MS07.7: Nonlinear Phenomena in Mechanical and Structural Systems

Flow-limiting valve is used to control hydrogen flow in the combination valve of hydrogen storage cylinder. The influence of stiffness on nonlinear motion of conical valve core in flow-limiting valve is studied in this research. The results show that the motion tends to be more stable under larger stiffness while the fluctuations of conical valve core tend to change in period under relatively small stiffness.

Nonlinear systems exhibit a wide variety of resonances of a primary or non-primary type. Among the latter, some can appear as isolated branches of solutions, making them difficult to obtain with traditional numerical and experimental approaches. In this work, we propose to leverage multiharmonic forcing to bridge different resonances associated with the same mode together. The method starts with a given harmonic forcing, and progressively increases the amplitude of a second harmonic component, all the while decreasing the amplitude of the first. It eventually reaches another harmonic forcing situation where only the second harmonic component subsists. By doing so, this multiharmonic transition method can continuously go from an easily attainable primary resonance to a (possibly isolated) non-primary resonance by transiting through a simultaneous resonance state. The method is illustrated numerically with a Duffing oscillator and a doubly-clamped Von Kármán beam.

The performance of a combination of two spherical pendulum vibration absorbers (SPVAs) to suppress the vibrations of a two-degree-of-freedom structure subjected to a unidirectional, horizontal, and harmonic excitation is theoretically investigated. The equations of motion of the system are expressed using new coordinates to prevent singularities at the zero inclination of the SPVAs. Van der Pol’s method is employed to determine the frequency response curves. Although the structure is excited in one direction by an external force, the structure and SPVAs exhibit whirling motions that depend on the excitation frequency. Localization of the two SPVAs may occur in specific ranges of excitation frequencies. The performances of the two SPVAs are evaluated and compared with those of a single SPVA.