristic of the aircraft structure are fatigue properties and rivets are usually critical areas in metal airframes due to fatigue cracks nucleation. According to literature, the NACA riveting method offers a huge increase in fatigue life of riveted lap joints. This paper presents FE simulations of quasi-static riveting on a press for standard countersunk rivets and the NACA riveting in two configurations: with a normal brazier rivet and a brazier rivet with a compensator. The analyzed configurations have been compared based on the stress courses on the sheets faying surfaces after riveting process. Due to a lack of data, the rivet length and the squeezing force value were assumed for NACA riveting based on FE simulations. The results indicated beneficial influence of the NACA riveting in the outer sheet (with a countersunk) and disadvantageous influence in the inner sheet. This effect was stronger in the case of the rivet with a compensator.