Nonlinear primary resonances of a pneumatic spring under simple harmonic excitations

The nonlinear primary resonances of a pneumatic spring with simple harmonic excitations were studied by the method of nonlinear dynamics. Through testing, load curve of the pneumatic spring under a certain initial pressure was got. According to the test data, the relative elastic force was fitted to relative displacement by cube polynomial equation. The method of multiple scales was used to solve nonlinear dynamics equations. Nonlinear primary resonances were obtained and the effect of the parameters were studied. The results show that the frequency-response curve have much to do with the parameters. The nonlinearity becomes evidence with cube stiffness increasing. As the amplitude of the excitation increases, the frequency-response curves bend away from the linear axis. The peak amplitude decreases with damping coefficient increasing. These can be quite useful for the designing of a pneumatic vibration isolation system.