Effect of Bearing Friction and Hole Clearance on the Clamp Load-Deformation Correlation in Bolted Joints 2007-01-1670

In this paper, the effect of bearing friction and the hole clearance on the out-of-plane surface deformation in bolted joints is studied. Series of clamp load-deformation correlations are established for different lubrication conditions and hole clearance values by using both FEA and experiment methods. To study the effect of bearing friction coefficient, values that range from 0.1 to 0.4 are adopted in the FEA model. Three lubrication conditions are used in experiments; namely, clean bolts, oil lubricated bolts and grease lubricated bolts. In order to investigate the effect of hole clearance, four different hole diameters are used in FEA model with M8 bolts; namely, 8.8mm, 9mm, 9.25mm and 9.7mm, three of them are used in the experiments. Experiments are conducted on a single-bolt joint made of an aluminum plate that is fastened with an M8 class 10.9 button head socket screw. Electronic Speckle Pattern Interferometry (ESPI) technique is used to measure the deformation field on the surface of the joint around the tightened fastener. Both FEA and experimental results show that the bearing friction has small effect on the clamp load-deformation relationship, while the hole clearance affects the clamp load-deformation relationship significantly.