Nonlinear passive damping of the X-shaped structure

Nonlinear damping can demonstrate excellent performance in vibration control. It is known that the ideal nonlinear damping could be performed as that the damping effect is as high as possible around resonance frequencies but as low as possible at other frequencies. However, how to realize such a nonlinear damping in real engineering practice with a convenient and passive manner would be an open problem in the literature. To this aim, this study investigates the nonlinear damping effect of an X-shaped structure which is inspired from biological limb skeleton systems. It is shown that, (a) the equivalent damping characteristic of the X-shaped structure is a nonlinear function of the vibration displacement and varies at different frequency; (b) the equivalent damping is adjustable with several structural parameters, and can be very high at around resonance frequencies but very low at other frequencies, showing an ideal passive and nonlinear damping property; (c) the linear horizontally-placed damper and joint friction can both produce the desired equivalent nonlinear damping in the vertical direction. The results of this study demonstrate an innovative and passive solution for designing desired nonlinear damping characteristics in various engineering practices by employing the X-shaped structure.