The characterization of nonlinear viscoelastic isolators

Viscoelastic materials may exhibit significant time-temperature dependence and nonlinear mechanical behavior. Nonlinear characteristics are reflected in mechanical properties such as stiffness and damping. The analytical modeling of the storage modulus and loss factor of a typical rubber isolator material as a function of excitation strain amplitude is modeled phenomenologically by using polynomial functions. In order to relate the performance of nonlinear viscoelastic isolators to that of traditional linear isolators, an equivalent linear damping coefficient is derived. Experiments are performed to show nonlinear effects, and to characterize nonlinear parameters. Also, experiments are performed to measure the normalized transmissibility to reflect the effect of material nonlinearity.; The example used for this study is an automotive vehicle front end cooling system. The time-temperature dependence and nonlinear behavior of rubber damping mounts is of great concern to those who are involved in the design of front end cooling rubber damping mounts. The effective front end cooling system isolator should reduce the loads transmitted between the front end cooling system and the vehicle frame.; It is the purpose of research to study and model the nonlinear response of rubber isolators as a function of excitation amplitude. The effects of excitation amplitude are measured and dynamic parameters are expressed using polynomial equations. The effectiveness of nonlinear isolators is compared with that of "linear" isolators and design recommendations are derived from the comparisons.