Influences of Various Parameters on Shear Stiffness of Bolted Joint Subjected to Shear Load

Abstract Multi-material structures have been required to reduce weight of vehicles in order to improve fuel efficiencies. To realize multi-material structures effectively, we have to select not only the optimum material for each structure but also the optimum joining techniques for each joint. Bolted joints are one of the most popular methods to join dissimilar materials. Various characteristics for the bolted joints had been revealed in the literatures. Especially self-loosening characteristics of bolted joints subjected to shear cyclic load have been still investigated. However it has not been sufficiently investigated which parameters effect on shear stiffness of bolted joints which is subjected to shear load. When two plates are joined by a bolt and a nut, it is important for functionally designing machines to know if the shear stiffness of the joining point is the same as the plate stiffness or not and if the stiffness changes or not. In this study, we have revealed experimentally and analytically the shear stiffness characteristics of bolted joints and which parameters determine the shear stiffness. Washers with different contact areas to the clamped plates were used in the experiments. The results showed that the shear stiffness of bolted joints increases with an increase in the contact area size between washers and clamped parts. The result indicates that the shear stiffness of bolted joint is mainly determined by the bending stiffness that is an easiness of bolted joints to rotate due to shear tensile force rather than the clamping force. But if the slippage occurs between the clamped plates, the shear stiffness of bolted joint markedly decreases. The results also showed that the tensile force with which the clamped plates begin to slip between them depends on the clamp force of bolted joints and the contact area size between the clamped plate and the washers.