A MODEL FOR GENERAL PERIODIC EXCITATION WITH RANDOM DISTURBANCE AND ITS APPLICATION

Many vibration problems involve a general periodic excitation such as those of a triangular or rectangular waveform. In practice, the period ic excitation may become disordered due to uncertainties. This paper p resents a stochastic model for general periodic excitations with rando m disturbance, which is constructed by introducing random amplitude an d phase disturbances to individual terms in the Fourier series of the corresponding deterministic periodic function. Mean square convergence of the random Fourier series are discussed. Monte Carlo simulation of disordered sawtooth, triangular, and quadratic wave forms are illustr ated. An application of the excitation is demonstrated by vibration an alysis of a single-degree-of-freedom (SDOF) hydraulic valve system sub jected to a disordered periodic fluid pressure. In the present study o nly the phase disturbance is considered. Effects of the intensity of p hase modulation on up to fourth order moment response and the converge nce rate of the random Fourier series are studied by numerical results . It is found that a small random disturbance in a general periodic ex citation may significantly change the response moment. (C) 1997 Academ ic Press Limited.