Various damping models are available to describe the dissipation energy present in structures. Among them, viscous and viscoelastic damping models are widely used to describe the damping in viscoelastic structures. Recent studies show that both viscous and viscoelastic damping of a structure varies as it experiences large amplitude vibrations. This makes it necessary to adjust the damping values with respect to the maximum vibration amplitude. The knowledge of damping values allows engineers to estimate the maximum vibration amplitude of a structure under various operating scenarios, thus improving the estimate of the safety margin and the efficiency of design.

However, the variation of hysteretic damping during large amplitude vibrations was not addressed yet. Hysteretic damping is defined as dissipation energy due to the internal friction between the internal planes of the material and is independent on frequency. Hysteretic damping is well defined in linear vibrations as the ratio of loss and storage energies. The concept is here extended and hysteretic damping is identified during nonlinear vibrations.

This paper presents the experimental data measured on a clamped-clamped rubber square plate under harmonic excitation at various force levels. A tool based on temporal method was developed to identify the nonlinear parameters and to calculate the hysteretic damping from the experimental data. The results show that hysteretic damping decreases with excitation frequency.

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