Estimating clamping pressure distribution and stiffness in aircraft bolted joints by finite-element analysis

In this study, a finite-element (FE) stress analysis of aircraft structural double-lap bolted joints was performed using the commercially available computational package ANSYS in order to obtain the clamping pressure distribution and to estimate the stiffness of the joined plates (members) within the clamped region. The joint consists of three aluminium alloy 7075-T6 plates clamped by a single bolt, washer, and nut. A three-dimensional (3D) FE model of the joint was generated, and then subjected to three different simulated clamping forces. 3D surface-to-surface contact elements were employed to model the contact between the various components of the bolted joint. The model included friction between all contacting surfaces, and also a clearance between the bolt shank and the joint hole. FE results revealed an overall crock-shaped pressure distribution at the joined plates. Moreover, some beneficial longitudinal compressive stresses were observed around the fastener hole as a result of the clamping compressive effect.