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Time-Dependent Decay Rate and Frequency for Free Vibration of Fractional Oscillator

This paper presents an investigation on the free vibration of an oscillator containing a viscoelastic damping modeled by fractional derivative (FD). Based on the fact that the vibration has slowly changing decay rate and frequency, we present an approach to analytically obtain the initial decay rate and frequency. In addition, ordinary differential equations governing the decay rate and frequency are deduced, according to which accurate approximation is obtained for the free vibration. Numerical examples are presented to validate the accuracy and effectiveness of the presented approach. Based on the obtained results, we analyze the decay rate and the frequency of the free vibration. Emphasis is put on their time-dependence, indicating that the decay rate decreases but the frequency increases with time increasing.