Elasto-plastic FEM stress analyses of the contact stress distributions at the bearing surfaces and an estimation of permanent sets in bolted joints using hexagon bolts with flange (in the case of initial clamping

The contact stress distributions and permanent sets at the bearing surfaces in bolted joints in initial clamping state are analyzed using an elasto-plastic FEM when hexagon bolts with flange are used. It is seen that the effect of the flange slope angle and the flange thickness are substantial on both of them. It is found that the difference in the contact stress distributions is larger between elastic analyses and elasto-plastic malyses when the bolt preload is larger. In the experiments, aluminum alloy specimens were compressed by the bolts with flanges and the permanent sets were measured. The permanent sets obtained from FEM are in a fairly good agreement with the measured results. In addition, the equivalent length for the bolt with flange is proposed as 1 .2d, where d is nominal bolt diameter. © 2011 The Japan Society of Mechanical Engineers.