Estimation of Back-Off Loosening Limit for Bolted Joints under Transverse Cyclic Loading.

In many bolted joint structures the mismatch of the thermal expansion coefficients between each component cause transverse cyclic relative slippage and back-off loosening of bolts. In the previous papers we expressed that the loosening behavior of these bolted joints under transverse loading can be estimated taking into account the relative slippage on the contact interface between the bolt head and the jointed body. The amount of this relative slippage can be calculated using the mismatch of the thermal expansion between both jointed bodies and the bending elastic deformation of the bolts. In the calculations of the bending elastic deformations of the bolts the estimation of the bending compliance on the bolt head contact areas are indispensable. So, in this paper we calculate this bending compliance on the bolt head contact area using finite element method considering contact conditions. Using these results we can derive a simple estimation expressions for bending compliance on bolt head contact areas. By using this estimation method of bending compliance on bolt head contact areas we can estimate the critical relative slippage for any bolted joint structures.