Abstract: On the basis of original shock load model of stranded wires helical springs, the improved model by introducing nonlinear stiffness is established. An improved method of multiple scales is also presented based on the resolution principles of strongly nonlinear oscillation, and the perturbation solution of nonlinear response of improved model is derived correspondingly. Then, comparison between the two models had been made according to the experimental data. The results show that the improved model reflects the characteristics of nonlinear stiffness and nonlinear vibration frequency and improves the fitting precision of experimental data. It can not only describe the dynamic movement characteristics of spring more accurately, but also is especially significant to research the nonlinear characteristics of the spring under the condition of shock load and large amplitude. This study can also provide the theoretical foundation for the dynamic response characteristics of stranded wires helical springs which is being studied.

Key words: nonlinear oscillation, perturbation method, shock load, stranded wires helical springs