We study the dynamics of a two-degrees-of-freedom (two DOF) nonlinear
oscillator representing a quartercar model excited by a road roughness profile.
Modelling the road profile by means of a harmonic function we derive the
Melnikov criterion for a system transition to chaos or escape. The analytically
obtained estimations are confirmed by numerical simulations. To analyze the
transient vibrations we used recurrences.Comment: 13 pages, 16 figures, in pres