COMPARISON OF THE STIFFNESS CHARACTERISTICS OF TWO TYPICAL BOLTED JOINTS

A comprehensive comparison of the stiffness characteristics is made for the bolted flange and socket joints of two typical connected structures between cabins. First, the finite element results of a 3D fine model reveal that the static axial stiffness of the two bolted joints is asymmetric and symmetric in tension and compression, respectively. With a larger average static stiffness of tension and compression, the bolted flange joint has a higher natural vibration frequency. Then, a unified dynamic model of the two bolted joints is established, the motion of the flange joint is shown to be coupled because of the asymmetric axial stiffness. By approximating the nonlinear stiffness by high precision power functions, under the transverse dynamic load, numerical solutions of the impact response demonstrate that the frequency of the coupled longitudinal vibration is twice of the transverse frequency. Finally, for the flange joint, the double-frequency coupling longitudinal vibration is confirmed by the impact experiments. The socket joint can provide a high modal damping ratio despite the lower frequency for the first mode according to experimental results.