Identification and modelling of dynamic parameters for round link chains subject to axial loads.

A round link chain subject to axial dynamic loads composes a nonlinear viscoelastic system. Unlike the classical pounding problems, the round link chain will not only suffer linear elastic deformation, but also nonlinear plastic or impacting deformation. Based on theoretical formulation and experiments, a new approach is presented in this paper to model and identify the nonlinear dynamic parameters, namely the stiffness and damping for the round link chain. With linear deformation, nonlinear deformation and energy dissipation considered, a modified nonlinear viscoelastic model is developed to describe the vibrational behavior of the chain with numbers of round links. The linear elastic model and impacting model are combined to derive the equivalent nonlinear stiffness, while experiments and the least square fitting method are employed to identify the nonlinear damping according to the modified nonlinear viscoelastic model. The influences of the key parameters such as the length of the chain, elastic module and loading frequency on the dynamic stiffness and damping are investigated. Another test is performed to validate the identification model and good agreements are observed.