Experimental study of parametric resonances of silicone cord induced by pulsating axial force

This paper presents the results of an experimental investigation into the dynamics of a silicone cord subjected to a pulsating tensile force. The system is examined to identify dynamic instabilities, with particular focus on the phenomenon of parametric resonance. Two measurement methods were used: a contact method using accelerometers and a non-contact method using two high-speed cameras. The recorded signals were subsequently analysed to gain insight into the system’s motion during resonant vibrations. To analyse the motion of the system in more depth, a numerical method was proposed to determine the mode shapes of the individual vibration components involved in parametric resonance. In the studied system, instability ranges were determined and identified, and the effects of amplitude and excitation frequency on the resulting vibrations were investigated. The study revealed diverse dynamic behaviours, including simple parametric resonances with periodic, polyharmonic, planar vibrations, as well as combination resonances involving more complex, non-periodic, spatial motion. Vibrations were examined both in two-mode combination resonances and in regions where multiple types of resonances were simultaneously excited. Especially in the latter cases, the nature of the motion of the system is particularly complex.