抄録
Bolted joints are widely used in mechanical structures. When dynamic characteristics of a cantilever beam are considered, the fixed end is assumed as an ideal fixation condition. In the actual case, the fixed end is often realized using bolted joints and the boundary condition isn't always an ideal fixation condition. In this study, dynamic characteristics of a cantilever beam with various boundary conditions are experimentally investigated. The normal condition is a bolted joint with adequate torque and locations of bolts. Other conditions are bolts joints with weak torque and adequate locations of bolts, and adequate torque and inadequate locations of bolts. And the natural frequencies and damping ratios are determined from the resonance curves. As a result, it is recognized that the natural frequencies and damping ratios are significantly changed in the case of an inadequate torque and locations of bolts and the higher harmonics of vibration can be observed at the condition. It is considered that the length of a cantilever beam changes during one period of vibration so that the nonlinear characteristics are appeared. These results can be applied to the diagnosis of machines and structures.
