Finite element modeling of single shear fastener joint specimens: a study of clamp-up, friction and plasticity effects

Abstract

A three dimensional solid finite element model was assembled to investigate the influence of parameters such as friction coefficient, fastener preload and material plasticity on the structural response of Hi-Lok bolted single-lap joints under remote tension/compression loading. Three different specimen types which produce nominal load transfer levels of 6%, 30% and 50% have been investigated. The effects of these parameters where characterized in terms of load transfer, fastener rotation, and stress concentration factor. Friction coefficient has been varied from 0 to 1.25 and the fastener preloads of 1.35lbs, 13.5lbs and 135lbs were assigned for different simulations. Furthermore, constant amplitude load cycles of 15, 20, 30 and 40Ksi were applied in different FE analysis. Results of elastic and isotropic hardening based elastic-plastic material models have been compared and effects of plasticity have been explored. The analysis results indicate that friction coefficient is the most important parameter and friction has a great influence on load transfer, stress concentration and fastener rotation, for all loading conditions, and for both elastic and elastic-plastic material models. Friction, which is affected by both friction coefficient and clamp-up force, has the most influence on load transfer and stress concentration factor at lower remote loads and smaller amount of load transfer. Plasticity which is more prevalent at high remote loads reduces load transfer and stress concentration factors, especially during tension.