A power-series method is presented for the analysis of a conservative stron
gly non-linear two-degree-of-freedom (d.o.f.) system with cubic non-lineari
ty. The method is based on transforming the time variable into an harmonica
lly oscillating time whereby the governing differential equations become we
ll conditioned for power-series analysis. The oscillating time frequency is
obtained by enforcing Rayleigh's energy principle. The results show good a
greement with those obtained using the Lindstedt-Poincare method. (C) 2000
Academic Press.