Effects of Volterra's formulation of heredity on vibrations in harmonic and Duffing oscillators

Abstract

In recent years, the effects of heredity on dynamical systems have been analysed using the fractional derivative. But, another way of considering the heredity is the integral formulation

proposed by Vito Volterra in 1912 and later almost forgotten. It can also be termed as long duration feedback. This paper presents some of the results of this formulation of the heredity on the dynamics of a linear harmonic oscillator and on that of the Duffing oscillator which are representatives of oscillating mechanical structures. For the linear oscillator, the heredity amplifies the vibration amplitude and shifts the resonance frequency to higher values. For the hereditary hardening Duffing oscillator, the analysis of the stability of the single equilibrium point reveals the existence of a Hopf bifurcation appearing at a given value of the heredity coefficient. This leads to self-sustained oscillations which are determined mathematically using the averaging method and confirmed numerically. The heredity also modifies the length of the hysteresis domain through the change of the effective stiffness and damping coefficients. It can also be a source of chaos in a system free of chaos which can appear through quasiperiodic routes and period-doubling. For the hereditary Duffing oscillator with single hump and double well potential or the bistable Duffing oscillator with three equilibrium points, one also finds the existence of a Hopf bifurcation appearing at a given value of the heredity coefficient. The hereditary bistable Duffing oscillator unveils monostable and bistable periodic characteristics, period doubling to monostable and bistable chaos and coexistence between chaotic and periodic characteristics.