The influence of a static axial preload on the vibrational behaviour of a viscoelastic beam: an experimental assessment

Viscoelastic materials have recently shown to be able to satisfy many requirements needed in several technological applications, from the automotive field to the biology, since they can be designed to serve a specific purpose, with properly tuned physical properties, as lightness, damping and mechanical resistance. The last two properties are strongly influenced by the complex viscoelastic modulus, which varies both in the time and in the frequency domain. By applying an axial tensile preload, a shift in the frequencies of the beam resonances has been observed. The aim of this paper is to experimentally assess how flexural vibrations can be influenced by the application of an axial tensile load. The setup consists of a chassis to which the beam is horizontally suspended, an accelerometer and an impact hammer useful for modal analysis. The results enable us to better understand how the static preloads may determine a variation of the nature of the system's eigenvalues, and therefore on the type of vibrational motion of the beam at a certain resonance frequency.