Abstract: The mechanical vibration response of a nonlinear system was discussed through the test and analysis of the nonlinear system composed of quality(product)一cushion material(polypropylene foam) under the vibration with sine sweep and fixed frequency. The first harmonic response was analyzed by the method of harmonic balance and obtained the amplitude-frequency response curve of the nonlinear stiffness system and reliable transfer function. The resonating peak of system was influenced by the valuc of the material damp, and the bigger the damp, the smaller the peak value. Based on the mastering of the frequency response curve of polypropylene foam cushion system, the random simple harmonics excitation vibration transmittance could be forecasted and the cushion design could be more reliability based on it.

Key words: polypropylene foam, vibration, nonlinear response, harmonic balance method