Effective variation analysis model for the riveting press process of a flush rivet

Most of the fatigue damage in aircraft structures can be linked to the stress concentration arising at the rivet joints. Interference-fit riveting of a flush rivet can form the uniform interference fit. Thanks to the uniform interference fit, large stress concentration can be avoided. The radial deformation, which is directly relative to interference fit, is therefore of prime importance. Parameters associated with a riveting process that directly affect the quality of rivets must be taken into account to observe the effect on radial deformation at rivet holes. This paper presents an effective variation analysis to calculate radial deformation at rivet holes by assuming that the axial stresses are constant both along the axial and radius of the rivet slug. Firstly, the rivet process model is built before variation analysis. Secondly, theoretical relationships between radial deformations and contact loads are proposed using elasto-plastic analysis. Later, the expressions of the contact loads are given according to geometrical relationships and analysis of deforming forces. Thirdly, an instance made up of the rivet, top sheet and bottom sheet is used to verify the analysis model. The model paves an efficient way to study the deforming law of the riveting press process and build the pre-estimate model of the rivet deformations and the parameter optimization model.