Loosening and Sliding Behavior of Bolt-Nut Fastener under Transverse Loading : 1st Report, Investigation and Modification of Equation which Evaluates the Reaction Force Moment(<Special Issue>Design or Process Technology for Mechanical and Adhesive Joint Structures)

Abstract

The thread joint has been frequently used for the efficient productivity and maintainability as a machine element. However, many troubles such as loosening of bolted joints or fatigue failure of bolt were often experienced. Many attentions must be paid on the improvement of the strength and the reliability of the thread joints. It is generally said that the fastening axial force rapidly decreases by the rotation loosening of nuts if the relative slippage on the interfaces between nuts and fastened body goes beyond a certain critical limit. This critical relative slippage (S_<cr>) that prescribes the upper limit for preventing the loosening behavior has been estimated according to the theoretically obtained equation considering the bending deformation of bolt and the geometrical constraint condition. In this paper, we present the investigated results of the deformation behavior of bolt-nut joint under transverse loading condition. The bending moment of bolt is measured by the quasistatic loading test. The reaction force moment by nut used in the equation for estimating the S_<cr> is evaluated by the comparison of experimental and analytical results from estimated equation. The new equation for estimating the reaction force moment which agrees with measured value is examined and proposed.